Ecosystems

Key Definitions

Ecosystem: a community of living organisms interacting with each other and their non-living environment. Habitat: where an organism lives. Population: all organisms of one species in a habitat. Community: all the populations of different species in a habitat. Biodiversity: the variety of species in an ecosystem.

Food Chains and Webs

A food chain shows the transfer of energy from one organism to the next. Producers (plants) → primary consumers (herbivores) → secondary consumers (carnivores) → tertiary consumers. A food web shows interconnected food chains in an ecosystem.

Abiotic and Biotic Factors

Abiotic factors are non-living conditions that affect organisms: temperature, light, water, pH, wind. Biotic factors are living factors: predation, competition, disease, food availability.

Key Points

Producers start every food chain (photosynthesis)
Energy is lost at each trophic level (heat from respiration)
Abiotic = non-living factors; Biotic = living factors
Biodiversity = variety of species

Exam Tips

Use precise definitions — examiners want key terms like "population", "community"
When explaining food web changes, trace the effect through multiple chains