Photochemical smog formed in congested metropolitan cities mainly consists of:

• ozone, peroxyacetyl nitrate and NO_x

• smoke, peroxyacetyl nitrate and SO₂

• hydrocarbons, SO₂ and CO₂

• hydrocarbons, ozone and SO_x

Assertion : Inhabitants close to very busy airports are likely to experience health hazards.

Reason : Sound level of jet aeroplanes usually exceeds 160 dB.

• If both Assertion and Reason are true and the reason is the correct explanation of the assertion

• If both Assertion and Reason are true but the reason is not the correct explanation of the assertion

• If Assertion is true statement but Reason is false

• If both Assertion and Reason are false statements

Zooplanktons are :

• parasites

• primary producers

• primary consumers

• primary decomposers

74.

When one organism is benefited without affecting the other, it is called

• parasitism

• commensalism

• saprophytis

• symbiosis

The equation $\frac{∆{\mathrm{N}}_{\mathrm{n}}}{\mathrm{N}∆\mathrm{t}}$= B represents, which of the following?

• Natality

• Growth rate

• Mortality

• All of these

What are mycorrhizae?

Scirpophage incertulus is an example of

• monophagus pest

• diphagus pest

• oligophagus pest

• polyphagus pest

Which one of the following is a population?

• A spider and some trapped flies in its web

• Earthworm that lives in a grassland along with other arthropods

• All the plants in a forest

• All the oak trees in a forest

A biologist studied the population of rats in a barn. He found that the average natality was 250, average mortality 240, immigration 20 and emigration 30. The net increase in population is

• 10

• 15

• 05

• Zero

A sedentary sea anemone gets attached to the shell lining of hermit crab. The association is

• ectoparasitism

• symbiosis

• commensalism

• amensalism