The ecosystem document discusses key concepts including ecosystems, environments, adaptation, habitats, living things, carnivores, herbivores, omnivores, food chains, food webs, and endangered and extinct species. An ecosystem refers to all the plants and animals that live together in an area and how they interact. Different ecosystems can exist close together. Animals are adapted to their environments through traits like body shape, claws, and teeth. A habitat provides an animal with food, water, shelter, and mates for survival. Living things depend on each other as carnivores eat other animals, herbivores eat plants, and omnivores eat both. Food chains show predator-prey relationships with the strongest predator