Changes in a population How do we define a population?. Population Individuals of a single species Occupy the same area Rely on the same resources Affected by same environmental factors Interact and breed. Population Dynamics. Why does it matter?.
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How do we define a population?
Individuals of a single species
Occupy the same area
Rely on the same resources
Affected by same environmental factors
Interact and breedPopulation Dynamics
e.g. Caulerpa taxifolia
Produces a linear graph.
Doubling occurs relatively slowly.
Example--2, 4, 8, 16, 32, 64, 128....
Produces an exponential (logarithmic) graph--a "J" curve.
Doubling occurs rapidly.
Populations tend to grow exponentially, when there are no limits to growth.
converts a "J" curve to an "S" curve
= logistic growth
e.g. space and hunting restricted elephant seals
& sets the carrying capacity (environmt. support)Limiting factors…
Population may stabilize if resources are renewable, and growth was not too severe.
Population may crash if resources are non-renewable or if growth outpaces renewal.
Density dependent growth was not too severe.
Factors that limit growth more severely as the population increases
E.g. food, nutrients, disease, etc.
Factors that effect population in a consistent way whether there are few or many individuals.
E.g. weather, climate, etc.Limiting factors
Assuming current trends… growth was not too severe.
Low range est.
At U.S. dietary standards....
At U.S. energy consumption....
< 1 billionWhat is the human carrying capacity for earth?
Regional differences growth was not too severe.
Sweden very stable
E.g. 28 births per 1000 people
E.g 11 deaths per 1000 people
Zero population growth (ZPG)
birth rates = death ratesWorld population depends largely on…