This document defines key concepts in ecology including ecosystems and biomes. It explains that an ecosystem is a system of living things that interact with each other and their environment. It lists several main biomes including desert, rainforest, ocean, taiga, tundra, chaparral, grassland, and temperate forest. It describes abiotic factors as nonliving physical influences on ecosystems like water, oxygen, temperature, and sunlight. Biotic factors refer to living influences like predation and disease. Ecosystems need to remain balanced, with populations in proportion to available resources, otherwise the ecosystem will fail. Organisms adapt through traits that help them succeed in their ecosystem.