Our Environment — Practice

Question 1

What does a food chain always start with?

Accepted Answer

The producer

Question 2

Which of the following do plants not compete for?

Accepted Answer

Food

Question 3

Identify the correct sentence according to Charles Elton

Accepted Answer

No producers at the top of the pyramid

Question 4

What happens to the amount of energy transferred from one trophic level to the next in a food chain?

Accepted Answer

It falls sharply: 80 to 90 per cent is dissipated as heat at each transfer, so only 10 to 20 per cent passes on.

Question 5

What is a trophic level, and what does it represent in an ecological pyramid?

Accepted Answer

A trophic level is a feeding level in a food chain, and in a pyramid each bar represents one level — producers at the base, then primary, secondary and tertiary consumers, with top carnivores at the tip.

Question 6

Write a short note on the pyramid of numbers for the chain tree, insects, birds. What do you conclude?

Accepted Answer

It is inverted at the bottom: one tree supports very large numbers of insects, which support a smaller number of birds, so the base bar is the narrowest.

Question 7

What will happen if we remove predators from a food web?

Accepted Answer

The populations they controlled would grow unchecked, exhaust their own food supply and then crash, and the effect would spread through every level connected to them.

Question 8

How does the use of toxic substances affect an ecosystem? Write a short note on bioaccumulation and biomagnification.

Accepted Answer

Pesticides act indiscriminately and can destroy predators and prey as well as the pest, upsetting food chains; and non-degradable ones enter the food chain, which is bioaccumulation, and become more concentrated at each level, which is biomagnification.

Question 9

Should we use pesticides to protect crops from pests, or should we think of alternatives? Give your opinion with reasons.

Accepted Answer

Pesticides cannot simply be banned, since pests must still be controlled and losses are significant even with them; but the long-term answer is control methods based on sound biological principles.

Question 10

Read the Kolleru table for 1967 and 2004 and explain what changed and why.

Accepted Answer

The total area is identical at 180.38 km2, but water spread area fell from 70.70 km2 to zero while aquaculture ponds rose from zero to 99.74 km2, and the land liable to flood in the rainy season, 100.97 km2, disappeared entirely.

Practice — Our Environment

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