Q 1 – What do you understand by the term ‘ecology’?
Ans. It is a scientific study of the interactions of organisms with their physical environment and with each other.
Q 2 – What is an ecological system? Identify the major types of ecos_ stems in the world.
Ans. The diversity of life-forms is maintained to bring a kind of balance. This balance is maintained in a particular proportion so that a healthy interaction between the biotic and the abiotic components goes on. 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 and aquatic. Terrestrial ecosystem can be further be classified into ‘biomes’. Aquatic ecosystems can be classed as marine and freshwater ecosystems.
Q 3 – What is food-chain? Give one example of a grazing food-chain identifying the various levels.
Ans. The sequence of eating and being eaten and the resultant transfer of energy from one level to another is known as the food chain. There are two types of food chain, grazing food chain and detritus food chain.
1. In a grazing food chain, the first level starts with plants as producers and ends with carnivores as consumers at last level, with the herbivores being at the intermediate level. A capture initiated by grazing detritus food chain is based on autographs energy capture initiated by grazing animals and involves the decomposition or breaking down of organic wastes and death matter derived from the grazing food chain. For example plant- beetle- paddy stalk-frog-snake-hawk
2. 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.
Q 4 – What do you understand by the term ‘food web’? Give examples.
Ans. The interconnecting network of species is known as food web. 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). In such situations, each of the carnivores may consume more than one type of prey. As a result, the food- chains get interlocked with one another.
Q 5 – What is a biome?
Ans. A biome is a plant and animal community that covers a large geographical area. The boundaries of different biomes on land are determined mainly by climate. Therefore, a biome can be defined as the total assemblage of plant and animal species interacting within specific conditions. These include rainfall, temperature, humidity and soil conditions. Some of the major biomes of the world are: forest, grassland, desert and tundra biomes.
Q 6 – What are bio-geochemical cycles? Explain how nitrogen is fixed in the atmosphere.
Ans. The sun is the source of all energy on earth. This energy initiates life processes in the biosphere through photosynthesis, the main source of food and energy for green plants. A very small fraction of about 0.1 percent of solar energy reaching earth is fixed in photosynthesis. More than half is used for plant respiration and the remaining part is temporarily stored or is shifted to other portions of the plant. During photosynthesis carbon dioxide is converted into organic compounds and oxygen.
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 cyclic movement of chemical elements of the biosphere between the organism and the environment are referred to as bio-geochemical cycles.
Fixing of nitrogen in the atmosphere Action of soil micro-organisms and associated plant roots on atmospheric nitrogen found in pore spaces of the soil comprise the principal source of free nitrogen. Lighting and cosmic radiation can also fix nitrogen in the atmosphere.
Q 7 – What is an ecological balance? Discuss the important measures needed to prevent ecological imbalance
Ans. 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. Gradual changes do take place but that happens only through natural succession. It can also be explained as a stable balance in the numbers of each species in an ecosystem. This occurs through competition and cooperation between different organisms where population remains stable.
This balance is brought about by the fact that certain species compete with one another determined by the environment in which they grow. This balance is also attained by the fact that some species depend on others for their food and sustenance. Such accounts are encountered in vast grasslands where the herbivorous animals (deer, zebras, buffaloes, etc.) are found in plenty.
Ecological balance may be disturbed due to the introduction of new species, natural hazards or human causes. Human interference has affected the balance of plant communities leading to disturbances in the ecosystems. Such disturbances bring about numerous . secondary successions. Human pressure on the earth’s resources has put a heavy toll on the ecosystem. This has destroyed its originality and has caused adverse effects to the general environment. Ecological imbalances have brought many natural calamities like floods, landslides, diseases, erratic climatic occurrences, etc. There is a very close relationship between the plant and animal communities within particular habitats. Diversity of life in a particular area can be employed as an indicator of the habitat factor. Proper knowledge and understanding of such factors provide a strong base for protecting and conserving the ecosystems.
Q 8 – Name important biomes of the world.
Ans. A biome is a plant and animal community that covers at large geographical area. Abiome can be defined as the total assemblage of plant and animal species interacting within specific conditions. These include rainfall, temperature, humidity and soil conditions. Some of the major biomes of the world are forest, grassland, desert and tundra biomes.
Q 9 – Who are primary and secondary consumers?
Ans. The primary consumers include herbivorous animals like deer, goats, 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.
Q 10 – On whom do primary, secondary and tertiary producers depend?
Ans. Primary consumers depend on producers who make the food themselves. Secondary consumers depend on primary consumers and tertiary consumers in turn depend on secondary consumers.
Q 11 – Give meaning of food chain with examples.
Ans. The sequence of eating and being eaten and the resultant transfer of energy from one level to another is known as food chain. There are two types of food chain: grazing food chain and detritus food chain. For example plant- beetle- paddy stalk-frog-snake-hawk.
Q 12 – What kind of changes take place during photosynthesis?
Ans. During photosynthesis, carbon dioxide is converted into organic compounds and oxygen. Out of the total solar insolation that reaches the earth’s surface, only a very small fraction (0.1 percent) is fixed in photosynthesis. More than half is used for plant respiration and the remaining part is temporarily stored or is shifted to other portions of the plant.
Q 13 – What is water cycle?
Ans. All living organisms, the atmosphere and the lithosphere maintain between them a circulation of water in solid, liquid or gaseous form referred to as the water or hydrologic cycle.
Q 14 – What is carbon cycle?
Ans. 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 result in the production of carbohydrates, glucoses 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 microorganisms decompose the remaining carbohydrates after the animal dies.
Q 15 – How many types of biogeochemical cycles are there?
Ans. There are two types of biogeochemical cycles: the gaseous and the sedimentary cycle. In the gaseous cycle, the main reservoir of nutrients is the atmosphere and the ocean. In the sedimentary cycle, the main reservoir is the soil and the sedimentary and other rocks of the earth’s crust.
Q 16 – How does biosphere get formed?
Ans. The biosphere includes all the living components of the earth. It consists of all plants and animals, including all the micro-organisms that live on the planet earth and their interaction with the surrounding environment. The biosphere and its components are very significant elements of the environment. These elements interact with other components of the natural landscape such as land, water and soil.
Q 17 – What is ecological adaptation?
Ans. Different types of ecosystems exist with varying ranges of environmental conditions where various plants and animals species have got adapted through evolution. This phenomenon is known as ecological adaption.
Q 18 – Write a short note on biosphere.
Ans. Life on the earth is found almost everywhere. Living organisms are found from the poles to the equator, from the bottom of the sea to several kilometres in the air, from freezing waters to dry valleys, from under the sea to underground water lying below the earth’s surface. The biosphere includes all the living components of the earth. It consists of all plants and animals, including all the micro-organisms that live on the planet earth and their interactions with the surrounding environment.
The biosphere and its components are very significant elements of the environment. These elements interact with other components of the natural landscape such as land, water and soil. They are also influenced by the atmospheric elements such as the temperature, rainfall, moisture and sunlight. The interactions of biosphere with land, air and water are important to the growth, development and evolution of the organism.
Q 19 – Write and explain about oxygen cycle.
Ans. Oxygen is the main by-product of photosynthesis. It is involved in the oxidation of carbohydrates with the release of energy, carbon dioxide and water. The cycling of oxygen is a highly complex process. Oxygen occurs in a number of chemical forms and combinations. It combines with nitrogen to form nitrates and with many other minerals and elements to form various oxides such as the iron oxide, aluminium oxide and others. Much of oxygen is produced from the decomposition of water molecules by sunlight during photosynthesis and is released in the atmosphere through transpiration and respiration processes of plants.
Q 20 – Explain the difference between terrestrial eco system and aquatic ecosystem.
Ans. Difference between terrestrial and aquatic eco system is summarized below:
Q 21 – How does nitrogen get fixed?
Ans. Nitrogen is a major constituent of the atmosphere comprising about seventy- nine percent 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.
Q 22 – Explain in detail about carbon cycle.
Ans. 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.
Q 23 – Explain in detail about food chain.
Ans. 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.
Q 24 – Explain about the working and structure of ecosystem.
Ans. 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.
Q 25 – Explain in detail about nitrogen cycle.
Ans. 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
Q 26 – Explain the features of different forest biomes of the world.
Ans. 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.
Q 27 – How does an ecosystem work?
Ans. An ecosystem works with the help of producers and consumers. The producers include all the green plants, which manufacture their own food through photosynthesis. The primary consumers include herbivorous animals like deer, goats, 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.
Q 28 – Use a diagram to clear the concept of food chain.
Ans.
Q 29 – Differentiate between food chain and food web.
Ans. Food chains follow a single path as animals eat each other
Example:
- The sun provides food for grass.
- The grass is eaten by a grasshopper.
- The grasshopper is eaten by a frog.
- The frog is eaten by a snake.
- The snake is eaten by a hawk.
Food webs show how plants and animals are interconnected by different paths.
Example:
- Trees produce acorns which act as food for many mice and insects.
- Because there are many mice, weasels and snakes have food.
- The insects and the acorns also attract birds, skunks, and opossums.
- With the skunks, opposums, weasels and mice around, hawks, foxes, and owls can find food.
- They are all connected. Like a spiders web, if one part is removed, it can affect the vchole web.
Q 30 – Name three natural realms of the earth.
Ans. The three natural realms of the earth are the atmosphere, lithosphere, and hydrosphere.
Q 31 – What is ecology?
Ans. Ecology is the science that studies the interaction of organisms with their environment.
Q 32 – Who is known as the father of Ayurveda?
Ans. Charak is known as the father of Ayurveda.
Q 33 – What is ‘Charak Samhita’?
Ans. It is the book of Indian medicine written by Charak, the first century A.D. scholar, who has listed over 200 kinds of animals and, about 340 kinds of plants in this book,
Q 34 – How many species of living organisms exist today?
Ans. Over 5 million species of living organisms exist in the world today.
Q 35 – What is the science of classification of organisms called?
Ans. The science of the classification of organisms is called taxonomy.
Q 36 – Define ecosystem.
Ans. The biotic community along with the physical environment forms an interacting system is called the ecosystem.
Q 37 – Name the positive biotic interactions.
Ans. Mutualism and communalism are two positive biotic interactions.
Q 38 – Name some abiotic factors of the environment.
Ans. Temperature, water, light, humidity, wind, topography and mineral elements,
Q 39 – Give two examples of fungi.
Ans. Yeast and mushrooms are two examples of fungi.
Q 40 – Give two examples of herbivores and carnivores each.
Ans. Cattle and deer are herbivores, whereas tigers and lions are carnivores.
Q 41 – What are the major determinants of nature and the extent of a biome?
Ans. Rainfall, temperature range, nature, soil, barriers, latitude, and altitude are the major determinants of the nature and extent of a biome.
Q 42 – Where would you find the greatest variety of hoofed herbivore species?
Ans. The greatest variety of hoofed herbivorous species is found in tropical savanna.
Q 43 – Give some examples of hoofed herbivore species.
Ans. They include zebra, giraffe, elephant, kangaroos, and several kinds of antelopes.
Q 44 – Which areas in the world consist of deciduous forests?
Ans. The deciduous forests are found in the temperate region of north-central Europe, eastern Asia, and the eastern United States.
Q 45 – Name the principal grasslands of the world.
Ans. The principal grasslands of the world include prairies of Canada and the USA, the pampas of South America, the steppes of Europe and Asia, and veldts of Africa.
Q 46 – What constitutes the dominant vegetation of Taiga?
Ans. Pine, fir, cedar, hemlock, and spruce constitute the dominant vegetation of Taiga.
Q 47 – What kind of topography characterizes Tundra?
Ans. Tundra is a region characterized by snow, ice, and frozen soil for the most part of the year.
Q 48 – Identify the important determinants 6f marine ecosystems.
Ans. The important determinants of marine ecosystems are depth of water, distance from the snow, and drainage of glaciers and rivers.
Q 49 – Mention three vertical zones of the ocean on the basis of the availability of light for photosynthesis.
Ans. The three zones of oceans on the basis of availability of light for photosynthesis are: photic, aphotic, and abyssal.
Q 50 – Name the water bodies which form the freshwater environment.
Ans. The freshwater environment is formed by stagnant water bodies like lakes and ponds, and flowing water bodies like rivers and streams.
Q 51 – Name the major grasslands of the world.
Ans. Prairies, pampas, steppes, veldts, and downs.
Q 52 – What is an estuary?
Ans. The estuary is a zone of mixing of fresh and salty water.
Q 53 – What are lianas?
Ans. The jungle edge is a tangle of sun-loving woody climbers called lianas.
Q 54 – What are xerophytes?
Ans. Plants that are able to survive in dry regions are called xerophytes.
Q 55 – What is a bio in?
Ans. Natural ecological groups of plants and animals extend over large areas. Each of these major terrestrial ecosystems or distinctive terrestrial areas with their group of plants and associated animals are recognized as biomes. A biome is, therefore, the largest terrestrial community of plants and associated animals in interaction with the environment.
Q 56 – What kind of animals live in tropical rain forests?
Ans. The animals living in tropical rain forests include monkeys, snakes, ant-eaters, tropical birds, bats, large carnivorous animals, and a variety of fish in the rivers. Of all the species of insects known nearly 70 to S0% occur in the tropical rain forests.
Q 57 – What kind of flora and fauna characterize the deserts?
Ans. Deserts are characterized by scanty flora and fauna. Desert plants include different kinds of acacias, cacti, euphorbias, and other succulents. Ants, locusts, wasps, scorpions, spiders, lizards, rattlesnakes, a large number of insect-eating birds such as swifts and swallows, seed-eating quails, doves, desert rats, rabbits, foxes, jackals, and various cats are the common desert animals.
Q 58 – What kind of plant and animal life is supported by tropical savanna?
Ans. Savannas are characterized by coarse grass and scattered trees on the margins of the tropics where rainfall is seasonal. Wet seasons alternate with dry seasons. Plants and animals are drought-tolerant and do not show much diversity. This biome supports the greatest variety of hoofed herbivore species including the zebra, giraffe, elephant, and several kinds of antelopes. Kangaroos are found in the savannas of Australia.
Q 59 – What are the important features of the Mediterranean scrub forest as a biome?
Ans. This biome is also known as Chapparal. This is marked by very limited winter rain followed by drought in the rest of the year. The temperature is moderate under the influence of the cool, moist air of the oceans. The biome is characterized by broad-leaved evergreen vegetation. It is made up of fire-resistant resinous plants and drought-adapted animals.
Q 60 – Write a note on deciduous forests.
Ans. The deciduous forests are found in the temperate regions of north-central Europe, eastern Asia, and the eastern United States. The annual precipitation ranges between 75-150 cm. With the onset of autumn, most of the trees and shrubs become leafless. The vegetation comprises broad-leaved, hardwood trees such as oak, elm, beech, maple, and hickory. The fauna includes frogs, salamanders, turtles, snakes, lizards, squirrels, rabbits, deer, bears, raccoons, foxes, and songbirds.
Q 61 – Describe various vertical zones of the ocean.
Ans. The vertical zones of the ocean can be determined by the availability of light for photosynthesis. The lighted upper 200 meters form the photic or euphotic zone. The next zone, up to the depth of 2000 meters, gets less light which is insufficient for photosynthesis. This layer is called an aphotic zone. Below 2000 meters is the area of perpetual darkness, called the abyssal zone.
Q 62 – Distinguish between food chain and food web.
Ans. The food relation in its simplest form representing a producer, a primary consumer (herbivore), a secondary consumer (carnivore), and a decomposer is called a food chain. The next circle of such a food chain is called the food web.
Q 63 – Describe various structural components of an ecosystem.
Ans. Various structural components of an ecosystem are classified into two main groups:
- biotic or living, and
- abiotic or non-living
The biotic component of an ecosystem comprises the kinds, numbers, and distribution of living organisms. The abiotic component consists of the kinds, quantity, and distribution of physical and chemical factors such as light, temperature, water, oxygen, carbon, nitrogen, and minerals.
Q 64 – Define ‘ecosystem’ with examples.
Ans. The biotic community, along with the physical environment, forms an interacting system called the ecosystem. An ecosystem can be natural or artificial, temporary or permanent. A large grassland or a forest, a small tract in a forest or a single log, an edge of the pond, a village, an aquarium, or a manned spaceship can all be regarded as ecosystems.
Q 65 – Distinguish between biotic and abiotic factors
Ans. They are two components of an ecosystem. The biotic component comprises the kinds, numbers, and distribution of living organisms. The abiotic component, on the other hand, consists of the kinds, quantity, and distribution of physical and chemical factors such as light, temperature, water, oxygen, carbon, nitrogen, and minerals.
Q 66 – Explain with examples the role of members of the fungi kingdom of organisms.
Ans. The fungi kingdom includes diverse kinds of multicellular heterotrophic organisms. There are over 100,000 species of fungi. Some are unicellular like yeast, others are complex like mushrooms. The fungi are the major decomposers and their activity is essential for the recycling of inorganic resources in the biosphere.
Q 67 – What do you understand by biogeochemical cycles?
Ans. The balance of the chemical elements in the atmosphere and hydrosphere is maintained by a cyclic passage through the tissues of plants and animals. The cycle starts by absorbing chemical elements by the organism and returned back to air, water, and soil through decomposition. These cycles are energized by solar insolation. These cyclic movements of chemical elements of the biosphere between the organism and the environment are referred to as biogeochemical cycles.
Q 68 – What is the hydrologic cycle?
Ans. All living organisms, the atmosphere, and the lithosphere maintain between them a circulation of water in solid, liquid, or gaseous form, referred to as water or hydrologic cycle.
Q 69 – What is denitrification?
Ans. Herbivorous animals feeding on plants in turn consume some of it. Dead plants and animals, excreted nitrogenous wastes are converted into nitrites by the attachment of bacteria present in the soil. Some bacteria can even convert nitrites into nitrates that can be used again by the green plants. There are still other types of bacteria capable of converting nitrates into free nitrogen, a process known as denitrification.
Q 70 – Food chains are not isolated linear chains of trophic levels.” Comment.
Ans. In nature, the food relationship cannot be explained only in terms of a single food chain. A herbivore consumes many types of plants or plant products. Many kinds of animals, other than tiger, derive food from herbivorous animals. Ticks and mites, leeches, and blood-sucking insects are dependent on herbivores and even on carnivores. Thus, food chains are not isolated linear chains of trophic levels.
Depending upon the availability and choice of food, different organisms at each level have a food relationship with more than one organism at the lower levels. A rat, for example, feeds on various kinds of stem, roots, fruits, and grains. In turn, it is consumed by a snake which is eaten by a falcon. The snakes feed on both, frogs and rats. Then, a network of food chains exist, which is called a food web. The food web becomes more complicated when taste and preference, availability, and compulsion are involved.
Q 71 – Describe the functions of various biotic components.
Ans. Various biotic components include producers, herbivores, carnivores, and decomposers. All organisms require energy for their life processes. Food supplies both energy and materials for the sustenance of life. Green plants produce carbohydrates by photosynthesis and also synthesize proteins and fats. The green plants, therefore, are called producers. The animals that consume this energy are called consumers.
The herbivores like cattle, deer, and goats derive their food or energy directly from plants and are called the first-order consumers. The carnivores like tiger and lion depend on herbivores for their food and energy and are therefore called the secondary or second-order consumers. The non-green organisms like fungi and some bacteria, which do not produce their own food, live on the dead and decaying plants or animals and are consumers of a special type called decomposers.
Q 72 – Describe the energy flow in the biosphere.
Ans. Energy from the sun enters the living world through photosynthetic organisms and passes on from one organism to another in the form of food.
The organisms which trap solar energy and act as producers also use some energy for their own life processes. Only a portion of the energy trapped is taken by the primary consumers. Animals being more active than plants use much of the energy acquired before they are consumed by the next trophic level. At each stage of energy transfer, some amount of energy is lost from the food chain. The amount of energy transferred to the next higher level thus gradually decreases. The decomposition of dead organisms also releases chemical energy. Eventually, all this solar energy that entered the living system through the producers goes back into the non-living world, not as light but as heat.
Q 73 – Describe the carbon cycle in brief.
Ans. Carbon is one of the basic elements of all living organisms. It forms the basic constituent of all organic compounds. The biosphere contains over half a million carbon compounds. 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 carbohydrates, glucose that may be converted to other organic compounds such as starch, cellulose, etc. Here, some of the carbohydrates are utilized 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 unutilized carbohydrates become part of the plant tissue.
The plant tissues are either eaten by the herbivorous animals or get decomposed by 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 get oxidized into carbon dioxide and are returned back to the atmosphere.
Q 74 – How many types of decomposers are there?
Ans. There are two types of decomposers Scavengers and micro-organisms. Scavengers feed on dead organisms, like vultures and crows. Further breaking down of the dead matter is done by other decomposing agents like bacteria and various micro-organisms.