Our Environment Test - 7

According to 10% law, the energy available to each successive trophic level is 10% of the previous trophic level. 

Given, energy available at the third trophic level = 50 KJ

Energy available at second trophic level = 50 KJ x 10 = 500 KJ

Therefore, energy available at the producer level (first trophic level) = 500 KJ x 10 = 5000 KJ

Substances that are not broken down into simpler substances by biological processes are said to be non-biodegradable. Polythene, detergents and PVC (Polyvinylchloride) are non-biodegradable substances. Substances that can be broken down by biological processes are said to be biodegradable. Paper, wood, grass, leather and cloth are biodegradable.

An ecosystem may be classified as a natural ecosystem or a man-made ecosystem. A garden is an example of a man-made ecosystem. Deserts, rivers and grasslands are examples of natural ecosystems.

A food chain consists of producers, herbivores and carnivores. Organisms in a food chain are arranged in order of who eats whom and form a chain. Producers (plants) are eaten by herbivores and herbivores are eaten by carnivores.

Each organism is generally eaten by two or more other kinds of organisms which in turn are eaten by several other organisms. This relationship, of eating and being eaten, between different organisms can be shown as a series of branching lines called a food web.

All the interacting organisms of an area together with the non-living constituents form an ecosystem. An ecosystem consists of biotic components comprising living organisms, as well as abiotic components comprising physical factors like rainfall, wind, soil and minerals.

Advantage of cloth bags over plastic bags is that they are biodegradable. Biodegradable substances are those substances that can be broken down by biological processes.

A food chain is a chain or series of organisms that are arranged in order of who eats whom. Each step or level of the food chain forms a trophic level.

The percentage of solar radiation absorbed by all the green plants for the process of photosynthesis is about one percent. The green plants (producers) use this solar energy for the process of photosynthesis, convert it into food energy and make the energy available to the rest of the ecosystem.

There is a decrease in energy as the energy is transferred from a lower trophic level to a higher trophic level. The energy available to each successive trophic level is 10% of the previous trophic level. This limits the number of trophic levels in a food-chain. The food chains generally consist of only three or four steps since very little usable energy is left after four trophic levels.