Definitions [9]
Define a consumer.
A consumer is an organism that obtains energy by feeding on other organisms. As it cannot produce its own food, consumers rely on plants or other animals for nourishment, which are a vital part of the food chain. Consumers are further classified into primary consumers, secondary consumers, and tertiary consumers.
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.
The conversion of humus into inorganic nutrients by microbial action is called mineralisation.
The dark-coloured, colloidal, nutrient-rich substance formed during decomposition that decomposes very slowly is called humus.
The dead remains of plants, animals and faecal matter that serve as raw material for decomposition is called detritus.
The enzymatic degradation of detritus into simpler inorganic substances by bacteria and fungi is called catabolism.
The formation and accumulation of a dark-coloured, amorphous, resistant substance during decomposition is called humification.
Key Points
- An ecosystem includes all living (biotic) and non-living (abiotic) components in an area that interact with each other.
- Producers like green plants and certain bacteria make food through photosynthesis, forming the base of the food chain.
- Consumers depend on producers for food and are classified as herbivores, carnivores, omnivores, and parasites.
- Decomposers such as bacteria, fungi, and insects break down dead matter and waste, recycling nutrients and maintaining soil fertility.
- Even dirty or unnoticed organisms (like caterpillars, termites, and dung insects) play a vital role in cleaning the environment and supporting the ecosystem.
- 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 |
Important Questions [21]
- What is Primary Productivity?
- Write the equation that helps in deriving the net primary productivity of an ecosystem.
- Answer the Following Question. Describe the Inter-relationship Between Productivity, Gross Primary Productivity, and Net Productivity.
- The primary productivity in an ecosystem is expressed as ______.
- How are productivity, gross productivity, net primary productivity and secondary productivity interrelated?
- Why Does Primary Productivity Vary in Different Types of Ecosystems?
- State the Relation Between Gross and Net Primary Productivity.
- Write the relationship between productivity, gross primary productivity, net primary productivity, and secondary productivity.
- What is the Primary Productivity of an Ecosystem and How is It Expressed?
- Explain What Does the Equation Given Below Show : Npp = Gpp – R
- Assertion (A): Decomposition process is slower if detritus is rich in lignin and cutin. Reason (R): Decomposition is largely an oxygen requiring process.
- Name the type of detritus that decomposes faster. List any two factors that enhance the rate of decomposition.
- Write the Different Steps Taken in Humification and Mineralisation During the Process of Decomposition.
- The process of mineralization by microorganisms helps in the release of ______.
- Answer the Following Question. Write Any Two Limitations of Ecological Pyramids.
- “The Pyramid of Biomass is Not Always Upright.” Explain the Statement.
- 'The pyramid of energy is always upright.' Explain
- Explain with the help of labelled diagrams, the difference between an upright pyramid of biomass and an inverted pyramid of biomass.
- “It is Often Said that the Pyramid of Energy is Always Upright. on the Other Hand, the Pyramid of Biomass Can Be Both Upright and Inverted.” Explain with the Help If Examples and Sketches.
- Why the Pyramid of Energy is Always Upright? Explain.
- Answer the Following Question. What is an Ecological Pyramid? Compare the Pyramids of Energy, Biomass, and Numbers.
