Ecosystems have living and non-living components.

• 15.1 What are ecosystems?
• 15.2 Biomes are large ecosystems that occur around the world, each determined by temperature and rainfall.

Interacting physical forces create weather.

• 15.3 Global air circulation patterns create deserts and rain forests.
• 15.4 Local topography influences the weather.
• 15.5 Ocean currents affect the weather.

Energy and chemicals flow within ecosystems.

• 15.6 Energy flows from producers to consumers.
• 15.7 Energy pyramids reveal the inefficiency of food chains.
• 15.8 Essential chemicals cycle through ecosystems.

Species interactions influence the structure of communities.

• 15.9 Each species’ role in a community is defined as its niche.
• 15.10 Interacting species evolve together.
• 15.11 Competition can be hard to see, yet it influences community structure.
• 15.12 Predation produces adaptation in both predators and their prey.
• 15.13 Parasitism is a form of predation.
• 15.14 Not all species interactions are negative: mutualism and commensalism.
• 15.15 This is how we do it: Investigating ants, plants, and the unintended consequences of environmental intervention.

Communities can change or remain stable over time.

• 15.16 Many communities change over time.
• 15.17 Some species are more important than others within a community.