Our Environment Test - 10

The sun is the ultimate source of energy. This energy is captured by the plants. The flow of this energy in an ecosystem is always unidirectional. Essential nutrients like nitrogen, carbon, oxygen and water are cycled in the environment in separate biogeochemical cycles. In these cycles, they are changed from one form to another. According to 10% law, the energy available to each successive trophic level is 10% of the previous trophic level. 

Forest, desert and pond are natural ecosystems. An aquarium or a garden is an example of a human-made ecosystem. Scavengers act as house-keepers and break down the dead remains and waste products of organisms in an ecosystem. Paper, plastic bags, etc are recyclable waste. 

Chlorofluorocarbons (CFCs) are used in the manufacture of aerosol sprays. Carbon dioxide is a green house gas (GHG) and contributes to the green house effect. It traps solar radiations and increase the temperature of the Earth. DDT (di-chloro di-phenyl tri-chloro-ethane) is used as a pesticide. It contributes to bio-magnification. Green plants are the producers in an ecosystem. They trap the solar energy and convert it into chemical energy.

Light is an abiotic (non-living) component of an ecosystem. Microorganisms are biotic (living) components of an ecosystem. Ozone depletion may lead to higher UV radiation on Earth and may cause skin cancer. Eutrophication is excessive richness of nutrients in a lake or other body of water, frequently due to run-off from the land, which causes a dense growth of plant life.

Excessive exposure of humans to UV (ultraviolet) rays results in damage to the immune system. Exposure to UV radiation is also a risk factor for most skin cancers.

Organisms in groups B and C do not make up a food chain. A food chain is a series of organisms in order of who eats whom. In B, grasshopper is out of place. In D, nobody out of wolf, snake or tiger eats grass.

A habitat is an ecological or environmental area that is inhabited by a particular species of organism. The term refers to the special environment in which an organism lives and breeds and where it can find food, shelter, and protection.

The second trophic level is of the primary consumers (herbivores). Small fish and grasshopper belong to this level. A snake is not a primary consumer. Free-living protozoa occupy a range of trophic levels.

All given ecosystems are terrestrial ecosystems. Forest, grassland and desert are natural ecosystems. An aquarium is an example of a human-made (artificial) ecosystem.

Different essential nutrients like nitrogen, carbon, oxygen and water are cycled and changed from one form to another in separate biogeochemical cycles in an ecosystem. The producers convert the solar energy received from the Sun into chemical energy and also fix up the nutrients from the soil, and make them available to the higher trophic levels in the ecosystem.