Levels of Organization To understand the relationships within the biosphere, ecologists ask questions about events and organisms that range in complexity from a single individual to the entire biosphere.

Organism An individual living thing. You are an organism.

Species A group of organisms that are closely related and that can mate to produce viable offspring.

Population All the members of the same species that live in the same place at the same time. Why is every organism in a species, not considered a population?

Community A group of various species that live in the same place and interact with one another. What make this a community of animals, and not a population?

Habitat The place an organism lives. What type of habitat do these polar bears live in? What type of habitat do these fish live in?

Ecosystem All the organisms living in an area together with their physical (abiotic) environment. What is the difference between a habitat and an ecosystem?

Biome A group of ecosystems that have the same climate and similar dominant communities.

Reflect: What is an ecosystem? Can a group of rabbits and a group of field mice make up the same population in an ecosystem? Explain. Could a biome in Brazil near the equator be the same as a biome in northern Canada? Explain.