Biology topic 19-20

F9 IGCSE

How much energy passes to the next trophic level?

Only about 10% of energy from one trophic level is transferred to the next, while the remaining 90% is lost as heat or used for metabolic processes.

How do decomposers help nutrient cycles?

They break down dead organic matter, returning essential nutrients to the soil and making them available for uptake by plants, thus facilitating nutrient cycling in ecosystems.

What is eutrophication?

It is the process by which water bodies become overly enriched with nutrients, leading to excessive growth of algae and depletion of oxygen, which can harm aquatic life.

What are the 4 stages of population growth?

lag phase, exponential growth phase, stationary phase, and death phase.

What processes release CO₂?

Respiration, decomposition, combustion

What is the effect of removing a species from a food web?

Its prey may increase, predators decrease → domino effect → ecosystem imbalance

Name the 4 types of bacteria in the nitrogen cycle.

Nitrogen-fixing, nitrifying, denitrifying, decomposers

What are 3 key conservation methods?

Nature reserves, captive breeding, laws/regulations, recycling

What does carrying capacity mean?

Maximum population size an ecosystem can support.

Give examples of human activities that harm ecosystems.

Pollution, hunting, deforestation, urbanisation, overfishing