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Factors that Influence Population Size - Coggle Diagram
Factors that Influence Population Size
Growth Factors
Growth Rate
A population will experience an increase (growth) if the Growth Rate exceeds the Death Rate
The Growth Rate for a population under
ideal conditions
is Biotic Potential
Immigration
Arrival of new residents
Increased Survivorship
If the death rate is decreasing due to the survivorship of individuals, then the population will grow
Consider how increased medical knowledge and access to healthcare has increased survivorship of humans, causing our Life Expectancy to increase (and therefore, have continued larger populations
Available Resources
Food
Water
Less Competition
Availability of Reproductive Mates
Reducing Factors
Emigration
Departure of individuals who take up permanent residence elsewhere
Death Rate
How quickly members within a population are dying, per unit time
When Growth Rate falls below the death rate, we will see a decrease in population size
This can be observed (or will be observed in the future) when countries are more economically developed (Demographic Transition Model)
Density Dependent Limiting Factors
Factor that limits population growth and has a greater effect in denser populations; for example, competition for a limited resource.
Intraspecific Competition
Competition for resources among members of the same species.
Density Independent Limiting Factors
Factor that limits population growth and arises regardless of population size
Abundance/Lack of Food
Natural Disasters
Pandemics (though increased population size increases risk)
Population Regulation
Carrying Capacity
The maximum number of individuals of a particular species that a population's environment can support indefinitely
K-Selection
Pattern of selection in which adaptive traits allow their bearers to outcompete others for limited resources; occurs when a population is near its environment’s carrying capacity.
r-Selection
Pattern of natural selection in which producing the most offspring the most quickly is adaptive; occurs when population density is low and resources are abundant.
Replacement Fertility Rate
This is the number of children a woman must bear to replace herself with 1 daughter of reproductive age.
Theoretically, a population will remain the same in number if this rate is 2.0, with a woman bearing 1 son and 1 daughter for a lifelong, monogamous relationship.