CBSE Class 7 Science Advanced Biology Our Ecosystem Short Answer Questions Set 01

Short Answer Questions

Teacher's Note:
1. Biotic things can reproduce; abiotic things cannot.
2. Both groups affect each other all the time.

Question 2. Give a note on terrestrial ecosystem.
Answer:
Land-based ecosystems are called terrestrial ecosystems.
They include forest, grassland, tundra, desert and mountain ecosystems.
Forest: a large land with huge trees, animals and microbes.
Grassland: land that is mostly covered with grasses.
Tundra: the coldest biome with shrubs, mosses and grasses.
Mountain: the living organisms found on mountain slopes.
Desert: dry land with very little rainfall.
In simple words: Terrestrial ecosystems are the ones found on land.

Teacher's Note:
1. Terrestrial means related to land.
2. Write all five types in the answer.

Question 3. Define the trophic levels and mention the organisms that occupy in each trophic level.
Answer:
The process of eating and being eaten is called the food chain, and each step in a food chain is called a trophic level.
Plants, being producers, occupy the first trophic level.
Herbivores (primary consumers) occupy the second trophic level.
Carnivores that eat herbivores occupy the third level, and the carnivores that eat them occupy the higher levels.
In simple words: A trophic level is one feeding step in a food chain.

Teacher's Note:
1. Example: grass, rabbit, fox, tiger fill four levels.
2. Energy decreases at each higher level.

Question 4. How does the deforestation affect wildlife?
Answer:
Deforestation is the reckless cutting of trees.
It destroys the natural habitat of many organisms.
Loss of habitat is the main reason for the extinction of many wild species.
In simple words: Cutting forests leaves animals without homes.

Teacher's Note:
1. Forests give shelter and food to wildlife.
2. Fewer species also upset the balance of the ecosystem.

Question 5. What is air pollution? What are the various reasons for air pollution?
Answer:
The undesirable change in the air is called air pollution.
It is caused by harmful substances such as gases and particles entering the air.
Reasons: harmful gases from vehicles, factories and industries, and the burning of fuels.
Breathing this air causes respiratory disorders.
In simple words: Dirty gases in the air make it harmful to breathe.

Teacher's Note:
1. Smog forms when emissions react with sunlight.
2. Public transport and CNG help reduce it.

Question 6. What are the different methods to conserve forest?
Answer:
Reduce the rate of deforestation.
Control forest fires, which can wipe out large areas.
Check and control clearing of forest for agriculture and housing.
Control the spread of diseases among forest plants.
Use forest resources wisely.
In simple words: Cut less, protect from fire and plant more.

Teacher's Note:
1. Conservation means wise use, not zero use.
2. Afforestation and reforestation also help.

Question 7. 'It is difficult for the survival of plants and animals in hot and dry desert in general'. Why?
Answer:
The hot and dry desert is warm all year and extremely hot in summer, with very scanty rainfall.
Water is scarce, so it is a harsh place for plants and animals to survive.
In simple words: Extreme heat and almost no water make life hard.

Teacher's Note:
1. Desert life needs special adaptations.
2. Some plants and animals do manage to live there.

Teacher's Note:
1. Compare in a table with three points.
2. Example: Sahara versus Thar.

Question 9. Give a note on Savannah.
Answer:
Savannah is a grassland ecosystem that is a mix of woodland and grassland.
It has a rainy season in summer and a dry season in winter, and stays warm throughout the year.
Animals like elephants, wildebeest, giraffes and ostriches live here, with predators such as lions, cheetahs, leopards and wild dogs.
It is found in South Africa, India and Australia.
In simple words: Savannah is a warm grassland with scattered trees and many big animals.

Teacher's Note:
1. It is a tropical grassland.
2. Mention both herbivores and predators.

Question 10. Give some examples for animals and plants which can be seen in desert ecosystem and tell us how they would adapt with the climate.
Answer:
Plants such as cactus and thorny weeds grow in deserts.
They have special modifications for the climate and extensive roots that absorb water from deep inside the earth.
Animals such as rodents and reptiles live there.
They hide in burrows in the daytime and come out at night to avoid heat.
In simple words: Desert plants save water and desert animals avoid the heat.

Teacher's Note:
1. Adaptations: deep roots, thorns, burrows and night activity.
2. Name at least two examples each.

Question 11. Write a brief note on pampas.
Answer:
Pampas are temperate grasslands of Argentina and Brazil in South America.
The climate is temperate with fairly uniform rain, mild winters and uniform summer temperatures.
Only small plants such as grasses and herbs grow; large trees are rare.
Animals include pampas deer, guinea pig and dwarf mara; the puma is the biggest predator, followed by pampas fox, maned wolf and Geoffroy's cat.
In simple words: The pampas are the temperate grasslands of South America.

Teacher's Note:
1. Remember the puma as the top predator.
2. Pampas lie in the Patagonia highland region.

Teacher's Note:
1. Temperate grassland soil is very fertile, which makes it good for farming and herding.
2. Examples: savannah (tropical), prairies (temperate).

Teacher's Note:
1. Add that rainforests get heavy rain and have very tall trees.
2. Temperate forests have evergreen or deciduous trees.

Question 14. Give a note on the various consequences of soil pollution.
Answer:
Soil pollution is caused by wastes from industries, hospitals and homes.
Biodegradable wastes decompose naturally, but non-biodegradable wastes remain in the soil.
Piled-up waste becomes a breeding place for flies and mosquitoes.
Decay causes foul smell and makes the area unfit for life.
Some wastes reach water bodies and even groundwater, making water unsuitable for use.
In simple words: Polluted soil spreads disease, smell and dirty water.

Teacher's Note:
1. Segregate waste into biodegradable and non-biodegradable.
2. Organic fertilizers reduce soil pollution.

Question 15. Explain food chain with the help of one example.
Answer:
The process of eating and being eaten in a linear manner is called a food chain; each step is a trophic level.
Example: Grass → Rabbit → Fox → Tiger.
Grass is the producer (first level). Rabbit is a herbivore (primary consumer).
Fox eats the rabbit, so it is the secondary consumer; tiger is the tertiary (top) consumer.
In simple words: A food chain shows who eats whom, starting with a plant.

Teacher's Note:
1. Draw the arrows in the direction of energy flow.
2. Energy decreases at each step.

Question 16. Write a note on the significance of forest.
Answer:
Forests give shelter to wildlife.
They are the natural home of many plants, animals and tribal groups.
They give timber, honey, animal products and medicinal compounds.
They control the climate, help rain and control soil erosion.
They provide firewood.
In simple words: Forests give homes, goods and a healthy climate.

Teacher's Note:
1. Write at least four points.
2. Mention climate and soil erosion for full marks.

Question 17. Give a note on water pollution.
Answer:
Water pollution is the addition of harmful wastes to water.
Sources: industries, homes and hospitals, and washing and bathing in water bodies.
Industrial waste has poisonous chemicals; domestic waste is rich in nutrients that make algae grow and discolour water.
Hospital waste contains germs that spread cholera, dysentery and typhoid.
In simple words: Dumping waste in water makes it unsafe to use.

Teacher's Note:
1. Treat sewage before releasing it.
2. Avoid throwing waste in water bodies.

Question 18. Describe carbon cycle.
Answer:
Carbon is the main component of living organisms and is found in carbohydrates and proteins.
Carbon in the air is carbon dioxide; plants take it in by photosynthesis, and animals get carbon by eating plants.
Carbon returns to the air as CO₂ through respiration of plants and animals, decay by decomposers and burning of fossil fuels.
This keeps the level of carbon dioxide in the air nearly constant.

In simple words: Carbon moves between air, living things and fuels in a loop.

Teacher's Note:
1. Study the figure arrows.
2. Remember photosynthesis removes CO₂ and respiration and burning add it.

Question 19. Is all the primary productivity available to a herbivore? If not, why?
Answer:
No.
A large part of the plant's productivity is used by the plant itself for respiration, and some is lost as heat to the environment.
So only the remaining part can be eaten by the herbivore.
In simple words: Plants use or lose part of their food energy before it is eaten.

Teacher's Note:
1. Same reason energy decreases at each trophic level.
2. This is a favourite reasoning question.

Question 20. What will happen if herbivores are removed from a grass type food chain?
Answer:
The number of primary carnivores will slowly decrease because they cannot get enough food.
Finally the carnivores would be eliminated as well.
Grass would also grow unchecked.
In simple words: Without plant-eaters, the meat-eaters starve.

Teacher's Note:
1. Every link in a food chain is needed.
2. Removing one level upsets the whole ecosystem.

Question 21. Why do birds and mammals not hibernate during winter season unlike other animals?
Answer:
Birds and mammals are warm-blooded.
They can keep their body temperature constant, so they do not need to hibernate in winter.
In simple words: Warm-blooded animals make their own body heat.

Teacher's Note:
1. Cold-blooded animals depend on the surroundings.
2. Hibernation is a long winter sleep.

Question 22. Smaller food chains are more efficient as compared to larger ones. Why?
Answer:
A smaller food chain has fewer trophic levels.
So less energy is lost, and more energy reaches the last level.
Hence smaller chains are more efficient.
In simple words: Fewer steps mean less energy wasted.

Teacher's Note:
1. Energy is lost as heat at every level.
2. This is why top carnivores are few.

Question 23. Why is it advised that automobiles should switch over to cleaner fuels, like CNG and LPG?
Answer:
Vehicles emit harmful gases like SO₂ that pollute the air.
CNG and LPG burn with far fewer harmful emissions than petrol and diesel.
So switching reduces air pollution and health problems.
In simple words: Cleaner fuels give smoke-free air.

Teacher's Note:
1. Public transport also helps.
2. Link the answer to air pollution prevention.