Shankar IAS Test: Ecology - UPSC

•  All organisms, except viruses, rely on other organisms and the environment for their basic needs such as food, energy, water, oxygen, and shelter.

• The relationship and interaction between organisms and environment are highly complex. It comprises both living (biotic) and non-living (abiotic) components. The environment is not static.

• Both biotic and abiotic factors are in flux and keep changing continuously.

• Biotic components, or biotic factors, can be described as any living component that affects another organism or shapes the ecosystem. This includes both animals that consume other organisms within their ecosystem and the organism that is being consumed.

Abiotic factors are the non-living parts of an environment. These include things such as sunlight, temperature, wind, water, soil and naturally occurring events such as storms, fires and volcanic eruptions.

1 and 3 Only. Population is a group of organisms occupying a defined area during a specific time. 

The main factors that make the population decrease are death and emigration.

• Types of Community: Based on size and degree of relatively independent communities may be divided into two types: Major Community:-These are large-sized, well organized and relatively independent. They depend only on the sun’s energy from one side and are independent of the inputs and outputs from adjacent communities. Minor Communities:- These are dependent on neighbouring communities and are often called societies.

• They are secondary aggregations within a major community and are not therefore completely independent units as far as energy and nutrient dynamics are concerned. e.g: A mat of lichen on a cow dung pad.

• Structure of a community: In a community, the number of species and size of their population vary greatly. A community may have one or several species. The environmental factors determine the characteristic of the community, as well as the pattern of organisation of the members in the community.

• The characteristic pattern of the community is termed as the structure which is reflected in the roles played by various population, their range, the type of area they inhabit, the diversity of species in the community and the spectrum of interactions between them.

Explanation- Scavengers are the animals that feed on the dead and rotting organisms. Scavengers provide an important service to the ecosystem by removing disintegrating organisms and acting as an innate sanitation system. Scavengers assist conserve energy and nutrients received from rotting flesh within the top trophic levels and thus are capable of transferring the energy and nutrients further away from the source of the carrion.

Neither 1 and 2. Latitude has a strong influence on an area’s temperature. As the altitude increases, the air becomes colder and less humid.

• Macro consumers, They feed on plants or animals or both and are categorised based on their food sources.

• Herbivores are primary consumers who feed mainly on plants. Secondary consumers feed on primary consumers e.g. wolves.

• Carnivores which feed on secondary consumers are called tertiary consumers e.g. lions which can eat wolves. Omnivores are organisms which consume both plants and animals.

• Micro consumers Saprotrophs (decomposers or osmotrophs).

• They are bacteria and fungi which obtain energy and nutrients by decomposing ng dead organic substances (detritus) of plant and animal origin.

• The products of decomposition such as inorganic nutrients which are released in the ecosystem are reused by producers and thus recycled.

• Earthworm and certain soil organisms (such as nematodes, and arthropods) are detritus feeders and help in the decomposition of organic matter and are called detrivores.

• A niche is the unique functional role or place of a species in an ecosystem. No two species have an identical niche.

It is a description of all the biological, physical and chemical factors that a species needs to survive, stay healthy and reproduce.