Transcript Population Ecology

Population Ecology
SNC1L Science
Populations Change
• A Population is all of the members of a single species living
in an area.
• The various populations of different species in one area are
called a community.
• Population size depends on four factors:
Births,
Deaths,
Immigration, and Emigration.
(migrating in)
(migrating out)
P = (N+I) – (M+E)
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Populations are limited
• A limiting factor is any biotic or abiotic factor that affects growth
of a population. Too much or too little of any one is not good!
• Populations will grow or decline depending on their Biotic Potential
• This depends on:
• Birth Potential
BIOTIC
ABIOTIC
• Capacity for Survival
Food resources Level of light
• Procreation
Predation
Temperature
Disease
Chemicals
• Reproductive Lifespan
Competition
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Water
Resources
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Birth Potential
• Maximum Number of offspring per
birth
• Humans have a much lower birth potential than
ducks, or salmon.
• Whooping Cranes only lay two eggs a year.
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Capacity for Survival
• Number of offspring that
survive to reproductive age
• Humans have a better chance at this
than many other species...
• Female Clams release five million
eggs at a time, but only 50 may
survive.
• Sea Turtles lay 50 – 100 eggs, but few
reach maturity.
• Parenting is not universal in nature!
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Procreation
• Number of times a species reproduces each year.
• Humans can only procreate once in a given year.
• Mice can have a litter of 10 – 14 pups every 6 to 8 weeks.
• Sparrows produce up to 3 broods of chicks annually.
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Reproductive Lifespan
• Age of sexual maturity & how many years reproduction is
possible.
• Humans need more than a decade to reach sexual maturity.
• African elephants need 15 years to mature, but may reproduce to 90!
• Dogs are mature at 1 year; they can reproduce for the rest of their lives.
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Carrying Capacity
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Population sizes go up and down, but like to be stable
Stability = when the population is in balance
Carrying Capacity = max # of individuals that the ecosystem can support
Populations can exceed their environment’s carrying capacity, but not for long.
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Carrying Capacity
• Example: Fluctuations in Elk & Wolf populations in Banff, Alberta
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Carrying Capacity
• Example: Fluctuations in Snowshoe Hare & Lynx populations, British Columbia
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Carrying Capacity
• Example: Human population from prehistory to modern day
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Population Density
• Population size per unit area of habitat
• Dense Populations = when there are a lot of organisms in a limited area
• Density determines population change, also.
Density Dependent Density Independent
Factors
Factors
Food shortage
Competition
Disease
Invasive species
Predation
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Flood, fire…
Pesticide use
Climate change
Drought
Habitat loss
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