1. Niches and Community Interactions

2. What is a Niche? Habitat: the general place where an organism lives
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
Resources: necessities of life
Plants: sunlight, water, nutrients
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

3. Tolerance
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

4. Tolerance Graph

5. Competition
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

6. Predation/Herbivory/Keystone Species
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

7. Symbiotic Relationships
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

8. Examples of Symbiotic Relationships
Mutualism Parasitism
Commensalism