July 11 is observed as:

• World population day

• No tobacco day

• World environment day

• World health day

The pyramid of energy-in a forest ecosystem is

• always upright

• always inverted

• both (a) and (b)

• none of the above

Biological Oxygen Demand (BOD) is a measure of

• industrial wastes poured into water bodies

• extent to which water is polluted with organic compounds

• amount of carbon monoxide inseparably combined with haemoglobin

• amount of oxygen needed by green plants during night

The driving force of an ecosystem is :

• producers

• biomass

• solar energy

• grassland

Assertion: In tropical rain forests, O-horizon and A-horizon of soil profile are shallow and nutrient-poor.

Reason: Excessive growth of micro-organisms in the soil depletes its organic content.

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

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

• If assertion is true but reason is false

• If both assertion and reason are false.

Assertion : In a food chain members of successive higher levels are fewer in number.

Reason : Number of organisms at any trophic level depends upon the availability of organisms which serve as food at the lower level.

• 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

Which of the following factor is biotic

• Photoperiod

• CO₂ content to the soil

• Texture and porosity of soil

• Rainfall

Acid rain is due to increase in atmospheric concentration of :

• Ozone

• CO₂ and CO

• SO₃ and CO

• SO₂ and nitrogen oxide

Given below is one of the types pyramids.

This type represents

• pyramid of numbers in a grassland

• pyramid of biomass in a fallow land

• pyramid of biomass in a lake

• energy pyramid in a spring

Identify which one of the following is an example, of incomplete ecosystem?

• Grassland

• Cave

• River

• Wetland