Science M.C.Q

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

The sun is considered the primary energy source since it is the source of nearly all the earth’s energy.
Plants produce food using sunlight, and the food we get from plants and animals also has its primary sunlight source.
The fossil fuels we use in our everyday lives come from dead plants and animals that have their origins as solar energy again.

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

In all the ecosystems, the sun is the ultimate source of energy. Green plants trap solar energy and convert it into a usable form, which can be used by other organisms at successive trophic levels.

In a grassland food chain, plants are the producers. Primary consumers like deer eat these plants. Secondary consumers like lions eat the primary consumers. So, a lion occupies the third level in a food chain.

Both biotic and abiotic factors are present 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.

Herbivores are called primary consumers, as they feed on autotrophs.
Secondary consumers feed on these primary consumers and are called so.
Large carnivores feed on these secondary consumers and hence are called tertiary consumers.

Radioactive substances however are not biodegradable, and some parts take hundreds of thousands of years to become harmless. And we just keep producing them.

Fossil fuels take thousands of years to form deep under the earth. Cow dung does not come under this category of fuels.

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

Examples of man made ecosystem includes agriculture based systems like a garden, orchards; products of land development like a lake, canals, park; products of observation and lively requirements like an aquarium, a building, and a city.

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

A food chain is a linear sequence of organisms through which nutrients and energy pass as one organism eats another.
Producers prepare food for themselves through the process of photosynthesis. Consumers eat producers. Consumers are themselves eaten by other higher consumers. Finally, when consumers die, the decomposers decompose their bodies to convert them into organic matter. The nutrients from the organic matter are taken up by producers.

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

Deers, giraffes, cows, goats, rabbits, horses, insects and snails, all consume the producers and hence are primary consumers.

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

Green plants are photosynthetic organisms. They trap solar energy and use it to synthesize carbohydrates. The carbohydrates are the useful form of energy. All the other organisms depend on plants either directly or indirectly.

Cloth bags have following advantages over plastic bags:
Cloth bags are biodegradable so they do not pollute the environment.
Cloth bags are capable of carrying more things.
They can be reused over and over again

The ecosystem is responsible for the flow of energy as the autotrophs convert the light energy provided by the sun to chemical energy which is further consumed by heterotrophs. In this way energy transferred from plants to herbivores and from them to carnivores.
When the complex organisms die, they are consumed by the bacteria and fungi, which are the decomposers, which break down the complex substances into simple inorganic forms. Thus, the cycling of nutrients takes place.

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.

Nowaday, which type of cups are being generally trains for serving tea, coffee, soup, etc. Disposable paper cups.

	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 flow of energy is unidirectional. The energy that is captured by the autotrophs does not revert back to the solar input and the energy which passes to the herbivores does not come back to autotrophs. As it moves progressively through the various trophic levels it is no longer available to the previous level.

Living organisms have effect on other living organisms and these constitute biotic factors or living factors.