SHORT ANSWER TYPE QUESTION:
Q1. What do you understand by the term ‘ecology’?
Answer
Ecology is a scientific study of the interactions of organisms with their physical environment and with each other.
Q2. What is an ecological system? Identify the major types of ecosystems in the world.
Answer
The interactions of a particular group of organisms with abiotic factors within a particular habitat resulting in clearly defined energy flows and material cycles on land, water and air, are called ecological systems.
Ecosystems are of two major types:
• Terrestrial
• Aquatic
Q3.What is a food-chain? Give one example of a grazing food-chain identifying the various levels.
Answer
Thes sequence of eating and being eaten and the resultant transfer of energy from one level to another is known as the food-chain.
Grass (first level) is eaten by deer (intermediate level) is eaten by lion (last level).
Q4. What do you understand by the term ‘food web’? Give examples.
Answer
A network of food chains mixed together to form a food web. For example, a mouse feeding on grain may be eaten by different secondary consumers (carnivores) and these carnivores may be eaten
by other different tertiary consumers (top carnivores).
Q5. What is a biome?
Answer
A biome is a plant and animal community that covers a large geographical area.
Q6. What are bio-geochemical cycles? Explain how nitrogen is fixed in the atmosphere.
Answer
The balance of the chemical elements is maintained by a cyclic passage through the tissues of plants and animals. The cycle starts by absorbing the chemical elements by the organism and is returned to the air, water and soil through decomposition. These cycles are largely energised by solar insolation. The cyclic movements of chemical elements of the biosphere between the organism and the
environment are referred to as biogeochemical cycles. Bio refers to living organisms and geo to rocks, soil, air and water of the earth.
Ninety per cent of fixed nitrogen is biological. The principal source of free nitrogen is the action of soil micro-organisms and associated plant roots on atmospheric nitrogen found in pore spaces of the soil. Nitrogen can also be fixed in the atmosphere by lightning and cosmic radiation. In the oceans, some marine animals can fix it.
Q7. What is an ecological balance? Discuss the important measures needed to prevent ecological imbalances.
Answer
Ecological balance is a state of dynamic equilibrium within a community of organisms in a habitat or ecosystem. It can happen when the diversity of the living organisms remains relatively stable.
Ecological imbalances: Ecological balance may be disturbed due to the introduction of new species, natural hazards or human causes.
The important measures to prevent ecological imbalances are:
• By not interfering in nature.
• By controlling population.
• By reusing and recycling things.
• By using natural resources judiciously.
• Afforestation should be encouraged.
Proper knowledge and management are necessary for protecting and conserving the ecosystems.
Long Answer Type Questions
Q1.Explain in detail about carbon cycle.
Answer:
The Carbon Cycle: Carbon is one of the basic elements of all living organisms. It forms the basic constituent of all the organic compounds. The biosphere contains over half a million carbon compounds in them. The carbon cycle is mainly the conversion of carbon dioxide. This conversion is initiated by the fixation of carbon dioxide from the atmosphere through photosynthesis. Such conversion results in the production of carbohydrate, glucose that may be converted to other organic compounds such as sucrose, starch, cellulose, etc. Here, some of the carbohydrates are utilised directly by the plant itself. During this process, more carbon dioxide is generated and is released through its leaves or roots during the day.
The remaining carbohydrates not being utilised by the plant become part of the plant tissue. Plant tissues are either being eaten by the herbivorous animals or get decomposed by the micro- organisms. The herbivores convert some of the consumed carbohydrates into carbon dioxide for release into the air through respiration. The micro-organisms decompose the remaining carbohydrates after the animal dies. The carbohydrates that are decomposed by the micro-organisms then get oxidised into carbon dioxide and are returned to the atmosphere.
Q2.Explain in detail about food chain.
Answer:
Food Chain: This sequence of eating and being eaten and the resultant transfer of energy from one level to another is known as the food-chain. Transfer of energy that occurs during the process of a food chain from one level to another is known as flow of energy. The food- chains get interlocked with one another. This inter- connecting network of species is known as food web. For example, a plant eating beetle feeding on a paddy stalk is eaten by a frog, which is, in turn, eaten by a snake, which is then consumed by a hawk. This sequence of eating and being eaten and the resultant transfer of energy from one level to another is known as the food-chain.
- Producers: The producers include all the green plants, which manufacture their own food through photosynthesis.
- Primary consumers: The primary consumers include herbivorous animals like deer, goats, mice and all plant-eating animals.
- Carnivores: The carnivores include all the flesh-eating animals like snakes, tigers and lions. Certain carnivores that feed also on carnivores are known as top carnivores like hawks and mongooses.
- Decomposers: Decomposers are those that feed on dead organisms (for example, scavengers like vultures and crows), and further breaking down of the dead matter by other decomposing agents like bacteria and various micro-organisms.
Generally, two types of food-chains are recognised: grazing food-chain and detritus food-chain.
- Grazing food chain: In a grazing food- chain, the first level starts with plants as producers and ends with carnivores as consumers at the last level, with the herbivores being at the intermediate level. There is a loss of energy at each level which may be through respiration, excretion or decomposition. The levels involved in a food- chain range between three to five and energy is lost at each level.
- A detritus food-chain: A detritus food chain is based on autotrophs energy capture initiated by grazing animals and involves the decomposition or breaking down of organic wastes and dead matter derived from the grazing food-chain.
Q3.Explain about the working and structure of ecosystem.
Answer:
The structure of an ecosystem involves a description of the available plant and animal species. From a structural point of view, all ecosystems consist of abiotic and biotic factors. Abiotic factors include rainfall, temperature, sunlight, atmospheric humidity, soil conditions, inorganic substances (carbon dioxide, water, nitrogen, calcium, phosphorus, potassium, etc.). Biotic factors include the producers, the consumers (primary, secondary, tertiary) and the decomposers. The producers include all the green plants, which manufacture their own food through photosynthesis.
The primary consumers include herbivorous animals like deer, goat, mice and all plant-eating animals. The carnivores include all the flesh-eating animals like snakes, tigers and lions. Certain carnivores that feed also on carnivores are known as top carnivores like hawks and mongooses. Decomposers are those that feed on dead organisms (for example, scavengers like vultures and crows), and further breaking down of the dead matter by other decomposing agents like bacteria and various micro- organisms.
Q4.Explain in detail about nitrogen cycle.
Answer:
Nitrogen is a major constituent of the atmosphere comprising about seventy- nine per cent of the atmospheric gases. It is also an essential constituent of different organic compounds such as the amino acids, nucleic acids, proteins, vitamins and pigments. Only a few types of organisms like certain species of soil bacteria and blue green algae are capable of utilising it directly in its gaseous form. Generally, nitrogen is usable only . after it is fixed. Ninety percent of fixed nitrogen is biological. The principal source of free nitrogen is the action of soil micro-organisms and associated plant roots on atmospheric nitrogen found in pore spaces of the soil.
Nitrogen can also be fixed in the atmosphere by lightning and cosmic radiation. In the oceans, some marine animals can fix it. After atmospheric nitrogen has been fixed into an available form, green plants can assimilate it. Herbivorous animals feeding on plants, in turn, consume some of it. Dead plants and animals, excretion of nitrogenous wastes are converted into nitrites by the action of bacteria present in the soil. Some bacteria can even convert nitrites into nitrates that can be used again by green plants. There are still other types of bacteria capable of converting nitrates into free nitrogen, a process known as denitrification.
Q5.Explain the features of different forest biomes of the world.
Answer:
Forest biomes are of following types:
1. Tropical Equatorial Forest: Found in 10° N-S
Temp. 20-25°C, evenly distributed Acidic, poor in nutrients Rich in nutrients
2. Tropical Deciduous Forest: Found in 10°-25° N-S
Temp. 25-30°C, Rainfall, ave. ann. 1,000 mm, seasonal
3. Temperate: Found in Eastern North America, N.E. Asia, Western and Central Europe
Temp. 20-30° C, Rainfall evenly distributed 750- 1,500 mm, Well- defined seasons and distinct winter. Fertile, en-riched with decaying litter
4. Boreal: Found in Broad belt of Eurasia and North America (parts of Siberia, Alaska, Canada and Scandinavia).
Short moist moderately warm summers and long cold dry winter; very low temperatures. Precipitation mostly snowfall 400 -1,000 mm.
Acidic and poor in nutrients, thin soil cover.
Rich in nutrients with little or no organic matter.
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