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NCERT Class 10 Science Textbook Chapter 15 With Answer PDF Free Download
Chapter 15: Our Environment
We have heard the word ‘environment’ often being used on the television, in newspapers, and by people around us.
Our elders tell us that the ‘environment’ is not what it used to be earlier; others say that we should work in a healthy ‘environment’, and global summits involving the developed and developing countries are regularly held to discuss ‘environmental’ issues.
In this chapter, we shall be studying how various components in the environment interact with each other and how we
impact the environment.
15.1 ECO-SYSTEM — What Are Its Components?
All organisms such as plants, animals, microorganisms, and human beings as well as the physical surroundings interact with each other and maintain a balance in nature.
All the interacting organisms in an area together with the non-living constituents of the environment form an ecosystem.
Thus, an ecosystem consists of biotic components comprising living organisms and abiotic components comprising physical factors like temperature, rainfall, wind, soil, and minerals.
For example, if you visit a garden you will find different plants, such as grasses, trees; flower-bearing plants like rose, jasmine, and sunflower; and animals like frogs, insects, and birds.
All these living organisms interact with each other and their growth, reproduction, and other activities are affected by the abiotic components of the ecosystem.
So a garden is an ecosystem. Other types of ecosystems are forests, ponds, and lakes. These are natural ecosystems while gardens and crop fields are humanmade (artificial) ecosystems.
We have seen in earlier classes that organisms can be grouped as producers, consumers, and decomposers according to the manner in which they obtain their sustenance from the environment.
Let us recall what we have learned through the self-sustaining ecosystem created by us above.
Which organisms can make organic compounds like sugar and starch from inorganic substances using the radiant energy of the Sun in the presence of chlorophyll?
All green plants and certain bacteria which can produce food by photosynthesis come under this category and are called the producers.
Organisms depend on the producers either directly or indirectly for their sustenance? These organisms which consume the food produced, either directly from producers or indirectly by feeding on other consumers are the consumers.
Consumers can be classed variously as herbivores, carnivores, omnivores, and parasites. Can you give examples for each of these categories of consumers?
Imagine the situation where you do not clean the aquarium and some fish and plants have died. Have you ever thought about what happens when an organism dies?
The microorganisms, comprising bacteria and fungi, break down the dead remains and waste products of organisms.
These microorganisms are decomposers as they break down the complex organic substances into simple inorganic substances that go into the soil and are used up once more by the plants.
What will happen to the garbage, and dead animals and plants in their absence? Will the natural replenishment of the soil take place, even if decomposers are not there?
| Author | NCERT |
| Language | English |
| No. of Pages | 10 |
| PDF Size | 4.1 MB |
| Category | Science |
| Source/Credits | ncert.nic.in |
NCERT Solutions Class 10 Science Chapter 15 Our Environment
Q1. Which of the following groups contain only biodegradable items?
a. Grass, flowers, and leather
b. Grass, wood, and plastic
c. Fruit peels, cake, and lime juice. Cake, wood, and grass
Solution:
a) Grass, flowers, and leather
c) Fruit peels, cake, and lime juice
d) Cake, wood, and grass
Above all are the groups that contain only biodegradable items. Since plastic is not a biodegradable substance, that group cannot be considered biodegradable.
Q2. 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
Solution:
b. Grass, goat and human
Here, the grass is the producer, the goat is the primary consumer and the human is the secondary consumer.
Q3. 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
Solution: d) All of the above
Q4. What will happen if we kill all the organisms in one trophic level?
Solution:
If we kill all the organisms at one trophic level, the food supply to the next level will strop resulting in an imbalance in the ecosystem.
As a result animals in the higher levels will die making the growth of animals in the lower trophic level increase enormously. All of this will affect the overall balance in the ecosystem.
Q5. Will the impact of removing all the organisms in the trophic level be different for different trophic levels? Can the organisms of any trophic level be removed without causing any damage to the ecosystem?
Solution:
Yes, the impact of removing all the organisms in a trophic level will be different for different trophic levels. For example, if all the producers are removed, there is a chance of death or migration of the primary consumers which will upset the trophic levels.
This is the same for all the levels. Therefore, the removal of organisms at any level would upset the whole ecosystem as the food chain is disturbed. The survival of the higher-level animals is completely dependent on the animals at the lower levels.
Q6. What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Solution:
Biological magnification can be defined as the progressive increase in the concentration of non-biodegradable wastes in the food chain.
As there is an increase in the magnification at the primary level of the ecosystems, all the other levels do get affected and the concentration may vary when compared to the first level.
Q7. What are the problems caused by the non-biodegradable wastes that we generate?
Solution:
Following are the problems caused by the non-biodegradable wastes:
- These substances cannot be decomposed by microorganisms.
- As the quantity increases, dumping becomes a problem.
- Non-biodegradable wastes like heavy metals may enter the food chain in the upper trophic levels.
- They may escape to the groundwater which causes soil infertility and disturbance in the pH of the soil.
Q8. If all the waste we generate is biodegradable, will this have no impact on the environment?
Solution:
Biodegradable wastes are decomposed by the microorganisms into simpler substances that can be used by the producers as raw material. But following are the effects of too many biodegradable wastes:
- As the decomposition of the biodegradable wastes is slow, they produce an awful smell and when inhaled by humans it can be harmful.
- The dumping areas can be a place where harmful organisms may start to breed which can be harmful to humans as well as plants and animals.
- An increase in the number of aquatic organisms may result in the depletion of oxygen.
Our Environment NCERT Textbook With Solutions PDF Free Download