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Populations
As you may recall….
Populations - the # of individuals of 1 species living in the same ecosystem
Many populations in nature find a point of balance.
The number of individuals a community can hold is called the Carrying Capacity
Populations Change Naturally
Four factors that determine population size:
(i) Natality (# of births / year)
Populations Change Naturally
Four factors that determine population size:
(ii) Mortality (# deaths / year)
Populations Change NaturallyFour factors that determine population
size: (iii) Immigration (# of individuals moving
into an area)
Populations Change Naturally
Four factors that determine population size:
(iv) Emigration (# of individuals moving away from an area)
Populations Change Naturally
•In open ecosystems, all 4 factors affect populations
Population Growth = Births + Immigration - Deaths - Emigration
Abiotic factors Affecting Populations• Every species is able to survive in a range of tolerance in the environment. Populations are largest when conditions are optimal. (usually in a midpoint between an upper and lower limits)
eg. Daphnia live in a temperature range 10°C - 45°C
Key Terrestrial Ecosystem Factors • light availability • water availability • nutrients availability • temperature availability
Key Aquatic Ecosystem Factors • light availability • nutrients availability • temperature availability • salinity • acidity
Biotic factors Affecting Populations• Given optimal abiotic factors, biotic factors will determine a species success
eg. Daphnia provide food to many species
Key Biotic factors • Predation/Parasitism • competition • Commensalism • Mutualism