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Living Things –> Plants, animals and microorganisms are the living things.
Non-living Things –> Some non-living thing are air, land, water and soil.
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Ecosystem –> The earth's surroundings of living and non-living things in an environment together form an ecosystem.
Interdependence in Nature
★ Plants require carbon-dioxide from the air, water and sunlight to prepare their food by photosynthesis.
★ Animals require oxygen from the air for breathing and water for drinking.
★ Animals depend on plants for shelters. For example: birds build nests on trees, Squirrels make holes called dreys in the trunk of trees.
★ Animals depend on plants for their food and also for oxygen to breathe.
★ Human beings get jute, cotton, paper, wood, rubber, gum, resins, medicines, etc. from plants.
Plants also depend on animals.
★ Animals give out carbon dioxide which is used by plants to make their food.
★ Many animals help in the dispersal of seeds.
★ Animals also help in pollination.
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Food Relationships
Plants need air, water and light to make their food by the process of photosynthesis.
Producers –> In an ecosystem, the green plants are called producers because they make their own food.
Herbivorous –> Herbivorous animals like cow, goat, horse, deer, etc. eat plants.
They are called primary consumers.
Carnivorous –> Carnivorous animals like lion, tiger, eagle, dog, etc. eat the flesh of other animals.
Omnivorous –> Omnivorous animals like bear, man, etc. eat both plants and animals.
Carnivores and omnivores are called secondary consumers.
Scavengers –> The animals that clean the environment by eating the flesh of dead animals are called scavengers. For exe. like hyena, vulture, raccoons, etc.
Decomposers –> Bacteria and fungi feed on dead and decaying matter and decompose them to produce nutrients are called decomposers. These nutrients are used by plants for growth.
Bacteria and fungi are the example of decomposers.
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Food Chain
In an ecosystem a cycle of eating and being eaten to obtain nutrition is known as food chain.
Or
This chain of who eats whom in an ecosystem to obtain nutrition is called a food chain.
Food Chain
Grass → Grasshopper → Frog → Snake → Eagle
Explanation
Plants and animals in an ecosystem depend on each other. Plants absorb nutrients from the soil and prepare food with the help of light. These plants are eaten by herbivores. Herbivores are eaten by carnivores. These carnivores are eaten by omnivores. When the herbivores, carnivores and omnivores die. They are eaten by scavengers. After the scavengers, the decaying matter is eaten by decomposers which release nutrients in the soil. So, the nutrients taken from the soil reach the soil again.
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Balance in Nature
Q. What will happen if we remove any one type of animal from the food chain.
Ans. It will disturb the whole nature. For example, in the above food chain, If all the eagles are killed, the number of snakes will increase rapidly. These snakes will eat up all frogs so the number of frogs will decrease.
In the absence of frogs, number of grasshoppers will increase and they will eat all the plants. The human beings will not get food and will die of starvation.
This shows that disturbance in any part of the food chain would disturb the whole nature.
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Environmental Problems
Humans are the only living things who can alter the environment according to their needs. Some of the human activities that have damaged the environment are as follows:
People have started cutting down trees to meet their needs of housing and agriculture. As a result, soil gets eroded and many wild animals like lions, zebras, elephants, etc. have lost their shelters or habitats. Some are even endangered and may extinct if this continues.
Poaching is yet another threat. People have started hunting wild animals for clothing, cosmetics and pleasure.
People have started dumping the wastes from factories, homes and other places into water and soil.
Humans have started releasing smoke from factories and mills into air and water. Thus, polluting our natural resources like air, water or soil and warming the environment.
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Greenhouse
The glasshouse in which we grow green plants or saplings mainly during winter is called Greenhouse.The glass walls of green house do not allow the heat to escape.
Greenhouse Gases
The gases which do not allow heat to escape back into space trapping the sun's energy. Thus, help in warming up the earth. These gases are called greenhouse gases like that Carbon-dioxide, nitrous oxide, methane and water vapour.
Greenhouse Effect
The green house gases traps the sun's energy and do not allow heat to escape back into space. Thus, help in warming up the earth. Effect of warming up the earth by greenhouse gases is called the greenhouse effect.
The infrared rays of the sun bring heat and light energy and warm up the atmosphere. Most of radiation is absorbed and re-emitted in all directions. The effect of this is to warm the Earth's surface and the lower atmosphere.
Some Greenhouse Gases
Carbon dioxide: Over the past few years, the amount of carbon dioxide in the atmosphere has been increasing gradually. The main reasons for this increase are the excessive burning of fossil fuels, smoke from chimneys of factories and powers stations and continuous destruction of forests. If the amount of carbon dioxide in the atmosphere keeps on increasing at a rapid rate, then more the temperatur will be trapped Due to this
Methane: Methane is a natural gas. It also heats up the earth. A large amount of methane gas is released into the atmosphere when herbivores digest their food.
Chlorofluorocarbon (CFC): Chlorofluoro- carbon (CFC) too heats up our planet. CFC is a chemical widely used in air conditioners and refrigerators.
Water vapour and Ozone (found in the stratosphere) also warm up our earth.
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Global Warming
Due to the increase in level of greenhouse gases in the atmosphere, there is an increase in temperature of the earth. This is known as global warming.
Due to the Melting of polar ice-caps, rise in water levels of oceans and floods in places near the sea are some of the effects of global warming.
Over the last hundred years, the average temperature of our planet has increased by 1°F and it is estimated that in the next century it may rise to about 2°-6° F. This will make the situation worse on earth.
Now, it is the duty of every country to reduce the use of greenhouse gases. In this way we can prevent a massive disaster.
Kyoto Protocol –> Most of the countries have signed. agreements which aimed at reducing greenhouse gases. Kyoto Protocol is one such agreement.
Early steps are required to reduce global warming.
If we use electricity carefully, reduce the use of fuels, use mass mode of transport such as bus, metros, grow more plant and lastly use recycled products, we can help in reducing the greenhouse gases and hence prevent a major disaster.
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Pollution
Pollution means the presence of harmful substances in air, water and land, which can cause harm or discomfort to all living things.
Smoke from vehicles and factories pollutes the air.
When nuclear power stations produce electricity, they release harmful and poisonous waste which mixes with the air.
Spilling of oil or petroleum and dumping of chemical waste released by factories, into rivers, seas and oceans cause harm to the animals and plants living in water.
How to Prevent Pollution?
To make the earth a better place to live in, we must take some steps.
These are as follows:
★ Restrict the use of vehicles and electricity.
★ Tall chimneys with filters must be fitted in industries that release smoke and gases very high, away from the populated places.
★ Factories and vehicles releasing smoke should be penalised.
★ Before letting dirty water into seas, rivers or lakes, it should be treated with chemicals which make it less harmful.
★ Avoid using plastic bags because they block drains and stop the flow of dirty water. If eaten by animals, they choke them.
★ Wet waste and dry waste must be disposed off separately and at a proper dumping place.
★ We need to start following the 3R that is Reduce, Reuse and Recycle The is mainly done to reduce the accumulation of waste such as meta cans, paper, rubber and plastic. Thes things can be recycled or reused directly
★ Nowadays, plastic is being used to mal a lot of useful. colourful and lightweigh things. Plastic cans can be used to mak things like flower pots and park furniture
Trees should not be cut.
★ More and more trees should be planted.
★ National parks and wildlife sanctuarie should be established.
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Note
In a food plants are producers, thus herbivores are called primary consumers. food carnivores and Omnivores are secondary consumers and bacteria and fungi are decomposers.
The heating or warming up of our earth globally is called Global Warming.
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Exercise
A. Tick (✔) the correct option.
1. Which of the following is a greenhouse gas?
a) CFC
b) carbon dioxide
c) methane
d) all of these
2. These are the primary consumers.
a) carnivores
b) decomposers
c) plants
d) herbivores
3. Which gas is used by plants for making their food?
a) carbon dioxide
b) methane
c) oxygen
d) nitrogen
4. This is not an effect of global warming.
a) Melting of polar ice caps.
b) Rise in level of water in oceans.
c) Spilling of oil or petroleum.
d)Flooding of places near the sea.
Ans. 1. d) all of these, 2. d) herbivores, 3. a) carbon dioxide, 4. c) Spilling of oil or petroleum.
B. Fill in the blanks.
1. Carnivores animals are ............. consumers
2. The chain of who eat whom in ecosystem to obtain nutrition is called ............. .
3. ............. is a chemical widely used in refrigerators and air-conditioners
4. ............. from factories and vehicles pollutes the air.
5. In a food chain, if all the eagles are killed, then the number of snakes will .............
Ans. 1. Primary, 2. Food chain, 3. CFC, 4. Smoke, 5. Increase.
C. Answer these questions in one or two sentences.
1. What are decomposers? Give any two examples of decomposers.
Ans. Decomposers –> Bacteria and fungi feed on dead and decaying matter and decompose them to produce nutrients are called decomposers. These nutrients are used by plants for growth.
Bacteria and fungi are the example of decomposers.
2. Define greenhouse.
Ans. The glasshouse in which we grow green plants or saplings mainly during winter is called Greenhouse.The glass walls of green house do not allow the heat to escape.
3. Name any three greenhouse gases.
Ans. The gases which do not allow heat to escape back into space trapping the sun's energy. Thus, help in warming up the earth. These gases are called greenhouse gases like that Carbon-dioxide, nitrous oxide, methane and water vapour.
4. Arrange the following in the order in which they occur in a food chain. Carnivores, Plants, Decomposers, Herbivores
Ans.
Plants –> Herbivores –> Carnivores –> Decomposers.
D. Answer these questions in detail.
1. What is pollution? List the ways by which we can prevent pollution.
Ans.
Pollution
The presence of unwanted and harmful materials or substances in the ------- is called ------ pollution.
★ Pollution means the presence of harmful substances in air, water and land, which can cause harm or discomfort to all living things.
How to Prevent Pollution?
To make the earth a better place to live in, we must take some steps.
These are as follows:
★ Restrict the use of vehicles and electricity.
★ Tall chimneys with filters must be fitted in industries that release smoke and gases very high, away from the populated places.
★ Factories and vehicles releasing smoke should be penalised.
★ Before letting dirty water into seas, rivers or lakes, it should be treated with chemicals which make it less harmful.
★ Avoid using plastic bags because they block drains and stop the flow of dirty water. If eaten by animals, they choke them.
★ Wet waste and dry waste must be disposed off separately and at a proper dumping place.
★ We need to start following the 3R that is Reduce, Reuse and Recycle The is mainly done to reduce the accumulation of waste such as meta cans, paper, rubber and plastic. Thes things can be recycled or reused directly
★ Nowadays, plastic is being used to mal a lot of useful. colourful and lightweigh things. Plastic cans can be used to mak things like flower pots and park furniture
2. What is global warming? List the effects of global warming.
Ans. Global Warming
Due to the increase in level of greenhouse gases in the atmosphere, there is an increase in temperature of the earth. This is known as global warming.
Due to the 1. Melting of polar ice-caps, 2. rise in water levels of oceans and 3. floods in places near the sea are some of the effects of global warming.
3. Write a short note on greenhouse gases.
(i) Producers
(ii) Secondary consumers.
Ans.
(i) Producers –> In an ecosystem, the green plants are called producers because they make their own food.
(ii) Carnivores and omnivores are called secondary consumers.
Carnivorous –> Carnivorous animals like lion, tiger, eagle, dog, etc. eat the flesh of other animals.
Omnivorous –> Omnivorous animals like bear, man, etc. eat both plants and animals.
4. Define the following (Think)
How do you think a programme like Vanmahotsava is helping in conserving the environment?
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