JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II Year ENVIRONMENTAL STUDIES Previous Question Paper (October - 2020 - R13)

The structure of an ecosystem is defined by the interaction between its biotic (living) and abiotic (non-living) components. It is organized into two primary structural aspects:

1. Abiotic Components: These include the physical and chemical factors that influence the survival of organisms, such as solar energy, water, climate, soil composition, and inorganic substances like carbon, nitrogen, and phosphorus.

2. Biotic Components: These are organized based on their nutritional relationships into three functional groups:

• Producers (Autotrophs): Primarily green plants and algae that synthesize organic compounds from inorganic substances using solar energy via photosynthesis.
• Consumers (Heterotrophs): Organisms that depend on producers for food. These are classified as primary consumers (herbivores), secondary consumers (carnivores), and tertiary consumers (top predators).
• Decomposers (Saprotrophs): Microorganisms like bacteria and fungi that break down dead organic matter into simpler inorganic nutrients, which are then recycled back into the environment.

Ecological pyramids are graphical representations of the relationship between different trophic levels in an ecosystem. They illustrate the flow of energy, biomass, or population numbers across these levels. The base of the pyramid represents the producers, while the successive levels represent consumers.

There are three main types of ecological pyramids:

• Pyramid of Numbers: Represents the total count of individual organisms at each trophic level. It can be upright (e.g., grassland ecosystem) or inverted (e.g., a single tree supporting many insects).
• Pyramid of Biomass: Represents the total dry weight of living organic matter at each level. It is generally upright in terrestrial ecosystems but can be inverted in aquatic ecosystems where phytoplankton biomass is lower than that of the zooplankton feeding on them.
• Pyramid of Energy: Represents the total amount of energy available at each trophic level. This pyramid is always upright because energy is lost as heat at each transfer, following the 10% law of energy flow.