Ecosystems, Food Chains and Biodiversity — O/L Science

An ecosystem is a community of living organisms (biotic factors) interacting with each other and with their non-living environment (abiotic factors: temperature, water, light, soil). Ecosystems range from a pond to a tropical rainforest.

Producers (green plants) convert solar energy to biomass via photosynthesis. Primary consumers (herbivores) eat producers; secondary consumers (carnivores) eat primary consumers, and so on. Decomposers (bacteria, fungi) break down dead organic matter, recycling nutrients back to the soil. Food webs show the complex feeding relationships in an ecosystem; removing one species can have cascade effects.

Biogeochemical cycles (carbon, nitrogen, water) continuously recycle elements through biotic and abiotic components. Human activities — deforestation, pollution, overfishing, invasive species introduction — disrupt ecosystem balance. Sri Lanka's wet zone rainforests and coral reefs are globally important ecosystems.