What happens to atoms of certain chemical elements such as carbon, oxygen and nitrogen in an ecosystem?

A) They move into the living systems and remain there

B) They move in and out of living systems

C) They move out of living systems and never return

D) They never enter a living system

Correct Answer: Option B – They move in and out of living systems.

Elements like carbon, oxygen and nitrogen are processed into food by plants. These plants are consumed by primary consumers and they in turn are consumed by secondary consumers. When these plants or secondary/ primary consumers die, their bodies decompose to release the elements of carbon, oxygen and nitrogen back to the environment. Hence, these atoms move in and out of a living system. Hence, Option B is the correct answer.

Since, the occurrence of the above described events is cyclical; atoms which enter the living system also get out and back again. Hence, options A, C and D are incorrect.

A) Type of seafloor

B) Availability of minerals

C) Amount of light

D) Absence of biotic factors

Correct Answer: Option C – Amount of Light

Presence of light is an important factor for the growth and survival of autotrophs. At great depths in oceans the amount of light reaching is very less, hence, making the survival of autotrophs difficult. Hence, Option C is the correct answer.

Deep sea has abundance of minerals and has a fertile sea floor and has a large number of animals adapted to that environment. Hence, options A, B and D are incorrect.

The diagram below shows a food chain:

Grass à Deer à Tiger

What is the effect on the population of deer if there is a decrease in the population of the Tigers?

A) It will decrease

B) It will increase

C) It will decrease and then increase

D) It will increase and then decrease

Correct Answer: Option D – It will increase and then decrease

According to the diagram of the food chain above, Deer feed on grass and Tigers feed on Deer. Hence, a decrease in the Tiger population will initially lead to an increase in the Deer population. However, the grass population does not increase proportionately. Hence, decreased availability of food will eventually lead to decrease in the Deer population. Hence, Option D is the correct answer.

The above description explains that options A, B and C are incorrect.

Earth’s water, land and the atmosphere would constitute:

A) A community

B) A Biome

C) A Biosphere

D) A Population

Correct Answer: Option C – A biosphere

The biosphere is the largest organizational grouping in ecology, it includes everyplace life is found on Earth. It is the global sum of all ecosystem containing water, land and atmosphere. Hence, Option C is the correct answer.

A community is a group of organisms sharing an environment. Hence, Option A is incorrect.

Biomes are climatically and geographically defined areas of ecologically similar climatic conditions such as communities of plants and animals. Hence, Option B is incorrect.

Population is the collection of inter-breeding organisms of a particular species. Such populations coexist in an ecosystem and several such ecosystems together form a biosphere. Hence, Option D is incorrect.

Most autotrophs store energy in the form of

A) Starch

B) Oxygen

C) Water

D) Nucleic acids

Correct Answer: Option A – Starch

Starch is a polysaccharide consisting of chains of glucose. When these glucose chains are broken by the activity of enzymes energy is released. Hence, Option A is the correct answer.

Water helps the plants to produce food and oxygen is released by plants during the process of photosynthesis. Hence, options B and C are incorrect.

Nucleic acids form the DNA and RNA. These carry genetic information and are not store houses of energy for autotrophs. Hence, Option D is incorrect.

A plant needs oxygen, carbon dioxide, water and minerals to survive. This statement shows that autotrophs depend on

A) Symbiotic relationships

B) Abiotic Factors

C) Biotic Factors

D) Food chains

Correct Answer: Option B – Abiotic factors

Oxygen, carbon dioxide, water and minerals are non living factors of an ecosystem and are referred to as abiotic factors and plants are autotrophs which generate their own food. Hence, Option B is the correct answer.

The elements mentioned above do not share any mutually dependent / symbiotic relationship. Hence, Option A is incorrect.

Biotic factors of an ecosystem are the living factors. But, oxygen, carbon dioxide, water and minerals are non living factors. Hence, Option C is incorrect.

Food chains involve producers, primary consumers and secondary consumers each dependent for food on the other. Plants are the producers in the food chain dependent on the abiotic factors. Food chains are not related to the statement above. Hence, Option D is incorrect.

Choose a statement that represents a biotic factor in an ecosystem.

A) Cold Climate of a given region

B) The predators feeding on herbivorous animals

C) The amount of nitrogen in the soil

D) The flow of water in the stream

Correct Answer: Option B – The predators feeding on herbivorous animals

Biotic factors in an ecosystem constitute the living entities. Predators are living entities. Hence, Option B referring to the biotic factors in that ecosystem is the correct answer.

Cold climate of a region, nitrogen in the soil and water are all non living elements in an ecosystem. These refer to abiotic factors. Hence, options A,C and D are incorrect.

All the different types of Cats can be classified as belonging to:

A) Class

B) School

C) Species

D) Phylum

Correct Answer: Option C – Species

A species is one of the basic units of biological classification and a taxonomic rank. It is defined as a group of organisms capable of interbreeding and producing fertile offspring. All cats come under one species. Hence, Option C is the correct answer.

Class and phylum are broader classifications of organisms used by scientists for taxonomic ranking. Hence, options A and D are incorrect.

School refers to a group of fish. This has no relevance to Cats. Hence, Option B is incorrect.

All plants, animals and micro-organisms living in a forest ecosystem constitute a:

A) Population

B) Species

C) Phylum

D) Community

Correct Answer: Option D – Community

All the living things at one place at a given time constitute a community. The above statement refers to plants, animals and micro-organisms which are living things/ biotic factors of an ecosystem. Hence, they are a community and Option D is the correct answer.

Population refers to one species of organisms at a given place and time.

Species is a group of organisms capable of interbreeding and producing fertile offspring.

Phylum is subdivision of a kingdom.

Plants, animals and micro-organisms together cannot be categorized as population, species or phylum. Hence, options A, B and C are incorrect.

If a short-term climate change arises such that ocean waters remain warm when they should be cool and these warm temperatures disrupt food webs; which occurrence would most likely appear among the below stated changes?

A) Some communities would become extinct and other communities would replace them

B) The energy flow through the ecosystem would be undisturbed

C) Some populations in affected areas would decrease, while other populations would increase temporarily

D) The genes of individual organisms would mutate to adapt to the new environmental condition.

Correct Answer: Option C – Some populations in affected areas would decrease, while other populations would increase temporarily

A short-term climate change is a temporary disruption in the balance of the climate of the ocean ecosystem. This would lead to the decrease in population of organisms which are affected by this increase in temperature. Those organisms which are the feed for the affected organisms will see an increase in population temporarily. Hence, Option C is the correct answer.

A short term climate change cannot lead to extinction of communities since, communities are a group of interdependent organisms living in an ecosystem.

The energy flow in the ecosystem is temporarily disturbed by the climate change.

Mutation occurs by long-term climatic changes. Since, this change in temperature is short-term it will not lead to mutation in organisms.

Hence, options A, B and D are incorrect.