In This Post we are providing Chapter-3 HUMAN REPRODUCTION NCERT MOST IMPORTANT QUESTIONS for Class 12 BIOLOGY which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.
NCERTMOST IMPORTANT QUESTIONS ON HUMAN REPRODUCTION
1. Differentiate between spermatogenesis and oogenesis. Ans.
Spermatogenesis
Oogenesis
1. It occurs inside the testes.
1. It occurs inside the ovary.
2. All the stages are completed inside the testes.
2. Majority occurs inside the ovary but last stages occur in the oviduct.
3. Spermatogonia develop from the germinal epithelium lining in the seminiferous tubules.
3. Oogonia develop from the germinal epithelium overlying the ovary.
4. All spermatogonia give rise to spermatocytes.
4. Only few oogonia give rise to oocytes.
5. Primary spermatocytes divide by meiosis I to give rise to two secondary spematocytes
5. Primary oocyte undergoes meiosis I to give rise to one secondary oocyte and a polar body.
6. Secondary spermatocyte divides by meiosisII to give rise to two spermatids.
6. Secondary oocyte divides by meiosisII to form the ovum and the second polar body.
7. Each spermatid differentiates into spermatozoan or sperm.
7. No differentiation is required after meiosisII.
8. The sperms formed are motile.
8. The ovum or egg is non- motile.
2. ‘A fertilized egg is the blue print of future development’. Explain Ans. The sperm carries the genetic information from the father in form of 23 chromosomes (including the male sex chromosome X or Y) while the egg bears the genetic information from the mother (including the female sex chromosome X). Thus during fertilization the fusion of the male and the female gametes produce new genetic combination which introduces variation in the progeny. The zygote or the fertilized egg contain the genetic information which accordingly controls the development of the embryo.
3. Briefly describe the stages of spermatogenesis in human? Ans. Spermatogenesis consists of two phases:- I. FORMATIDN OF SPERMATIDS :- It further consist of 3 phases
Multiplication phase :- undifferentiated germ cells undergo repeated division to produce sperm mother cell or spermatogonia.
Growth phase :- Spermatogonia increase in volume & is now called PRIMARY SPERMATOCYTES.
Maturation phase: – primary spermatocyte undergoes meiosis I to produce small size haploid secondary spermatocyte secondary spermatocyte divides by meiosis – II & forms haploid Spermatids.
II.FORMATION OF SPERMS :- The tramsformation or differentiation of spermatids into spermatozoa or sperm is called spermiogenesis & occurs under the influence of FSH
4. Describe the hormonal control of human male reproduction system with the help of a flow chart & highlight the inhibitory & stimulatory directions in it? Ans. i) Spermatogenesis is initiated due to an increase in the secretion of Gonadotropin releasing hormone from hypothalamus at the age of puberty.
The increased levels of GnRH act on anterior pituitary& stimulate the secretion of two gonadotropins i-e. leuteinizing hormone (LH) & follicle stimulating hormone (FSH)
LH acts on leydig cells & stimulate them to secrete testosterone
FSH acts on sertoli cells & stimulate secretion of some factors help in spermiogenesis
5. A sperm has just fertilized a human egg in the fallopian tube. Trace the events that the fertilized eggs will undergoes upto implantation of blastocyst in the uterus. Ans. 1. CLEAVAGE :-Fertilized egg starts dividing lay specific mitotic divisions called cleavage. The zygotes undergoes mitotic division in the isthmus of oviduct to form daughter cell the cells formed as a result of cleavage called blastomere 2. BLASTOCYST :- 3-4 days after fertilization, the morula twins into large mass of cells called blastocyst Outer peripheral cells enlarge & flatten further & form trophoblast. Trophoblast cells secretes a fluid into interior & form a cavity called blastocoel. The embryonic stage with blastocoels is called blastula.
6. Where oogenesis does takes place. Describe the stages of this process? Ans. The process of formation & maturation of ovum is called oogenesis. It takes place in ovary & is initiated during embryonic development of female foetus. It consists of 3 phases :–
Multiplication phase :- The primordial germ cells divide by meiosis to produce oogonia. These oogonia divide lay repeated mitotic divisions forming clusters. In each cluster only one of them enters into growth phase & is called primary oocyte.
Growth phase :- Growth phase occurs only after attainment of puberty. It involves – increase in size of oocyte to many folds & synthesis of you.
Maturation phase :- The first division is meiotic as a result two haploid (n) cells are produced. In this division, cytobinesis is unequal, large daughter cell with almost all cytoplasm is called secondary oocyte & smaller me with less cytoplasm is called polar body. The secondary oocyte then undergoes second meiotic division to form an ovum & second polar body.
7. Ans. (i) ’D’ Spermatids = undergo spermiogenesis (ii) ‘A’= Spermatogonium; B = Primary spermatocyte (iii) ‘B’ = Diploid E = Haploid (iv) ‘F’ = Sertoli cells – Nutrition to germ cells (v) Mitosis in Cell ‘A’, Meiosis in cell ‘B’
8. Explain the development of human embryo with diagrams. Ans. The Fusion of the sperm and the egg in humans result into formation of the diploid structure called zygote. The zygote starts dividing mitotically as it moves through the oviduct into the uterus to form 2,4,8,16 daughter cells called blastomeres. The stage is called morula. The Morula divides further and differentiates into blastocysts. The outer layer of blastomeres called trophoblast gets attached to the endometrial layer of the uterus. The uterine wall divides and encloses the blastocysts and this is referred to as implantation. The inner layer of blastomeres in the blastocysts gives rise to the embryo.
9. What is menstruation? What are the specific actions of FSH, LH, estrogen & progesterone in menstrual cycle? Ans. During menstrual phase of menstrual cycle which starts on 28th day the endometrial lining of female genital tract break down due to lack of progesterone As a result bleeding occurs. This monthly flow of blood is caller menstruation. During menstrual cycles, the various changes occurs in the ovary under the influence of various hormones :-
Menstrual phase :- The levels of hormones LH ,FDH estrogen & progesterone is very less which results in breakdown of endometrial lining of uterus.
Follicular phase :- In this phase , the levels of pituitary hormones FSH & LH increases which causes ovarian hormone estrogen to release,. FSH controls the follicular phase , it stimulates the growth of follicles. Both FSH & LH reach their peak level in middle of cycle (14th day)
OVULATORY PHASE :- The level of LH hormones reaches its peak (called LH swing) induces the ruptures of mature Graffian follicle & there by release of ovum
Luteal phase :- The LH & FSH hormones begins to decline. After ovulation, the follicle becomes to ruptures & is transformed into corpus Luteum which secretes large quantities of progesterone
10. A woman has conceived & implantation has occurred within her uterus. Discuss the sequence of changes up to parturition which will take place within her body under the influence of various hormones. Ans. The following changes takes place in the body of women after implantation :-
The trophoblast differentiates into two layers outer layer secretes enzymes to dissolve the endometrium of uterus.
The inner layer grows out as finger – like projections called chorionic villi into uterine stoma. The chorionic villi & the uterine tissue become inter digitated to form structural & functional unit called placenta.
Placenta secretes hormones like HCG, HPL , estrogen & progesterone that are necessary to maintain pregnancy
Umbilical cord, the structure that connects the placenta with the foetus is formed.
Simultaneously, inner cell mass differentiates into outer layer called ectoderm & inner layer called endoderm. & a middle layer called mesoderm appears between ectoderm & endoderm.
The primary germ layers give rise to all the tissues & organs of the adults e.g. after one month heart is formed & after second month digits & limbs are formed.
By the end of ninth month of pregnancy, foetus is completely developed & is ready for delivery.
During parturition, ovary secretes a hormone called relaxin that facilitates parturition which softens the connective tissue. Mild contraction called foetal ejection reflex is induced. This triggers release of oxytocin from posterior pituitary. Oxytocin induces stronger leads to expulsion of baby from uterus, through birth canal.
In This Post we are providing Chapter-1 REPRODUCTION IN ORGANISM NCERT MOST IMPORTANT QUESTIONS for Class 112BIOLOGY which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.
NCERTMOST IMPORTANT QUESTIONS ON REPRODUCTION IN ORGANISM
Question 1. Define: (i) juvenile phase,
Answer: Juvenile phase. The period of growth in the life of organisms before they start reproducing sexually and attain a level of maturity is called juvenile phase. It is followed by the reproductive phase.
(ii) reproductive phase Answer: Reproductive phase. The period of active reproductive behaviour, when the organisms show marked morphological and physiological changes is called reproductive phase. It is followed by senescence phase.
(iii) senescence phase. Answer: Senescence phase. The period when the reproductive phase ends and concomitant changes occur in the body such as slowing of metabolism is called senescence phase. It is followed by death.
Question 2. Distinguish between asexual and sexual reproduction. Why is vegetative reproduction also considered as a type of asexual reproduction?
Answer: 1. Differences between asexual reproduction and sexual reproduction.
Asexual Reproduction
Sexual Reproduction
1. The process involves only one cell or one parent.
1. This process involves two cells or gametes belonging to either the same or different parents.
2. The whole body of the parent may act as a reproductive unit or it can be a single cell or a bud.
2. The reproductive unit is called gamete which is unicellular and haploid.
3. The offspring are genetically similar to the parent.
3. The offspring differ from the parents.
4. Only mitotic division takes place.
4. Meiosis and mitosis both take place.
5. No formation of sex organs.
5. Formation of sex organs is essential.
6. No evolutionary significance.
6. It introduces variation; hence it is of evolutionary significance.
2. Vegetative reproduction is also considered a type of asexual reproduction because it does not involve meiotic division and there is no formation and fusion of gametes.
Question 3. How does an encysted Amoeba reproduce on the return of favourable conditions?
Answer: Multiple fission in encysted Amoeba:
Amoeba withdraws pseudopodia and secretes a cyst wall around itself. This phenomenon is called encystation.
Amoeba divides by multiple fission.
It produces a large number of pseudo- conidiospores.
The cyst wall breakdown.
The spores are liberated and settle down on suitable substrates and grow as amoebae. This process is also called sporulation.
Question 4. Discuss the advantages and disadvantages of asexual reproduction.
Answer: Advantages of asexual reproduction:
It involves simple mitotic division in single-parent and it may produce a large number of young ones.
Young ones produced by asexual methods are genetically similar to the parent.
It helps in the dispersal of offspring to far off places.
Disadvantages of asexual reproduction.
The young ones thus produced do not possess much capacity to adapt rapidly to the environmental changes taking place in quick succession.
No genetic recombination occurs; thus no variation occurs.
Question 5. Discuss the advantages and disadvantages of sexual reproduction.
Answer: Advantages of sexual reproduction:
Genetic recombination, interaction, etc. take place which causes variations in the offspring, thus also form raw materials for evolution.
The offspring adapt more comfortably and quickly to the change in environmental conditions and have better chances of survival.
Disadvantages of sexual reproduction. Usually, two parents of opposite sexes are required (except in hermaphrodite).
Question 6. List various methods of natural vegetative propagation. Give examples:
Answer:
Vegetative propagation by stems, e.g.Grasses, Turmeric, Onion, Colocasia, Potato, Gladiolus and Crocus.
Vegetative propagation by roots, e.g. Murraya sp., Albizzia Lebbac, Dalbergia sissoo, Tuberous roots of sweet potato, Asparagus, Tapioca, Dahlia and Yams (Dioscorea).
Vegetative propagation from reproductive organs. Flower buds of century plant (Agave sp.) develop into bulbils.
Question 7. Define external fertilisation. Mention its disadvantages:
Answer: The fertilisation in which the fusion of gametes occurs outside the body of the female in an external medium, i.e. water, is called external fertilisation.
Examples. Bony fishes, amphibians, etc. Organisms that exhibit external fertilisation show great synchrony between the sexes in order to liberate the gametes at the same time.
Disadvantages of external fertilisation:
A large number of gametes are produced to ensure fertilisation, thus there is wastage.
The offspring formed are extremely vulnerable to predators, thus threatening their survival up to adulthood.
Question 8. Explain the process of budding in yeast.
Answer: Budding in yeast. It is a common type of vegetative reproduction. In a medium which is abundantly supplied with sugar, yeast cytoplasm forms a bud-like outgrowth. The growth soon enlarges and a part of the nucleus protrudes into the bud and breaks off. The bud then begins to grow and then separates from the mother cell. Often it will itself form a bud before it breaks away, and straight or branched chains are produced.
Thus, as a result, branched or unbranched chains of cells called pseudo my cilium are produced. The cells are loosely held together. Sooner or later they become independent.
Question 9. Describe the importance of vegetative propagation.
Answer: Merits of vegetative propagation:
Plants produced by vegetative propagation are genetically similar and constitute a uniform population called a clone.
Plants with reduced power of sexual reproduction, long dormant period of seed, poor viability, etc. are multiplied by vegetative methods.
Some fruit trees like banana and pineapple do not produce viable seeds. So these are propagated by only vegetative methods.
It is a more rapid and easier method of propagation.
Good characters are preserved by vegetative propagation.
Some plants such as doob grass (Cynodon dactylon) which produce only a small quantity of seed are mostly propagated by vegetative propagation.
Grafting helps in getting an economically important plant having useful characteristics of two different individuals in a short time.
Question 10. Write a note on sexuality in plants. Or Coconut palm is monoecious while date palm is dioecious. Why are they called so?
Answer: Sexuality in organisms: Sexual reproduction in organisms generally involves the coming together of gametes from two different individuals. But this is not always true.
Sexuality in Plants: Plants may have both male and female reproductive structures in the same plant (bisexual) or on different plants (unisexual). In several fungi and plants, terms such as homothallic and monoecious are used to denote the bisexual condition, and heterothallic and dioecious are used to describe the unisexual condition.
In flowering plants, the unisexual male flower is staminate, i.e. bearing stamens, while the female is pistillate or bearing pistils. In some flowering plants, both male and female flowers may be present on the same individual (monoecious) or on separate individuals (dioecious). Some examples of monoecious plants are cucurbits and coconuts and dioecious plants are papaya and date palm.
In This Post we are providing Chapter-2 SEXUAL REPRODUCTION IN FLOWERING PLANTS NCERT MOST IMPORTANT QUESTIONS for Class 12 BIOLOGY which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.
NCERTMOST IMPORTANT QUESTIONS ON SEXUAL REPRODUCTION IN FLOWERING PLANTS
1. Trace the development of microsporocyte into mature pollen grains. Ans. i) When the anther is young, the microsporangium contains compactly arranged homogenous cells forming the Sporogeneous tissues.
Every cell of the sporogenous tissue is a potential Pollen mother cell (PMC) & give rise to microspore tetrad or Pollen grains.
But Some of them forego this Potential & become differentiated into pollen or microspore mother cell (MMC)
Each microspore mother cell undergoes meiosis to form a cluster of four haploid cells called microspore tetrad.
As the anther matures, microspores dissociate from tetrad & develop into pollen grains.
The nucleus of microspore undergoes mitosis to form large vegetative cell & small generative cell. They develop a two layered wall – outer exine made up of sporopollenin & inner intine made up of cellulose & pectin. Usually Pollen grains are liberated at two celled stage.
2. i) Explain the structure of a maize grain with the help of a diagram ii) Why cannot we use the term maize seeds for maize grains? Ans. (i) In grass family ( eg. Maize ) fruit is single seeded where pericarp & seed coat are fused together to form the husk. Just below husk, there is a layer of cells called aleurone layer, with stores proteins. There is a large endosperm that stores starch. The embryo lies on one side of endosperm & consists of a single cotyledon called scutellum & embryonal axis. The region of embryonal axis that points down ward from point of attachment of cotyledons is radicle & is covered by protective sheath called coleorhiza. The region of embryonal axis that points upward from point of attachment of cotyledon is plumule, it is covered by foliaceous sheath called coleoptite (ii) We cannot use the term seeds for maize grain because seed is not completely developed from embryo but retains a part of endosperm.
3. Trace the development of megasporocyte into mature ovule. Ans. i. A single Megaspore mother cell is differentiated in the micropylar region of nucleus of an ovule & undergoes meiosis & forms a cluster of haploid cells called megaspore tetrad. Of these, soon three degenerates & only one megaspore becomes functional ii. Functional megaspore enlarges to form embryo sac. Its nucleus undergoes mitotic division & two nuclei move to opposite poles forming 2-nucleate embryo Sac. iii. Two successive mitotic divisions in each of these two nuclei results in formation of 8-nucleate embryo sac. iv. Three cells are grouped together at micropylar end to form egg apparatus. consisting of two synergids & a female egg cell . v. Three cells are grouped together at the chalazal end, they are called antipodal cells. vi. The remaining two nuclei are called Polar nuclei, they move to centre of embryo sac & fuse to form Secondary nucleus. Thus a typical angiospermic embryo sac is 8-nucleate 7-celled
4. “Incompatibility is the natural barrier in fusion of gamete”. Justify this statement. Ans. Pollen grains of a plant species cannot germinate on stigma of other unrelated species because both the species are incompatible & process is called pollen – pistil incompatibility. In many angiospermic plants, it is seen that pollen grains germinate on stigma of unrelated species but male gametes produced in pollen tube cannot fertilize egg. This is called gametic incompatibility Self incompatibility can be achieved by any of the following ways :-
Pollen Stigma interaction: – In this phenomenon, pollen grains fails to germinate on Stigma because of incompatibility.
Pollen tube style interaction: – In this phenomena, pollen grains become able to germinate on stigma & pollen tube penetrate stigmatic surface but due to incompatibility growth of pollen tube within stigma & style is inhibited.
Pollen – ovule interaction: – pollen tube successfully pierces & grows within style & its growth is inhibited at micropyle of ovule.
5. How dose pollination takes place in salivia. List any four adaptations required for such type of pollination. Ans. In salivia, entomophily or pollination lay insects occurs. The flowers of salivia are bilipped. Its upper lip consists of two petals & lower lip consists of three petals. The lower lip functions as sitting pad for insects. In normal conditions, the connective remains upright. When insect enters the tube of corolla towards nectar sitting on lower lip, it pushes sterile anther lobe which automatically brings about fertile anther to touch the back of insects gets the blow of fertile lobe. Pollen grains are dusted on back feather & legs of insects. ADAPTAIONS EOR ENTOMOPHILY :-
Flowers are brightly coloured.
Flowers possess nectar glands.
pollen grains are usually sticky & spiny
flowers are large – sized & stout
6. Explain the formation of an embryo sac with diagrams. Ans.
The functional megaspore grows in size.
The nucleus divides mitotically to form two nuclei which move to opposite poles.
Each nucleus at the poles undergoes two mitotic divisions to form four nuclei in each pole or a total of 8 nuclei.
two nuclei from each pole move to the centre to form the polar nuclei.
the other nuclei, three at each pole get surrounded by bit of cytoplasm to form cells.
the female gametophyte or the embryo sac thus has 7 cells and eight nuclei.
7. Explain the development of embryo in a dicotyledonous plant with neatly labeled diagrams. Ans. The embryo develops at the micropylar end where the zygote is located. The zygote starts developing only after certain amount of endosperm is formed to assure nutrition to the embryo. The zygote divides mitotically to form various stages including pro- embryo, globular, heart shaped and finally the mature embryo
8.Describe the post-fertilization changes taking place in a flowering plant? Ans. The major events taking place in a flowering plant after fertilization:- (i) DEVELOPMENT OF ENDOSPERM:- Endosperm development proceeds embryo development . The most common method of endosperm development is nuclear type where triploid endosperm (PEN) undergoes repeated mitotic divisions without cytokinesis – Subsequently cell wall formation occurs from periphery & endosperm store food materials which is later used up by embryo. (ii) DEVELOPMENT OF EMBRYO :- The zygote divides lay mitosis to for a pro-embryo first . Later development results in formation of globular & heart shaped embryo & that ultimately become horseshoe – shaped embryo with one or more cotyledons. In dicot embryo, the portion of embryonal axis about the level of attachment is epicotyl & it terminates into plumule while portion of embryonal axis below the level of attachment is hypocotyl & terminates into radicle.
9.Trace the events that would take place in flower from the time of Pollen grain of species fall on stigma up To completion of fertilization. Ans. GERMINATION OF POLLEN GRAINS ON STIGMA The pollen grains absorb fluid present on stigma & swell up. The exine ruptures at the place of germ pore & intine comes out in the form of tube with its internal contents. This small tubular structure is called pollen tube & process is called pollen germination. ii) Entry of pollen tube into Ovule: – The entry of pollen tube into ovule occurs through micropyle or chalaza or through lateral sides of ovule. Only one pollen tube enters inside the embryo sac of an ovule. Normal two synergids are destroyed while entry of pollen tube into embryo sac. iii) Discharge of Mate Gametes :- After enter of pollen tube both the male gametes discharged into embryo sac by either forming two pores into pollen tube & each male gamete is discharged through every pore or sometime pollen tube may burst & release the male gametes into embryo sac. iv) Fertilization:- The fusion of first male gamete (n) with egg (n) is called fertilization. It results in formation of a diploid zygote (2n). The second male gamete fuses with secondary nucleus (2n) to form triploid endosperm nucleus (3n). This fusion between second male gamete & secondary nuclei is triple fusion. Since process of fertilization occurs twice. It is called double fertilization.
10. i)Why is zygotes dominant for sometime in fertilized ovule. ii) What is polyembryony? Give an example. iii) In fruits, what is formed from following parts :- a) Ovary wall b) Outer integument c) Inner integument d) zygote e) primary endosperm f) Ovary g) Nucellus Ans.(i) Zygote remain dominant for sometime in a fertilized ovule because embryo develops after formation of endosperm therefore zygote wants for formation of endosperm which supplies food material for developing embryo (ii) The presence of more than one embryo in a seed is called polyembryony eg. Sometimes more than one embryo is formed within an embryo sac either by cleavage or splitting of egg, synergid, antipodal or endosperm. (iii) In fruits, the following is formed from given parts:-
Q1. What do you mean by rocks? Name the three major classes of rocks.
Answer
A rock is an aggregate of one or more minerals. The earth’s crust is composed of rocks.The three major classes of rocks are:• Igneous rocks• Sedimentary rocks• Metamorphic rocks
Q2. What is an igneous rock? Describe the method of formation and characteristics of igneous rock.
Answer
Igneous rocks are those rocks which are formed through the cooling and solidification of magma or lava. These rocks are formed when magma in its upward movement cools and turns into solid form. The process of cooling and solidification can happen in the earth’s crust or on the surface of the earth. Characteristics of Igneous rocks: • These rocks are consist of crystals. • These rocks are extremely hard in nature. • Fossils are not present in these rocks.
Q3. What is meant by sedimentary rock? Describe the mode of formation of sedimentary rock.
Answer
Sedimentary rocks are those rocks which are formed by the deposition at favorable sites by agents of denudation such as wind, river and sea waves. These deposits gradually turn into rocks. The rocks of the earth’s surface are exposed to denudational agents, and are broken up into various sizes of fragments. Such fragments are transported by different exogenous agencies and deposited. These deposits through compaction turn into rocks. This process is called lithification.
Q4. What relationship explained by rock cycle between the major type of rock?
Answer
Rock cycle is a continuous process through which old rocks are transformed into new ones. • Igneous rocks are primary rocks and other rocks (sedimentary and metamorphic) form from these primary rocks. • Igneous rocks can be changed into sedimentary rocks or metamorphic rocks. • The fragments derived out of igneous and metamorphic rocks form into sedimentary rocks. • Sedimentary rock can change into metamorphic rock or into igneous rock. • Metamorphic rock can change into igneous or sedimentary rock.
Q5.Define the term ‘mineral’ and name the major classes of minerals with their physical characteristics.
Answer
A mineral is a naturally occurring inorganic substance, having an orderly atomic structure and a definite chemical composition and physical properties. A mineral is composed of two or more elements. But, sometimes single element minerals like sulphur, copper, silver, gold, graphite etc. are found. Major minerals with their physical properties:• Feldspar: It has light cream to salmon pink colour. It is used in ceramics and glass making. Half of the earth’s crust is composed of feldspar. • Quartz: It consists of silica. It is a hard mineral virtually insoluble in water. It is white or colourless and used in radio and radar. • Pyroxene : It consists of calcium, aluminium, magnesium, iron and silica. It forms 10% of the earth’s crust. It is commonly found in meteorites. • Amphibole : Its major elements are silica, aluminium, calcium and iron. They form the 7% of the earth’s crust. It is used in the asbestos industry. It is black or green in colour. • Mica : It comprises potassium, aluminium, magnesium, iron, silica etc. It forms 4% of the earth’s crust. It is uses in the electrical instruments. • Olivine : Magnesium, iron and silica are the major elements of olivine. It is used in jewellery. It is usually a greenish crystal often found in basaltic rocks.
Q6. Describe the nature and mode of origin of the chief types of rock at the earth’s crust. How will you distinguish them?
Answer
There are three chief types of rock at the earth’s crust:
• Igneous Rocks: These are formed when magma cools and solidifies. The process of cooling and solidification can happen in the earth’s crust or on the surface of the earth. → These are extremely hard in nature. → Texture depends upon size and arrangement of grains or other physical conditions of the materials. If molten material is cooled slowly at great depths, mineral grains may be very large. Sudden cooling results in small and smooth grains.
• Sedimentary Rocks: Rocks (igneous, sedimentary and metamorphic) of the earth’s surface are exposed to denudational agents, and are broken up into various sizes of fragments. Such fragments are transported by different exogenous agencies and deposited. These deposits through compaction turn into rocks. The deposited material is known as sediment and the rocks formed are called sedimentary rocks.→ The sedimentary rocks are soft in nature.→ These rocks have many layers of varying thickness. • Metamorphic Rocks: These rocks form under the action of pressure, volume and temperature (PVT) changes. Metamorphism is a process by which already consolidated rocks undergo recrystallisation and reorganisation of materials within original rocks. → These rocks are crystalline in nature. → The materials of rocks chemically alter and recrystallise due to thermal metamorphism.
Q7.What are metamorphic rocks? Describe the types of metamorphic rock and how are they formed? Answer
Metamophic rocks are formed by the physical or chemical alteration by heat and pressure of an existing igneous or sedimentary rocks. Metamorphism occurs when rocks are forced down to lower levels by tectonic processes or when molten magma rising through the crust comes in contact with the crustal rocks or the underlying rocks are subjected to great amounts of pressure by overlying rocks. Metamorphism is a process by which already consolidated rocks undergo recrystallisation and reorganisation of materials within original rocks.
Types of Metamorphic rocks:
• Foliated rocks: These rocks are formed in the inerior of the earth under extremely high pressures that are unequal occurring when the pressure is greater in one direction than in the others. These rocks develop a platy or sheet-like structure. Slate, schist are examples.
• Non-foliated rocks: These rocks are formed around igneous intrusions where the temperatures are high but the pressures are relatively low and equal in all directions. These are not flat or elongate. Marble, quartzite are examples.
Long Answer Type Questions:
Q1.Explain any six physical characteristics? Answer: Brief information about some important minerals in terms of their nature and physical characteristics is given below :
External crystal form: Determined by internal arrangement of the molecules- cubes octahedrons, hexagonal prism, etc.
Fracture: Internal molecular arrangement so complex there are two planes of molecules; the crystal will break in an irregular manner, not along planes of cleavage.
Lustre: Appearance of a material without regard to color; each mineral has a distinctive lustre like metallic, silky, glossy, etc.
Streak: Colour of the ground powder of any mineral. It may be of the same colour as the mineral or may differ malachite is green and gives green streak.
Structure: Particular arrangement of the individual crystal; fine, medium or coarse grained; fibrous separable, divergent and radiating.
Specific gravity: The ratio between the weight of a given object and the weight of an equal volume of water; object weighted in air and then weighed in water and divide weight in air by the difference of the two weights.
Q2.Explain some important minerals and their characteristics. Answer: Some major minerals and their characteristics
Feldspar: Silicon and oxygen are common elements in all types of feldspar and sodium, potassium, calcium, aluminium etc. are found in specific feldspar variety.
Question uartz: It is one of the most important components of sand and granite. It consists of silica. It is a hard mineral virtually insoluble in water.
Pyroxene: Pyroxene consists of cak ium, aluminum, magnesium, iron and silica. Pyroxene forms 10 percent of the earth’s crust.
Amphibole: Aluminium, calcium, silica, iron, magnesium are the major elements of amphiboles. They form 7 per cent of the earth’s crust.
Mica: It comprises of potassium, aluminium, magnesium, iron, silica etc. It forms 4 per cent of the earth’s crust.
Olivine: Magnesium, iron and silica are major elements of olivine. It is used in jewellery. It is usually a greenish crystal, often found in basaltic rocks.
Q3.Rocks do not remain in their original form for long but may undergo transformation. Explain. Answer: Rocks do not remain in their original form for long but may undergo transformation. Rock cycle is a continuous process through which old rocks are transformed into new ones. Igneous rocks are primary rocks and other rocks form from these primary rocks. Igneous rocks can be changed into metamorphic rocks. The fragments derived out of igneous and metamorphic rocks form into sedimentary rocks. Sedimentary rocks themselves can turn into fragments and the fragments can be a source for formation of sedimentary rocks. The crustal rocks (igneous, metamorphic and sedimentary) once formed may be carried down into the mantle through subduction process and the same melt down due to increase in temperature in the interior and turn into molten magma, the original source for igneous rocks
Q1. What were the forces suggested by Wegener for the movement of the continents?
Answer
Wegener suggested that the movement responsible for the drifting of the continents was caused by pole-fleeing force and tidal force. The polar-fleeing force relates to the rotation of the earth. The earth is not a perfect sphere; it has a bulge at the equator. This bulge is due to the rotation of the earth. The second force, the tidal force is due to the attraction of the moon and the sun that develops tides in oceanic waters. Wegener believed that these forces would become effective when applied over many million years.
Q2.How are the convectional currents in the mantle initiated and maintained? Answer
The convectional currents in the mantle are generated due to radioactive elements causing thermal differences in the mantle portion. The hot material rises up from greater depths and comparatively cold material goes down from above. The occurrence of this process repetitively give birth to convectional currents.
Q3. What is the major difference between the transform boundary and the convergent or divergent boundaries of plates?
Answer
Transform Boundary
Convergent Boundary
Divergent Boundary
Where the crust is neither produced nor destroyed as the plates slide horizontally past each other.
Where the crust is destroyed as one plate dived under another.
Where new crust is generated as the plates pull away from each other.
Q4.What was the location of the Indian landmass during the formation of the Deccan Traps?
Answer
The Deccan Traps were formed during the movement of the Indian plate towards the Asiatic plate. This started somewhere around 60 million years ago and continued for a long period of time. At that time, Indian landmass was located in the south of the equator.
Q5.What are the evidences in support of the continental drift theory?
Answer
The evidences in support of the continental drift theory are:
• The Matching of Continents (Jig-Saw-Fit): The shorelines of Africa and South America facing each other have a remarkable and unmistakable match. • Rocks of Same Age Across the Oceans: The belt of ancient rocks of 2,000 million years from Brazil coast matches with those from western Africa. The earliest marine deposits along the coastline of South America and Africa are of the Jurassic age. This suggests that the ocean did not exist prior to that time. • Tillite: It is the sedimentary rock formed out of deposits of glaciers. The Gondawana system of sediments from India is known to have its counter parts in six different landmasses of the Southern Hemisphere. The glacial tillite provides unambiguous evidence of palaeoclimates and also of drifting of continents. • Placer Deposits: The occurrence of rich placer deposits of gold in the Ghana coast and the absolute absence of source rock in the region is an amazing fact. The gold bearing veins are in Brazil and it is obvious that the gold deposits of the Ghana are derived from the Brazil plateau when the two continents lay side by side. • Distribution of Fossils: When identical species of plants and animals adapted to living on land or in fresh water are found on either side of the marine barriers, a problem arises regarding accounting for such distribution. The observations that Lemurs occur in India, Madagascar and Africa led some to consider a contiguous landmass “Lemuria” linking these three landmasses.
Q6. Bring about the basic difference between the drift theory and Plate tectonics.
Answer
Drift Theory
Plate tectonics
Drift theory suggested that in the past, there was a super continent called Pangaea. Over time, this super continent split apart to form the seven continents we have today.
Plate Tectonics is a theory of global tectonics which proposes that the earth’s lithosphere is divided into seven major and some minor plates.
It only covers the movement of continents.
It covers movements of both Continents and Oceans.
The evidences in support of drift theory are Jig-Saw-Fit, Placer Deposits, Distribution of Fossils and others.
It is based on scientific analysis of the processes inside the earth’s surface.
It does not give any future prediction.
This theory says that all plates shall continue to move in the future period as well.
Q7. What were the major post-drift discoveries that rejuvenated the interest of scientists in the study of distribution of oceans and continents?
Answer
A number of post-drift discoveries during the post-war period added new information to geological literature. Particularly, the information collected from the ocean floor mapping provided new dimensions for the study of distribution of oceans and continents.
• All along the midoceanic ridges, volcanic eruptions are common and they bring huge amounts of lava to the surface in this area.
• The rocks equidistant on either sides of the crest of mid-oceanic ridges show remarkable similarities in terms of period of formation, chemical compositions and magnetic properties. Rocks closer to the mid-oceanic ridges are normal polarity and are the youngest. The age of the rocks increases as one moves away from the crest.
• The ocean crust rocks are much younger than the continental rocks. The age of rocks in the oceanic crust is nowhere more than 200 million years old.
• The sediments on the ocean floor are unexpectedly very thin.
• The deep trenches have deep-seated earthquake occurrences while in the midoceanic ridge areas, the quake foci have shallow depths.
Long Answer Type Questions:
Q1.According to tectonic plates theory in how many plates has the earth been divided? Explain. Answer: The theory of plate tectonics proposes that the earth’s lithosphere is divided into seven major and some minor plates. The major plates are as follows:
Antarctica and the surrounding oceanic plate
North American plate
South American plate
Pacific plate
India-Australia-New Zealand plate
Africa with the eastern Atlantic floor plate
Eurasia and the adjacent oceanic plate. Some important minor plates are:
Cocos plate: It is between Central America and Pacific plate
Nazca plate: It is between South America and Pacific plate
Arabian plate: It includes mostly the Saudi Arabian landmass
Philippine plate: It is between the Asiatic and Pacific plate
Caroline plate: It is between the Philippine and Indian plate (North of New Guinea)
Fuji plate: It includes North-east of Australia.
Pacific plate is largely an oceanic plate whereas the Eurasian plate may be called a continental plate. Plates are not static. Plates may converge or diverge. Plates may break as well.
Q2.Explain tectonic plate theory and its j working. Answer: These plates have been constantly moving over the globe throughout the history of the earth.
The theory of plate tectonics was introduced by Mckenzie, Parker and , Morgan in 1967.
A tectonic plate is also called as lithosphere plate.
It is a massive irregularly shaped slab of solid rock.
Consists of oceanic and continental sphere.
Plates move horizontally over the asthenosphere.
Average thickness is 100 km of oceanic part and 200 km of continental part.
It may be oceanic or continental.
Pacific plate is largest oceanic plate whereas Eurasian plate is the largest continental plate.
These plates are moving constantly throughout geological time not the continent, believed by Wegener. It creates three types of boundaries.
Divergent boundaries
New crust is generated
Plates move away from each other
These are called spreading sites
Ex. Mid atlantic ridge
Convergent boundaries |
Crust is destroyed
Sinking of plate is called “subduction zone”. There are three ways in which subduction occurs (i) between an oceanic and continental plates; (ii) between two oceanic plates; and (iii) between two continental plates.
Transform boundaries: Where the crust is neither produced nor destroyed as the plates slide horizontally past each other.
Q3.Explain important theories associated with the movement of continents. Answer: Continental drift: Abraham Ortelius a Dutch map maker in 1596 first proposed the possibility of joining the continents such as America with Europe and Africa. Antonio Pellegrini drew a map showing the three continents together. Alfred Wegener, a German meteorologist put forth the continental drift theory. According to him, all continents formed a single continental mass called Pangaea.
All oceans formed a single universal ocean called Panthalassa around 200 million years ago. The Pangaea began to split into two large continental masses called Laurasia and Gondwanaland. By further splitting Laurasia formed northern continents and Gondwanaland formed southern continents.
Sea Floor Spreading: The deep trenches have deep-seated earthquake occurrences while in the mid- oceanic ridge areas, the quake foci have shallow depths. These facts and a detailed analysis of magnetic properties of the rocks on either sides of the mid-oceanic ridge led Hess in 1961 to propose his hypothesis. It was called the “sea floor spreading”. Hess argued that constant eruptions at the crest of oceanic ridges cause the rupture of the oceanic crust forces and the new lava wedges into it, pushing the oceanic crust on either side. The ocean floor, thus spreads. Two facts made Hess think about the consumption of the oceanic crust.
The younger age of the oceanic crust.
The spreading of one ocean does not cause the shrinking of the other.
He further maintained that the ocean floor that gets pushed due to volcanic eruptions at the crest, sinks down at the oceanic trenches and gets consumed. Plate Tectonics: It was in 1967, McKenzie and Parker and also Morgan, independently collected the available ideas and came out with another concept termed Plate Tectonics. The theory of plate tectonics proposes that the earth’s lithosphere is divided into seven major and some minor plates. These plates have been constantly moving over the globe throughout the history of the earth. It is not the continent that moves as believed by Wegener. Continents are part of a plate and what moves is the plate. All the plates, without exception, have moved in the geological past, and shall continue to move in the future as well.
Q4.The ocean floor may be segmented into how many divisions based on the depth as well as the forms of relief? Answer: The ocean floor may be segmented into three major divisions based on the depth as well as the forms of relief. These divisions are:
(i) Continental margins, (ii) Abyssal plains and (iii) Mid-oceanic ridges.
Continental margins
Form transitional zone between continental shore and deep sea basins
They include continental slope , shelf, continental rise and deep oceanic trenches
Abyssal plains
Extensive plains
Found between continental margin and mid oceanic ridge
Continental sediments get deposited
Mid-oceanic ridges
Distribution of volcanoes and earthquakes
All volcanoes and earthquakes are parallel to the coast
This line also co-incides with mid- Atlantic ridge and Alpine Himalayan system
Around the Pacific Ocean it is called ring of fire mid oceanic ridges.
Body waves are earthquake waves which are generated due to the release of energy at the focus and move in all directions travelling through the body of the earth.
Q2. Name the direct sources of information about the interior of the earth.
Answer
The direct sources of information about the interior of the earth are:
• Mining: It is the process of extracting valuable minerals from the earth. Surface rock or the rocks we get from mining areas provide most easily available solid earth material.
• Drilling: Scientists are working on two major projects such as “Deep Ocean Drilling Project” and “Integrated Ocean Drilling Project”. This and many deep drilling projects have provided large volume of information through the analysis of materials collected at different depths. • Volcanic eruption: It forms another source of obtaining direct information. As and when the molten material (magma) is thrown onto the surface of the earth, during volcanic eruption it becomes available for laboratory analysis.
Q3.Why do earthquake waves develop shadow zone?
Answer
Earthquake wave develop shadow zone because P and S waves follow a curved path inside the earth due to increasing capacity. The shadow zone of S-wave is much larger than that of the P-waves.
Q4. Briefly explain the indirect sources of information of the interior of the earth other than those of seismic activity.
Answer The indirect sources of information of the interior of the earth are:
• Temperature, Pressure and Density: These increase with the increasing distance from the surface towards the interior in deeper depths. The rate of change of Temprature, pressure and density are known. Knowing the total thickness of the earth, scientists have estimated the values of temperature, pressure and the density of materials at different depths.
• Meteors: These are not from the interior of the earth but the material and the structure observed in the meteors are similar to that of the earth. This make them another source of information about the interior of the earth.
• Gravitation force: It is greater near the poles and less at the equator. The gravity values also differ according to the mass of material. The uneven distribution of mass of material within the earth influences this value.
• Magnetic Field: Magnetic surveys also provide information about the distribution of magnetic materials in the crustal portion, and thus, provide information about the distribution of materials in this part.
Q5.What are the effects of propagation of earthquake waves on the rock mass through which they travel?
Answer
The earthquake waves cause vibration in the body of the rocks through which they pass. P-waves vibrate parallel to the direction of the wave. This exerts pressure on the material in the direction of the propagation. As a result, it creates density differences in the material leading to stretching and squeezing of the material. Other three waves vibrate perpendicular to the direction of propagation. The direction of vibrations of S-waves is perpendicular to the wave direction in the vertical plane. Hence, they create troughs and crests in the material through which they pass. Surface waves are considered to be the most damaging waves.
Q6.What do you understand by intrusive forms? Briefly describe various intrusive forms.
Answer
The lava that is released during volcanic eruptions on cooling develops into igneous rocks. These forms are called intrusive forms.
Various intrusive forms are:
• Batholiths: A large body of magmatic material that cools in the deeper depth of the crust develops in the form of large domes. These are the cooled portion of magma chambers.
• Lacoliths: These are large dome-shaped intrusive bodies with a level base and connected by a pipe-like conduit from below. It resembles the surface volcanic domes of composite volcano, only these are located at deeper depths.
• Lapolith: As and when the lava moves upwards, a portion of the same may tend to move in a horizontal direction wherever it finds a weak plane. It may get rested in different forms. In case it develops into a saucer shape, concave to the sky body, it is called lapolith.
• Phacolith: A wavy mass of intrusive rocks located near the top of an anticline or the bottom of a syncline.
• Sills: The near horizontal bodies of the intrusive igneous rocks are called sill or sheet, depending on the thickness of the material. The thinner ones are called sheets while the thick horizontal deposits are called sills.
• Dykes: When the lava makes its way through cracks and the fissures developed in the land, it solidifies almost perpendicular to the ground. It gets cooled in the same position to develop a wall-like structure. Such structures are called dykes.
Long Answer Type Questions:
Q1.Explain different types of earthquakes. Answer: The various types of earthquakes are:-
Tectonic earthquake: The most common ones are the tectonic earthquakes. These are generated due to sliding of rocks along a fault plane.
Volcanic earthquake: A special class of tectonic earthquake is sometimes recognised as volcanic earthquake. However, these are confined to areas of active volcanoes.
Collapse earthquake: In the areas of intense mining activity, sometimes the roofs of underground mines collapse causing minor tremors. These are called collapse earthquakes.
Explosion earthquake: Ground shaking may also occur due to the explosion of chemical or nuclear devices. Such tremors are called explosion earthquakes.
Reservoir Induced earthquake: The earthquakes that occur in the areas of large reservoirs are referred to as reservoir induced earthquakes. Sometimes earthquakes also occur in mines due to mining processes. Sometimes earthquakes also occur below the oceans on surface of the ocean causing tsunamis.
Q2.What are different sources of information | about the interior of the earth? Answer: Some of the direct sources are:-
Mining: It is a process by which commercially variable valuable mineral resources are extracted from Earth’s surface which includes precious stones, rocks and solid fuels.
Drilling: Scientists world over are working on two major projects such as “Deep Ocean Drilling projects” and “integrated ocean drilling project”. The deepest drill at kola, in Arctic Ocean, has so far reached a depth of 12 km.
Volcanic Eruptions: When molten material is thrown onto the surface of the earth during volcanic eruption it becomes available for analysis. Some of the indirect sources of information: Analysis of properties of matter indirectly provides information about the interior. Knowing the total thickness of the earth, scientists have estimated the values of temperature, pressure and the density of materials at different depths.
Meteors that at times reach the earth: However, it may be noted that the material that becomes available for analysis from meteors, is not from the interior of the earth. The material and the structure observed in the meteors are similar to that of the earth. They are solid bodies developed out of materials same as, or similar to, our planet. Hence, this becomes yet another source of information about the interior of the earth.
Gravitation: The gravitation force (g) is not the same at different latitudes on the surface. It is greater near the poles and less at the equator. This is because of the distance from the centre at the equator being greater than that at the poles. The gravity values also differ according to the mass of material.
Magnetic surveys: Magnetic surveys also provide information about the distribution of magnetic materials in the crustal portion, and thus, provide information about the distribution of materials in this part.
Q3.Explain different types of earthquake waves. Answer: Earthquake waves are basically of two types body waves and surface waves.
Body waves: These are generated due to the release of energy at the focus. They move in all directions in all directions travelling through the body of the earth. These are less destructive than the surface waves.
Surface waves: The body waves interact with the surface rocks and generate new set of waves called surface waves. These waves move along the surface. These waves are more destruction. The surface waves are the last to report on seismograph. These waves are more destructive. They cause displacement of rocks, and hence, the collapse of structures occurs. There are two types of body waves. They are called P- and S-waves,
P-waves: They move faster and are the first to arrive at the surface. These are also called ‘primary waves’. The P-waves are similar to sound waves. They travel through gaseous, liquid and solid materials.
S-Waves: S-waves arrive at the surface with some time lag. These are called secondary waves. An important fact about S-waves is that they can travel only through solid materials. This characteristic of the S-waves is quite important. It has helped scientists to understand the structure of t he interior of the earth. Reflection causes was es to rebound whereas refraction makes waves move in different directions. The variations in the direction of waves are inferred with the help of their record on seismograph.
Q4.Explain how does shadow zone emerge. Use a diagram. Answer: Earthquake waves get recorded in seismographs located at far off locations. However, there exist some specific areas where the waves are not reported. Such a zone is called the ‘shadow zone’. The study of different events reveals that for each earthquake, there exists an altogether different shadow zone.
Seismographs located at any distance within 105° from the epicentre, recorded the arrival of both P and S -waves. However, the seismographs located beyond 145° from epicentre, record the arrival of P-waves but not that of S-waves. Thus, a zone between 105° and 145° from epicentre was identified as the shadow zone for both the types of waves. Figures given below show the shadow zones of P- and S-waves.
Q5.Explain the interior structure of the earth. Answer: The interior structure f the earth can be classified into three parts: 1. Crust; (ii) Mantle; (iii) Core (i) Crust: It is the outermost solid part of the earth. It is brittle in nature. The thickness of the crust varies under the oceanic and continental areas. Oceanic crust is thinner as compared to the continental crust. The mean thickness of oceanic crust is 5 km w’hereas that of the continental is around 30 km. The continental crust is thicker in the areas of major mountain systems. It is as much as 70 km thick in the Himalayan region. It is made up of heavier rocks. It is having density of 3 g/cm3. This type of rock found in the oceanic crust is basalt. The mean density of material in oceanic crust is 2.7 g/cm3.
2. Mantle: The portion of the interior beyond the crust is called the mantle. The mantle extends from Moho’s discontinuity to a depth of 2,900 km. The upper portion of the mantle is called asthenosphere. The word astheno means weak. It is considered to be extending upto 400 km. It is the main source of magma that finds its way to the surface during volcanic eruptions. It has a density higher than the crust’s (3.4 g/ cm3). The crust and the uppermost part of the mantle are called lithosphere. Its thickness ranges from 10-200 km. The lower mantle extends beyond the asthenosphere. It is in solid state.
3. Core: The earthquake wave velocities helped in understanding the existence of the core of the earth. The core- mantle boundary is located at the depth of 2,900 km. The outer core is in liquid state while the inner core is in solid state. The density of material at the mantle core boundary is around 5 g/cm3 and at the centre of the earth at 6,300 km, the density value is around 13g/cm3. The core is made up of very heavy material mostly constituted by nickel and iron. It is sometimes also called the nife layer.
Q6.In how many groups are volcanoes classified on the basis of nature of eruption and the form developed at the surface? Explain. Answer: Volcanoes are classified on the basis of nature of eruption and the form developed at the surface into following types:
1. Shield Volcanoes: These volcanoes are mostly made up of basalt, a type of lava that is very fluid when erupted. For this reason, these volcanoes are not steep. They become explosive if somehow water gets into the vent; otherwise, they are characterised by low-explosivity. Barring the basalt flows, the shield volcanoes are the largest of all the volcanoes on the earth. The Hawaiian volcanoes are the most famous examples. The upcoming lava moves in the form of a fountain and throws out the cone at the top of the vent and develops into cinder cone.
2. Composite Volcanoes: These volcanoes are characterised by eruptions of cooler and more viscous lavas than basalt. These volcanoes often result in explosive eruptions. Along with lava, large quantities of pyroclastic material and ashes find their way to the ground. This material accumulates in the vicinity of the vent openings leading to formation of layers, and this makes the mounts appear as composite volcanoes.
3. Calderas: These are the most explosive of the earth’s volcanoes. They are usually so explosive that when they erupt they tend to collapse on themselves rather than building any tall structure. The collapsed depressions are called calderas. Their explosiveness indicates that the magma chamber supplying the lava is not only huge but is also in close vicinity. The hills produced by them are similar to the one made by composite volcanoes.
4. Basalt Flood Provinces: These volcanoes outpour highly fluid lava that flows for long distances. Some parts of the world are cohered by thousands of sq. km of thick basalt lava flows. There can be a series of flows with some flows attaining thickness of more than 50 m. Individual flows may extend for hundreds of km. The Deccan Traps from India, presently covering most of the Maharashtra plateau, are a much larger flood basalt province. It is believed that initially the trap formations covered a much larger area than the present.
5. Mid-Ocean Ridge Volcanoes: These volcanoes occur in the oceanic areas. There is a system of mid-ocean ridges more than 70,000 km long that stretches through all the ocean basins. The central portion of this ridge experiences frequent eruptions.
• The terrestrial planets were formed in the close vicinity of the parent star where it was too warm for gases to condense to solid particles. Jovian planets were formed at quite a distant location.
• The solar wind was most intense nearer the sun; so, it blew off lots of gas and dust from the terrestrial planets. The solar winds were not all that intense to cause similar removal of gases from the Jovian planets.
• The terrestrial planets are smaller and their lower gravity could not hold the escaping gases.
Q2. What is the basic difference in the arguments related to the origin of the earth given by : (a) Kant and Laplace (b) Chamberlain and Moulton
Answer
The Nebular Hypothesis, proposed by Immanuel Kant and later revised by Laplace in 1796 considered that the planets were formed out of a cloud of material associated with a youthful sun, which was slowly rotating while, in 1900, Chamberlain and Moulton considered that a wandering star approached the sun. As a result, a cigar-shaped material separated from the solar surface. As the passing star moved away, the material separated from the sun, continued to revolve around the sun and it slowly condensed into planets.
Q3. What is meant by the process of differentiation? Answer The process by which earth forming material got separated into different layers is called differentiation. Starting from the surface to the central parts, we have layers like the crust, mantle, outer core and inner core. From the crust to the core, the density of the material increases.
Q4. What was the nature of the earth surface initially? Answer The planet earth initially was a barren, rocky and hot object with a thin atmosphere of hydrogen and helium. This is far from the present day picture of the earth.
Q5.What were the gases which initially formed the earth’s atmosphere? Answer
Hydrogen and helium were the gases which intially formed the earth’s atmosphere. The early atmosphere, with hydrogen and helium, is supposed to have been stripped off as a result of the solar winds. During the cooling of the earth, gases and water vapour were released from the interior solid earth. This started the evolution of the present atmosphere.
Q6. Write an explanatory note on the ‘Big Bang Theory’. Answer The ‘Big Bang Theory’ also known as expanding universe hypothesis. Edwin Hubble, in 1920, provided evidence that the universe is expanding. The distance between the galaxies is also found to be increasing and thereby, the universe is considered to be expanding.
Various stages in the development of the universe according to Big Bang Theory are: • In the beginning, all matter forming the universe existed in one place in the form of a “tiny ball” (singular atom) with an unimaginably small volume, infinite temperature and infinite density.
At the Big Bang the “tiny ball” exploded violently. This led to a huge expansion. It is now generally accepted that the event of big bang took place 13.7 billion years before the present. The expansion continues even to the present day. As it grew, some energy was converted into matter. There was particularly rapid expansion within fractions of a second after the bang. Thereafter, the expansion has slowed down. Within first three minutes from the Big Bang event, the first atom began to form.
• Within 300,000 years from the Big Bang, temperature dropped to 4,500K (Kelvin) and gave rise to atomic matter. The universe became transparent.
Q7. List the stages in the evolution of the earth and explain each stage in brief. Answer Stage I: The earth was mostly in a volatile state during its primordial stage. Due to gradual increasein density the temperature inside has increased. As a result, the material inside started getting separated depending on their densities.
• This allowed heavier materials (like iron) to sink towards the centre of the earth and the lighter ones to move towards the surface. With passage of time it cooled further and solidified and condensed into a smaller size which led to the formation of the crust.
• During the formation of the moon, due to the giant impact, the earth was further heated up. It is through the process of differentiation that the earth forming material got separated into different layers. Starting from the surface to the central parts, the crust, mantle, outer core and inner core formed.
Stage II: The early atmosphere, with hydrogen and helium, is supposed to have been stripped off as a result of the solar winds. During the cooling of the earth, gases and water vapour were released from the interior solid earth which started the evolution of the present atmosphere.
• The early atmosphere largely contained water vapour, nitrogen, carbon dioxide, methane, ammonia and very little of free oxygen. The process through which the gases were outpoured from the interior is called degassing.
• As the earth cooled, the water vapour released started getting condensed. The carbon dioxide in the atmosphere got dissolved in rainwater and the temperature further decreased causing more condensation and more rains. The rainwater falling onto the surface got collected in the depressions to give rise to oceans. • Life was confined to the oceans for a long time. Oceans began to have the contribution of oxygen through the process of photosynthesis.
Stage III: The last phase in the evolution of the earth relates to the origin and evolution of life. • The origin of life as a kind of chemical reaction, which first generated complex organic molecules and assembled them. This assemblage was such that they could duplicate themselves converting inanimate matter into living substance.
Long Answer Type Questions:
Q1.Explain how did life evolve on the earth? Answer: The origin of life as a kind of chemical reaction, which first generated complex organic molecules and assembled them. This assemblage was such that they could duplicate themselves converting inanimate matter into living substance. The record of life that existed on this • planet in different periods is found in rocks in the form of fossils. The microscopic structures closely related to the present form of the blue algae have been found in geological formations m uch older than some 3,000 million years. It can be assumed that life began to evolve sometime 3,800 million years ago.
Q2.Explain different phases of evolution of planets. Answer: Evolution of planets can be understood in three stages:
1. Formation of Disc; The stars are localised lumps of gas within a nebula. The gravitational force within the lumps leads to the formation of a core to the gas cloud and a huge rotating disc of gas and dust develops around the gas core.
2. Formation of Planetesimals: In the next stage, the gas cloud starts and getting condensed and the matter around the core develops into small rounded objects. These small rounded objects by the process of collision develop into what is called planetesimals. Larger bodies start forming by collision and gravitational attraction causes the materials to stick together. Planetesimals are a large number of smaller bodies.
3. Formation of Planets: In the final stage, these large number of small planetesimals accrete to form fewer large bodies in the form of planets.
Q3.Explain the earliest theory associated with the origin of the earth. Answer: A large number of hypotheses were put forth by different philosophers and scientists regarding the origin of the earth. One of the earlier and popular arguments was by German philosopher Immanuel Kant. Mathematician Laplace revised it in 1796. It is known as Nebular Hypothesis. According to this theory there was a hot and rotating gas cloud called Nebula in the space. From Nebula there was a gradual loss of heat due to its rotation which resulted in cooling of its outer surface. This gradual cooling caused contraction in size of Nebula, but its speed increased due to angular momentum. The outer layer was separated from the remaining part of Nebula.
The centre of Nebula became ‘Sun’ and the planets were formed of the smaller units. The lighter material gases and the heavier dust particle gave the fact of inner and outer planets. In 1950, Otto Schmidt in Russia and Carl Weizasear in Germany somewhat revised the ‘nebular hypothesis’, though differing in details. They considered that the sun was surrounded by solar nebula containing mostly the hydrogen and helium along with what may be termed as dust. The friction and collision of particles led to formation of a disk-shaped cloud and the planets were formed through the process of accretion.
Q4.Explain the modern theory associated with evolution of the earth. Answer: In modern theory the evolution of the earth is associated with Big Bang Theory. It was put forth by Edwin Hubble in 1920. In the beginning, all matter forming the universe existed in one place in the form of a ‘tiny ball” \yith an unimaginably- small volume infinite temperature and infinite density. At the Big Bang “tiny ball” exploded violently. This led to a huge” expansion. it is now generally? accepted that the event of big. bang took place 13.7 billion years before the present. The expansion continues even to the present day. As it grew, some energy’ was converted into matter. There was particularly rapid expansion within fractions of a second’ after the bang. Thereafter, the expansion has slowed down. Within first Big Bang event, the first atom began to form.
Within 300,000 years from the Big Bang, temperature dropped to 4,500k and gave rise to atomic matter. The universe became transparent. The expansion of universe means increase in space between the galaxies. An alternative to this was Hoyle’s concept of steady state. It considered the universe to be roughly the same at any point of time. However, with greater evidence becoming available about the expanding universe, scientific community at present favours argument of expanding universe.
Q5.Explain the collision and accretion I hypothesis associated with the evolution of the earth. Answer: Collision hypothesis and accretion hypothesis are described below in short. 1. Collision Hypothesis: It was given by Sir James and Harold Jeffrey.
According to this theory, a large nebula ’wandering in the space came very close to smaller nebula (Sun) and its huge upsurge of matter on the surface of smaller nebula. The matter was detected from the smaller nebula and on cooling condensed into planets.
2. Accretion Hypothesis: It was given by? Schmidt and Carl Weizascar.
According to them, solar system started out as a cloud of gas and dust drifting in a space called nebula. This gaseous cloud exploded violently to form supernova. The exploitation left the vast spinning cloud and gases and thus to collapse under its own gravity and develop as denser core.
The denser core became larger and hotter and began to burge. Later it developed into protostar which finally evolved as ‘infant Sun.
Away from its central surface, particles of dust began to clump together and converted into first smaller fragments of rocks and then becoming larger bodies which were called planetesimals which collided with one another to form rocky inner planets like Mercury, Venus, Earth and Mars and the remaining were outer planets.
Q1. What important cultural features do you observe while going to school? Are they similar or dissimilar? Should they be included in the study of geography or not? If yes, why?
Answer While going to school, we see some cultural features like shops, schools, clubs, offices, temples, mosques, houses. These features are dissimilar.Yes, they should be included in the study of geography as they are an essential part of human geography.
Q2.You have seen a tennis ball, a cricket ball, an orange and a pumpkin. Which one amongst these resembles the shape of the earth? Why have you chosen this particular item to describe the shape of the earth? Answer An orange resembles the shape of the earth because all others are almost sphere while pumpkin is long in shape.Earth is not a perfect sphere, it rotates on its axis. It is of geoid shape, flatter toward poles like an orange.
Q3.Do you celebrate Van Mahotsava in your school? Why do we plant so many trees? How do the trees maintain ecological balance?
Answer Yes, we do celebrate Van Mahotsava in our school.We plant so many trees because trees provide us food, oxygen, clean air, economical products such as rubber and paper. help in making medicine etc.By taking in carbon dioxide and giving oxygen, trees maintain ecological balance.
Q4. You have seen elephants, deer, earthworms, trees and grasses. Where do they live or grow? What is the name given to this sphere? Can you describe some of the important features of this sphere?
Answer The sphere where elephants, deer, earthworms, trees and grasses live and grow is known as biosphere. Important features of this sphere are:→ The biosphere is the layer of the planet Earth where life exists.→ Since life exists on the ground, in the air, and in the water, thus, biosphere overlaps all other three spheres→ Plants and animals are biotic elements of biosphere while soil, water, air are abiotic elements.
Q5. How much time do you take to reach your school from your house? Had the school been located across the road from your house, how much time would you have taken to reach school? What is the effect of the distance between your residence and the school on the time taken in commuting? Can you convert time into space and vice versa? Answer It takes me around half an hour to reach my school. Had my school been located across the road from my house, I could reach there within four minutes. Due to the long distance between my residence and school, a lot of time gets wasted in commuting which affects my studies hour as well as playing hours negatively. Time can be converted into space, vice versa is also true, i.e., we can convert space into time.
Q6. You observe every day in your surroundings that there is variation in natural as well as cultural phenomena. All the trees are not of the same variety. All the birds and animals you see, are different. All these different elements are found on the earth. Can you now argue that geography is the study of “areal differentiation”? Answer There is vast variation in natural as well as cultural phenomena. The study of ‘areal differentiation’ is part of geography, however, geography is not only limited to ‘areal differentiation’. Geography as a discipline is related to space and takes note of spatial characteristics and attributes. It studies the patterns of distribution, location and concentration of phenomena over space and interprets them providing explanations for these patterns. It takes note of the associations and inter-relationships between the phenomena over space and interprets them providing explanations for these patterns. It also takes note of the associations and inter-relationships between the phenomena resulting from the dynamic interaction between human beings and their physical environment.
Geography helps in understanding the reality in totality in its spatial perspective. Geography, thus, not only takes note of the differences in the phenomena from place to place but integrates them holistically which may be different at other places.
Q7.You have already studied geography, history, civics and economics as parts of social studies. Attempt an integration of these disciplines highlighting their interface. Answer • Geography and History: Geography influences historical events. Spatial distance itself has been a very potent factor to alter the course of history of the world. Spatial depth provided defence to many countries, particularly in the last century. In traditional warfare, countries with large size in area, gain time at the cost of space. Every geographical phenomenon undergoes change through time and can be explained temporally. The changes in landforms, climate, vegetation, economic activities occupations and cultural developments have followed a definite historical course.
• Geography and Civics: The core concern of political science is territory, people and sovereignty while political geography is also interested in the study of the state as a spatial unit as well as people and their political behaviour.
• Geography and Economics: Economics deals with basic attributes of the economy such as production, distribution, exchange and consumption. Each of these attributes also has spatial aspects and here comes the role of economic geography to study the spatial aspects of production, distribution, exchange and consumption.
Long Answer Type Questions:
Q1.What is the importance of Physical Geography? Answer: Physical geography includes study of Lithosphere, Atmosphere, Hydrosphere and Biosphere. Each element is very important for human beings. Landforms provide base for agriculture, industries, transport and communication, and settlements. Mountains provide water to rivers, forests-center for tourist spots. Climate influences on the cropping pattern, livestock, food and clothes of the people. Climate and precipitation influence the type of forests. Oceans provide food, water transport, and influence the climate; they are the source of hydrological cycle.
Each element of physical environment is important for human beings. Landforms provide the base on which human activities are located. The plains are utilised for agriculture. Plateaus provide forests and minerals. Mountains provide pastures, forests, tourist spots and are sources of rivers providing water to lowlands. Climate influences our house types, clothing and food habits.
The study of physical geography is emerging as a discipline of evaluating and managing natural resources. In order to achieve this objective, it is essential to understand the intricate relationship between physical environment and human beings. Physical environment provides resources, and human beings utilise these resources and ensure their economic and cultural development. Accelerated pace of resource utilisation with the help of modern technology has created ecological imbalance in the world. Therefore, abetter understanding of physical environment is essential in study of Geography.
Q2.Physical and human factors both are dynamic not static. Explain. Answer: The geographical phenomena, both the physical and human, are not static but highly dynamic. They change over times as a result of the interactive processes between ever changing earth and untiring and ever-active human beings.
1. Primitive human societies were directly dependent on their immediate environment. Human beings have come to terms with nature through adaptation and modification.
2. The present society has passed the stage of primitive .societies, which were directly dependent on their immediate physical environment for sustenance. Present societies have modified their natural environment by inventing and using technology and thus, have expanded the horizon of their operation by appropriate utilisation of the resources provided by nature.
3. With the gradual development of technology, human beings were able to loosen the shackles of their physical environment. Technology helped in reducing the harshness of labour, increased labour efficiency and provided leisure to human beings to attend to the higher needs of life. It also increased the scale of production and the mobility of labour. The interaction between the physical environment and human beings has put their imprints everywhere and created new possibilities in collaboration with nature. Thus, we find humanised nature and naturalised human beings and geography studies this interactive relationship.
4. The space got organised with the help of the means of transportation and communication network. The links (routes) and nodes (settlements of all types and hierarchies) integrated the space and gradually, it got organised.
5. It takes note of the associations and interrelationships between the phenomena over space and interprets them providing explanations for these patterns. It also takes note of the associations and inter-relationships between the phenomena resulting from the dynamic interaction between human beings and their physical environment.
Q3.Explain different branches of Physical geography. Answer: It has four sub-branches which are as fallows:
Geomorphology: It is concerned with the study of landforms, their evolution and related processes.
Climatology: It is concerned with the study of structure of atmosphere and elements of weather and climates and climatic types and regions.
Hydrology: It studies the realm of water over the surface of the earth including oceans, lakes, rivers and other water bodies and its effect on different life forms including human life and their activities.
Soil Geography: It is concerned with the study of the processes of soil formation, soil types, their fertility status, distribution and use.
Q4.What matters are studied under Human Geography? Answer: Following facts are studied under Human Geography:
Social/Cultural Geography: It is concerned with the study of society and its spatial dynamics as well as the cultural elements contributed by the society.
Population Geography: It studies population growth, distribution, density, sex ratio, migration and occupational structure, etc.
Settlement Geography: It studies the characteristics of rural and urban settlements.
Economic Geography: It studies economic activities of the’people including agriculture, industry, tourism, trade, and transport, infrastructure and services, etc.
Historical Geography: It studies the historical processes through which the space gets organised. In other words, it studies how history has influenced the geography of a region.
Political Geography: It studies the impact of political events and studies boundaries, space relations between neighbouring political units, delimitation of constituencies, election scenario and develops theoretical framework to understand the political behaviour of the population.
In This Post we are providing Chapter-22 CHEMICAL COORDINATION AND INTEGRATION NCERT MOST IMPORTANT QUESTIONS for Class 11 BIOLOGY which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.
NCERTMOST IMPORTANT QUESTIONS ON CHEMICAL COORDINATION AND INTEGRATION
Question 1. What hormones are secreted by the posterior pituitary gland? What function do they serve? Where are these hormones actually produced? How these hormones are transported to the region from which they are released? Answer: 1. Vasopressin: Released from the axon terminals of hypothalamic neurons into the blood in the posterior lobe of the pituitary. It reduces the volume of urine by increasing the reabsorption of water from the urine, collecting tubules, and collection ducts in the kidney, hence called Antidiuretic hormone.
2. Oxytocin: It is released from the axon terminals of hypothalamic neurons into the blood in the posterior lobe of the pituitary due to the distension of the uterus by the full-term fetus.
It helps in childbirth. It is also known as milk ejection hormone.
Question 2. What are the examples of antagonistic hormones associated with basal metabolism? How does each pair function? Answer: Para hormone (PTH) and thyroid hormone calcitonin act agonistically to regulate the calcium phosphorous balance in the blood. The release of parathormone increases the blood calcium to normal by drawing calcium from the bones into the plasma, by increasing calcium absorption in the digestive tract, and by reducing loss of calcium in the urine. It lowers calcium-phosphorus balance and is necessary for the growth of bones and teeth.
Calcium is vital for blood clotting, muscle tone, and for normal nervous activity. It is also needed for the activities of many enzymes.
Question 3. What two hormones are produced by the adrenal medulla? What non-hormonal function do they serve? Answer: The hormone Adrenaline and Nor-adrenaline are secreted by the adrenal medulla. Function: These hormones act on organs and tissues supplied by sympathetic fibers and produce effects like those of sympathetic stimulation.
Question 4. From what chemical compounds are ail steroid hormones derived? Mention at least two examples of steroidal hormones. Answer: The adrenal cortex is the outer layer of the adrenal gland. It secretes steroidal hormones. Examples, Glucocorticoids, and mineralocorticoids.
The adrenal cortex produces steroid hormones through the modification of cholesterol.
Question 5. In general, how the steroid hormones affect changes in their target cells? Answer: Steroid hormones have minor differences, the various hormones have strikingly different functions. They bind to different receptors in the target cell and affect sets of chemical reactions.
Cortical steroids can be grouped into three functional categories.
Mineralocorticoids: They regulate saltwater balance through their effect on kidney and blood pressure.
Glucocorticoids: They regulate carbohydrate, protein, and lipid metabolism.
Ganado corticoids: It is a sex hormone and helps chemically and functionally to the sex.
Question 6. What hormones are produced when the body’s blood glucose levels drop below normal? How do these hormones act to return the level to normal? What hormone is produced when the body’s blood glucose levels become elevated? How does this hormone act to return the level to normal? Answer: B-cells secrete insulin. T-cells secrete somatostatin.
These two hormones regulate the level of glucose in the blood:
When the blood glucose level becomes excessive, insulin acts on the three target tissues: liver, muscle, and adipose cells. Insulin causes the liver to take up glucose and convert it into glycogen and fat. It facilitates the liver to take up glucose in the muscle and adipose cells causing the levels of the glucose in the blood lowered.
Somatostatin: acts as a paracrine, to inhibit the secretion of glycogen and insulin, decreases secretion, mortality, and absorption in the digestive tract.
Question 7. What is diabetes? What is the ultimate hormonal deficiency in these diseases? How does this affect an individual’s ability to use glucose? What are some possible treatments for adult-onset diabetes? Answer: Diabetes mellitus is a group of disorders that lead to an increase in the level of glucose in the blood. The deficiency of insulin hormone causes diabetes mellitus.
In this disease, the patient cannot use or store glucose. Thus, glucose accumulates in the blood from where it is excreted by kidneys in die urine.
Glucose increases the osmotic pressure of urine, causing loss of water from the body in urine. This produces excessive thirst. Degradation of fats increases, producing ketone bodies such as acetoacetate and acetone. Blood cholesterol rises, injuries may change into gangrenes. Healing power is ^ impaired leading to the damage of tissues.
A diabetic person has blurred vision and is weak, tired, irritable, nauseated, and underweight. In extreme cases, the patient may pass into a coma and die.
Treatment: Administration of insulin gives relief by lowering blood glucose levels. Diabetes caused by insufficient insulin production is called Insulin-dependent diabetes. Diabetes due to a person’s ability to use insulin is termed as insulin ) independent diabetes. It is more common than insulin-dependent diabetes. Diabetes mellitus may also be caused by the failure of insulin to move glucose from the blood into the cells for storage or consumption.
This is due to the defective insulin receptors or cell surfaces, starving the cells of glucose, or to an abnormality in pancreatic protein amylin, which regulates insulin’s activity.
Question 8. What are thyroids? Describe the disorders of thyroids hormones. Answer: The thyroid gland is situated in the neck close to the trachea in human beings. It consists of two elongated oval lobes joined together by a narrow band called ISTHMUS. It highly vascular organ and contains many- spherical or oval sac-like follicles.
Cells of the follicle secrete jelly-like semi-fluid called Colloid of Thyroid stored in the lumen of the follicle. This contains iodinated forms of an amino acid called THYRONINE. When required, two thyroid hormones, THYROXINE, and TRIIODOTHYRONINE are released from the colloid to the blood. (a) and (b) Thyroid gland
Disorders:
Failure of the thyroid from infancy or childhood causes a disease called cretinism. In it, there is slow body growth and mental development. There is also a low metabolic rate.
The deficiency of thyroid hormones in adults produces Myxedema. The patient shows a puffy appearance and lacks intelligence, lateness, and initiative. There is also a low metabolic rate.
The deficiency of iodine produces enlargement of thyroids causing Iodine Deficiency to Goitre.
Some thyroid enlargement is accompanied by a bulging of the eyeball. The disease is called Grave’s Disease or Exophthalami Goitre. The excessive amount of thyroid is secreted. ,
Question 9. Give an account of the primary male sex organ in man and mention briefly the functions of the hormone testosterone. Answer: The testis is the primary sex organ. There are pair of tests. Each testis is covered by a thick connective tissue sheath, Tunica Albuginea. Both testes normally remain suspended in a pouch called Scrotum outside the abdominal cavity. Each testis consists of many small and highly convoluted tubules, called seminiferous tubules, constituting its spermatogenic tissue.
Cells lining the tubules give rise to spermatozoa, which are released into the lumen of the tubule. These are present groups of polyhedral cells.
Interstitial cells of Leydig in the connective tissue around the seminiferous tubules. This constitutes the endocrine tissue of the testis. These cells secrete Testosterone into the blood. Somniferous tubules unite to form a large number of straight tubules, which open into irregular cavities in the posterior part of the testis. The vasa efferentia arise from these cavities and conduct spermatozoa out from the testis.
Functions of Testosterone:
It stimulates the growth and development of male secondary sex organs (prostate, seminal vesicles, and penis).
It stimulates and maintains the normal function of secondary sex organs in reproduction.
It also stimulates and maintains the development of external male characters such as beards, mustaches, and low-pitch male voices in males and combs and wattles in cock.
It also stimulates the formation of sperms in the testes.
It promotes the growth of many body tissues including bones and muscles.
T.S. of testis of an adult man
Question 10. Distinguish between (a) Follicle-stimulating hormone and luteinizing hormone. Answer: Follicle-stimulating hormone and luteinizing hormone:
Stimulating hormone (FSH)
Luteinizing hormone
(i) It stimulates the testes in the male to produce sperms.
(i) It stimulates the testes to secrete the male sex hormone.
(ii) It stimulates the ovaries in the female to produce ova.
(ii) It stimulates the ovaries to secrete the female sex hormone- progesterone.
(b) Somatostatin and somatomedin Answer: Somatostatin and somatomedin:
Somatostatin
Somatomedin
(i) It is secreted by the anterior lobe of the pituitary.
(i) It is secreted by the hypothalamus.
(ii) It stimulates body growth
(ii) It inhibits the secretion of the growth hormone from the anterior pituitary.
(c) Vasopressin and Oxytocin Answer: Vasopressin and Oxytocin:
Vasopressin
Oxytocin
(i) Vasopressin is released from the axon terminal of hypothalamic neurons into the blood in the posterior lobe of the pituitary due to the rise in blood osmotic pressure caused by the loss of water from the body.
(i) Oxytocin is released from the axon terminals of hypothalamic neurons into the blood in the posterior lobe of the pituitary due to distension of the uterus by the full-term fetus or due to the sucking of the breast by an infant.
(ii) It reduces the volume of urine by increasing the reabsorption of water from the urine in the distal convoluted tubules, collecting tubules, and collection ducts in the kidney, hence called Antidiuretic Hormone (ADH).
(ii) It helps in childbirth by causing uterine contractions at the end of pregnancy, hence called birth hormones.
(iii) It increases arterial blood pressure by causing constriction or narrowing of arterioles.
(iii) It causes the contractions of the mammary gland and muscles that help in the flow of stored milk from the mammary gland to the mouth of the sucking infant, hence called milk ejection hormone.
(d) Estrogen and progesterone Answer: Estrogens and Progesterone:
Estrogens
Progesterone
(i) These are secreted by the cells of maturing Grrafian follicle.
(i) Corpus luteum and placenta secrete progesterone.
(ii) Estrogen stimulates growth, maturation, and functions of female secondary sex organs at puberty.
(ii) Progesterone brings about most of the pregnancy changes such as uterine growth, attach¬ment of the embryo to the uterine wall, placenta formation.
(iii) These also develop and maintain external female sex characters like the high pitch female voice and the female pattern of body hair distribution.
(iii) No such action.
(e) Glucocorticoids and mineralcorticoids Answer: Glucocorticoids and Mineralocorticoids:
Glucocorticoids
Mineralocorticoids
(i) Glucocorticoids such as cortisols regulate the metabolism of carbohydrates, fats, and proteins.
(i) Mineralocorticoids such as Aldosterones regulate the metabolism of sodium and potassium.
(ii) These are secreted from the middle cellular layer (ZONA Fasciculate) of the adrenal cortex
(f) Diabetes mellitus and diabetes insipidus Answer: Diabetes mellitus and Diabetes insipidus:
Diabetes mellitus
Diabetes insipidus
(i) It is due to failure of insulin secretion.
(i) It is due to the failure of secretion of vasopressin.
(ii) The blood sugar is abnormally high and the glucose appears in the urine.
(ii) The blood sugar is normal and no glucose appears in the urine.
(iii) There are high blood cholesterol and ketone body formation.
(iii) There is no such phenomenon.
(g) Exophthalamia goiter and iodine deficiency goiter Answer: Exophthalmic Goitre and Iodine Deficiency goiter:
Exophthalmic Goitre
Iodine Deficiency goiter
(i) It is accompanied by a bulging of eyeballs, i.e., exophthalmos.
(i) It is accompanied by cretinism in children and myxedema in adults.
(ii) The thyroid is overactive and secretes an excessive amount of thyroid hormones.
(ii) The dietary deficiency of iodine causes the deficiency of thyroid hormones.
(h) Cretinism and dwarfism. Answer: Cretinism and dwarfism:
Cretinism
Dwarfism
(i) It is due to over secretion of so gonadotropin from childhood.
(i) It is due to the failure of secretion of somatotropin from an early age.
(ii) There is an abnormal elongation of all long bones.
(ii) There is stoppage of growth of long bones and of the body prematurely making the patient dwarf
In This Post we are providing Chapter-21 NEURAL CONTROL AND CORDINATION NCERT MOST IMPORTANT QUESTIONS for Class 11 BIOLOGY which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.
NCERTMOST IMPORTANT QUESTIONS ON NEURAL CONTROL AND CORDINATION
Question 1:
Briefly describe the structure of the following:
Brain (b) Eye (c) Ear
ANSWER:
(A)Brain: Brain is the main coordinating centre of the body. It is a part of nervous system that controls and monitors every organ of the body. It is well protected by cranial meninges that are made up of an outer layer called dura mater, a thin middle layer called arachnoid, and an inner layer called pia mater.
It is divided into three regions − forebrain, midbrain, and hindbrain.
Forebrain: It is the main thinking part of the brain. It consists of cerebrum, thalamus, and hypothalamus.
(a) Cerebrum:
Cerebrum is the largest part of the brain and constitutes about four-fifth of its weight. Cerebrum is divided into two cerebral hemispheres by a deep longitudinal cerebral fissure. These hemispheres are joined by a tract of nerve fibre known as corpus callosum. The cerebral hemispheres are covered by a layer of cells known as cerebral cortex or grey matter. Cerebrum has sensory regions known as association areas that receive sensory impulses from various receptors as well as from motor regions that control the movement of various muscles. The innermost part of cerebrum gives an opaque white appearance to the layer and is known as the white matter.
(b) Thalamus:
Thalamus is the main centre of coordination for sensory and motor signalling. It is wrapped by cerebrum.
(c) Hypothalamus:
It lies at the base of thalamus and contains a number of centres that regulate body temperature and the urge for eating and drinking. Some regions of cerebrum, along with hypothalamus, are involved in the regulation of sexual behaviour and expression of emotional reactions such as excitement, pleasure, fear, etc.
Midbrain:
It is located between the thalamus region of the forebrain and pons region of hindbrain. The dorsal surface of midbrain consists of superior and inferior corpora bigemina and four round lobes called corpora quadrigemina. A canal known as cerebral aqueduct passes through the midbrain. Midbrain is concerned with the sense of sight and hearing.
Hindbrain:
It consists of three regions − pons, cerebellum, and medulla oblongata.
(a) Pons is a band of nerve fibre that lies between medulla oblongata and midbrain. It connects the lateral parts of cerebellar hemisphere together.
(b) Cerebellum is a large and well developed part of hindbrain. It is located below the posterior sides of cerebral hemispheres and above medulla oblongata. It is responsible for maintaining posture and equilibrium of the body.
(c) Medulla oblongata is the posterior and simplest part of the brain. It is located beneath the cerebellum. Its lower end extends in the form of spinal cord and leaves the skull through foramen magnum.
(B) Eye: Eyes are spherical structures that consist of three layers.
(a) The outer layer is composed of sclera and cornea.
(i) Sclera is an opaque tissue that is usually known as white of the eye. It is composed of a dense connective tissue.
(ii) Cornea is a transparent anterior portion of eye that lacks blood vessels and is nourished by lymph from the nearby area. It is slightly bulged forward and helps in focusing light rays with the help of lens.
(b) The middle layer of eye is vascular in nature and contains choroid, ciliary body, and iris.
(i) Choroid lies next to the sclera and contains numerous blood vessels that provide nutrients and oxygen to the retina and other tissues.
(ii) Ciliary body: The choroid layer is thin over posterior region and gets thickened in the anterior portion to form ciliary body. It contains blood vessels, ciliary muscles, and ciliary processes.
(iii) Iris: At the junction of sclera and cornea, the ciliary body continues forward to form thin coloured partition called iris. It is the visible coloured portion of eye.
The eye contains a transparent, biconvex, and elastic structure just behind the iris. It is known as lens. The lens is held in position by suspensory ligaments attached to the ciliary body. The lens divides the eye ball into two chambers – an anterior aqueous and posterior vitreous chamber.
(c) The innermost nervous coat of eye contains retina. Retina is the innermost layer. It contains three layers of cells – inner ganglion cells, middle bipolar cells, and outermost photoreceptor cells. The receptor cells present in the retina are of two types – rod cells and cone cells.
(a) Rod cells –The rods contain the rhodopsin pigment (visual purple) that is highly sensitive to dim light. It is responsible for twilight vision.
(b) Cone cells –The cones contain the iodopsin pigment (visual violet) and are highly sensitive to high intensity light. They are responsible for daylight and colour visions.
The innermost ganglionic cells give rise to optic nerve fibre that forms optic nerve in each eye and is connected with the brain.
(C) Ear: Ear is the sense organ for hearing and equilibrium. It consists of three portions – external ear, middle ear, and internal ear.
1. External ear:
It consists of pinna, external auditory meatus, and a tympanic membrane.
(a) Pinna is a sensitive structure that collects and directs the vibrations into the ear to produce sound.
(b) External auditory meatus is a tubular passage supported by cartilage in external ear.
(c) Tympanic membrane is a thin membrane that lies close to the auditory canal. It separates the middle ear from external ear.
2.Middle ear:
It is an air-filled tympanic cavity that is connected with pharynx through eustachian tube. Eustachian tube helps to equalize air pressure in both sides of tympanic membrane. The middle ear contains a flexible chain of three middle bones called ear ossicles. The three ear ossicles are malleus, incus, and stapes that are attached to each other.
3.Internal ear:
It is also known as labyrinth. Labyrinth is divided into bony labyrinth and a membranous labyrinth. Bony labyrinth is filled with perilymph while membranous labyrinth is filled with endolymph. Membranous labyrinth is divided into 2 parts.
(a) Vestibular apparatus
Vestibular apparatus is a central sac-like part that is divided into utriculus and sacculus. A special group of sensory cells called macula are present in sacculus and utriculus.
Vestibular apparatus also contains three semi-circular canals. The lower end of each semi-circular canal contains a projecting ridge called crista ampularis. Each ampulla has a group of sensory cells called crista. Crista and macula are responsible for maintaining the balance of body and posture.
(b) Cochlea:
Cochlea is a long and coiled outgrowth of sacculus. It is the main hearing organ. Cochlea consists of three membranes. The organ of corti, a hearing organ, is located on the basilar membrane that has hair cells.
Question 2:
Compare the following:
(a) Central neural system (CNS) and Peripheral neural system (PNS)
(b) Resting potential and action potential
(c) Choroid and retina
ANSWER:
(a) Central neural system (CNS) and Peripheral neural system (PNS)
Central neural system
Peripheral neural system
1.
It is the main coordinating centre of the body.
1.
It is not the main coordinating centre of the body.
2.
It includes brain and spinal cord.
2.
It includes cranial and spinal nerves that connect central nervous system to different parts of the body.
(b) Resting potential and action potential
Resting potential
Action potential
1.
It is the potential difference across the nerve fibre when there is no conduction of nerve impulse.
1.
It is the potential difference across nerve fibre when there is conduction of nerve impulse.
2.
The membrane is more permeable to K+ ions than to Na+ ions.
2.
The membrane is more permeable to Na+ ions than to K+ ions.
(c) Choroid and retina
Choroid
Retina
1.
Choroid is the middle vascular layer of eye.
1.
Retina is the innermost nervous coat of eye.
2.
It contains numerous blood vessels that provide nutrients and oxygen to retina and other tissues.
2.
It contains photoreceptor cells, rods and cones that are associated with twilight and colour vision respectively.
Question 3:
Explain the following processes:
(a) Polarisation of the membrane of a nerve fibre
(b) Depolarisation of the membrane of a nerve fibre
(c) Conduction of a nerve impulse along a nerve fibre
(d) Transmission of a nerve impulse across a chemical synapse
ANSWER:
(a) Polarisation of the membrane of a nerve fibre
During resting condition, the concentration of K+ ions is more inside the axoplasm while the concentration of Na+ ions is more outside the axoplasm. As a result, the potassium ions move faster from inside to outside as compared to sodium ions. Therefore, the membrane becomes positively charged outside and negatively charged inside. This is known as polarization of membrane or polarized nerve.
(b) Depolarisation of the membrane of a nerve fibre
When an electrical stimulus is given to a nerve fibre, an action potential is generated. The membrane becomes permeable to sodium ions than to potassium ions. This results into positive charge inside and negative charge outside the nerve fibre. Hence, the membrane is said to be depolarized.
(c) Conduction of a nerve impulse along a nerve fibre
There are two types of nerve fibres – myelinated and non-myelinated. In myelinated nerve fibre, the action potential is conducted from node to node in jumping manner. This is because the myelinated nerve fibre is coated with myelin sheath. The myelin sheath is impermeable to ions. As a result, the ionic exchange and depolarisation of nerve fibre is not possible along the whole length of nerve fibre. It takes place only at some point, known as nodes of Ranvier, whereas in non-myelinated nerve fibre, the ionic exchange and depolarization of nerve fibre takes place along the whole length of the nerve fibre. Because of this ionic exchange, the depolarized area becomes repolarised and the next polarized area becomes depolarized.
(d) Transmission of a nerve impulse across a chemical synapse
Synapse is a small gap that occurs between the last portion of the axon of one neuron and the dendrite of next neuron. When an impulse reaches at the end plate of axon, vesicles consisting of chemical substance or neurotransmitter, such as acetylcholine, fuse with the plasma membrane. This chemical moves across the cleft and attaches to chemo-receptors present on the membrane of the dendrite of next neuron. This binding of chemical with chemo-receptors leads to the depolarization of membrane and generates a nerve impulse across nerve fibre.
The chemical, acetylcholine, is inactivated by enzyme acetylcholinestrase. The enzyme is present in the post synaptic membrane of the dendrite.
It hydrolyses acetylcholine and this allows the membrane to repolarise.
The neural system provides rapid coordination among the organs of the body. This coordination is in the form of electric impulses and is quick and short lived. All the physiological processes in the body are closed linked and dependent upon each other. For example, during exercise, our body requires more oxygen and food. Hence, the breathing rate increases automatically and the heart beats faster. This leads to a faster supply of oxygenated blood to the muscles. Moreover, the cellular functions require regulation continuously. These functions are carried out by the hormones. Hence, the neural system along with the endocrine system control and coordinate the physiological processes.
(b) Forebrain
It is the main thinking part of the brain. It consists of cerebrum, thalamus, and hypothalamus.
(i) Cerebrum:
Cerebrum is the largest part of the brain and constitutes about four-fifth of its weight. Cerebrum is divided into two cerebral hemispheres by a deep longitudinal cerebral fissure. These hemispheres are joined by a tract of nerve fibres known as corpus callosum. The cerebral hemispheres are covered by a layer of cells known as cerebral cortex or grey matter. Cerebrum has sensory regions known as association areas that receive sensory impulses from various receptors as well as from motor regions that control the movement of various muscles. The innermost part of cerebrum gives an opaque white appearance to the layer and is known as the white matter.
(ii) Thalamus:
Thalamus is the main centre of coordination for sensory and motor signalling. It is wrapped by cerebrum.
(iii) Hypothalamus:
It lies at the base of thalamus and contains a number of centres that regulate body temperature and the urge for eating and drinking. Some regions of cerebrum, along with hypothalamus, are involved in the regulation of sexual behaviour and expression of emotional reactions such as excitement, pleasure, fear, etc.
(c) Midbrain
It is located between the thalamus region of the forebrain and pons region of hindbrain. The dorsal surface of midbrain consists of superior and inferior corpora bigemina and four round lobes called corpora quadrigemina. A canal known as cerebral aqueduct passes through the midbrain. Midbrain is concerned with the sense of sight and hearing.
(d) Hindbrain
It consists of three regions – pons, cerebellum, and medulla oblongata.
(i) Pons is a band of nerve fibres that lies between medulla oblongata and midbrain. It connects the lateral parts of cerebellar hemisphere together.
(ii) Cerebellum is a large and well developed part of hindbrain. It is located below the posterior sides of cerebral hemispheres and above the medulla oblongata. It is responsible for maintaining posture and equilibrium of the body.
(iii) Medulla oblongata is the posterior and simplest part of the brain. It is located beneath the cerebellum. Its lower end extends in the form of spinal cord and leaves the skull through foramen magnum.
(e) Retina
Retina is the innermost layer. It contains three layers of cells – inner ganglion cells, middle bipolar cells, and outermost photoreceptor cells. The receptor cells present in the retina are of two types – rod cells and cone cells.
(i) Rod cells –The rods contain rhodopsin pigment (visual purple), which is highly sensitive to dim light. It is responsible for twilight vision.
(ii) Cone cells –The cones contain iodopsin pigment (visual violet) and are highly sensitive to high intensity light. They are responsible for daylight and colour visions.
The innermost ganglionic cells give rise to optic nerve fibre that forms optic nerve in each eye and is connected with the brain. In this region, the photoreceptor cells are absent. Hence, it is known as the blind spot. At the posterior part, lateral to blind spot, there is a pigmented spot called macula lutea. This spot has a shallow depression at its middle known as fovea. Fovea has only cone cells. They are devoid of rod cells. Hence, it is the place of most distinct vision.
(f) Ear ossicles
The middle ear contains a flexible chain of three middle bones called ear ossicles. The three ear ossicles are as follows.
(i) Malleus
(ii) Incus
(iii) Stapes
The malleus is attached to tympanic membrane on one side and to incus on the other side. The incus is connected with stapes. Stapes, in turn, are attached with an oval membrane, fenestra ovalis, of internal ear. The ear ossicles act as a lever that transmits sound waves from external ear to internal ear.
(g)Cochlea
Cochlea is a long, coiled outgrowth of sacculus. It is the main hearing organ. The cochlea forms three chambers.
(i) Upper − scala vestibule
(ii) Middle − scala media
(iii) Lower − scale tympani
The floor of the scala media is basilar membrane while its roof is Reissner’s membrane. Reissner’s membrane gives out a projection called tectorial membrane. The organ of corti, a hearing organ, is located on the basilar membrane. Organ of corti contains receptor hair cells. The upper scala vestibule and lower scala tympani contain perilymph.
(h) Organ of corti
Organ of corti is the hearing organ. It is located on the basilar membrane that contains hair cells. Hair cells act as auditory receptors. They are present on the internal side of organ of corti.
(i) Synapse
Synapse is a junction between the axon terminal of one neuron and the dendrite of next neuron. It is separated by a small gap known as synaptic cleft.
There are two types of synapses.
(a) Electrical synapse
(b) Chemical synapse
In electrical synapses, the pre and post synaptic neurons lie in close proximity to each other. Hence, the impulse can move directly from one neuron to another across the synapse. This represents a faster method of impulse transmission.
In chemical synapses, the pre and post synaptic neurons are not in close proximity. They are separated by a synaptic cleft. The transmission of nerve impulses is carried out by chemicals such as neurotransmitters.
Question 6:
Give a brief account of:
(a) Mechanism of synaptic transmission
(b) Mechanism of vision
(c) Mechanism of hearing
ANSWER:
(a) Mechanism of synaptic transmission
Synapse is a junction between two neurons. It is present between the axon terminal of one neuron and the dendrite of next neuron separated by a cleft.
There are two ways of synaptic transmission.
(1) Chemical transmission
(2) Electrical transmission
1. Chemical transmission – When a nerve impulse reaches the end plate of axon, it releases a neurotransmitter (acetylcholine) across the synaptic cleft. This chemical is synthesized in cell body of the neuron and is transported to the axon terminal. The acetylcholine diffuses across the cleft and binds to the receptors present on the membrane of next neuron. This causes depolarization of membrane and initiates an action potential.
2. Electrical transmission – In this type of transmission, an electric current is formed in the neuron. This electric current generates an action potential and leads to transmission of nerve impulse across the nerve fibre. This represents a faster method of nerve conduction than the chemical method of transmission.
(b)Mechanism of vision
Retina is the innermost layer of eye. It contains three layers of cells – inner ganglion cells, middle bipolar cells, and outermost photoreceptor cells. A photoreceptor cell is composed of a protein called opsin and an aldehyde of vitamin A called retinal. When light rays are focused on the retina through cornea, it leads to the dissociation of retinal from opsin protein. This changes the structure of opsin. As the structure of opsin changes, the permeability of membrane changes, generating a potential difference in the cells. This generates an action potential in the ganglionic cells and is transmitted to the visual cortex of the brain via optic nerves. In the cortex region of brain, the impulses are analysed and image is formed on the retina.
(c)Mechanism of hearing
The pinna of the external region collects the sound waves and directs it towards ear drum or external auditory canal. These waves strike the tympanic membrane and vibrations are created. Then, these vibrations are transmitted to the oval window, fenestra ovalis, through three ear ossicles, named as malleus, incus, and stapes. These ear ossicles act as lever and transmit the sound waves to internal ear. These vibrations from fenestra ovalis are transmitted into cochlear fluid. This generates sound waves in the lymph. The formation of waves generates a ripple in the basilar membrane. This movement bends the sensory hair cells present on the organ of corti against tectorial membrane. As a result of this, sound waves are converted into nerve impulses. These impulses are then carried to auditory cortex of brain via auditory nerves. In cerebral cortex of brain, the impulses are analysed and sound is recognized.
Question 7:
Answer briefly:
(a) How do you perceive the colour of an object?
(b) Which part of our body helps us in maintaining the body balance?
(c) How does the eye regulate the amount of light that falls on the retina?
ANSWER:
(a) Photoreceptors are cells that are sensitive to light. They are of two types – rods and cones. These are present in the retina. Cones help in distinguishing colours. There are three types of cone cells – those responding to green light, those responding to blue light, and those responding to red light. These cells are stimulated by different lights, from different sources. The combinations of the signals generated help us see the different colours.
(b) Vestibular apparatus is located in the internal ear, above the cochlea and helps in maintaining body balance. Crista and macula are the sensory spots of the vestibular apparatus controlling dynamic equilibrium.
(c) Pupil is the small aperture in the iris that regulates the amount of light entering the eye. Cornea, aqueous humour, lens, and vitreous humour act together and refract light rays, focussing them onto the photoreceptor cells of the retina.
Question 8:
Explain the following:
(a) Role of Na+ in the generation of action potential.
(b) Mechanism of generation of light-induced impulse in the retina.
(c) Mechanism through which a sound produces a nerve impulse in the
inner ear.
ANSWER:
(a) Sodium ions play an important role in the generation of action potential. When a nerve fibre is stimulated, the membrane potential decreases. The membrane becomes more permeable to Na+ ions than to K+ ions. As a result, Na+ diffuses from the outside to the inside of the membrane. This causes the inside of the membrane to become positively-charged, while the outer membrane gains a negatively charge. This reversal of polarity across the membrane is known as depolarisation. The rapid inflow of Na+ ions causes the membrane potential to increase, thereby generating an action potential.
(b) Retina is the innermost layer of the eye. It contains three layers of cells – inner ganglion cells, middle bipolar cells, and outermost photoreceptor cells. Photoreceptor cells are composed of a protein called opsin and an aldehyde of vitamin A called retinal. When light rays are focused on the retina through the cornea, retinal gets dissociated from opsin. As a result, the structure of opsin gets changed. This in turn causes the permeability of the membrane to change, thereby generating a potential difference in the cells. Consequently, an action potential is generated in the ganglion cells and is transmitted to the visual cortex of the brain via the optic nerves. In the cortex region of the brain, the impulses are analysed and the image is formed on the retina.
(c) The pinna of the external ear collects the sound waves and directs them to the tympanic membrane (ear drum) via the external auditory canal. The ear drum then vibrates the sound waves and conducts them to the internal ear through the ear ossicles. The ear ossicles increase the intensity of the sound waves. These vibrating sound waves are conducted through the oval window to the fluid in the cochlea. Consequently, a movement is created in the lymph. This movement produces vibrations in the basilar membrane, which in turn stimulate the auditory hair cells. These cells generate a nerve impulse, conducting it to the auditory cortex of the brain via afferent fibres. The auditory cortex region interprets the nerve impulse and sound is recognised.
Question 9:
Differentiate between:
(a) Myelinated and non-myelinated axons
(b) Dendrites and axons
(c) Rods and cones
(d) Thalamus and Hypothalamus
(e) Cerebrum and Cerebellum
ANSWER:
(a) Myelinated and non-myelinated axons
Myelinated axons
Non-myelinated axons
1.
Transmission of nerve impulse is faster
1.
Transmission of nerve impulse is slower
2.
Myelinated axon has a myelin sheath.
2.
Myelin sheath is absent
3.
Node of Ranvier is present between adjacent myelin sheaths.
3.
Node of Ranvier is absent
4.
Found in the brain, the spinal cord, the cranial and spinal nerves
4.
Found in autonomous and somatic neural systems
5.
Schwann cells are observed inside the myelin sheath
5.
Schwann cells are not observed inside the myelin sheath
(b) Dendrites and axons
Dendrites
Axons
1.
Dendrite is a small projection arising from the neuron. It conducts the nerve impulse toward the cell body.
1.
Axon is a single, long projection that conducts the nerve impulse away from cell body to the next neuron.
2.
Nissl’s granules are present in dendrites.
2.
Nissl’s granules are absent from axons.
3.
Dendrites are always non-myelinated.
3.
Axons can be myelinated or non-myelinated.
(c) Rods and cones
Rods
Cones
1.
Rods help in twilight vision.
1.
Cones help in colour vision.
2.
They have visual purple pigment called rhodopsin.
2.
They have visual violet pigment called iodopsin.
3.
Rods are the photoreceptor cells of the retina that are sensitive to dim light.
3.
Cones are the photoreceptor cells of the retina that are sensitive to bright light.
(d) Thalamus and Hypothalamus
Thalamus
Hypothalamus
Thalamus is the part of the forebrain that receives nerve impulses of pain, temperature, touch, etc., and conducts them to the cerebral hemisphere.
Hypothalamus is the part of the forebrain that controls involuntary functions such as hunger, thirst, sweating, sleep, fatigue, sexual desire, temperature regulation, etc.
(e) Cerebrum and Cerebellum
Cerebrum
Cerebellum
It is the part of the forebrain that controls voluntary functions. It is the place where intelligence, will power, memory, etc., reside.
It is the part of the hindbrain that controls voluntary functions and controls the equilibrium.
Question 10:
Answer the following:
(a) Which part of the ear determines the pitch of a sound?
(b) Which part of the human brain is the most developed?
(c) Which part of our central neural system acts as a master clock?
ANSWER:
(a) Cochlea determines the pitch of a sound.
(b) Forebrain is largest and the most developed part of the human brain.
(c) Hypothalamus acts as a master clock in the human body.
