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 The study of interactions that take place between organisms and their environment.  It explains how living organisms affect each other and the world they live in. 2

 Habitat is the place an organism lives.  Niche is the unique position occupied by a species both in terms of its physical use of its habitat and its function within an ecological community.  “total way of life” or its “role” in the ecosystem. 3

 Abiotic factors- the nonliving parts of an organism’s environment.  affect an organism’s life  Ex: air currents, temperature, moisture, light, and soil. 4

 Biotic factors- all the living organisms that inhabit an environment.  All organisms depend on others directly or indirectly for food, shelter, reproduction, or protection. 5

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 Ecologists have organized the interactions of organisms, based on different levels of complexity. 7

 Atom  Molecule  Organelle  Cell  Tissue  Organ  System  Organism  Population  Community  Ecosystem  Biosphere 8

 Organism: An individual living thing that demonstrates these characteristics: Made of cells, Metabolizes, Reproduces, Responds to Stimuli Evolves Heredity Homeostasis 9

 Population: A group of organisms, all of the same species, which interbreed and live in the same place at the same time. 10

 Community: All the populations of different species that live in the same place at the same time. 11

 Ecosystem: Populations of plants and animals that interact with each other in a given area with the abiotic components of that area. 12

 Biosphere: The portion of Earth that supports life. 13

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