PSEB Solutions for Class 10 Science Chapter 15 Our Environment

PSEB Solutions for Class 10 Science Chapter 15 Our Environment

PSEB 10th Class Science Chapter 15 Our Environment

→ A biotic community survives in an environment entirely by materials and energy provided by its environment.

→ The environment is the sum total of all external conditions and influences that affect the life and development of an organism, i.e., the environment includes all the physical or abiotic and biological or biotic factors.

→ The ecosystem is defined as the interaction between the physical environment and the biotic community.

→ An ecosystem is a unit of the environment that can be identified and studied. The term ‘Ecosystem’ was coined by Sir Arthur Tansley (1935).

→ The various components of an ecosystem are interdependent.

→ An ecosystem can be natural or artificial, small or large, and temporary or stable. An ecosystem has a defined organization having two structural components i. e. biotic and abiotic.

→ The ecosystem may vary in sizes such as a small pond or a large forest or ocean.

→ Two major categories of ecosystems are terrestrial and aquatic ecosystems.

→ Its functional components include the volume and rate at which materials circulate and energy flow as well as the process of interaction between biotic and abiotic components.

→ The biotic components of any natural ecosystem comprise

  • producers
  • consumers (primary and secondary)
  • decomposers.

→ Both materials and energy enter the living world through the producers.

→ There is always a unidirectional flow of energy in a food chain.

→ We have an impact on our environment.

→ Different materials are cycled in the environment in separate biogeochemical cycles.

→ In these cycles, essential nutrients change from one form to another.

→ Enzymes are always specific in their action.

→ Plastic can neither be decayed by micro-organisms nor by other dead organisms.

→ Those substances which can be decayed by micro-organisms are called biodegradable substances. And those which cannot be decayed are known as non-biodegradable substances.

→ The organisms like plants, animals, micro-organisms, human beings, and their physical surroundings interact with each other. They maintain a balance in nature.

→ Forest, ponds, and waterfalls are examples of natural ecosystems whereas gardens and fields are man-made artificial ecosystem.

→ All green plants and blue-green algae are called producers because they trap sunlight and prepare their own food.

→ All organisms directly or indirectly are dependent on producers for their survival.

→ Those organisms which are dependent on producers for food are called consumers.

→ Consumers mainly are of three types: herbivores, carnivores, or omnivores.

→ Various organisms are linked together for their food requirements and form a food chain.

→ Each step of a food chain forms a trophic level.

→ Autotrophs trap solar energy and transform it into chemical energy.

→ The green plants in the terrestrial ecosystems capture about 1% of the energy of sunlight and convert it into food energy.

→ Primary consumers change almost 10% of consumed food into organic matter.

→ A food chain basically consists of three or four levels.

→ The length and compressibility of food chains vary greatly.

→ Instead of a straight-line food chain, a branched relationship is developed. This branched-chain forms a web called a food web.

→ Many chemicals mix with soil and enter water bodies and become part of the food chain.

→ Non-biodegradable substances accumulate in our body which is called Bio-magnification.

→ The ozone layer protects us from ultraviolet rays coming from the sun towards the earth.

→ At higher levels of the atmosphere ozone (O3) is a product of UV radiation acting on oxygen (O2) molecules.

→ Chemicals like chlorofluorocarbons (CFCs) are responsible for the depletion of the ozone layer.

→ Improvements in our lifestyle have resulted in a greater amount of garbage.

→ Acid rain is the result of air pollution.

→ Global warming is due to the slow rise in the earth’s temperature due to an increase of CO2 concentration in the atmosphere.

→ Global warming can be stopped by cutting down the use of fossil fuels.

→ Wastes are of two types i.e. biodegradable and non-biodegradable waste.

→ WHO (World Health Organisation) has defined solid waste as “a matter in the wrong place i.e., a non-liquid, no-gaseous substance no longer useful to the holder.”

→ Solid Waste is a by-product of human development and growth.

→ Approximately every resident of urban India generates about 500 g of solid waste.

Its generation is directly proportional to sources of income. Higher the income – greater is the consumption and bigger is the waste.

→ Solid waste is a heterogeneous mixture and may have different types of components.

→ Collection, treatment, and disposal of waste are important aspects requiring urgent consideration.

→ Modes of disposal of wastes are:

  • Landfills: It is the method used in urban areas to bury the solid waste in low-lying areas to level the uneven ground.
  • Recycling: It is the method of recovery and processing of biodegradable wastes or materials after they have been used, which enables them to be reused.
  • Composting: In this method, domestic waste like fruit and vegetable waste, left-over food, leaves of potted plants, etc., can be converted into compost and used as manure.
  • Incineration: It means ‘reduction to ashes’. The burning of a substance at a high temperature to form ash is called incineration. It is used to destroy household waste, chemical waste, and biological waste. Incineration is carried out in an incinerator.

→ Ecosystem: The interchange of energy and matter between biotic and abiotic components is called an ecosystem.

→ Biome: When ecosystems combine, a larger system is formed which is called a Biome.

→ Biosphere: When all the biomes of the world combine together resulting in a large unit it is termed as the biosphere. It is considered to be the largest biological system.

→ Hydrosphere: The part of Earth covered with water is called the hydrosphere.

→ Lithosphere: The outer crust of our planet Earth is called the lithosphere.

→ Atmosphere: The multi-layered gaseous envelope of air that covers the whole of our planet Earth like a blanket is termed as atmosphere.

→ Consumer: Those organisms which cannot produce their own food and consume already formed food are called consumers.

→ Nutrition: Nutrition is the process of providing or receiving nourishing substances with the help of the food chain.

→ Food chain: A chain formed by producers, consumers, and decomposers is called a food chain. It is a series of organisms feeding on one another at various biotic levels.

→ Food web: The network of overlapping food chains is called the food web.

→ Biogeochemical cycle: A constant interaction between the biotic and abiotic components of the biosphere makes it a dynamic but stable system. These interactions consist of a transfer of matter and energy between the different components of the biosphere.

→ Macronutrients: The nutrients which are required in large amounts by the body are called macronutrients, e.g. H, N, C, O, P.

→ Micronutrients: The nutrients which are required in small amounts by the body are called micronutrients, e.g. Mn, Zn, Cu, etc.

→ Water cycle: The whole process in which water evaporates and falls on the land as rain and water flow back into the sea via rivers is known as the water cycle.

→ Primary Consumers: Those organisms which eat plants or their products are known as herbivores or primary consumers.

→ Secondary consumers: Those organisms which eat the flesh of other animals are known as carnivores or secondary consumers.

→ Flora: The population of plants and trees in a region.

→ Fauna: The animal population of a region.

→ Community: Group of plants and animals living together e.g. plants and animals living in a pond.

→ Bio-magnification: Accumulation of non-biodegradable substances in large amounts in our body is called bio-magnification.

→ Biodegradable substances: Those substances which are broken down into simple substances by the decomposers in the life cycle are called biodegradable substances.

→ Non-biodegradable substances: Those substances which cannot be decayed by decomposers are called non-biodegradable substances.

→ Environment: Living organisms and their surroundings constitute the environment.

→ Ecology: It is a branch of science which deals with the relationship between living organisms and their environment on the basis of living and non-living components.

→ Components of Ecosystem: Physical, chemical, and living parts that form the ecosystem are called the components of the ecosystem.

→ Biogeochemical cycle: The constant interaction between biotic and abiotic components of the biosphere makes it a dynamic but stable system. These interactions consist of a transfer of matter and energy between different components of the biosphere.

→ Biological Magnification: The successive increase in the concentration of some toxic substances through different trophic levels of a food chain is called biological magnification.

→ Producer: Those plants and animals which convert solar energy into chemical energy and prepare their own food are called producers.

→ Decomposer: Those organisms which break down complex organic compounds from the surface of their bodies and convert them into simple inorganic substances with the help of enzymes are called decomposers.

→ Herbivores: Organisms that consume only plants and their products as food is called Herbivores.

→ Carnivores: Organisms which eat the flesh of other animals for survival are called carnivores.

→ Omnivores: Organisms that eat plants, animals, and their products are called omnivores.

→ Food Web: Branched food chain is called a food web.

→ Ozone layer: The layer of ozone in the stratosphere is called as ozone layer.

→ Garbage: The waste accumulated by common domestic and agricultural activities is known as garbage.

Science Guide for Class 10 PSEB Our Environment InText Questions and Answers

Question 1. Why are some substances biodegradable and some non-biodegradable?
Some substances such as paper, clothes, vegetables, wood etc. can be broken down into simple substances by the action of living organisms or biological processes in nature are said to be biodegradable.

There are other substances such as metals, plastics etc. which cannot be broken down into simpler substances by the action of living organisms or biological processes are termed non-biodegradable substances.

Question 2. Give any two ways in which biodegradable substances would affect the environment.

  • Biodegradable substances get simplified by the action of micro-organisms and the simple components are restored to environment, organisms or biological processes.
  • They help in recycling. Gobar gas plant is best example of recycling in which dung and faeces are utilized to produce gas for cooking and the remains form important manures.
  • Organic matter of biodegradable substances cause the growth of mosquitoes, flies etc. which spread diseases.

Question 3. Give any two ways in which non-biodegradable substances would affect the environment.

  • The non-biodegradable substances add to the pollution.
  • Biomagnification of pesticides such as D.D.T. in the body of living system is very harmful.
  • Solid waste leads to generation of methane which is causing global warming.

Question 4. What are trophic levels? Give an example of food chain and state the different trophic levels in it.
Trophic levels. The various steps in a food chain where transfer of food (energy) takes place are called trophic levels. Producer formed by green plants form first trophic level in a food chain.

Food chain: It is a sequential list of one organism consuming the other.

A simplest form of food chain is represented as
Producer → Herbivore → Carnivore

Characters of food chain.

Topic levels-a food chain

  • It is always straight.
  • In shorter food chain, the greater is the available energy.
  • The number of steps in any food chain is restricted to four or five.
  • There is always unidirectional flow of energy in a food chain.

Question 5. What is the role of decomposers in the ecosystem?
These oganisms feed on the dead bodies of plants and animals. Bacteria, fungi and some lower invertebrates are examples of decomposer. They breakdown the organic components into simple inorganic molecules. They carry out natural process of decomposition. They return the simple components to soil and help in making the steady state of ecosystem. Decomposers are essential component of an ecosystem. They create a balance in the environment. They are called natural changing agents.

Question 6. What is ozone and how does it affect any ecosystem?
Ozone. Ozone is a molecule formed by three atoms of oxygen in the presence of

  • Oxygen is essential for all aerobic forms of life but ozone is a deadly poison.
  • Ozone is very poisonous at ground level. Ozone performs an important function at the higher level of the atmosphere.
  • Ozone absorbs UV rays from the sun. Thus protects the living system on earth from any kind of damage.

Question 7. How can you help in reducing the problem of waste disposal? Give any two methods.

  • Recycling of wastes
  • Reduction at source
  • Better management
  • Vermicomposting
  • Use of eco-friendly products such as disposable paper cups in place of plastic cups.

PSEB 10th Class Science Guide Our Environment Textbook Questions and Answers

Question 1. Which of the following groups contains only biodegradable items :
(A) Grass, flowers and leather
(B) Grass, wood and plastic
(C) Fruit-peels, cake and lime-juice
(D) Cake, wood and grass.
(A), (C) and (D) groups.

Question 2. Which of the following constitute a food chain?
(A) Grass, wheat and mango
(B) Grass, goat and human
(C) Goat, cow and elephant
(D) Grass, fish and goat.
(B) Grass, goat and human.

Question 3. Which of the following are environment-friendly practices?
(A) Carrying cloth-bags to put purchases in while shopping
(B) Switching off unnecessary lights and fans
(C) Walking to school instead of getting your mother to drop you on her scooter
(D) All of the above.
(D) All of the above.

Question 4. What will happen if we kill all the organisms in one trophic level?

  • If we kill all the organisms in one trophic level, imbalances will be created in the food chain.
  • The population of organisms in pervious trophic level will increase. If we kill population of frogs in the following food chain, the population of insects will increase to a great level and in turn they will damage the green plants.
    Green plants → Insects → Frog
  • The population of organisms in the next trophic level will decrease.

Question 5. Will the impact of removing all the organisms in a trophic level be different for different trophic levels? Can the organisms of any trophic level be removed without causing any damage to the ecosystem?

  • If we kill all the organisms in one trophic level, imbalances will be created in the food chain.
  • The population of organisms in pervious trophic level will increase. If we kill population of frogs in the following food chain, the population of insects will increase to a great level and in turn they will damage the green plants.
    Green plants → Insects → Frog
  • The population of organisms in the next trophic level will decrease..

Question 6. What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
What is biological magnification? What are its effects?
Biological magnification. The phenomenon in which the harmful pollutants (such as pesticides) enter the food chain and get concentrated more and more at each successive trophic level of organisms is called biological magnification.
The level of biological magnification will be different at different trophic levels of the ecosystem.

This can be illustrated by the following example :
A large number of toxic chemicals like pesticides, weedicides, insecticides and fungi-cides are used to protect the crop plants from pests and diseases. Some of these chemi-cals get mixed up with the soil whereas others get washed down into the surface water bodies like ponds, rivers, etc., and the underground water bodies.

Water in a pond, lake or river contain only a small amount (0.02 ppm) of the harmful chemicals. The algae (phytoplankton) and protozoa (zooplankton) which utilize this wa-ter, contain a higher proportion (5 ppm). The fish which feeds on these organisms has a still higher amount of chemicals (240 ppm.) Birds which feed on these fish contain the highest amount (1600 ppm).

Therefore, we observe that as we go higher and higher in the food chain, the concentration of pesticides in the body of the organisms gradually increases. For example, in the above cited example, the biological magnification of harmful pesticides goes up to 8000 times from water to fish eating birds.

Effects of biological magnification. This is the reason why our food grains such as wheat and rice, vegetable and fruits and even meat contain varying amounts of pesticides residues. So, the highest trophic level at the extreme right of food chain has the maximum concentration of harmful chemicals in a food-chain.

Question 7. What are the problems caused by the non-biodegradable wastes that we generate?
Explain two ways in which non-biodegradable substances affect our envi¬ronment.
Problems caused by non-biodegradable wastes

  1. Non-biodegradable solid waste is a great environmental hazard.
  2. Plastic and their waste products such as carry bags, waste glasses, bottles, cups, plates are most dangerous. They choke in drain.
  3. They cause soil pollution and degrade the soil.
  4. They prevent growth of vegetation when dumped underground.
  5. Water pollution will make this water not fit for drinking.
  6. The plastic wastes when mixed with municipal waste make them unfit for recycling.
  7. Non-biodegradable substances may be inert and simply persist in the environment for a long time and may harm various members of the ecosystem.

Question 8. If all the wastes we generate is biodegradable, will this have no impact on the enviroment?
If all the wastes are biodegradable they will help in maintaining a neat, clean and stable environment.

Question 9. Why damage to the ozone layer is a cause of concern? What steps are being taken to limit this damage?
Ozone layer absorbs ultraviolet radiation of the sunlight which is very harmful to human beings. If the ozone layer in the atmosphere is depleted, these radiations would reach the earth and would cause many damages such as skin cancer, genetic disorders in human and other living beings.

The steps taken to limit the damage of ozone layer are as follows :

  • Judicious use of aerosol spray propellants such as fluorocarbons and chlorofluorocarbons which cause depletion or hole in ozone layer.
  • Limited use of supersonic planes.
  • Control over large scale nuclear explosions.

PSEB 10th Class Science Important Questions Chapter 15 Our Environment

Multiple Choice Questions

Question 1.  Biotic components include:
(A) producers only
(B) consumers only
(C) producers and consumers only
(D) producers, consumers and decomposers.
(D) producers, consumers and decomposers.

Question 2. The word ecosystem was coined by:
(A) Writer
(B) Tansley
(C) Odum
(D) Darwin.
(B) Tansley

Question 3. Green plants are:
(A) autotrophs
(B) heterotrophs
(C) parasites
(D) saprophytes.
(A) autotrophs

Question 4. Which organism Is a decomposer?
(A) Vukure
(B) Fungus
(C) Fox
(D) Frog.
(B) Fungus

Question 5. Grass-insect-frog-snake-hawk. In this food chain the secondary consumers are:
(A) insects
(B) frog
(C) snake
(D) grass.
(B) frog

Question 6. Which one is a primary consumer in a pond ecosystem?
(A) Green algae
(B) Zooplankton
(C) Snake
(D) Bacteria.
(B) Zooplankton

Question 7. The best arrangement of an energy system consisting of hawks, snakes, mice and grasses is:
(A) grass → mice → snake → hawks
(B) grass → snake → mice → hawks
(C) grass → mice — hawks → snakes
(D) mice → snake → hawks → grass.
(A) grass → mice → snake → hawks

Question 8. They can be put in the category of primary consumers:
(A) Eagles and tigers
(B) Fishes and whales
(C) Snakes and frogs
(D) Insects and cattles.
(D) Insects and cattles.

Very Short Answer Type Questions

Question 1. What do you mean by the word environment?
Environment is the sum total of all external conditions and influences that affect the life and development of an organism i.e. the environment includes all physical or abiotic and biological or biotic factors.

Question 2. Where do different countries discuss their problem based on environmental issues?
Developed and developing countries discuss their issues regarding environmental problems in world conferences regularly.

Question 3. In whi ch biogeochemical cycles do various interactions take place?
Nitrogen, carbon, oxygen and water cycles.

Question 4. Which substances are called waste substafices?
Substances which become unuseful and remain of no worth for us are called waste substances.

Question 5. What helps in digestion of food in our body?

Question 6. Which substances are specific in their action?

Question 7. Which man made material cannot be decomposed by bacteria and decomposers?

Question 8. Which physical conditions affect plastic?
Heat and Pressure.

Question 9. What are biodegradable sub-stances?
The substances which get decomposed in their life cycle by decomposers are bio-degradable substances.

Question 10. Give four examples of biodegrad-able substances.
Peals of fruits and vegetables, paper, fodder, husk.

Question 11. What are non-biodegradable substances?
Those substances which cannot be decomposed throughout their life by the decomposers are called non-biodegradable substances.

Question 12. Give two examples of non-biodegradable substances.
Plastic, Glass.

Question 13. Give examples of natural ecosystem.
Forest, ponds, lakes.

Question 14. Give two examples of man made ecosystem.
Garden, Agricultural field.

Question 15. In which three categories are the organisms categorised?
Producers, consumers and decomposers.

Question 16. What are Producers?
The organisms those convert inorganic substances into organic substance during photosynthesis with the help of sunlight and chlorophyll are called producers.

Question 17. Give two examples of organisms which can do photo-synthesis.
Green plants and blue green algae.

Question 18. On what do all organisms directly or indirectly dependent for their food?
Producers which means plants undergoing photosynthesis.

Question 19. What are consumers?
The organisms which depend directly or indirectly on producers for food are called consumers.

Question 20. Give four examples of consumers.
Human beings, Lion, Monkey, Sparrow.

Question 21. Which two organisms decompose waste substances?
Microbes and Fungi.

Question 22. Why are micro-organisms called decomposers?
Micro-organisms convert complex organic substances into simple inorganic substances which mix with the soil and are again used by plants.

Question 23. Where are living organisms found?
They are found in sea water, ice-covered regions, air and soil.

Question 24. What is biosphere?
All environmental regions found on earth and the organisms living there together form biosphere.

Question 25. List four components which help in making biosphere a non-living component.
Air, water, soil and minerals are non-living components of biosphere.

Question 26. Do living and non-living components dependent on each other?
Yes, they are dependent on each other and affect each other also.

Question 27. List the living components of biosphere.
Plants and organisms.

Question 28. What is the main activity of decomposers?
The micro-organisms decompose the dead remains of plants and animals. This category comprises microbes and fungi.

Question 29. Give one example each of autotrophs and heterotrophs.
Autotrophs—Green plants Heterotrophs—Human beings.

Question 30. Is energy increased or decreased during transformation in food chain?
Energy is decreased at every coming trophic level.

Question 31. Grass → deer → lion.
Who is the producer and why?
Grass is the producer because it traps sunlight to store food in form of carbohydrates.

Question 32. What are omnivores?
Organisms which eat both plants and flesh of other animals are called omnivores, e.g. Man.

Question 33. Name two ecosystems of this world.
Forests and oceans.

Question 34. Grass → insects → frog → birds → human.
In this food chain (i) Who gets maximum energy? (ii) Who gets minimum energy?
Insects get maximum energy and human beings get least energy.

Question 35. Give an example of food chain in water.
Algae → small organisms → small fish → large fish.

Question 36. What is formed when various food chains combine?
Food web.

Question 37. Who will get more energy-herbivores or carnivores?

Question 38. What is the main activity of food chain?
Transformation of food and energy are main activities of food chain.

Question 39. What are planktons?
Planktons are extremely small micro-organisms which float independently in ponds, sea, rivers, etc.

Question 40. What are phytoplanktons?
Phytoplanktons are producers those can easily float on the surface of water.

Short Answer Type Questions

Question 1. Define environment. What are its major components?
The immediate surroundings where we live is called our environment. The major components of it are biotic and abiotic.

Biotic components: All living organisms, plants and human beings are considered in biotic components.
Abiotic components: Physical or non-living components include air, water, soil. Air is used for respiration, water is used for drinking and soil (land) where we live. Apart from this there are climatic components like solar energy, heat, light, rain, humidity, air, etc.

Question 2. What is environmental pollution? Write three examples of non- hiodegradables which are harmful for human beings.
Environment is mainly comprised of physical and living components. Any unsuitable change in the natural conditions of these components is called pollution. Environmental pollution is mainly of three types—water pollution, soil pollution, air pollution.

Water pollution is mainly caused due to inorganic waste from various industries. This dirty liquid waste is made to flow in rivers which leads to pollution of river water. Various chemicals used in agricultural lands, excreation in open garbage, dead bodies, etc. are the main causes of soil pollution. Excess percentage of oxygen in air has no ill effect on air but the change in quantity of other gases in air makes it unfit for respiration. This is called air pollution. Decomposition of non-biodegradable substances is very slow and their life is long. e.g. DDT, compounds of arsenic, etc.

Question 3. How does development affect our environment?
Excessive developments always effects our environment. Imbalance in environment is the result of development made by we people. To meet the increasing needs and demands resources are always tapped. For this, we have to depend on environment. Our natural resources are limited. And their unjudicious use gives an adverse effect on environment. Environment gets polluted when land suitable for agriculture is used for making hotels and buildings. In this way development affects our environment.

Question 4. Define Pollution.
The appearance of unwanted and harmful changes in our biological, physical and chemical environment is called pollution. Mainly pollution is of three types—soil, air and water pollution.

Question 5. Differentiate biodegradable and non-biodegradable pollutants. Classify the following under the above two categories : DDT, Paper, Cotton cloth, Plastics.

Biodegradable pollutants Non-biodegradable pollutants
1. These pollutants can be broken down into non poisonous substances in nature by the action of living organisms such as bacteria, fungi. 1. These pollutants cannot be broken down into non poisonous substances by living organisms.
2. They get recycled thus do not need any dumping sites. 2. They cannot be recycled thus require dumping sites.
3. They cause minimum environmental pollution. Example : Paper and cotton cloth. 3. They cause environmental pollution. Example : DDT and plastics.

Question 6. Define Biosphere.
Biosphere means: ‘Sphere of living beings’. Land, water and air are present on earth. These help plants and animals to live. All these three combine together as a unit to help the survival of life on earth. It is the largest biological system and is called biosphere.

Question 7. What happens when we add waste to the environment? Explain.
Problems caused by the wastes

  1. Solid waste is a great environmental hazard.
  2. Plastic and their waste products such as carry bags, waste glasses, bottles, cups, plates are most dangerous as they choke in drain.
  3. They cause soil pollution and degrade the soil.
  4. They prevent growth of vegetation when dumped underground.
  5. Water pollution will make the water non-potable.
  6. The plastic waste when mixed with municipal waste make them unfit for recycling.
  7. Non-biodegradable substances may be inert and simply persist in the environment for a long time and may harm various members of the ecosystem.

Question 8. List the biotic and abiotic components of ecosystem.
Differences between Biotic and Abiotic components of ecosystem

Biotic Components:

  • Biotic components of an ecosystem are those living substances which are different members of a community.
  • Biotic components of an ecosystem are :
    1. Producers
    2. Consumers
    3. Decomposers

Abiotic Components

  • Abiotic components are non-living factors.
  • It includes water, minerals, salts, humidity, light, temperature, pH, wind, topography and background.

Question 9. Explain functions of ecosystem.
Functions of ecosystem

  • Energy flow: The energy flow from producers to consumers. There is loss of energy at every trophic level.
  • Biogeochemical cycle: The cyclic flow of nutrients between non-living environment and living organisms is called biogeochemical cycles.

Question 10. List the key functional aspects of ecosystems.

  • Productivity and energy flow.
  • Nutrient cycling.
  • Development and stabilization.

Question 11. Differentiate between producers and consumers.

Producers Consumers
1. The organisms which can prepare their own food by the process of photosynthesis are called producers. 1. The organisms which are dependent on other organisms for their food are called consumers.
2. Green plants are called producers. 2. All animals are called consumers.

Question 12. How different levels will be affected if frogs are removed from the following food chain?
Grass → Grass Hopper → Frog → Snake → Peacock

  1. Number of grass hoppers will increase on removing frogs.
  2. Grass will decrease due to increase in population of grass hoppers.
  3. Due to less grass, there wall be struggle between grass hoppers for their survival.
  4. Due to non-availability of frogs, snakes and peacocks will start consuming some different food for their survival.
  5. Snakes and peacocks may change their place for getting their food.

Question 13. Write food chains of various trophic levels. At which level energy will be maximum?
Examples of food chain are :

  1. Plants → human
  2. Grass → deer → snake
  3. Grass → insects → frog → snake
  4. Alga → small organism → small fish → large fish
  5. Grass → grass hopper → frog → snake → peacock.

In these food chains, first level is always of producers.

In these food chains :
1st is two-level, 2nd is three-level, 3rd and 4th are four-level and 5th is five-level food chain.

Question 14. How does energy reach from environment to the consumer and in which form?
Plants have green pigment in them called chlorophyll due to which they can trap solar energy. Energy from environment enters through photosynthesis. 1% of sunlight is used by the plants through photosynthesis. Plants change this energy to chemical energy and is stored in the form of carbohydrates. A part of this energy is used in respiration by the plants which helps in their growth and development. Chemical energy stored in the eatable goes to the first trophic level (herbivores) and is used for respiration and growth.

Question 15. What will happen if all the decomposers are removed from the ecosys¬tem?
If the decomposers are removed from the ecosystem :

  • Complex organic matter will not be broken. So nutrients will not return to nutrient pool.
  • Different nutrient cycles will be disturbed.
  • Balance in the eco-system will be disturbed.
  • Waste materials will get accumulated.

Question 16. Write four characteristics of food web.
What is food web?
Characteristics of Food Web

  • Unlike food chains, food webs are never straight.
  • Food web is formed by inter-linking of food chains.
  • Food web helps in ecosystem development.
  • Food web provides alternative pathways of food availability. Example, if a particular species of producers is destroyed by a disease in the ecosystem the herbivores of that area can feed on other species of producers.

Question 17. What results do you get from the transformation of energy?
Energy transformation takes place from producer to consumer in a food chain. Following results are found from this transformation :

  • Energy is changed from one form to the other. During photosynthesis light energy changes to chemical energy. Only plants can transform energy from one form to another. This is why they are called as transformers.
  • Energy level during transformation continuously decreases from one trophic level to the other trophic level. Some part of energy is utilised by these for their growth and the remaining is released in the form of heat.
  • The energy available at any trophic level becomes less than the energy at producer level.

Question 18. How do harmful insecticides concentrate in our bodies?
Many pesticides are sprayed on crops to protect them from various pests and diseases. These chemicals get dissolved in water and by dripping through soil reach the underground water level. Plants absorb these with other minerals in the form of water received from the soil. In this way, they enter our food chain. During transformation of energy at different levels of food chain, these chemicals get concentrated in our bodies.

These harmful chemicals are found in large amount in human bodies. Concentration of DDT is maximum in our bodies which is used as insecticide to kill mosquitoes.

Question 19. How are human beings responsible for ecological imbalance?
Various modern agricultural techniques are used by man which are responsible for ecological imbalance because of the following reasons :

  • Use of machinery and other impliments.
  • Use of fertilizers and harmful medicines.
  • Burning animal dung and other things.
  • Deep Mining.

Question 20. (i) What is 10% law?
According to this law only 10% of energy is transferred to the organisms of next trophic level from the previous one.

(ii) Which man will get more energy-vegetarian or meat eater? Give reason.
By energy concept, herbivores are more benefitted.

Reason: Plants are at first trophic level. 10% of the energy is transferred to next level which clears that herbivores (vegetarians) get more energy as compared to carnivores (meat eaters).

Question 21. Explain with the help of a diagram how is life on earth dependent on sun?
In biosphere various organisms live and all these are dependent on sun for their various activities. Sun is the basic and ultimate source of energy. Solar energy enters the biosphere through photosynthesis.

Life on Earth is dependent upon Sun.

Question 22. How is ecological balance maintained?
Food chains are connected in nature. Sometimes, a level of food chain comes to an end. Then that food chain connects itself to some other level of the food chains and stability remains maintained. The flow of food material and energy remains intact. If all deers living in a forest are destroyed, then lion will start killing some other animal as it’s alternative and will complete the cycle. Ecological balance is thus maintained by nature.

Question 23. Name the chemicals which are considered responsible for hole in ozone layer.

  1. Aerosols
  2. Modern fire extinguishers
  3. Nuclear Explosion
  4. Halogen
  5. Sulphate aerosol
  6. CFCs, (Chlorofluoro carbons), CBC (Chlorobromo carbons) etc. which are used in refrigeration.

Question 24. Name the activities of human beings those have caused much harm to environment.

  1. Rapidly increasing population
  2. Industrialisation
  3. Excessive use of fertilizers and pesticides
  4. Deforestation
  5. Mining of mountains
  6. Excess use of fossil fuels
  7. Misuse of fertile agricultural land
  8. Unplanned and uncontrolled expansion of cities.

Question 25. Name the problems created by human beings for whole of the world.

  1. Depletion of ozone layer
  2. Acid rain
  3. Rapid changes in environment
  4. Natural disasters-Land slides, Floods
  5. Mountain Slide
  6. Green house effect
  7. Irregular rainfall
  8. Increase in Cancer, Heart diseases etc.
  9. Drought and expansion of deserts.

Question 26. Distinguish between decomposers and parasites.

Decomposers Parasites.
1. These are often not harmful for living beings. 1. These cause harm to living beings.
2. These change complex carbonic material to simple carbon matter and absorb them. Example: Mushroom. 2. These get their food from the bodies of other living beings. Example: Ascaris, Taenea.

Question 27. A food chain is given below :
Grass → Deer → Lion
What will happen if lion is removed from this food chain?
If all lions are removed from this food chain the growth of deer will become uncontrolled and their number will increase very rapidly. They will graze the grass to its extinction and that area will change into a desert.

Question 28. Think about the food chains given below :
(I) Plants → Rats → Snakes → Hawks
(II) Plants → Rats → Hawks
If in these two food chains 100 joule of energy is present in both at the producer level, write from which food chain will hawk get more energy and how much? Justify your answer.
Hawks will get more energy from three steps food chain because hawks are comparatively nearer to the plants. According to 10% law, energy available to next level is 10% of the energy transferred from the previous level. Hawks will get more energy in second food chain and that will be (10 – 01) joule excess.

Question 29. Explain with the help of a food chain how does bio-magnification of harmful chemicals take place.
The entry of harmful chemicals in our food chain with the help of various methods and its continuous accumulation and concentration is called bio-magnification.

These chemicals can enter our bodies by many means. Suppose 0 02 ppm insecticide was there in water of a lake. 5 ppm of it got concentrated in phytoplankton and 240 ppm in fish. Consumed 1600 ppm insecticide was accumulated in those birds who consumed these fishes. It clearly shows that bio-magnification increases with the increase in food chain.

Question 30. If plants get 20,000 J of energy from sun, how much energy will be available to lion in the following food chain? Calculate.
Plants → Deer → Lion
We know that 10% energy flow takes from one trophic level to the other.
∴ Lion will get only 20 J of energy.

Question 31. Why do the food habits of first and third tropic levels differ?
First trophic level is a result of producers. All green plants are related to first trophic level. They are autotrophs whereas third trophic level is of carnivores. They are second level consumers.

Question 32. How much joules of energy will be received by vulture in the chain of three living beings—vulture, snakes and paddy. Sun provides 10,000 J energy to Paddy.
Food chain
Wheat → Mouse → Snake → Vulture

According to 10% law, only 10% of energy will be available to next level. That’s why vulture will get 10 J of energy.

Question 33. How does ecological pyramid represents the graphical representation of food system of living being in biosphere?
Ecological pyramid shows the graphical representation of food chain and its various trophic levels. Ecological pyramid shows different trophic levels in such a way that base of it is shown by producer. As we move from base to upper direction the higher trophic levels are seen. The peak of pyramid is shown by extreme carnivores.

Ecological pyramid of food system in living beings

Question 34. How is ozone made in atmosphere? How is it depleting?
O3 molecule is a result of combining three atoms of oxygen. The oxygen molecule has two atoms of oxygen. Oxygen is necessary for respiration of organisms. But ozone is deadly poisonous in nature. At higher levels of atmosphere ozone performs a vital role. It protects earth from ultra violet radiations coming from sun towards earth. U.V. radiations are extremely harmful for all organisms on earth. These radiations causes skin cancer. On the higher level of air U.V. radiations disintegrate O2 and produces free oxygen (O). The free atom of oxygen (O) combines with oxygen that results in the formation of ozone (O3).

Question 35. In railway trains, tea/coffee is served in earthen pots and disposal cups made of paper? What are the harms of it?
Tea/Coffee is served in railway trains just because of two reasons-cleanliness and convenience. But soil of fertile lands is used for making these cups which is very harmful for the fertility of agricultural lands. Also disposal paper cups are made of paper which is made of wood. It is very difficult to recycle these. It will increase the process of deforestation. These cups also cause pollution.

Our environment will get disturbed because of this.

Question 36. What is ozone hole? What is its significance?
Ozone hole: It means a complete disappearance of ozone layer over a part of atmosphere. During the period 1956-1970 the spring time 03 layer thickness above Antarctica varied from 280-325 Dobson unit. Thickness was sharply reduced to 225 DU in 1979 and 136 DU in 1985. The decline in ozone layer thickness is called ozone hole. It was first noted in 1985 over Antarctica.

Cooling of the stratosphere (where ozonosphere is located) will produce bigger ozone hole not only over Antarctica but also over Arctic region. Ozone layer will further thin out
from rest of the stratosphere. It will be accompanied by major climatic changes all over the globe. Forests will be wiped out from many places. Radio communications will be disrupted.

Question 37. Write the harmful effects of ozone depletion.
Effects of ozone depletion

  1. UV radiation striking the earth and these radiations cause skin cancer and damage to eye.
  2. These damage defence (immune) system of body.
  3. May lead to variations in global rainfall.
  4. It causes ecological disturbances such as floods, shortage of food etc.

Question 38. Explain global warming.
Global Warming or Greenhouse Effect: Carbon dioxide content of the air is increasing due to deforestation and combustion in industries, automobiles and planes, and is likely to become double by 2020. This increase is affecting the atmospheric composition and balance gases, which are among the factors that control earth’s climate.

Green house

Increase of carbon dioxide may cause rise in atmospheric temperature, producing what is called the greenhouse effect. A rise of global temperature by more than 2 or 3 degrees may melt glaciers and polar ice. This will cause rise in ocean level and consequent flooding of coastal towns and submission of islands. Rainfall pattern may also change, affecting agricultural output.

Question 39. How is acid rain formed? Effect
Acid rain: When S02 and S03 produced from incomplete combustion of fossil fuel and smelting of non-ferrous metals combine with water, form H2S03 and H2S04. They fall down in the form of rain, it is called acid rain.

Question 40. What is global warming?
The increase in global temperature due to rise in amount of C02 concentration in the atmosphere.

Question 41. List four common disposal methods.

  1. Incineration: Reduction to ashes.
  2. Recycling: Recovery and processing to be used again.
  3. Composting: Converting into compost to be used as manure.
  4. Landfill: Bury the waste in low lying area.

Question 42. Complete the sketch by labelling A, B, C, D to illustrate food web.

Food Web
Food web:
(A) Rats
(B) Frog
(C) Snake
(D) Vulture.

Question 43. Match the following :

Column I Column II
(a) Phyto planktons (i) Fish
(b) Larvae/Insects (ii) Bird
(c) Carnivore (iii) Primary Consumers
(d) Top Carnivore (iv) Producers.


Column I Column II
(a) Phyto planktons (iv) Producers.
(b) Larvae/Insects (iii) Primary Consumers
(c) Carnivore (iii) Primary Consumers
(d) Top Carnivore (ii) Bird

Long Answer Type Questions

Question 1. Differentiate the following :
(i) Ecosystem and Biome

Ecosystem Biome
1. It is the self sustaining unit. 1. It is the group of ecosystems.
2, It is formed by living organisms and non living environment. 2. It has ecosystems with almost same climate and specific geographical conditions.
3. It is a comparatively small unit of the living world. 3. It is a huge form of living world.

(ii) Food Chain and Food Web
Food Chain and Food Web

Food Chain Food Web
1. It is a food and energy flow in an ecosystem that shows which organism is consumed by the other organism. 1. It is a network of different inter connected food chains of an ecosystem.
2. It is a systematic straight chain of getting food. 2. It is a web composed by various interconnected food chains.
3. There are a few number of trophic levels. 3. There are large number of organisms in it that show natural balance in ecosystem.
4. It is limited and small.
4. It is a web of many food chains.

(iii) Carnivore and Omnivore
Carnivore and Omnivore

Carnivore Omnivore
1. These are flesh eating animals e.g. lion, cheetah, etc. 1. These animals eat both flesh and plants e.g. human beings, eagle, etc.
2. These are given place on 3rd trophic level or above. 2. These are often given place on second trophic level.

Question 2. Why it is said that flow of energy is always unidirectional?
Flow of energy is always unidirectional in this world. Flow of energy begins with the solar energy. Green plants get this energy with the help of photosynthesis. The energy of sun enters the organisms through environment. Only those plants and animals absorb sunlight in which a green pigment called chlorophyll is present. After absorbing this energy, plants change it into chemical energy which is stored in the form of carbohydrates. A part of it is utilized by the plants for their grow’th and development and the rest of energy is released in the form of heat.

Trophic level

Herbivores eat these plants as their food. Chemical energy stored in food enters herbivores w’hen they eat these plants. Organisms spend some part of energy in their normal activities and development and some of its part in respiratory activities. A part of energy, which is not being used, is released as heat. Carnivores eat herbivores organisms and first cycle of energy begins. Energy which is not being used is released as heat. Energy released in the form of heat cannot be reused in the process of photosynthesis by plants. This is why the energy flow is called unidirectional.

Question 3. Why does food chain become short?
Energy flow’ is unidirectional and its transformation takes place at different levels. Energy is always transferred from lower level to the higher levels. Only 10% of the energy gets transferred ahvays when energy is transferred from one trophic level to the next. A lot of energy gets wrnsted if many transfers are present there in a food chain. Food chains should be small to save loss of energy.

Maximum energy is wasted if there are many trophic levels in a food chain. To save energy from getting wasted, food chain should be short. During energy transformation in food chain, maximum energy is present at producer level. Energy availability becomes low on moving towards right hand side in a food chain.
e.g. Grass → Grass Hopper → Frog → Snake → Peacock

If all frogs are killed in this chain, then it will be adversely affected. The following changes will be seen :

  • Population of grass hoppers will increase.
  • Population of snakes will decrease due to non-availability of frogs.
  • Population of peacocks will be affected due to less number of snakes.

Due to unwanted and unnecessary deeds of human beings the food chain becomes small and that creates imbalance in nature.

Question 4. Can there be more than six trophic levels in a food chain? If not, why?
Energy transformation takes place at every level of a food chain and energy starts decreasing. After three or four levels, energy remains almost negligible. During photosynthesis plants absorb only 1% of solar energy and rest of the energy goes waste in environment. When herbivores consume plants, only 10% of energy is absorbed by them. If we assume that energy trapped by the sun provides 1000 J then plants absorb only 10 J and herbivores get 1 J from it. In the same way, when carnivores eat herbivores, they trap only 0.01 J of energy. Hence, when level of food chain increases, energy availability becomes low that is why it results in that a food chain cannot have more than six levels. The availability of energy is maximum at producer level and then keeps on decreasing and is least at last level.

Question 5. In the context of energy which level of food chain is considered beneficial for us? Why?
At producer level of food chain, maximum energy is available. It means that closer we are to producer level (plants) more energy we get. That is why in concept of energy, two or three level food chains are considered very beneficial.
Two level food chain : Producer → Human.

Green vegetables etc. are comparatively more beneficial. We get more energy from the vegeterian habits that’s why we get more energy by eating vegetables directly.
Third level food chain : Producer → Goat → Human. The energy which we get from this food chain is less because some amount of energy is absorbed by goat and some amount is released as heat energy and human beings get less amount of energy. This is why we say that second and third level food chains are beneficial for us.

Question 6. Write in brief the role of decomposers in recycling.
All the organisms on earth are differentiated as producers, consumers and decomposers on the basis of their food habits. Decomposers are the organisms which can carry out breakdown of complex organic compounds into simple compounds. They help in decaying dead bodies of plants and animals. These are parasites because simple compounds can also be absorbed by them through their body surface.

Plants absorb minerals from soil through water and carbon-dioxide from air is used in the process of photosynthesis. Major elements which participate in this process are C, N, O, S and P. These elements move to other tropic levels. These elements are released when dead bodies of the plants and animals are decayed with the help of decomposers. These elements can be absorbed by plants and they become a part of cycle again.

Question 7. What is meant by soil erosion? What are agents of soil erosion? Write effects of soil erosion.
Soil Erosion: It is the removal of top, fertile, mineral rich soil layer by water and wind.
Agents of Soil Erosion. The agents of soil erosion are water and wind, each contributing a significant amount of soil loss every year in our country. Soil erosion may be a slow process that continues relatively unnoticed or it may occur at an alarming rate causing serious loss of top soil.

Worldwide erosion removes about 25.4 billion tons of soil each year.

Effects of soil erosion. It has several adverse effects :

  • Loss of productive land.
  • Loss of crop/pasture.
  • Reduced yield as fertilizers may also be washed out.
  • It may damage roads, bridges, trees and houses.

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