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Habitat: the general place where an organism lives
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Niche: a range of biotic and abiotic conditions in which species live, and the way the species obtains what is needs to survive and reproduce
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Resources: necessities of life
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Plants: sunlight, water, nutrients
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Animals: nesting, space, shelter, food
Physical (abiotic): environment, weather, natural disasters
Biological (biotic): how it eats, how it reproduces, how it interacts with other species

Tolerance: the ability to survive and reproduce under a range of environmental circumstances
- Organisms have an upper and lower limit of tolerance for every environmental factor
- Once they reach their optimum range, the organism experiences stress
- Beyond their tolerance level, the organism will not survive

- Competition can occur between similar species ( intraspecific competition ) and between member of different species ( interspecific competition )
Competitive Exclusion Principle: no 2 species can occupy the same niche in the same habitat and exactly the same time
Instead species will divide resources

Predator-Prey Relationships: predators can affect the size of the prey population and determine where the prey can live and feed
Herbivory-Plant Relationships: herbivores can affect both size and distribution of plants and where the plants can grow and survive
Keystone species: a newly introduced species affects the population of another species
algae → sea urchin → sea otter

Symbiosis: any relationship between two species that live closely together
Three types of symbiosis:
Mutualism: a relationship between two species in which both benefit
Example: Clownfish and Anemone
Parasitism: a relationship between two species in which one lives on or in the other organism with intentions to harm it (they do not kill the host)
Example: Tapeworms/Lice/Leeches
Commensalism: a relationship between two organisms where one organism is help and the other is neither helped nor harmed
Example: Barnacles and Whales

Mutualism
Parasitism
Commensalism