Yearly Archives: 2022

SHORT ANSWER TYPE QUESTION:

Q1. What are waves?
Answer
Waves are energy, not the water which moves across the ocean surface. It generated by wind driving against water.

Q2. Where do waves in the ocean get their energy from?

Answer

Wind provides energy to the waves. Wind causes waves to travel in the ocean and the energy is released on shorelines.

Q3. What are tides?

Answer

The periodical rise and fall of the sea level, once or twice a day, mainly due to the attraction of the sun and the moon, is called a tide.

Q4. How are tides caused?

Answer

The tides are caused by the gravitational pull of the sun and the moon and the centrifugal force

Q5.How are tides related to navigation?

Answer

Tides helps the navigators and fishermen plan their activities. Tidal flows are of great importance in navigation. Tidal heights are very important, especially harbours near rivers and within estuaries having shallow ‘bars’ at the entrance, which prevent ships and boats from entering into the harbour.

Q6. How do currents affect the temperature? How does it affect the temperature of coastal areas in the N. W. Europe?

Answer

The currents directly affect the temperature. The temperature varies depending on whether currents are warm or cold:
• Cold currents bring cold water into warm water areas. These currents are usually found on the west coast of the continents in the low and middle latitudes (true in both hemispheres) and on the east coast in the higher latitudes in the Northern Hemisphere
• Warm currents bring warm water into cold water areas and are usually observed on the east coast of continents in the low and middle latitudes (true in both hemispheres). In the northern hemisphere they are found on the west coasts of continents in high latitudes.

In North West Europe, warm currents are present which increase the temperature in coastal areas in the North West Europe.

Q7.What are the causes of currents?
Answer

Oceans currents are caused by two forces mainly:
(i) primary forces that initiate the movement of water
(ii) secondary forces that influence the currents to flow.

The primary forces that influence the currents are:

• Heating by solar energy:  Heating by solar energy causes the water to expand. That is why, near the equator the ocean water is about 8 cm higher in level than in the middle latitudes. This causes a very slight gradient and water tends to flow down the slope.

• Wind: It blowing on the surface of the ocean pushes the water to move. Friction between the wind and the water surface affects the movement of the water body in its course

• Gravity: It tends to pull the water down the pile and create gradient variation.

• Coriolis force: This intervenes and causes the water to move to the right in the northern hemisphere and to the left in the southern hemisphere. These large accumulations of water and the flow around them are called Gyres. These produce large circular currents in all the ocean basins.

The secondary forces that influence the currents are:

• Difference in water density: It affect vertical mobility of ocean currents. Denser water tends to sink, while relatively lighter water tends to rise.

• Difference in Salinity: Water with high salinity is denser than water with low salinity and in the same way cold water is denser than warm water.

Long Answer Type Questions :

Q1.In how many categories can tides be classified on the basis of their height and frequency?
Answer:

• Semi-diurnal tide: It is the most common tidal pattern, featuring two high tides and two low tides each day. The successive high or low tides are approximately of the same height.
• Diurnal tide: There is only one high tide and one low tide during each day. The successive high and low tides are approximately of the same height.
• Mixed tide: Tides having variations in height are known as mixed tides. These tides generally occur along the west coast of North America and on many islands of the Pacific Ocean.
• Spring tides: The position of both the sun and the moon in relation to the earth has direct bearing on tide height. When the sun, the moon and the earth are in a straight line, the height of the tide will be higher. These are called spring tides.
• Neap tides: Wlien the sun and moon are at right angles to each other and the forces of the sun and moon tend to counteract one another. The moon’s attraction, though more than twice as strong as the sun’s, is diminished by the counteracting force of the sun’s gravitational pull. These are called neap tides.

Q2.White the characteristics of waves in the oceanic water.
Answer:
Characteristics of waves in the oceanic water are given below:

• The highest and lowest points of a wave are called the crest and trough.
• Wave height is the vertical distance from the bottom of a trough to the top of a crest of a wave.
• Wave amplitude is one-half of the wave height.
• Wave period is merely the time interval between two successive wave crests.
• Wavelength is the horizontal distance between two successive crests.
• Wave speed is the rate at which the wave moves through the water, and is measured in knots.
• Wave frequency is the number of waves passing a given point during a one- second time interval.

Q3.Explain how do heating of solar energy, wind, gravitation and coriolis force affect the ocean currents.
Answer:
Heating by solar energy: Heating by solar energy causes the water to expand, that is why, near the equator the ocean water is about 8 cm higher in level than in the middle latitudes. This causes a very slight gradient and water tends to flow down the slope.

• Wind: Wind blowing on the surface of the ocean pushes the water to move. Friction between the wind and the water surface affects the movement of the water body in its course.
• Gravity: Gravity tends to pull the water down the pile and create gradient variation.
• The Coriolis force: The coriolis intervenes and cause the water to move to the right in the northern hemisphere and to the left in the southern hemisphere.

Q4.Differentiate between warm currents and cold currents.
Answer:

S.no.	Warm currents	Cold currents
1.	They flow from equatorial regions to high latitudes.	They flow from polar region to low latitudes.
2.	Its temperature is higher than the surrounding water.	Its temperature is below than the surrounding water.
3.	It raises the temperature of coastal areas and are observed normally on the east coast of lower and middle latitude.	It reduces the temperature of the coastal area and are observed on the west of continent in lower and middle latitudes.
4.	Winds passing over warm currents absorb a good amount of moisture and bring heavy rainfall on the coastal areas.	Winds passing over cold currents becomes dry and little rainfall on the coaarea.
5.	Warm currents are of great help to navigation because they melt ice bergs.	Cold currents hinder navigation because they create ice bergs.
6.	Warm currents keep the ports open in the polar regions free from ice.	Cold currents make the parts unoperational in lower latitudes as they are ice bound.

SHORT ANSWER TYPE QUESTION:

Q1. Why do we call the earth a Blue Planet?
Answer
The earth is called as a Blue Planet because of abundant supply of water on its surface. Water is a rare commodity in our solar system. There is no water on the sun or anywhere else in the solar system.

Q2. What is a continental margin?
Answer
The continental slope together with the continental shelf is called the continental margin.

Q3. List out the deepest trenches of various oceans.
Answer
There are 57 trenches have been explored so far; of which 32 are in the Pacific Ocean; 19 in the Atlantic Ocean and 6 in the Indian Ocean

Q4.What is a thermocline?
Answer
The boundary region, from where there is a rapid decrease of temperature, is called the thermocline. This layer lies below the first layer and is characterised by rapid decrease in temperature with increasing depth.

Q5. When you move into the ocean what thermal layers would you encounter? Why the temperature varies with depth?
Answer
When we move into the ocean we will encounter three thermal layers.The temperature varies with the depth because the temperature structure of oceans over middle and low latitudes can be described as a three layer system. The first layer is about 500m thick with temperatures ranging between 20° and 25° C. The second layer is 500 -1,000 m thick. The third layer is very cold and extends upto the deep ocean floor

Q6. What is salinity of sea water?
Answer
Salinity is the term used to define the total content of dissolved salts in sea water . It is calculated as the amount of salt (in gm) dissolved in 1,000 gm (1 kg) of seawater. It depend mainly on evaporationand precipitation.

Q7. How are various elements of the hydrological cycle interrelated?
Answer
Water is a cyclic resource. It can be used and re-used. The hydrological cycle, is the circulation of water within the earth’s hydrosphere in different forms i.e. the liquid, solid and the gaseous phases. It also refers to the continuous exchange of water between the oceans, atmosphere, landsurface and subsurface and the organisms. The distribution of water on earth is quite uneven. Many locations have plenty of water while others have very limited quantity. About 71 per cent ofthe planetary water is found in the oceans. The remaining is held as freshwater in glaciers and icecaps, groundwater sources, lakes, soil moisture, atmosphere, streams and within life. Nearly 59 per cent of the water that falls on land returns to the atmosphere through evaporation from over the oceans as well as from other places. The remainder runs-off on the surface, infiltrates into the ground or a part of it becomes glacier

Q8.Examine the factors that influence the temperature distribution of the oceans.
Answer
The factors which affect the distribution of temperature of ocean water are :
(i) Latitude: The temperature of surface water decreases from the equator towards the poles because the amount of insolation decreases poleward.
(ii) Unequal distribution of land and water: The oceans in the northern hemisphere receive more heat due to their contact with larger extent of land than the oceans in the southern hemisphere.
(iii) Prevailing wind: The winds blowing from the land towards the oceans drive warm surface water away form the coast resulting in the upwelling of cold water from below. It results into the longitudinal variation in the temperature. Contrary to this, the onshore winds pile up warm water near the coast and this raises the temperature.
(iv) Ocean currents: Warm ocean currents raise the temperature in cold areas while the cold currents decrease the temperature in warm ocean areas. Gulf stream (warm current) raises the temperature near the eastern coast of North America and the West Coast of Europe while the Labrador current (cold current) lowers the temperature near the north-east coast of North America.

Long Answer Type Questions

Q1.The average temperature of water on oceans floor keeps on falling from equator to poles systematically. Explain.
Answer:
The average temperature of surface water of the- oceans is about 27°C and it gradually decreases from the equator towards the poles. The rate of decrease of temperature with increasing latitude is generally 0.5°C per latitude. The average temperature is around 22°C at 20° latitudes, 14° C at 40° latitudes and 0° C near poles.

The oceans in the northern hemisphere record relatively higher temperature than in the southern hemisphere. The highest temperature is not recorded at the equator but slightly towards north of it.

The average annual temperatures for the northern and southern hemisphere are around 19° C and 16° C respectively. This variation is due to the unequal distribution of land and water in the northern and southern hemispheres.

Q2.Explain about horizontal distribution of salinity.
Answer:
Horizontal distribution of salinity:

• The salinity for normal Open Ocean ranges between 33% and 37%. In the land locked Red Sea records higher salinity due to high evaporation.
• Salinity is, however, very low in Black Sea due to enormous fresh water influx by rivers.
• The average salinity of the Indian Ocean is 35 %.
• The low salinity trend is observed in the Bay of Bengal due to influx of river water.
• On the contrary, the Arabian Sea shows higher salinity due to high evaporation and low influx of fresh water.

Q3.Explain about vertical distribution of salinity.
Answer:
Vertical distribution of salinity

• Salinity changes with depth, but the way it changes depends upon the location of the sea. Salinity at the surface increases by the loss of water to ice or evaporation, or decreased by the input of fresh waters, such as from the rivers.
• Salinity at depth is very much fixed, because there is no way that water is ‘lost’, or the salt is ‘added.’
• There is a marked difference in the salinity between the surface zones and the deep zones of the oceans. The lower salinity water rests above the higher salinity dense water.
• Salinity, generally, increases with depth and there is a distinct zone called the halocline, where salinity increases sharply.
• Other factors being constant, increasing salinity of seawater causes its density to increase. High salinity seawater, generally, sinks below the lower salinity water. This leads to stratification by salinity.

Q4.Explain about vertical distribution of temperature.
Answer:
The temperature structure of oceans over middle and low latitudes can be described as a three-layer system from surface to the bottom.

• The first layer represents the top layer of warm oceanic water and it is about 500 m thick with temperatures ranging between 20° and 25° C. This layer, within the tropical region, is present throughout the year but in mid-latitudes it develops only during summer.
• The second layer called the thermocline layer lies below the first layer and is characterised by rapid decrease in temperature with increasing depth. The thermocline is 500 – 1,000 m thick.
• The third layer is very cold and extends upto the deep ocean floor. In the Arctic and Antarctic circles, the surface water temperatures are close to 0 C and so the temperature change with the depth is very slight.

Q5.Explain the features of the deep sea plains, submarine ridges, ocean deeps and seamount.
Answer:
Abyssal plains (the deep sea plains):

• These are the world’s flattest and smoothest regions.
• About 40% of the oceanic floor is flat.
• It is formed accumulation of sediments on the sea floor.
• Its depth varies from 3000-6000 m.

Submarine ridges:

• Oceanic floors have submarine narrow and elongated ridges.
• They resemble mountain ridges on the earth surface.
• Peak of these ridges may rise above the sea level to form islands.
• Eg-Philippines Ice land is a mid-Atlantic ridge.

Oceanic deeps of submarine trenches:

• Deep narrow steep sided depression is found along the abyssal plain.
• The depth of these trenches may vary from 6,000 to 11,000 m. Example, Marina trenches is the deepest trench in Pacific Ocean.
• Trenches are formed as a result of tectonic forces and normally occur along the marines of Pacific Ocean.
• They occur at the base of the continental slopes and along the island area. Normally associated with volcanoes and strong earthquake.
• There are 32 trenches in Pacific Ocean, 19 in Atlantic Ocean and just 6 in Indian Ocean.

Seamount:

• It is the mount with a pointed submit rising from the sea floor but do not reach the surface of ocean. For example
  • Emperor seamount, an extension of Hawaiian islands in Pacific Ocean
  • The tallest seamount between Soman and New Zealand.
• Seamounts are volcanic in origin and can be 3000 to 4500 m tall.

SHORT ANSWER TYPE QUESTION:

Q1. Which two climatic variables are used by Koeppen for classification of the climate?
Answer
Temperature and precipitation are two climatic variables are used by Koeppen for classification of the climate.

Q2.How is the “genetic” system of classification different from the “empirical one”?
Answer
Empirical classification is based on observed data, particularly on temperature and precipitation. Genetic classification attempts to organise climates according to their causes.

Q3. Which types of climates have very low range of temperature?
Answer
Tropical Humid Climates have very low range of temperature. It exist between Tropic of Cancer and Tropic of Capricorn.

Q4.What type of climatic conditions would prevail if the sun spots increase?
Answer

When the number of sunspots increase, cooler and wetter weather and greater storminess occur.

Q5. Make a comparison of the climatic conditions between the “A” and “B” types of climate.
Answer

“A” Type of Climate	“B” Type of Climate
It belongs to tropical climate.	It belongs to sub-tropical climate.
It exist between Tropic of Cancer and Tropic of Capricorn.	These are found in low or mid latitudes in the area of subtropical high where subsidence and inversion of temperature do not produce rainfall
Annual range of temperature is very low and annual rainfall is high.	Very low rainfall that is not adequate for the growth of plants.
The tropical group is divided into three types, namely (i) Af-Tropical wet climate; (ii) Am – Tropical monsoon climate; (iii) Aw- Tropical wet and dry climate.	Dry climates are divided into steppe or semi-arid climate (BS) and desert climate (BW).

Q6. What type of vegetation would you find in the “C” and “A” type(s) of climate?
Answer
Vegetation in “A” type of climate: The sun being overhead throughout the year and gigh rainfall make the condition appropriate for the growth of plants. It supports rainforests. Tropical evergreen forests with dense canopy cover and large biodiversity are found in Tropical Wet Climate. Deciduous forest and tree-shredded grasslands occur in Tropical Wet and Dry Climate.

Vegetation in “C” type of climate: Warm temperate climates extend from 30° – 50° of latitude mainly on the eastern and western margins of continents. These climates generally have warm summers with mild winters. It is same as tropical forest. The forests have trees, shrubs and bushes. Broadleaf trees provide a continuous and dense canopy in summer and shed their leaves in winter. The shorter trees and shrubs of different heights and grow rapidly in summer and warm spring. Ferns, mosses and other plants which grow quickly in spring but disappear in winter.

Q7.What do you understand by the term “Greenhouse Gases”? Make a list of greenhouse gases.

Answer

A greenhouse is made up of glass. The glass which is transparent to incoming short wave solar
radiation is opaque to outgoing long wave radiation. The glass, therefore, allows in more radiation and prevents the long wave radiation going outside the glass house, causing the temperature inside
the glasshouse structure warmer than outside. Due to the presence of greenhouse gases, the atmosphere is behaving like a greenhouse. The atmosphere also transmits the incoming solar
radiation but absorbs the vast majority of long wave radiation emitted upwards by the earth’s surface. The gases that absorb long wave radiation are called greenhouse gases. The processes that warm the atmosphere are often collectively referred to as the greenhouse effect.

The primary Greenhouse Gases are:
• Carbon dioxide (CO₂)
• Chlorofluorocarbons (CFCs)
• Methane (CH₄)
• Nitrous oxide (N₂O)
• Ozone (O₃).

Some other gases such as nitric oxide (NO) and carbon monoxide (CO) easily react with GHGs and affect their concentration in the atmosphere.

Long Answer Type Questions :

Q1.Explain the major climate categories by Koeppen.
Answer:
The first level recognises six major climatic types with each group being designated by a capital letter. These major climate categories have the following broad characteristics:

•  Tropical moist climates: These are very warm climates found in the tropics that experience high quantities of precipitation. The primary distinguishing characteristic of these climates is that all months have average temperatures above 18 C (64 F).
• Dry climates: These are climates that experience little precipitation during most of the year. Further, potential losses of water from evaporation and transpiration greatly exceed atmospheric input.
• Moist mid-latitude climates with mild winters: In these climates, summer temperatures are warm to hot and winters are mild. The primary distinguishing characteristic of these climates is that the coldest month has an average temperature between 18 C (64 F) and -3 C (27 F).
• Moist mid-latitude climates with cold winters: In these climates, summer temperatures are warm and winters are cold. The primary distinguishing characteristic of these climates is the average temperature of warmest month exceeds 10 C (50 F), and average temperature of coldest is below -3 C (27 F).
• Polar climates: These climates have very cold winters and summers, with no real summer season. The primary distinguishing characteristic of these climates is the warmest month has an average temperature below 10 C (50 F).
• Highland climates: These are climates that are strongly influenced by the effects of altitude. As a result, the climate of such locations is rather different from places with low elevations at similar latitudes.

Q2.Explain the climatic changes that has taken place since ancient times. Also explain its causes.
Answer:
The type of climate we experience now might be prevailing over the last 10,000 years with minor and occasionally wide fluctuations. The planet earth has witnessed many variations in climate since the beginning. Geological records show alteration of glacial and inter-glacial periods. The sediment deposits in glacial lakes also reveal the occurrence of warm and cold periods. The rings in the trees provide clues about wet and dry periods. Historical records describe the diversities in climate. All these evidences indicate that change in climate is a natural and continuous process. Archaeological findings show that the Rajasthan desert experienced wet and cool climate around 8,000 B.C. During the Pleistocene epoch, glacial and inter-glacial periods occurred, the last major peak glacial period was about 18,000 years ago. The present inter-glacial period started 10,000 years ago. Variability in climate occurs all the time. The nineties decade of the last century witnessed extreme weather events. The 1990s recorded the warmest temperature of the century and some of the worst floods around the world. Europe witnessed “Little Ice Age” from 1550 to about 1850. From about 1885¬1940 world temperature showed an upward trend. After 1940, the rate of increase in temperature slowed down.
Causes of Climate Change: The causes for climate change can be grouped into astronomical and terrestrial causes.

1. The astronomical causes: These are the changes in solar output associated with sunspot activities. Sunspots are dark and cooler patches on the sun which increase and decrease in a cyclical manner. According to some meteorologists, when the number of sunspots increase, cooler and wetter weather and greater storminess occur. A decrease in sunspot numbers is associated with warm and drier conditions.

2. Volcanism: It is considered as another cause for climate change. Volcanic eruption throws up lots of aerosols into the atmosphere. These aerosols remain in the atmosphere for a considerable period of time reducing the sun’s radiation reaching the Earth’s surface. After the recent Pinatoba and El Cion volcanic eruptions, the average temperature of the earth fell to some extent for some years.

3. Greenhouse gases: The most important anthropogenic effect on the climate is the increasing trend in the concentration of greenhouse gases in the atmosphere which is likely to cause global warming.

Q3.Explain about Polar climate (E).
Answer:
Polar Climates (E) exist poleward beyond 70 latitude. Polar climates consist of two types:

1. Tundra (ET);
2. Ice Cap (EF).

1. Tundra Climate (ET): The tundra climate (ET) is so called after the types of vegetation, like low growing mosses, lichens and flowering plants. This is the region of permafrost where the sub soil is permanently frozen. The short growing season and water logging support only low growing plants. During summer, the tundra regions have very long duration of day light.

2. Ice Cap Climate (EF): The ice cap climate (EF) occurs over interior Greenland and Antarctica. Even in summer, the temperature is below freezing point. This area receives very little precipitation. The snow and ice get accumulated and the mounting pressure causes the deformation of the ice sheets and they break. They move as icebergs that float in the Arctic and Antarctic waters. Plateau Station, Antarctica ,79 S, portray this climate.

Q4.Explain about Cold snow forest climates (D).
Answer:
Cold Snow Forest Climates (D) occur in the large continental area in the northern hemisphere between 40 -70 north latitudes in Europe, Asia and North America. Cold snow forest climates are divided into two types:

1. Df- cold climate with humid winter;
2. Dw- cold climate with dry winter.

The severity of winter is more pronounced in higher latitudes.
1. Cold climate with humid winters (Df): Cold climate with humid winter occurs poleward of marine west coast climate and mid latitude steppe. The winters are cold and snowy. The frost free season is short. The annual ranges of temperature are large. The weather changes are abrupt and short. Poleward, the winters are more severe.

2.Cold climate with dry winters (Dw): Cold climate with dry winter occurs mainly over Northeastern Asia. The development of pronounced winter anti cyclone and its weakening in summer sets in monsoon like reversal of wind in this region. Poleward summer temperatures are lower and winter temperatures are extremely low with many locations experiencing below freezing point temperatures for up to seven months in a year. Precipitation occurs in summer. The annual precipitation is low from 12-15 cm.

Q5.Write a detailed note on Tropical monsoon climate (Am).
Answer:
Tropical monsoon climate, occasionally also known as a tropical wet climate or tropical monsoon and trade-wind littoral climatein climate classification, is a relatively rare type of climate that corresponds to the Koppen climate classification category “Am”.

Tropical monsoon climates have monthly mean temperatures above 18 C in every month of the year and feature wet and dry seasons, as Tropical savanna climates do. Unlike tropical savanna climates however, a tropical monsoon climate’s driest month sees less than 60 mm of precipitation but more than (100 [total annual precipitation [mm}/25]). Also, a tropical monsoon climate tends to see less variance in temperatures during the course of the year than a tropical savanna climate. This climate has a driest month which nearly always occurs at or soon after the “winter” solstice for that side of the equator. Tropical monsoon climates are most commonly found in South and Central America. However, there are sections of South Asia, Southeastsia, Africa (particularly West and Central Africa), the Caribbean, and North America that also features this climate.

SHORT ANSWER TYPE QUESTION:

Q1. Name the three types of precipitation.
Answer
The three types of precipitation are:• Rainfall:  The precipitation in the form of water.• Snowfall:  The precipitation in the form of fine flakes of snow.• Hailstones: Sometimes, drops of rain after being released by the clouds become solidified into small rounded solid pieces of ice and which reach the surface of the earth.

Q2. Explain relative humidity.
Answer
The percentage of moisture present in the atmosphere as compared to its full capacity at a given temperature is known as the relative humidity. 

Q3. Why does the amount of water vapour decreases rapidly with altitude?
Answer

The water vapour is greater over the oceans and least over the continents. There is absence of these water bodies on high altitudes. Temperature decreases with higher altitudes, therefore, rates of evaporation also decreases as a result water vapour also decreases rapidly with altitude.

Q4. How are clouds formed? Classify them.

Answer

Cloud is a mass of minute water droplets or tiny crystals of ice formed by the condensation of the water vapour in free air at considerable elevations.
According to their height, expanse, density and transparency or opaqueness clouds are grouped under four types :
• Cirrus
• Cumulus
• Stratus
• Nimbus.

Q5.Discuss the salient features of the world distribution of precipitation.

Answer

Different places on the earth’s surface receive different amounts of rainfall in a year and that too in different seasons.
• The rainfall decreases as we go from equator towards poles.
•  The coastal areas of the world receive greater amounts of rainfall than the interior of the continents. • The rainfall is more over the oceans than on the landmasses of the world because of being great sources of water.
• Between the latitudes 35° and 40° N and S of the equator, the rain is heavier on the eastern coasts and goes on decreasing towards the west.
• Between 45° and 65° N and S of equator, due to the westerlies, the rainfall is first received on the western margins of the continents and it goes on decreasing towards the east.
• Wherever mountains run parallel to the coast, the rain is greater on the coastal plain, on the windward side and it decreases towards the leeward side

Q6.What are forms of condensation? Describe the process of dew and frost formation.

Answer

The transformation of water vapour into water is called condensation. Condensation is caused by the loss of heat.

The forms of condensation are dew, frost, fog and clouds.

Formation of dew: When the moisture is deposited in the form of water droplets on cooler surfaces of solid objects such as stones, grass blades and plant leaves, it is known as dew. The ideal conditions for its formation are clear sky, calm air, high relative humidity, and cold and long nights. For the formation of dew, it is necessary that the dew point is above the freezing point.

Formation of frost: Frost forms on cold surfaces when condensation takes place below freezing point i.e. the dew point is at or below the freezing point. The excess moisture is deposited in the form of minute ice crystals instead of water droplets. The ideal conditions for the formation of white frost are the same as those for the formation of dew, except that the air temperature must be at or below the freezing point.

Long Answer Type Questions :

Q1.Explain about condensation in detail.
Answer:
1. Meaning: The transformation of water vapour into water is called condensation. Cause: Condensation is caused by the loss of heat.

2. Sublimation: When moist air is cooled, it may reach a level when its capacity to hold water vapour ceases. Then, the excess water vapour condenses into liquid form. If it directly condenses into solid form, it is known as sublimation.

3. Process: In free air, condensation results from cooling around very small particles termed as hygroscopic condensation nuclei. Particles of dust, smoke and salt from the ocean are particularly good nuclei because they absorb water. Condensation also takes place when the moist air comes in contact with some colder object and it may also take place when the temperature is close to the dew point. Condensation, therefore, depends upon the amount of cooling and the relative humidity of the air.

Factors affecting condensation:

• When the temperature of the air is reduced to dew point with its volume remaining constant;
• When both the volume and the temperature are reduced;
• When moisture is added to the air through evaporation.

However, the most favourable condition for condensation is the decrease in air temperature. After condensation the water vapour or the moisture in the atmosphere takes form of dew, frost, fog and clouds.

Q2.Explain about fog and mist.
Answer:
When the temperature of an air mass containing a large quantity of water vapour falls all of a sudden, condensation takes place within itself on fine dust particles. So, the fog is a cloud with its base at or very near to the ground.

• Because of the fog and mist, the visibility becomes poor to zero. In urban and industrial centres smoke provides plenty of nuclei which help in the formation of fog and mist.
• Such a condition when fog is mixed with smoke, is described as smog.
• The only difference between the mist and fog is that mist contains more moisture than the fog.
• In mist each nuceli contains a thicker layer of moisture. Mists are frequent over mountains as the warm air rises up the slopes and meets a cold surface.
• Fogs are drier than mist and they are prevalent where warm currents of air come in contact with cold currents. Fogs are mini clouds in which condensation takes place around nuclei provided by the dust, smoke, and the salt particles.

NCERT MCQ ON RECORDING OF TRANSACTION-I:

Q1.Which of the following equation’s correct?
(a) Assets = Liabilities – Capital
(b) Assets = Capital – Liabilities
(c) Assets = Liabilities + Capital
(d) Assets = External Equities

Answer: (c) Assets = Liabilities + Capital

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Q2.Which of the following is correct?
(a) Profit/Loss = Closing Capital + Additional Capital – Drawings – Opening Capital
(b) Profit/Loss = Closing Capital-Drawings-Additional Capital – Opening Capital
(c) Profit/Loss = Opening Capital + Drawings made – Additional Capital – Closing Capital
(d) Profit/Lose = Closing Capital + Drawings made – Additional Capital – Opening CapitalAnswer

Answer: (d) Profit/Lose = Closing Capital + Drawings made – Additional Capital – Opening Capital

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Q3.The liabilities of a firm are Rs. 60,000 and the capital of the proprietor is Rs. 40,000. The total assets are:
(a) 60,000
(b) 1,00,000
(c) 20,000
(d) 40,000

Answer: (b) 1,00,000

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Q4.If a film borrows a sum of money, there will be
(a) Increase in capital
(b) Decrease in capital
(c) No effect on capital
(d) None of the above

Answer: (a) Increase in capital

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Q5.Debit Means
(a) an increase in asset
(b) a decrease in asset
(c) an increase in liability
(d) an increase in capital

Answer: (a) an increase in asset

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Q6.Journal is a book of in accounting.
(a) All non-cash transactions
(b) Secondary entry
(c) Original entry
(d) All cash transaction.Answer

Answer: (c) Original entry

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Q7.The following account has a debit balance
(a) Creditor’s A/c
(b) Capital A/c
(c) Building A/c
(d) Loan A/c

Answer: (c) Building A/c

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Q8.Ledger is a book of …………. in accounting.
(a) All non-cash transactions
(b) Secondary entry
(c) Original entry
(d) All cash transactions

Answer: (b) Secondary entry

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Q9.The process of recording a business transaction in the journal is called
(a) Costing
(b) Balancing
(c) Posting
(d) Journalising

Answer: (d) Journalising

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Q10.Which of the following is a cash transaction?
(a) Sold goods
(b) Sold goods to Ravinder
(c) Sold goods to Ravinder on credit
(d) Sold goods to Ravinder on account.Answer

Answer: (a) Sold goods

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Fill in the blanks

Q1.The accounting voucher are based on …………….

Answer: Supporting

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Q2.Both debit and credit aspects of a transaction are shown by …………… vouchers.

Answer: Transfer

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Q3.Accounting equation satisfies the …………….. concept of accounting.

Answer: Dual

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Q4.Liabilities = ……………….. – Capital

Answer: Assets

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Q5.Accounting equation serves as a basis for preparing …………….

Answer: Balance Sheet

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Q6.Journalising is the process of entering transactions in ………………

Answer: Journal

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Q7.The explanation of a Journal entry is known as ……………….Answer

Answer: Narrations

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Q8.Transactions, when recorded in journal, are known as ………………

Answer: Entries

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Q9.Ledger account gives the folio of ………………….Answer

Answer: Journal

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Q10The balance of capital account is usually ………………… balance.

Answer: Credit

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NCERT MCQ ON THEORY BASE OF ACCOUNTING:

Q1.During the lifetime of an entity accounting produce financial statements in accordance with which basic accounting concept:
(a) Conservation
(b) Matching
(c) Accounting period
(d) None of the aboveAnswer

Answer: (c) Accounting period

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Q2.When information about two difference enterprises have been prepared presented in a similar manner the information exhibits the characteristic of:
(a) Verifiability
(b) Relevance
(c) Reliability
(d) None of the aboveAnswer

Answer: (d) None of the above

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Q3.concept that a business enterprise will not be sold or liquidated in the near future is known as :
(a) Going concern
(b) Economic entity
(c) Monetary unit
(d) None of the aboveAnswer

Answer: (a) Going concern

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Q4.The primary qualities that make accounting information useful for decision-making are
(a) Relevance and freedom from bias
(b) Reliability and comparability
(c) Comparability and consistency
(d) None of the aboveAnswer

Answer: (b) Reliability and comparability

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Fill in the blank with correct word:
Q1.Recognition of expenses in the same period as associated revenues is called ………………. concept.

Answer: Matching

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Q2.The accounting concept that refers to the tendency of accountants to resolve uncertainty and doubt in favour of understating assets and revenues and overstating liabilities and expenses is known as ………………….

Answer: Conservatism

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Q3.Revenue is generally recognised at the point of sale denotes the concept of ………………….

Answer: Revenue Realisation

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Q4.The ………………… concept requires that the same accounting method should be used from one accounting period to the next.

Answer: Consistency

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Q5.The ……………….. concept requires that accounting transaction should be free from the bias of accountants and others.

Answer: Objectivity.

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NCERT MCQ ON INTRODUCTION TO ACCOUNTING:

Q1.Which of the following is not a business transaction?
(a) Bought furniture of Rs. 10,000 for business
(b) Paid for salaries of employees Rs. 5,000
(c) Paid sons fees from her personal bank account Rs. 20,000
(d) Paid sons fees from the business Rs. 2,000

Answer: (c) Paid sons fees from her personal bank account Rs. 20,000

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Q2.Deepti wants to buy a building for her business today. Which of the following is the relevant data for his decision?
(a) Similar business acquired the required building in 2000 for Rs. 10,00,000
(b) Building cost details of 2003
(c) Building cost details of 1998
(d) Similar building cost in August, 2005 Rs. 25,00,000Answer

Answer: (a) Similar business acquired the required building in 2000 for Rs. 10,00,000

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Q3.Which is the last step of accounting as a process of information?
(a) Recording of data in the books of accounts
(b) Preparation of summaries in the form of financial statements
(c) Communication of information
(d) Analysis and interpretation of informationAnswer

Answer: (c) Communication of information

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Q4.Which qualitative characteristics of accounting information is reflected when accounting information is clearly presented?
(a) Understandability
(b) Relevance
(c) Comparability
(d) ReliabilityAnswer

Answer: (a) Understandability

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Q5.Use of common unit of measurement and common format of reporting promotes
(a) Comparability
(b) Understandability
(c) Relevance
(d) ReliabilityAnswer

Answer: (a) Comparability

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Complete the following sentences with appropriate words

Q1.Information in financial reports’is based on ……………. transactions.

Answer: economic

Q2.Internal users are the ……………… of the business entity.

Answer: management/employees

Q3.A ………………. would most likely use an entities financial report to determine whether or not the business entity is eligible for a loan.

Answer: creditor

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Q4.The Internet has assisted in decreasing the ………………… in issuing financial reports to users.Answer

Answer: time-gap

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Q5.………………….. users are groups outside the business entity, who uses the information to make decisions about the business entity.Answer

Answer: external

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Q6.Information is said to be relevant if it is ……………….Answer

Answer: free from bias

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Q7.he process of accounting starts with …………….. and ends with ……………….Answer

Answer: identifying the transactions, communicating information

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Q8.Accounting measures the business transactions in terms of ……………….. units.

Answer: monetary

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Q9.Identified and measured economic events should be recording in ……………….. order.

Answer: chronological

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In This Post we are  providing Chapter- 16 ENVIRONMENTAL ISSUES 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

NCERT MOST IMPORTANT QUESTIONS ON ENVIRONMENTAL ISSUES

Question 1.
Define pollution. Compare the biodegradable and non-biodegradable pollutants.
Answer:
Pollution: “Environmental pollution is an unfavorable alteration of our surroundings largely as a by-product of man’s actions through direct or indirect effects of changes in energy patterns, radiation levels, chemical and physical conditions and abundance of organisms.”

Differences between biodegradable and non-biodegradable pollutants:

Biodegradable Pollutants	Non-biodegradable Pollutants
1. These wastes can be broken down into harmless substances naturally.	1. These cannot be broken down into harmless substances naturally.
2. The disposal of biodegradable wastes is easy and therefore, maintains balance in the ecosystem. Example. Cattle dung	2. Their disposal is not easy and is a problem. Example. D.D.T., plastics.

Question 2.
What is air pollution? List various air pollutants.
Answer:
Air pollution: The release of harmful materials into the air is called air or atmospheric pollution. It is the degradation of air quality and atmospheric conditions.

Air pollutants include gaseous materials, suspended particles, and radioactive substances.
1. The gaseous pollutants of the air come from combustion in motor vehicles and industries. These include CO, C0₂, NO, N0₂, S0₂, S0₃, hydrocarbons, fluorides, and photochemical oxidants such as peroxyacetyl nitrate (PAN), ozone (0₃), and aldehydes. PAN is a secondary pollutant formed in the air by the interaction between nitrogen oxides and hydrocarbons in the presence of sunlight. It is more toxic than the primary pollutants. An increase in toxicity by the reaction among pollutants is called synergism.

2. The particulate contaminants of air also come from industries and automobiles. These include fly-ash, soot, metal dust, cotton fibers, asbestos, fibers, lead, aerosols (chlorofluorocarbons or CFCs), polychlorinated biphenyls (PCBs), tobacco smoke, smog, pollen, spores, cysts, and bacteria.
(in) Radioactive substances released by nuclear explosions and war explosives are also very harmful air pollutants.

Question 3.
Define a pollutant. How many types of pollutants are there?
Answer:
Pollutant: It is a substance (e.g. dust, smoke), chemical (e.g. S0₂), or factor (e.g. heat, noise) that on release into the environment has an actual or potentially adverse effect on human interests. A pollutant can also be defined as a constituent in the wrong amount, at the wrong place, or at the wrong time.

Question 4.
What measures do you suggest to control pollution from automobile exhaust?
Answer:
Control of pollution from automobile exhaust:

1. Efficient engines can reduce the number of unburnt hydrocarbons from vehicuLar emissions.
2. Use of cataLytic converters to convert harmful gases to harmless.
3. Use of good quality fuel.
4. Unleaded petroL can reduce the amount of lead in the exhaust.
5. The use of CNG (compressed natural gas) Lowers the toxic contaminants in the exhaust.

Question 5.
Blends of polyblend and bitumen, when used, help to increase road life by a factor of three. What is the reason?
Answer:
Polyblend is a fine powder of recycled modified plastic. The binding property due to increased cohesion and enhanced water-repelling property of plastic makes the road last longer besides giving added strength to withstand more loads.

This is because:

• Plastic increases the melting point of the bitumen which would prevent it from melting in India’s hot and extremely humid climate, where temperature frequently crosses 45°C.
• Rainwater will not seep through because of the plastic in the tar.

Question 6.
“Indiscriminate human activities have strengthened the greenhouse effect resulting in Global Warming.” Give the relative contribution of various Greenhouse Gases in the form of a pie chart and explain the rate of the energy of sunlight reaching the earth’s surface contributing towards Global Warming. (CBSE Sample Paper 2020)
Answer:
a)
(b) Rate of the energy of sunlight:

• Clouds and gases reflect one-fourth of incoming solar radiations.
• Some of the energy is absorbed by clouds and gases.
• Thus only half of the solar energy falls on the surface of the earth.
• The small amount of energy is reflected back.
• Earth surface re-emits heat in the form of infrared radiations.
• The major fraction of solar energy is absorbed by atmospheric gases.

Question 7.
How does a scrubber function?
Answer:
Scrubber: A scrubber can remove gases like sulfur dioxide. In a scrubber, the exhaust is passed through a spray of water or lime. Water dissolves gases and lime reacts with sulfur dioxide to form a precipitate of calcium sulfate or sulfite.

Question 8.
Discuss the causes and effects of global warming.
Answer:
Global warming: The increase in global mean temperature due to the enhanced greenhouse effect is called global warming.

Effects of global warming:
1. Effect on weather and climate.
(а) The average temperature of the earth may increase by 1.4° to 5.8°C by the year 2100.
(б) Winter precipitation may decrease at lower altitudes.
(c) Frequency of droughts, floods may increase.
(d) Climatic change is a threat to human health in tropical and subtropical countries.

2. Sea level change. Sea level had been raised by 1 to 2 mm per year during the 20th century. It is predicted that by the year 2100, the global mean sea level can increase up to 0.88 m over the 1990 level. Global warming may contribute to sea-level rise due to the thermal expansion of the ocean.

3. Effect on a range of species distribution. Vegetation may extend 250-600 km poleward with a global rise in temperature by 2 to 5°C during the 21st century.

4. Effect on food production. Increased temperature will cause an eruption of plant diseases and pests and vast growth of weeds.

Question 9.
Show the relative contribution of greenhouse gases to total global warming.
Answer:
Greenhouse gases:

The relative contribution of various greenhouse gases to total Global warming.

Question 10.
Make a chart illustrating the kinds of water pollutants.
Answer:
Classification of water pollutants:

In This Post we are  providing Chapter- 13 ORGANISMS AND POPULATIONS 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

NCERT MOST IMPORTANT QUESTIONS ON ORGANISMS AND POPULATIONS

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1. How does the shape of age pyramid reflect the growth status of a population?
Ans.Shape of pyramids reflects growth statusof the population (a) growing (b) Stable (c) declining.

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2. Darwin showed that even a slow growing animal like elephant could reach enormous number in absence of checks. With the help of your understanding of growth models, explain when is this possible? Why is this notion unrealistic?
Ans. Possible if the growth model is Exponential, i.e., having unlimited resources. Its an unrealistic situation because resources are limited. Hence, it follows logistic growth model.

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3. How will you measure population density in following cases?
(i) fish in a lake
(ii) tiger census in a national park
(iii) single huge banyan tree with large canopy .
Ans. (i) fish caught per trap.
(ii) number per unit area
(iii) percentage cover in biomass.

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4. Species facing competition might evolve mechanism that promotes coexistence rather than exclusion. Justify this statement in light of Gause’s competitive exclusion principle, citing suitable examples.
Ans.State Gause’s competitive exclusion principle.Mechanisms is resource partitioning. E.g., experiment of Mac Arthur on Warblers (Refer page 325, NCERT book, Biology – XII).

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5.Describe the specific adaptation of xerophytes with respect to root system, stem & leaves.
Ans. i) ADAPTATIONS INROOTS :- Xerophytes have well developed & extensively branched long rootsystem. While some perennial xerophytes of succulent nature possess extensive but shallow root system.They can absorb water from dew drops & small rain droplets.
ii) ADAPTATION IN STEM:- stems of woody xerophytes are comparatively stunted hard & rigid. Theymay be covered with thick e.g. Acacia main stem & branches may occur as think, fleshy, flattened & greenmodified structure called phylloclade.
iii) ADAPTATION IN LEAVES:- Leaves are usually short sized which decreases the chances of gettingover – heated when exposed to solar radiation & thus by reducing rate of transpiration. Leaves ofssxerophytes are usually thick, fleshy green & leathery which are known to store water.

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6.List the important characteristics of a population & Explain?
Ans.A population has following four major characteristics :-
i) Population Density :- The size of a population in relation to a definite unit of space is termed aspopulation density. The maximum limit of density depends upon energy flow in an ecosystem, nutritionalstatus of trophic level & metabolic equilibrium. Population density can be mathematically calculatedas : D=N/atD=N/at
ii) Birth Rate / Natality :- The birth rate or natality denotes the produced number of new individuals byany natural method in per unit time. The birth can be expressed lay formula B=NntB=Nnt
iii) Death Rate / Mortality :- It refers to death rate of individuals in the population. It is expressed in asnumber of individual dying in a given period.Death Rate = no of death in population Timeno of death in population Time
iv) Carrying Capacity:- Each habitat or ecosystem has a certain space which can accommodate a finitenumber of organisms depending on its size & productivity. This is called carrying capacity

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7.Describe the specific adaptations of hydrophytes with respect to roots, stem & leaves?
Ans. i) ADAPTATIONS IN ROOTS:- Root system is feebly developed &unbranched some floating plants orsubmerged plants lack roots Root hairs are absent except rooted floating hydrophyte. True root caps areabsent.
ii) ADAPTATIONS IN STEM :- In submerged hydrophytes, stems are long slender & flexible whereas inthe free – floating hydrophytes stem are modified as thick, stout, stoloniferous& occur horizontal onwater surface.
iii) ADAPTATIONS IN LEAVES:- Leaves are thin, long, ribbon shapes submerged forms. In free floatingplants, the petioles of leaves show indefinite power of growth.

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8.Name& explain the bind of interaction in the following.
i) Algae & fungi in
ii) Head louse & humans
iii) Hermit crab & sea anemone.
Ans. i) Algae & fungi in lichens :- Lichens shows an intimate mutualistic interaction in with both fungushelps in absorption of nutrients & provides protection, while algae or cyanobacterium prepares the food.
ii) Head louse & humans:- Head louse shows ectoparasitism on humans in which head louse is gettingnutrition from human body & is thus benefited while human beings are harmed.
iii) Hermit crab & sea anemone:- Hermit crab & sea anemone shows commensalism as hermit crab isbenefited because it gets protection from predators which stays away from stinging tentacles of the seaanemone.

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9.Mention the different defense mechanism to reduce the impact of predation?
Ans.plant species evolved various defense mechanism to reduce impact of predation :-
i) Certain insect species & frogs have camouflage or cryptic colouration to avoid detection by their predators.
ii)Some animals like monarch butterfly are highly distasteful to their predators because they accumulate a certain chemical by feeding on poisonous weeds during its caterpillar stage.
iii)Some prey are poisonous & hence are avoided by predators .
iv)Plants have evolved certain morphological, or chemical defense mechanism against herbivores e.g. thorns in bougainvillea.
v)plants also produce certain chemicals which functions as :-

• They make animal feel sick.
• They may inhibit them from feeding.
• They may interfere with digestion.
• They may directly kill them.

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10.Mutualism often involves co-evolution of mutualists. Describe taking the example of animal plant (wasp-fig) relationship.
Ans.Plants need the help of animals for pollination their flowers & dispersing their seeds. Animals obviously have to be paid fees for the services that plants expect from them. Plants offer rewards or fees in the form of seed dispersers “plant – animal interactions often involve co-evolution of the mutualists that is, the evolution of the flower & its pollinator species can be pollinated only by its partner wasp species & no other species. The female wasp uses the fruit not only as an oviposition site but uses the developing seeds within the fruit for nourishing its larvae. The wasp pollinates the fig inflorescence while searching for suitable egg-laying sites. In return for the favors of pollination the fig offers the wasp some of its developing seeds as food for the developing wasp larvae.

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In This Post we are  providing Chapter- 14 ECOSYSTEM 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

NCERT MOST IMPORTANT QUESTIONS ON ECOSYSTEM

Question 1.
What is an ecosystem? Write its main components.
Answer:
Ecosystem. A stable, self-supporting ecological unit resulting from an interaction between a biotic community (living organisms) and its abiotic environment is called an ecosystem.

An ecosystem comprises two main components:

1. biotic including plants, animals, and microorganisms and
2. abiotic mainly including substratum, water, minerals, temperature, carbon dioxide, and oxygen. It must also receive a constant supply of energy (light).

Question 2.
Briefly describe the biotic components of an ecosystem.
Answer:
Biotic components: Of an ecosystem’s biotic components, the plants are producers as they introduce food materials and energy into the living world. The animals are consumers because they get food and energy by consuming plants directly thus called primary consumers (herbivores); secondary/ tertiary consumers (carnivores) obtain energy and food indirectly from plants, and microorganisms are decomposers for they flourish by breaking dead organic matter to simple substances that are returned to environment for reuse by plants.

In an ecosystem, nutrients are used again and again in a cyclic manner, whereas energy trapped from sunlight is lost as heat.

Question 3.
Give an account of factors affecting the rate of decomposition.
Answer:
Factors affecting decomposition:

1. The upper layer of soil is the main site of decomposition processes in the ecosystem.
2. The rate of decomposition of detritus is affected by climatic factors and the chemical quality of detritus.
3. Temperature and soil moisture affect the activities of root microbes.
4. The chemical quality of detritus is determined by the relative proportion of water-soluble substances, polyphenols, lignin, and nitrogen.

Question 4.
List the important differences between producers and decomposers.
Answer:
Differences between producers and decomposers:

Producers	Decomposers
(i) These are organisms that synthesize their own food by the process of photosynthesis. These are also called autotrophs.	(i) These organisms feed on the dead bodies of plants and animals.
(ii) They convert the raw materials in the earth and water into carbohydrates which give them food.	(ii) They enrich the earth with raw materials trapped in dead bodies of plants and animals.
(iii) They are dependent on decomposers for soil nutrients.	(iii) They are dependent on plants and animals for their food.

Question 5.
Explain the terms standing crop, biomass, and standing state.
Or
State what does a standing crop of a trophic level represent? (CBSE Outside Delhi 2013)
Answer:
Standing crop: Each trophic level has a certain mass of living material at a particular time called the standing crop. Biomass. The standing crop is measured as the mass of living organisms (biomass) or the number in a unit area. The biomass of a species is expressed in terms of fresh or dry weight. Measurement of biomass in terms of dry weight is more accurate as the moisture content of biomass fluctuates greatly.

Standing State: Organisms need a constant supply of nutrients to grow, reproduce and regulate various body functions. The amount of nutrients, such as carbon, nitrogen, phosphorus, calcium, etc. present in the soil at any given time, is referred to as the standing state. It varies in different kinds of ecosystems and also on a seasonal basis.

Question 6.
Give a diagrammatic representation of trophic levels in an ecosystem.
Answer:

Diagrammatic representation of trophic levels in an ecosystem.

Question 7.
Sometimes due to biotic/abiotic factors, the climax remains in a particular serai stage (pre-climax) without reaching climax. Do you agree with this statement? If yes give a suitable example.
Answer:
Sometimes pre-climax stage remains in a particular serai stage without reaching the climax because during ecological succession any change in abiotic and biotic components may affect the particular serai stage, leading to the pre-climax stage before the climax is achieved.

This type of condition occurs in the presence of seeds and other propagules. This secondarily based area may be invaded by moss or exotic weeds thus exhibiting succession seriously and the climax community is never regenerated.

Question 8.
Explain the meaning of the food web and illustrate with a ray diagram.
Answer:
Food web. In nature, the food chains are not strictly linear, but are interrelated and interconnected with one another. Generally, the various food chains in a community are so interlinked as to form a sort of web. As a result, one animal may be a link in more than one food chain.

A network of food chains in a community is referred to as a food web. A food web may have all or some of the three types of food chains, i.e. detritus, predator, and parasitic. The food webs become more complicated because of the variability of taste and preference, availability and compulsion, and several other factors at each level. For example, tigers normally do not eat fish or crab, but they are forced to feed on them in the Sundarbans.

Question 9.
Starting from a bare rock or a site of volcanic eruption, trace the organisms that participate in the process of succession.
Or
Describe the process of succession on a base rock. (CBSE 2012)
Answer:

1. Simple organisms appear first of all on such an exposed site as lichens. Lichens make conditions suitable for mosses (bryophytes).
2. Gradually a variety of complex organisms join the community.
   Stages of biotic succession.
3. Finally, large plants, trees, etc. appeared. It can be illustrated that lichens are pioneers, followed by mosses, annual grasses, perennial herbs, shrubs, and finally trees along with their characteristic animal populations.

Question 10.
How does succession differ in terrestrial and aquatic systems? Give salient points. (CBSE Delhi 2019)
Answer:
Differences between terrestrial and aquatic succession:

Succession on land/rock	Succession In Water
1. lichens and mosses are the pioneer community.	1. Phytoplankton is a pioneer community.
2. Soil is formed by the action of lichens.	2. Waterbodies are prone to silting due to soil erosion.
3. There is a deficiency of water.	3. Water is abundant.
4. The various stages are crustose lichen stage, foliose lichen stage, moss stage, herb stage, shrub stage, and forest stage.	4. The various stages are the plankton stage, floating stage, rooted stage, swamp stage, woodland stage, and forest stage.