LAKHMIR SINGH AND MANJIT KAUR Solutions for Class 10 Biology Chapter 5 - Our Environment

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Chapter 5 - Our Environment Exercise 226

Solution 1
Ecosystem.
Solution 2
Natural ecosystems - Grass land and forest.

Artificial ecosystems - Parks and Gardens.
Solution 3
Aquarium.
Solution 4
Plants are called producers because green plants prepare their own food from simple inorganic substances like carbon dioxide and water by using sunlight energy in the presence of chlorophyll.
Solution 5
Decomposers.
Solution 6
Planktons are very minute or microscopic organisms freely floating on the surface of water in a pond, lake, river or ocean.
Solution 7
(a) False.
(b) True.

Solution 8
Producer.
Solution 9
Goat and Rat (Both are herbivores).
Solution 10
Tree and Grass (Both are producers).
Solution 11
Solution 12
Second trophic level: Insects

Fourth trophic level: Snakes
Solution 13
Trophic levels
Solution 14
Solution 15

Solution 16
Third Trophic level: Snakes.
Fourth trophic level: Hawk.

Solution 17
Environment.
Solution 18
Energy.
Solution 19
(a) Specific.
(b) Producers.
(c) Food Chain.
(d) Ecology.
(e) Non - biodegradable; Biodegradable.

Solution 20
(i) Producers are the organisms which can be prepare their own food from simple inorganic substances like carbon dioxide and water by using sunlight energy in the presence of chlorophyll.

Example - Green plants and certain blue-green algae.

(ii) Those organisms which consume food (eat food) prepared by producers are called consumers.

Example - Lion and Tiger.
Solution 21
(a) The micro-organisms which break down the complex organic compounds present in dead organisms like dead plants and animals and their products like faeces, urine, etc., into simpler substances are called decomposers.
Example - Bacteria and Fungi.
(b) The decomposers help in decomposing the dead bodies of plants and animals, and hence act as cleansing agents of environment.

Solution 22
(i) The animals which eat only plants are called Herbivores. All herbivores are primary consumers.

Example - Goat

(ii) The small carnivores which feed on herbivores (primary consumers) are called secondary consumers.

Example - Frog

(iii) The Large carnivores (or top carnivores) which feed upon the small carnivores (secondary consumers) are called tertiary consumers.

Example - Lion

Chapter - Exercise

Solution
Solution

Chapter 5 - Our Environment Exercise 227

Solution 42
(a) The waste materials which cannot be broken down into non-poisonous or harmless substances in nature are called non-biodegradable waste materials.

Example - D.D.T and Plastics.

(b) Animal Bones and Leather Belts.

Solution 23

Solution 24
(a) Trophic Levels - The various steps in a food chain at which the transfer of food takes place are called trophic levels. In a food chain, each step representing an organism forms a trophic level.



(b) If we kill all the organisms in one trophic level, then the transfer of food (and energy) to the next trophic level will stop due to which the organisms of next trophic level will starve and die or migrate to other areas. The killing of all the organisms in one trophic level will also lead to the overpopulation of organisms in the previous trophic level. These effects will cause an imbalance in the ecosystem. For example, if we kill all the herbivorous animals like deer, rabbits, etc., in a forest, then the carnivorous animals like lions, tiger, etc., will not get food. Due to this, the lions and tigers etc., will starve and die or migrate from forest and go towards human settlements and attack people. Moreover, in the absence of herbivores like deer, rabbits, etc., the population of the previous trophic level 'plants' (or vegetation) will increase too much (because there are no deer or rabbits to eat them). All these effects will create an imbalance in the ecosystem.
Solution 25
The organisms belonging to the first trophic level are producers which make their own food with the help of sun's energy. For example - Green plants. The organisms of third trophic level are carnivores that feed upon herbivores. For example - Lion and Tiger.
Solution 26
No. The impact of removing all the organisms of a trophic level will be different for different trophic levels.
Solution 27
If all the lions are removed, then there will be no predator control over the population of deer due to which its populations will greatly increase and deer will eat all grass. Over grazing will eliminate the grass and other green plants completely and turn the lush green forest into a desert area having no vegetation at all.
Solution 28
Frogs eat up mosquitoes. In the absence of frogs, the number of mosquitoes increase too much and spread malaria.
Solution 29
Bioderghradable Wastes Non-Biodegradable Wastes

 

1. Those waste materials which can be broken down to non-poisonous substances in nature by the action of microorganisms (like bacteria) are called biodegradable wastes.



2. They get recycled and therefore do not require dumping sites.



3. They do not cause any pollution to the soil.

 

 

Example:- Paper, Wood, etc.

 

1. Those waste materials which cannot be broken down to non-poisonous substances in nature are called non-biodergradable wastes.

2. They cannot be recycled easily and therefore are to be dumped which requires lot of space. This cause wastage of land.

3. The harmful chemical leach out of these wastes when they are dumped in soil. This leads to soil pollution.

Example:- DDT, Plastic and Polythene bags

Solution 30
Glass bottle - Non-biodegradable

Paper - Biodegradable

Ball point pen refill - Non- biodegradable

Hay - biodegradable

DDT - Non- biodegradable

Wheat - Biodegradable

Cake - Biodegradable

Wood - Biodegradable

Polythene Bag - Non-biodegradable

Jute Bag - Biodegradable

Cotton Cloth - Biodegradable

Grass - Biodegradable

Vegetable peels - Biodegradable
Solution 32
Solution 33
(a) Third trophic level
(b) Second trophic level
(c) Third trophic level
(d) Second trophic level
(e) Fourth trophic level

  

 

Solution 34
(a) Weed  Tadpole Water beetle

(b) Three
Solution 35
Solution 36
(a) Jute bags should be used for shopping because these are biodegradable whereas plastic bags are non- biodegradable.
(b)

Solution 37
Pond is a complete eco system having decomposer organisms which are the cleansing agents themselves. Aquarium is an incomplete ecosystem and does not have decomposer organisms for cleansing purposes.
Solution 38
In the absence of decomposers, the dead bodies of plants and animals would keep lying as such and the elements of plant and animal bodies would never be returned to their original pool like soil, air and water. The cycling process of life and death would be disrupted. The nutrient pool will not be replenished and would exhaust soon.
Solution 39

Solution 40
(a) Trophic Level

(b) Abiotic components

(c) Consumers

(d) Environment

(e) Ecosystem

Chapter 5 - Our Environment Exercise 228

Solution 44
(a) The sequence of living organisms in a community in which one organism consumes other organisms to transfer food energy is called a food chain. The simple food chain operating in grass land is:



(b) The interconnected food chains operating in an ecosystem which establish a network of relationships between various species is called a food web.



In this food web, we can see a network of numerous pathways along which the food flows within grass land community. This food web starts from the plants which is producer and end in top carnivore hawk.
Solution 45
(a) The physical and biological world together is called environment.

(b) The non- biodegradable wastes pollutes the environment like plastic and polythene bags.

(c) Human beings are the only organisms which change the natural environment to fulfill their needs. The uncontrolled activities of human beings are damaging the balanced and healthy environment.

(d) Paper bags should be used for shopping because these are biodegradable whereas plastic bags are non- biodegradable.
Solution 43
(a) An eco system is a self contained unit of living things(plants, animals and decomposers), and their non living environment (soil, air and water).

Example - a grassland and a forest.

(b)

(i) Biotic component - The biotic components of the ecosystem is a community of organisms which is made up of many different inter-dependent populations. It includes - producers, consumers and decomposers.

(ii) Abiotic components - The abiotic components of the ecosystem (non living components) include the physical environment like soil, water and air alongwith the in organic substances like carbon dioxide, nitrogen, water and phosphorous.

Chapter 5 - Our Environment Exercise 240

Solution 1
1%.
Solution 2
10%.
Solution 3
Biological Magnification.
Solution 4
Bird.
Solution 5
Cat.
Solution 6
Ultra Violet radiations.
Solution 7
Chlorofluro Carbons.
Solution 8
Paper and Plastics.
Solution 9
Incineration.
Solution 10
0.05 J.
Solution 11
False.
Solution 12
Sun.
Solution 13
Because after that the energy available for the next organism will be so small that it will be insufficient to sustain the life of that organism.
Solution 14
Peacock and hawk.
Solution 15
(a) Cancer.

(b) Producer.

(c) Goat.

(d) Rabbit.

(e) Lion.

Chapter 5 - Our Environment Exercise 241

Solution 25
The various modes of waste disposal are:

(i) Recycling

(ii) Preparation of compost

(iii) Incineration

(iv) Landfill

(v) Sewage treatment
Solution 26
The solid wastes like papers, plastics and metals are recycled. For example - waste paper is send to paper mills where it is reprocessed to form new paper once again.
Solution 27
Preparation of compost is a method in which the disposal of household wastes such as left-over food, fruit and vegetable peels and leaves of potted plants can be converted into compost by burying in a pit dug into the ground and is used as manure.
Solution 28
Incineration means reducing to ashes. It is used to destroy the household waste, chemical waste and biological waste.
Solution 29
Most of the solid waste in urban areas is dumped in low line areas of ground and covered with earth to level the uneven ground. This method is called landfill.
Solution 30
The advantages of using disposable paper cups over disposable plastic cups are:

(i) Paper cups are biodegradable. So, even if paper cups are thrown away after use, they will decompose (break down) automatically by the action of micro-organisms in due course of time. On the other hand, plastic cups are non-biodegradable. They will remain as such and pollute the environment.

(ii) Paper cups can be disposed off by burning without causing much air pollution. On the other hand, burning of plastic cups produces toxic gases (poisonous gases) which causes too much air pollution.
Solution 31
The dirty drain water containing urine and faeces which is carried from our homes by the underground pipes (called sewers) is called sewage. Sewage is disposed off by treating it at the sewage treatment plant (or sewage works). The treatment of sewage produces clean water which is discharged into the river. The organic matter present in sewage is 'digested' in the digesters of sewage treatment plant to produce 'sewage gas' (which is kind of biogas) and manure.
Solution 32
Harmful effects of ozone depletion are:

(i) It can cause skin cancer.

(ii) It damages the eyes by causing the eye disease called cataract.

(iii) It damages the immune system by lowering the body's resistance to diseases.
Solution 33
If the ozone layer in the atmosphere disappears completely, then all the extremely harmful ultraviolet radiations coming from the sun would reach the earth. These ultraviolet radiations would cause skin cancer and other ailments in men and animals, and also damage the plants.
Solution 34

(a) The energy from sun flows through various trophic levels. The food and energy are transferred from producer organisms to herbivores and from herbivores to carnivores, through the food chain.

First Step - The green plants trap solar energy with the help of green pigment called chlorophyll which converts the sunlight energy into chemical energy. This gets stored as carbohydrates in the plants. About 1% of the sun's energy falling on the leaves is used by the plants in the process of photosynthesis and stored as chemical energy of food. The plants utilize the stored energy for their metabolic activities like respiration and growth. Some of the energy is not utilised and it is released as unusable heat into the environment.

Second Step - The plants are eaten up by herbivores and the chemical energy of plants is transferred to them. The herbivores utilize this energy for various metabolic activities and release unused energy as heat energy to the environment.

Third Step - The herbivores are eaten up by carnivores. The chemical energy stored in the flesh of herbivores is transferred to the carnivores and they utilise this energy for their metabolic activities like respiration and growth and some of the energy which remains unutilised, is released into the environment. This process of transfer of energy is repeated with large carnivores and so on.



(b) The flow of energy in the ecosystem is said to be unidirectional because the energy lost as heat from the living organisms of a food chain cannot be reused by plants in photosynthesis.

Solution 35
(a) Ozone is a poisonous gas. It is made up of three atoms of oxygen combined together. It is formed high up in the atmosphere by the action of ultraviolet radiation on oxygen gas. The high energy ultraviolet radiation (UV radiation) coming from the sun splits oxygen gas into free oxygen atoms.



The free oxygen atoms thus produced are very reactive. One oxygen atom reacts with an oxygen molecule to form an ozone molecule:



(b) Ozone layer protect us from harmful effects as it absorbs most of the ultraviolet radiations coming from the sun and prevents them from reaching the earth.

(c) UNEP - United Nation Environment Program. In 1987, in an attempt to protect ozone layer, the United Nations Environment Program (UNEP) forged an agreement among its member countries to freeze CFC production at 1986 levels.
Solution 36
(a) The energy enters the living components of the ecosystem through the process of photosynthesis.

(b)

(i) The producer level in the food chain are plants, so 100 J of energy is available in plants as food. Applying the 10% law to the above food chain:

1. According to the 10% law, 10% of energy of plants will be available as food in mice. Thus, the energy available to mice will be 10% of 100 J, which is 10 J.

2. The energy available to snakes will be 10% of 10 J, which is 1 J.

3. The energy available to hawks will be 10% of 1 J, which is 0.1 J.



(ii) The producer level in the food chain is plants, so 100 J of energy is available in plants as food. Applying the 10% law to the above food chain:

1. According to the 10% law, 10% of energy of plants will be available as food in mice. Thus, the energy available to mice will be 10% of 100 J, which is 10 J.

2. The energy available to hawks will be 10% of 10 J, which is 1 J.



Hawks will get more energy in food chain (ii) because in this food chain there are three trophic levels so the energy available will be more as compared to food chain (i) which has four trophic levels.
Solution 37
(a) Food chain generally consists of three or four steps because after that the energy available for the next organism will be so small that it will be insufficient to sustain the life of that organism.

(b)

(i) Small algae can trap only 1% of the sun's energy falling on them. 1% of 10,000 J is 100 J, so the small algae have 100 J of energy available.

(ii) Small algae are eaten up by zooplankton. According to the 10% law, 10% of 100 J is 10 J of energy which is available in zooplankton.

(iii) The zooplankton will transfer 10% of its 10 J energy to the fish. Thus, the food energy available to the fish will be 10% of 10 J, which is 1 J.

(iv) 10% of 1 J will be transferred to big fish which will be 0.1 J.

The above result can be clearly shown as:

Solution 38
(a) The law given by Lindeman is 10% law. According to 10% law, only 10% of the energy entering a particular trophic level of organisms is available for transfer to next higher trophic level.

(b) (i) Paddy can trap only 1% of the sun's energy falling on them. 1% of 10,000 J is 100 J, so paddy have 100 J of energy available in them as food.

(ii) Paddy is eaten up by mice. Now according to the 10% law, 10% of 100 J is 10 J of energy which is available in mice.

(iii) The mice will transfer 10% of its 10 J energy to the snake. Thus, the food energy available to the snake will be 10% of 10 J, which is 1 J.

(iv) 10% of 1 J will be transferred to hawk which will be 0.1 J.

Solution 16

Ten PerCent Law - According to ten per cent law, only 10 per cent of the energy entering a particular trophic level of organisms is available for transfer to the next higher trophic level.
Example - Suppose 1000 Joules of light energy emitted by the sun falls on the plants.
Consider a food chain:

The plants or first trophic level has 10 joules of energy in it. Now according to 10 percent law, only 10% of 10 joules of energy (which is 1 joule) will be available for transfer to the next trophic level, so that the herbivore will have only 1 joule of energy stored as food at the second trophic level. 10% of the remaining 1 joule will be transferred to third trophic level of carnivore. So, the energy available in the lion as food will be only 0.1 joule.

Solution 17
CFC - Chlorofluorocarbons.
Chlorofluorocarbons released into the air react with ozone gas present in the ozone layer and destroy it gradually.

Solution 18
Ozone layer absorbs most of the harmful ultra violet radiations coming from the sun and prevents them from reaching the earth.
Solution 19
The depletion of ozone layer is due to the use of chemicals called chlorofluorocarbons. Skin cancer is caused if the ozone layer will become thinner.
Solution 20
Pesticides are poisonous chemical substances which are sprayed over crop plants to protect them from pests (harmful small animals) and diseases. These chemical pesticides mix up with soil and water. From soil and water, these pesticides are absorbed by the growing plants alongwith water and other minerals. When herbivorous animals eat plant food, then these poisonous chemical pesticides go into their bodies through the food chain. And when the carnivore animals eat herbivores, then the pesticides get transferred to their bodies. Man being an omnivore; eat plant food as well as herbivores. So the pesticides present in plant food and herbivores also get transferred to the man's body through food. Thus, pesticides enter the food chain at the producer level (plant level) and in the process of transfer of food through food chains these harmful chemicals get concentrated at each trophic level.
Solution 21
Pesticides are non - biodegradable chemicals, so they get accumulated at each trophic level. Since humans occupy the top level in any food chain, so the maximum amount of harmful chemical pesticides gets accumulated in our bodies. This damages our health gradually.
Solution 22

The increase in concentration of harmful chemical substances like pesticides in the body of living organisms at each trophic level of a food chain is called biological magnification.
The organism which occurs at the highest trophic level (on the extreme right side) in the food chain will have the maximum concentration of harmful concentration of harmful chemicals in its body. In this case grass is eaten by grasshopper; grasshopper is eaten by frog; frog is eaten by snake and finally snake is eaten by peacock. So, the food chain will be:

Since the peacock occurs at the highest trophic level (on the extreme right side) in this food chain, it will have the maximum concentration of harmful chemicals in its body.

Solution 23
The accumulation of harmful chemicals such as pesticides in the living organisms like plants, animals and humans (men) through the food chain is called bio-concentration of pesticides. DDT has accumulated in human body through food chains.
Solution 24
The household wastes are called garbage. It includes left -over food, fruit and vegetable peels, waste paper, unwanted plastic objects etc.