Definitions [5]
Define decomposition.
Decomposition is the process that involves the breakdown of complex organic matter or biomass from the bodies of dead plants and animals with the help of decomposers into inorganic raw materials such as carbon dioxide, water, and other nutrients.
Decomposition is the process by which decomposers break down complex organic matter into simple inorganic substances like carbon dioxide, water, and nutrients.
Define ecological pyramids.
An ecological pyramid is a graphical representation of various environmental parameters, such as the number of individuals present at each trophic level, the amount of energy, or the biomass present at each trophic level. Ecological pyramids represent producers at the base, while the apex represents the top-level consumers present in the ecosystem.
Define ‘Ecological succession’.
The gradual and predictable changes in the species composition of a given area are called ecological succession.
The circular movement of nutrients between living organisms and the physical environment of an ecosystem is called biogeochemical cycle.
Key Points
- Productivity is the rate at which producers fix solar energy into organic matter through photosynthesis or chemosynthesis.
- Gross Primary Productivity (GPP) is the total rate of photosynthesis, while Net Primary Productivity (NPP) is the stored energy after respiration (NPP = GPP – R).
- Net Community Productivity refers to the organic matter stored in an ecosystem after subtracting heterotrophic consumption.
- Secondary Productivity is the rate of organic matter formation at consumer levels and depends on primary productivity.
- Productivity varies among ecosystems and depends on plant species, nutrients, climate, and photosynthetic efficiency.
| Trophic Level | Meaning | Examples | Role in Energy Flow |
| Producers (Autotrophs) | Organisms that synthesise their own food using sunlight through photosynthesis. | Green plants, algae, phytoplankton | Convert solar energy into chemical energy, forming the base of the food chain. |
| Primary Consumers (Herbivores) | Organisms that directly depend on producers for their food. | Grasshopper, squirrel, elephant, deer | Consume plant material, store energy for the next trophic level, and act as a link to higher consumers. |
| Secondary Consumers (Carnivores) | Carnivores that feed on herbivores to obtain energy. | Frog, owl, fox, snake | Transfer energy from herbivores to higher levels and help control herbivore populations. |
| Apex or Top Consumers (Carnivores) | Predators at the highest level of the food chain, feeding on herbivores and carnivores. | Tiger, lion, eagle, crocodile | Regulate populations of secondary consumers, maintain ecosystem stability, and have no natural predators. |
| Omnivores (Mixed Consumers) | Organisms that consume both plants (producers) and animals (herbivores and carnivores). | Humans, bears, raccoons | Diversify energy flow by feeding across multiple levels and connecting various parts of the food chain. |
| Type of Pyramid | What it Represents | Shape | Example / Key Feature |
|---|---|---|---|
| Pyramid of Energy | Energy flow at each trophic level | Always upright | Energy decreases at each level due to heat loss |
| Pyramid of Numbers | Number of organisms at each trophic level | Upright or inverted | Upright in grassland, inverted in parasitic chain |
| Pyramid of Biomass | Total biomass at each trophic level | Upright or inverted | Upright on land, inverted in aquatic ecosystems |
- Biotic succession is the orderly, gradual, and predictable change in community structure at a given place over time, resulting from interactions among organisms and their environment.
- Succession begins with pioneer species, progresses through a series of seral stages (sere), and ends in a climax community.
- During succession, communities modify their environment, making it less suitable for themselves and more suitable for succeeding communities.
- The climax community is a stable, self-maintaining community controlled mainly by climate and is also called the climatic or prevailing climax.
