Matric Notes Biology Class 10th Ch 16 Man and His Environment Long Questions
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Q1: Describe the nitrogen cycle in detail. What would happen if nitrogen cycle stopped working?
ANS: Nitrogen cycle:
Occurrence: Nitrogen is an important component of many biomolecules, like:
• Nucleic acids ( DNA and RNA)
• Atmosphere is the reservoir of free gaseous nitrogen.
Living organisms cannot pickup this gaseous nitrogen directly from atmospheric except for nitrogen fixing bacteria. It has to be converted into nitrates to be utilized by plants.
Nitrogen cycling involves several stages.
➢ Formation of nitrates: It is done by the following ways:
The conversion of nitrogen gas into nitrates is called nitrogen fixation. It occurs in the following ways:
Atmospheric nitrogen fixation: Thunderstorms and lightening convert atmospheric gaseous nitrogen to oxides of nitrogen. These oxides dissolve in water and form nitrous acid and nitric acid. The acids in turn combine with other salts to produce ‘nitrates’. It is called as atmospheric nitrogen fixation.
Biological nitrogen fixation: Some bacteria also have the ability to transform gaseous nitrogen into nitrates. It is called biological nitrogen fixation. Some of these nitrogen fixing bacteria live as symbioses and many are free-living.
Industrial nitrogen fixation: Nitrogen fixation is also done in industries. In industries nitrogen fixation, hydrogen is combined with atmospheric nitrogen under high pressure and temperature. It produces ammonia which is further converted into ammonium nitrate.
➢ Ammonification and nitrification The breakdown of the proteins of dead organisms and nitrogenous wastes (urea, uric acid etc.) to ammonia is called ammonification. It is done by ammonifying bacteria.
Nitrification: The process of conversion of ammonia into nitrites and nitrates is called nitrification. It is done by nitrifying bacteria.
Formation of nitrites: First, ammonia is converted into nitrites by bacteria like:
• Nitrosomonas
Formation of nitrates: The nitrites are then converted into nitrates by other bacteria like:
• Nitrobacteria
➢ Assimilation:
Definition: The utilization of nitrates by organisms is called assimilation.
Explanation: The nitrates formed by the process of nitrification, are absorbed by plants and are utilized for making proteins etc. Animals take nitrogenous compounds from plants.
➢ Denitrification: The biological process in which nitrates and nitrites are reduced to nitrogen gas by denitrifying bacteria is called denitrification. By this process nitrogen is returned to atmosphere.
Excessive denitrification reduces soil fertility and is stimulated by:
• Lack of aeration
Stoppage of nitrogen cycle: If there was not nitrogen cycle. There would likely be no living things. Nitrogen is needed to create amino acids which in turn build proteins in all plants and animals. Without a nitrogen cycle that converts atmospheric nitrogen into other compounds, living creatures would not be able to grow.
Q2: Compare the flow of materials and the flow of energy in ecosystem.
Ans: Flow of materials: The materials flow from one trophic level to the next by means of food chains and food webs.
Trophic level: Trophic level is the level at which an organism feeds in food chain. The first trophic level is made of producers; the second of primary consumers and so on.
➢ Food chain
Definition: A series of organisms within an ecosystem, in which each organism feeds on the one before it and is fed by the one after it is called food chain.
Example: Following is the food chain in an ecosystem:
Explanation: The base of food chain is always formed by a plant (producer). It is eaten by a primary consumer, which is preyed upon by a secondary consumer. The secondary consumer may be eaten by a tertiary consumer. A food chain, can therefore be presented as, 𝑃𝑟𝑜𝑑𝑢𝑐𝑒𝑟→𝑃𝑟𝑖𝑚𝑎𝑟𝑦 𝑐𝑜𝑛𝑠𝑢𝑚𝑒𝑟 →𝑆𝑒𝑐𝑜𝑛𝑑𝑎𝑟𝑦 𝑐𝑜𝑛𝑠𝑢𝑚𝑒𝑟→𝑇𝑒𝑟𝑡𝑖𝑎𝑟𝑦 𝑐𝑜𝑛𝑠𝑢𝑚𝑒𝑟
Advantages: A food chain involves a nutritive interaction among the biotic components of an ecosystem.
Number of Trophic level: Usually there are 4 or 5 trophic levels. Shorter food chain provide greater available energy and vice versa.
➢ Food web: A network of food web which are interconnected at various trophic levels is called food web.
Explanation: In nature, food chain are very complex, as one organisms may be food source of many other organisms. Thus, instead of a simple linear food chain, there is web like structure formed by these inter-linked food chains. Such interconnected food chain collective make food webs.
➢ Flow of energy: In an ecosystem, energy travels from one trophic level to next.
Trophic level: Trophic level is the level at which one organism feed in food chain. The first trophic level is made of producers; the second of primary consumers and so on.
Unidirectional flow: The flow of energy of Trophic level in different trophic levels of ecosystem is unidirectional.
Primary source: The sun is the primary source of energy for all ecosystem.
Energy in producers: Producers get solar energy and transform it into chemical energy by the process of photosynthesis. They store their energy in their tissues and also transform it into mechanical and heat energy during their metabolic activities.
Energy herbivores: The energy in producers tissues flows to herbivores when producers are eaten. Herbivores transform it into mechanical and heat energy during their metabolic activities and store the rest in their tissues.
Energy in carnivores: Carnivores eat herbivores and get energy. They also use it for their body activities and store the rest in their tissues.
Energy in decomposers: After the death of producers and consumers, the energy stored in their tissues is used by decomposers.
Law of thermodynamics: The storage and expenditure of energy in an ecosystem is in accordance with the basic law of thermodynamics.
• Statement: Energy can neither be created nor destroyed but can be transformed from one form to another. Energy within ecosystem:
In an ecosystem there is:
Constant flow: Constant flow or transfer of energy from the sun through producers to consumers and decomposer.
➢ Decrease in energy: A significant decrease in useful energy during transfer of energy at each trophic level.
Q3: What are the different ways through which organism of the ecosystem interact with each other?
Ans: Interaction in the ecosystem: The existence of the living world depends on the flow of energy and circulation of materials through the ecosystem. In all ecosystem, the organisms living in the same area interact with each other. These interactions may be intraspecific i.e. between the organisms of the same species or inter-specific. The following are some of the important interactions among organisms.
➢ Competition: In ecosystem, the natural resources e.g. nutrients, space etc. are usually in short supply. So, there is a competition among the organisms of ecosystem for the utilization of resources.
Types of competition:
The competition may be intraspecific or interspecific.
• Intraspecific Competition:
The competition among the individuals of the same species is called intraspecific competition.
• Interspecific competition:
The competition among the individuals of the different species is called interspecific competition.
Comparison:
Intraspecific competition is always stronger and more severe than the interspecific competition.
Advantage:
Competitions helps in maintaining a balance between the available resources and the number of individuals of a species.
Competitions in plants:
Plants also show competition for:
• Light
• Water
• Minerals
➢ Predation:
Introduction: It is an interaction between two animals of different species or between a plant and an animal.
Definition: The relationship between predator and prey is called predation.
Predator: The organisms that attacks, kills and feeds on other organisms is called predator.
Prey: The organisms that is being hunted upon is called prey.
Examples: All carnivore animals are predators. Some examples of predation are given below:
• Fox preys upon rabbit.
• Tiger prey upon zebra.
There are some examples where a predator is preyed upon by a second predator then the second one is preyed upon by a third predator.
For example: Frog (predator 1) is preyed upon by a snake (predator 2) and the snake is preyed upon by an eagle (predator 3).
Predation in plants: Certain plants are carnivorous and live as predators. Such plants live in the areas where minerals and other nutrients are lacking. They feed on insects to fulfill their nitrogen requirements. These plants have mechanism to attract insects. For example, they secrete sweet nectar that attract the insects searching food. Their leaves are also modified to capture the pray.
Examples:
• Sundew
• Venus fly trap
Advantage: Predation keeps the prey population under check, so as to maintain an ecological balance. Human benefit from this interaction in the biological control of weeds and pests. In order to control pests in an area, their predators are released there.
Symbiosis: A relationship between members of different species, in which they live together for longer or shorter periods of time, is called symbiosis.
Type of symbiosis: Symbiosis is of three types:
2. Mutualism
3. Commensalism
➢ Parasitism: A type of symbiosis between members of different species, in which smaller partner (parasites) derive food and shelter from the body of larger partner (host) and, in turn, harms it is called parasitism.
Temporary parasitism: In temporary parasitism, the parasite spends most of its life cycle as parasites.
Examples: Leech, Bed bug, Mosquito.
Permanent parasitism: In permanent parasitism spend their whole life cycle as parasites.
Examples: Disease causing bacteria, all viruses etc.
Classification of parasites: Parasites may also be classified as ectoparasites and endoparasites.
Ectoparasites:- The parasites that live outside i-e on the surface of host’s body and get food from there are called ectoparasites.
Examples:- Mosquitoes, Leeches, Lice etc.
Endoparasites:- The parasites that live inside the body of host and get food and shelter from there are called endoparasites.
Examples:- Bacteria, Viruses, Tapeworm, Ascaris, Entamoeba etc.
Parasitic plants:- Some plants are parasites on other plants. Parasitic plants grow special types of roots called haustoria into host body and suck the required nutrients from the vascular tissues of host.
Example:- Cuscuta, also called dodder.
Survival of host and parasite:- Host can survive without parasite, but parasite cannot survive without host.
➢ Mutualism:
Definition:- The type of symbiotic interaction in which both partners of different species get benefit and neither is harmed is called mutualism.
Examples: Termites and zoo flagellates:
Termites eat wood but are not able to digest it. A protozoan lives in its intestine. It secrete “cellulase” enzyme to digest the cellulose of wood. In return, the termite provides food and shelter to the protozoan.
Root nodules: The nitrogen fixer bacteria Rhizobium live in the root nodules of leguminous plants like pea, gram etc. The bacteria obtain food and shelter from plants while in return they fix gaseous nitrogen into nitrates for the plant which is required for their growth.
➢ Commensalism:
Definition: It is a type of symbioses in which one partner is benefited while the other is neither benefited nor harmed.
Examples: Epiphyte are small plants found growing on other larger plants for space only. They absorb water and minerals from atmosphere and prepare their own food. The larger plants are neither benefited nor harmed in any way.
Sucker fish: Sucker fish attaches to the surface of sharks by its sucker. In this way, the shark provides easy transport to the sucker fish to new feeding grounds.
Barnacles on the body of whale
Q5: Discuss the biotic components of the ecosystem.
Ans: Biotic components: All the living part (organisms) of the ecosystem are called as biotic components.
Classification: Biotic components are further classified as:
ii. Consumers
iii. Decomposers
➢ Producers: The producers are the autotrophs present in ecosystem. These organisms are able to synthesize complex organic compounds (food) from inorganic raw material. Producers from the basic of any ecosystem.
Examples:
• Plants
• Algae
• Photosynthetic bacteria
Terrestrial ecosystem: In terrestrial ecosystem, plants are the main producers.
Aquatic ecosystem: In aquatic ecosystem, the main producers are the floating photosynthetic organisms (mainly algae) called phytoplankton and shallow water rooted plants.
➢ Consumers: The consumers are heterotrophs. They cannot synthesize their food and so depend upon producers for food.
Examples: Consumers include:
• Fungi
• Protozoans
• Many of the bacteria
➢ Herbivores ( primary consumers): The animals that feed on plants are called herbivores. The herbivores are the primary consumers. They feed directly on plants or products of plants.
For example:
• Deer
• Rabbit
• Grasshopper
➢ Primary carnivores: Primary carnivores (secondary consumers) feed on herbivores.
Example:
• Frog
• Predatory birds
• Many fishes
• Snakes
Secondary carnivores: Secondary carnivores (tertiary consumers) feed on primary carnivores.
Example:
• Owl
Tertiary carnivores:
• Tiger
➢ Decomposers: Decomposers or reducers breakdown the complex organic compounds of dead matter of plants and animal into simple compounds. They secrete digestive enzymes into dead and decaying plant and animal remains to digest the organic material. After digestion, decomposers absorb the products for their own use. The remaining substances are added to environment.
Examples:
• Fungi
Q6: Write a note on three types of symbiosis.
Ans: Symbiosis: A relationship between members of different species, in which they live together for longer or shorter periods of time, is called symbiosis.
Type of symbiosis: Symbiosis is of three types:
2. Mutualism
3. Commensalism
➢ Parasitism: A type of symbiosis between members of different species, in which smaller partner (parasites) derive food and shelter from the body of larger partner (host) and, in turn, harms it is called parasitism.
Temporary parasitism: In temporary parasitism, the parasite spends most of its life cycle as parasites.
Examples: Leech, Bed bug, Mosquito.
Permanent parasitism: In permanent parasitism spend their whole life cycle as parasites.
Examples: Disease causing bacteria, all viruses etc.
Classification of parasites: Parasites may also be classified as ectoparasites and endoparasites.
Ectoparasites:- The parasites that live outside i-e on the surface of host’s body and get food from there are called ectoparasites.
Examples:- Mosquitoes, Leeches, Lice etc.
Endoparasites:- The parasites that live inside the body of host and get food and shelter from there are called endoparasites.
Examples:- Bacteria, Viruses, Tapeworm, Ascaris, Entamoeba etc.
Parasitic plants:- Some plants are parasites on other plants. Parasitic plants grow special types of roots called haustoria into host body and suck the required nutrients from the vascular tissues of host.
Example:- Cuscuta, also called dodder.
Survival of host and parasite:- Host can survive without parasite, but parasite cannot survive without host.
➢ Mutualism:
Definition:- The type of symbiotic interaction in which both partners of different species get benefit and neither is harmed is called mutualism.
Examples: Termites and zoo flagellates:
Termites eat wood but are not able to digest it. A protozoan lives in its intestine. It secrete “cellulase” enzyme to digest the cellulose of wood. In return, the termite provides food and shelter to the protozoan.
Root nodules: The nitrogen fixer bacteria Rhizobium live in the root nodules of leguminous plants like pea, gram etc. The bacteria obtain food and shelter from plants while in return they fix gaseous nitrogen into nitrates for the plant which is required for their growth.
➢ Commensalism:
Definition: It is a type of symbioses in which one partner is benefited while the other is neither benefited nor harmed.
Examples: Epiphyte are small plants found growing on other larger plants for space only. They absorb water and minerals from atmosphere and prepare their own food. The larger plants are neither benefited nor harmed in any way.
Sucker fish: Sucker fish attaches to the surface of sharks by its sucker. In this way, the shark provides easy transport to the sucker fish to new feeding grounds.
Barnacles on the body of whale
Q7: Enlist the causes of water pollution and also describe how water pollution can be controlled.
ANS: Water pollution:-
Definition: The change in the composition of water by the addition of harmful substances is called water pollution.
Causes of water pollution:-
• Sewage: Sewage is one of the major pollutants of water. It contains organic matter and the excrete of human and other animals. Organic matter encourages the growth of micro-organisms which spread diseases.
• Industrial wastes: The wastes industries (acids, alkalis, dyes and other chemicals) are disposed in nearby water bodies. These wastes change the pH of water and harmful or even fatal to aquatic organisms.
• Hot water: Certain industries release a lot of hot water from their cooling plants. It results in heating up of water bodies and kills aquatic life.
• Fertilizers and pesticides: Fertilizers and pesticides enter into water bodies with the rain water flow and the ground water by seepage. These chemicals remain in water for a long time and can enter food chains.
• Oil leakage: Oil tankers and offshore petroleum refineries cause leakage into water. Oil floats on the water surface and prevents atmospheric oxygen from mixing in water. So, aquatic animals begin to die due to oxygen shortage.
• Heavy metals: Some heavy metals e.g. lead, mercury, arsenic and calcium also make the water polluted. Such metals can be present in the water, released from industrial and urban areas.
Effects of water pollution:
The following are major effects of pollution.
➢ Eutrophication: The enrichment of water with inorganic nutrients like nitrates and phosphates is called eutrophication.
➢ Algal blooms: The sewage and fertilizers contain large amount of inorganic material (nutrients). When sewage and fertilizers reach water bodies, the nutrients present in them promote algal blooms (excessive growth) present in water and it results in the depletion of oxygen. Algal bloom also reduces the light reaching the lower layers in water.
➢ Food chain contamination: The non-biodegradable water pollutants may stay in water for long times. From water, they enter into small organisms, which are fed upon by fish. The fish in turn are fed upon by land animals including human.
➢ Epidemics: Organic pollutants in water facilitate the growth of germs. Such polluted water causes epidemics like cholera, gastroenteritis etc.
➢ Effect of heavy metals: If water with such heavy metals is given to plants, the metals enter the vegetables that grow on these plants. Such contaminated vegetables are harmful for human health. Following are the adverse effects of heavy metals.
• Cause cancer
• Damage to nervous system
➢ Effects of mercury and land: Mercury and land can cause:
• Diseases of kidneys
• Diseases of circulatory system and nervous system
Control of water pollution:
➢ Public awareness: Public should be made aware of the dangerous of water pollution.
➢ Sewage treatment: Before releasing the sewage into water bodies, it must be purified through sewage treatment techniques.
➢ Industrial waste treatment: Industrial wastes should also be treated before they are released into water bodies.
Q8: Write a comprehensive note on land pollution.
Land pollution:-
Definition: The change in the composition of soil by the addition of harmful substances is called land pollution.
Control of land pollution:
o Disposals of wastes: There should be suitable and safe disposal of wastes including nuclear wastes.
o Recycling: Non-biodegradable materials like plastics, glass, metals, etc. should be recovered and recycled.
o Less use of Inorganic Pesticides: Inorganic Pesticides should be replaced by organic pesticides.
Importance of land:
Land is an important resource as it is the basis for the growth of producers. In the recent times, soil has been subjected to pollution.
Sources of land pollution:- Following are the main sources of land pollution.
✓ Pesticides: The pesticides used in agriculture have chemicals that stay in soil for long times.
✓ Acid rains: The acid rain change the pH of soil making it unsuitable for cultivation.
✓ Garbage: The household and other city garbage lies scattered in soil in the absence of a proper disposal system.
✓ Polythene material: Materials like polythene block the passage of water into soil and so decrease the water holding capacity.
✓ Industrial wastes: Many industries produce harmful chemicals which are disposed without being treated.
Nuclear wastes: Improper disposal of nuclear wastes also causes radioactive substances to remain in soil for a long time.
Improper sewerage system: Open latrines in villages and some parts of cities are also the source of land pollution.
CONTROL OF LAND POLLUTION:-
Disposal of wastes: There should be suitable and safe disposal of wastes including nuclear wastes.
Recycling: Non-biodegradable materials like plastic, glass, metals etc. should be recovered and recycled.
Less use of inorganic pesticides: Inorganic pesticides should be replaced by organic pesticides.
Q9: Explain, by making diagrams, pyramids of number and biomass.
ANS: Ecological pyramids
Introduction: In 1927, Charles Elton (an English ecologist) developed the concept of ecological pyramids. Organisms in food chain.
Observation: He noted that the animals present at the beginning of food chain are abundant in number while the animals present at the end of food chain are fewer in number.
Definition: A representation of the number of individuals or amount of biomass or energy present in various trophic levels of food chain.
Types of pyramids:
Ecological pyramids are of three types. The two are:
2. Pyramid of biomass
1. Pyramid of numbers
Definition: The graphic representation of the number of individuals per unit area at various trophic levels is called pyramid of numbers.
Explanation: Usually, producers are present in large number, primary consumers are in lesser in number, and secondary consumers are fewer, and so on. So, the producers are of smallest size but maximum in number, while the tertiary consumers are larger in size but lesser in number.
2. Pyramid of biomass:
Definition: The graphic representation of biomass present per unit area at different trophic levels is called pyramid of biomass.
Biomass: The total amount of living organic matter in an ecosystem at any time is called biomass.
Explanation: In a terrestrial ecosystem, the maximum biomass occurs in producers, and there is progressive decrease in biomass from lower to higher trophic levels.
Q10: Write a note on the causes and effect of air pollution.
Ans: Air pollution:-
Major issue: Air pollution is one of the major environmental issues of today.
Definition: The change of composition of air by the addition of harmful substances is called air pollution.
Harmful substances: The harmful substances causing air pollution may be:
• Automobile gases
• Particular matter
Sources or causes: All sources of air pollution are related to human activities.
Combustion: Burning of coal produces a lot of smoke and dust whereas burning of petroleum produces sulphur dioxide.
Air pollutants: In addition to these, air pollutants include:
2. Carbon dioxide
3. Nitrogen oxides
4. Hydrocarbons
5. Particular matter
6. Fluorine
In thermal industries: Thermal industries are coal based and their pollutants are:
2. Soot
3. Sulphur dioxide
Textile industries: Textile industries release.
2. Nitrogen oxides
3. Chlorine
4. Smoke
5. Sulphur dioxide
Steel industries: Steel industries release:
2. Carbon dioxide
3. Sulphur dioxide
4. Phenol
5. Fluorine
6. Cyanide
7. Particular matter
Effects of air pollution:-
Global warming: Global warming is one of the consequences of air pollution.
Smog formation: When pollutants like hydrocarbons and nitrogen oxides combine in the presence of sunlight, smog is formed. This is a mixture of gases. It forms a yellowish brown haze especially during winter.
Effects: The bad effects of smog are:
2. It cause many respiratory disorders.
3. It causes allergies as it contains polluting gas.
✓ Acid rains: The air pollutes like sulphur dioxide and nitrogen oxides react with water atmosphere producing acid rains.
✓ Ozone depletion: The upper layer (stratosphere) of the atmosphere has ozone (O3) which absorbs ultraviolet (UV) rays present in the sun’s radiation. However the air pollutants like chlorofluorocarbons (CFCs) destroy the ozone molecules and so break the ozone layer. Ozone holes are created which permit UV rays to reach the Earth surface. The UV rays increase the temperature and also cause skin cancer.
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