Ecology studies the interactions between organisms and their environment. An ecosystem consists of all living organisms (biotic factors) in an area and their physical environment (abiotic factors like temperature, water, and sunlight.
Energy flows through ecosystems in one direction, starting with producers (plants and algae) that capture solar energy through photosynthesis. Primary consumers (herbivores) eat producers. Secondary consumers eat primary consumers. Decomposers break down dead organisms, recycling nutrients.
Food chains show linear feeding relationships. Food webs are interconnected food chains that better represent the complexity of real ecosystems. Each level is a trophic level, and only about 10% of energy transfers between levels.
Biomes are large-scale ecosystems classified by climate and vegetation. Major biomes include tropical rainforest, desert, grassland, tundra, and temperate forest. Each has distinct temperature, precipitation, and biodiversity characteristics.