Question

Write explanatory notes on: (i) Productivity (ii) Consumers.

Hint:

Productivity: GPP, NPP = GPP - respiration. Consumers: primary/secondary/tertiary.

Answer 1

Step 1: Explain Productivity (2.5 marks):
Productivity in an ecosystem refers to the rate of production/generation of biomass (organic matter) per unit area per unit time. Gross Primary Productivity (GPP) is the total rate of production of organic matter by producers through photosynthesis; Net Primary Productivity (NPP) is what remains after subtracting the producers' own respiratory losses (NPP = GPP - Respiration), and it represents the biomass actually available to consumers. Secondary productivity refers to the rate of formation of new organic matter by consumers using the food they eat.

Step 2: Explain Consumers (2.5 marks):
Consumers are heterotrophic organisms that cannot produce their own food and depend directly or indirectly on producers. They are classified as primary consumers (herbivores, feeding directly on producers, e.g. deer, grasshoppers), secondary consumers (carnivores that eat primary consumers, e.g. a fox eating a rabbit), and tertiary consumers (carnivores that eat secondary consumers, often the top predators in a food chain).

Final Answer:
Productivity measures the rate of organic matter formation (GPP, NPP, secondary productivity), while consumers are the heterotrophic primary/secondary/tertiary levels of a food chain that rely on that productivity.