Please refer to Assignments Class 10 Science Our Environment Chapter 15 with solved questions and answers. We have provided Class 10 Science Assignments for all chapters on our website. These problems and solutions for Chapter 15 Our Environment Class 10 Science have been prepared as per the latest syllabus and books issued for the current academic year. Learn these solved important questions to get more marks in your class tests and examinations.
Our Environment Assignments Class 10 Science
Very Short Answer Type Questions
Question. Name two natural ecosystem.
Answer : Pond ecosystem and forest ecosystem.
Question. Which component of sunlight is used for the formation of ozone?
Answer : Ultra violet radiation.
Question. What is bad Ozone?
Answer : Ozone at ground level is deadly poisonous and is called as bad Ozone.
Question. Name 4 abiotic components of any ecosystem.
Answer : Temperature, rainfall, wind, soil.
Question. Name two artificial ecosystem.
Answer : Garden and crop-field.
Question. Name the natural cleansing agent in an ecosystem.
Answer : Decomposers, scavengers
Short Answer Type Questions
Question. Minimum energy is available at highest trophic level while maximum energy is at lowest level. Explain.
Answer : Since non-biodegradable substances cannot be broken down into simpler forms hence they keep on accumulating in nature causing ecological imbalance.
Question. Give one advantage and one disadvantage of Ozone.
Answer : Advantage of Ozone–When it is in the stratosphere it does not allow the ultraviolet radiations to reach the earth, as UV radiations cause skin cancer and cataract.
Disadvantage of ozone: On ground level ozone is poisonous gas.
Question. Aquarium requires regular cleaning whereas lakes normally do not. Why?
Answer: Normally a lake has more diverse forms of life and hence a larger number of food chains. This leads to natural cleaning. Thus, the ecosystem is more stable. The aquarium has a very limited number of food chains and unable to sustain itself. But, sometimes there is excessive growth of algae in lake. Then it also needs to be cleaned.
Question. Why is plastic not degraded by bacteria?
Answer: Plastic is not degraded by bacteria because they do not have enzymes to degrade plastic.
Question. Using Kulhads as disposable cups to serve tea in trains, proved to be a bad idea. Why?
Answer: Making Kulhads on large scales leads to the loss of top soil.
Question. DDT has entered food chain. Which food habit is safer- vegetarian or nonvegetarian?
Answer: Vegetarian habit is safer. Being closer to producers, less DDT will accumulate in our body. Bio magnification leads to higher level of DDT in higher trophic levels.
Question. Why are green plants called producers?
Answer : Green plants can prepare complex organic matter as food from simple inorganic substances like CO2, H2O in presence of sunlight and chlorophyll. They produce food and hence called producers.
Question. What is biological magnification?
Answer : The accumulation of chemicals in the bodies of the organism that belongs to the top most tropic level is called biological magnification. As human beings occupy highest trophic level its maximum concentration was found in human beings only, which resulted in neurological disorders due to damaging of CNS (Central Nervous System).
Question. What are the problems caused by the non-biodegradable waste that we generate?
Answer : Non-biodegradable waste doesn’t decompose under the action of bacteria and other microorganisms.
• When these substances, e.g., polythene, plastics are buried under soil render that area barren and leads to soil pollution.
• These wastes don’t burn completely in presence of oxygen and release toxic gases which causes air pollution.
• The substances may be harmful on accumulating in food chain like DDT due to biomagnification.
Question. Why is damage to ozone layer a cause for concern? What steps are being taken to limit this damage?
Answer : Ozone layer doesn’t allow harmful ultra violet rays of the sun to reach the earth’s surface.
In order to stop further depletion of ozone layer we must scale down the use of CFC’s in form of aerosols, refrigerants etc and check their release in the atmosphere.
Moreover stress should be laid on using eco-friendly techniques and proper disposal of toxic material.
Question. Why are bacteria and fungi called decomposers? List any two advantages of decomposers to the environment.
Answer : Bacteria and fungi are called decomposers as they break down the dead remains and
waste of organisms. They convert the organic complex substance into simple inorganic
substances that go into the soil and are used up by plants.
Two advantages of decomposers:
1. They return the components back to nature and creates balance in the environment.
2. They act as cleansing agents of the atmosphere.
Question. (a) Distinguish between producers and decomposers.
(b) Classify the following as producers and decomposers.
Green plants, bacteria, fungi, blue-green algae.
Answer : (a)
|1. Producers convert simple inorganic substances into complex organic substances.|
2. Producers are autotrophs that can prepare food with CO2, H2O, chlorophyll and sunlight e.g., green plants.
|Decomposers break the complex organic substances into simple inorganic substances.|
Decomposers decompose the complex substances present in the plants, animals e.g., bacteria, fungi.
Question. Why decomposers are necessary in environment?
Answer : Decomposers act on all biodegradable substances and break them into simple inorganic materials and maintain the balance of materials in the ecosystem and cleanse the environment.
Question. Why is the ozone layer getting depleted at the higher levels of the atmosphere?
Answer : Ozone is present at higher levels of the atmosphere where CFC – Cholorofluorocarbons reach, chlorine separates and acts on O3 to split it into O2 and (O). The conditions required to do this are available at higher levels i.e., clouds and sunlight.
Question. Give one example of grassland ecosystem and one example of pond ecosystem.
Answer : Grass land Ecosystem: Grass → grasshopper → frog → snake → peacock.
Pond Ecosystem : Blue-green algae → small fish → big fish → birds
Question. Energy flow in a food chain is unidirectional. Explain.
Answer : The energy from the sun flows into autotrophs and it passes to herbivores and then to carnivores. The energy does not revert from autotrophs to the solar input or from herbivores back to autotrophs. Hence the flow is unidirectional.
Question. Name any two abiotic components of an environment.
Answer : Water, air.
Long Answer Type Questions
Question. What is ozone and how does it affect any ecosystem?
Answer : Ozone is a molecule of oxygen with 3 atoms its formula is O3. The ultra violet radiations split oxygen into free oxygen atoms, these atoms combine with oxygen molecules to form ozone.
O2 —→UV rays O + O
O2 + O ⎯⎯→ O3(Ozone)
Ozone in Ecosystem:
At ground level ozone is poisonous but at higher level it is very useful as it protects all living organisms from harmful UV radiations of the sun. It doesn’t allow the ultra violet radiations to enter the surface of earth. The UV radiations cause ionizing effect that leads to skin cancer in human beings.
Question. It is the responsibility of the government to arrange for the management and disposal of waste. As an individual you have no role to play. Do you agree? Support your answers with two reasons.
Answer: I do not agree. As an individual, I also have the responsibility and can contribute in the following ways:-
(i) Cut down waste generation.
(ii)Make compost pit for bio degradable waste.
(iii) Recycle non biodegradable waste.
Question. Look at the following figures. Choose the correct one and give reason for your answer.
Answer: Fig. “A” is correct.
• In an ecosystem, the number of individuals at producer level is maximum. This number reduces at each successive level. Therefore, the shape is a pyramid with broader base and tapering apex.
• On an average 10% of the food changes into body mass and is available for the next level of consumers .
Question. How will accumulation of bio degradable waste effect our environment?
Answer: Accumulation of bio degradable waste will:
(a) Not let minerals return to mineral pool.
(b) Become site of pest breeding.
Question. How can you help in reducing the problem of waste disposal? Give any two methods.
Answer : To reduce the problem of waste disposal we can
(i) Segregate the bio-degradable waste from non-biodegradable waste before dumping it.
(ii) Remove all materials which can be recycled and send it for recycling. e.g., paper, glass, metal, rubber.
Question. Enlist various categories of consumers giving examples of each.
Answer : The various categories of consumers are:
Herbivores — Grass eating animals, e.g., deer, rabbit.
Carnivores — Flesh eating animals, e.g., tiger, lion.
Omnivores — Animals that eat both plants and other small animals i.e., flesh e.g., crow, human being.
Parasites — Those organisms which depend on other living organisms and harm them for food, e.g., lice, tapeworm.
Saprophytes — Organisms that depend on dead and decaying matter for their food, e.g., fungi, bacteria.
Question. What three informations are obtained from the energy flow diagrams?
Answer : The information we get are:
(i) The energy flow is unidirectional, it flows from sun → autotrophs → herbivores → carnivores → decomposers
(ii) The flow of energy is 10% i.e., 90% of the energy is used by a given level of food chain for metabolic activities.
(iii) The unwanted chemicals like pesticides gets accumulated in the highest organism in the food chain.
Question. What will happen if we kill all the organisms in one trophic level?
Answer : If all the organisms in one trophic level are killed then all the organisms of next trophic level which are dependent on these are killed. Next trophic levels will not get food to eat and the entire food chain gets disturbed. At the same time the organisms at the lower trophic level will reproduce and the population will increase in abundance there by disturbing the ecosystem.
Question. 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?
Answer : The impact of removing all the organisms in a trophic level will be same. If the organisms of any trophic level be removed it will certainly damage the ecosystem.
Grass → Grass hopper → Frog → Snake → Peacock
In this if all grasshoppers are killed/removed frogs will strive and grass will reproduce in abundance.
If snakes are removed then the number of frogs will increase which will disturb the entire ecosystem.
Question. What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Answer : The pesticides and chemicals are absorbed by plants from the soil and enter the food chain. Being non-biodegradable they accumulate progressively at each trophic level.
As human occupy the top level of any food chain, the maximum concentration of chemicals is found in our bodies. This is called biological magnification.
The level of magnification will be different at different trophic levels, the maximum concentrations will be at the highest trophic level and the chemical will be less at lower trophic levels.
Question. Explain the interlink of biotic and abiotic factors in any ecosystem.
Answer : In an ecosystem biotic and abiotic factors are interdependent and interlinked.
For example: The grass in grassland will grow only if it gets soil which can hold water and gets sunlight with proper temperature hence the grass grows in a place which has all abiotic factors responsible for its growth but in desert these abiotic factors are not available for the growth of grass.
Question. Why are some substances biodegradable and some non-biodegradable?
Answer : Substances which can be decomposed and broken down to simpler substances by micro-organisms acting on it is called bio-degradable and those substances which cannot be acted upon by micro-organisms and are not broken down into simpler substances are called non-biodegradable substances.
Question. Give any two ways in which bio-degradable substances would affect the environment.
Answer : Two ways in which bio-degradable substances would affect the environment are:
(i) During decomposition of the substances lot of foul smell spreads in the surrounding areas.
(ii) The place where these bio-degradable substance are present with some moisture becomes breeding ground for insects like mosquitoes, housefly which are vectors in carrying parasites that cause different diseases.
Question. Give any two ways in which non-biodegradable substances would affect the environment.
Answer : (i) The non-biodegradable substances get accumulated and doesn’t get decomposed hence it remains in the ecosystem and causes pollution, chokes the system of
many animals and kill them.
(ii) These substances due to accumulation cause water and soil pollution e.g.,pesticides, detergents, polythene.
Question. Explain the formation of ozone layer and its importance.
Answer : Ozone is formed when high energy ultra violet radiations split oxygen molecule into oxygen atoms. The oxygen atom combines with oxygen molecules to form a new molecules with three oxygen atoms named ozone.
O2 —→UV rays O + O
O2 + O ⎯⎯→ O3(Ozone)
Importance of Ozone: It is very protective when present in stratosphere it does not allow the harmful ultra violet radiations to enter the earth’s surface which can cause skin cancer in human beings.
Value Based Question
Question. All eco-club students collect the vegetable peels from canteen and use them in compost pit
made in their school.
(a) Name items that can be added in compost pit other than vegetable peels.
(b) What type of reaction is seen in the pit?
(c) State the values seen among eco-club members.
Answer : (a) Students can use leftover food and fruit peels, dried leaves.
(b) Fermentation i.e., anaerobic decomposition.
(c) The eco-club students show team work, collaborative work and good behaviour.