Science M.C.Q

Organisms of a higher trophic level that feed on several types of organisms belonging to a number of lower trophic levels constitute a food web.

Energy always flows in one direction in an ecosystem, from a lower trophic level to a higher trophic level.

Incineration, which means burning harmful wastes into ashes, is the best method to dispose of biological wastes from hospitals.

As mice are in the lowest trophic level, they will have the minimum concentration of pesticides in their body.

A grasshopper eats grass; hence, the grasshopper is the primary consumer.
A frog eats the grasshopper, so the frog becomes the secondary consumer.
The energy transfer is from the primary consumer to the secondary consumer,
i.e., from the grasshopper to the frog.

Grass is eaten by goats, and goats are eaten by humans.

If deer are removed from the given food chain, the population of tigers will decrease as they will not have deer for their food and will starve to death. The density of grass will increase as there is no organism to consume it as food.

Only one per cent of the sun's energy falling on the leaves of green plants is utilised by the plants in the process of photosynthesis and stored as the chemical energy of food.

Larvae feed on algae for their nutrition, so they get the energy they require directly from the producers. Thus, they get the maximum energy among all the consumers.

Algae are producers, which prepare their food themselves through photosynthesis. They are not consumers.

In a pond, green algae are the primary producers. Green algae are consumed by mosquito larvae, which therefore become the primary consumers. Mosquito larvae are consumed by fish, which then become the secondary consumers.

Decomposers convert the organic matter present in the bodies of dead organisms into inorganic forms and mix them with the soil.

The initial organism of a food chain is the producer, which produces food through photosynthesis.

Green plants are producers that prepare carbohydrates as food from inorganic compounds, such as carbon dioxide and water, by using sunlight as the radiant energy.

The concentration of harmful pesticides in the bodies of birds and animals increases at each trophic level, and hence the dog in the given food chain will have the maximum concentration of harmful pesticides.

Oxygen is converted into ozone by ultraviolet radiations.

A jute carry bag is made from jute, which is a plant fibre. Hence, it is biodegradable.

A crop field is an artificial ecosystem, because it is made by man.

Putrefying bacteria decompose dead organisms, and hence act as decomposers in an ecosystem.

The food prepared by plants is in the form of chemical energy, which is passed on to the next trophic level in an ecosystem.

Excessive exposure of humans to ultraviolet rays results in skin cancer and damage to the immune system.

This is an incorrect statement as green plants prepare their food themselves; they do not get readymade organic compounds as their food.

Saprotrophs such as bacteria and fungi recycle the organic matter present in the bodies of dead organisms by mixing it with the soil.

Sunlight provides energy to plants for preparing food, and this energy is then passed on to the next trophic levels through a food chain.

Excessive killing of lions resulted in an increase in the number of herbivores, which in turn consumed all the vegetation.
Hence, the Sahara Desert was formed.

	Bactaria	Fungi	Viruses
(C)	Yes	Yes	No

Explanation:

Bacteria and fungi are decomposers of dead organisms.

The grass is eaten by the insect, which is eaten by the frog, which is eaten by the snake. Hence, the grass is the producer, the insect is the primary consumer, the frog is the secondary consumer and the snake is the tertiary consumer.

The third trophic level is always occupied by carnivores. The first trophic level is occupied by producers, the second by herbivores and the fourth by decomposers.

In an ecosystem, the flow of energy is unidirectional and the flow of materials is cyclic.

The accumulation of non-biodegradable pesticides in the food chain in an increasing amount at each higher trophic level is known as biomagnifications.