Ecology Basics — Set 2

Correct Answer: B. Saprophytes

Saprophytes, such as many fungi and bacteria, obtain nutrients from dead organic material. They play a vital role in nutrient cycling by breaking down complex organic molecules. These organisms are also referred to as decomposers or reducers.

Correct Answer: D. Niche

An ecological niche describes how an organism responds to the distribution of resources and competitors. While a habitat is an organism's 'address', the niche is its 'profession' or role. No two species can occupy the exact same niche in the same habitat indefinitely.

Correct Answer: B. Biogeochemical Cycle

Biogeochemical cycles represent the movement of nutrients like carbon, nitrogen, and phosphorus between living and non-living parts. These cycles ensure that essential elements are recycled and made available for life processes. They are broadly classified into gaseous and sedimentary cycles.

Correct Answer: C. Grasshopper

Grasshoppers are primary consumers because they feed directly on the producers, which is grass. They occupy the second trophic level in the food chain. Organisms that eat primary consumers are known as secondary consumers.

Correct Answer: A. Standing Crop

Standing crop refers to the total biomass of living organisms in a given area at a specific time. It is usually expressed as the mass of living organisms or the number per unit area. In contrast, 'standing state' refers to the amount of inorganic nutrients present.

Correct Answer: D. Commensalism

Commensalism is an interaction where one species gains benefit while the other remains unaffected. An example is the relationship between an orchid growing as an epiphyte on a mango branch. The orchid gets support and sunlight, while the tree is not affected.

Correct Answer: C. Ecotone

The edge effect refers to the changes in population or community structures that occur at the boundary of two habitats. In an ecotone, the density and variety of species are often greater than in either of the flanking communities. This is particularly noticeable in bird populations at the forest-grassland edge.

Correct Answer: C. Nitrogen Fixation

Nitrogen fixation is the process where atmospheric nitrogen ($N_2$) is converted into ammonia or nitrates. This is carried out by lightning or specific bacteria like Rhizobium in the root nodules of legumes. Most plants cannot use nitrogen in its gaseous form directly.

Correct Answer: A. Pond

In a pond or marine ecosystem, the pyramid of biomass is often inverted because the biomass of fishes far exceeds that of phytoplankton. Phytoplankton have a very high turnover rate but a small standing crop at any given time. This is a common exception to the upright biomass rule.

Correct Answer: A. Resilience

Ecological resilience is the ability of an ecosystem to absorb changes and still persist in a stable state. It involves returning to the original equilibrium after being displaced by a disturbance. High biodiversity generally increases the resilience of an ecosystem.