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Chapter 54

BIOA02H3 Chapter Notes - Chapter 54: Life Table, Electronic Tagging, Introduced Species

Biological Sciences
Course Code
Mary Olaveson

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Biology Chapter 54
Population: the individuals of a species within a given area
Population Structure: The age distribution of individuals in a population and the ways those
individuals are spread over the environment
Population Density: the number of individuals of a population per unit area (volume)
Demographic Events: Events such as births, deaths, immigrations, and emigrations that influence the
change of the structure of a population
The study of the births, deaths, and movement rates that create a population dynamics are known as
To study these populations, it requires ecologists to count the number of individuals in the area as well
as the number of deaths, births, and immigrations/emigrations. This is often done by mapping/tagging
the animals
Electronic tagging also tell a lot about the environment and the animal
Population densities
In many cases, population densities are far too vast to count; therefore densities must be estimated by
counting the number of individuals in a sample of representative habitats and extrapolating them to
cover the entire area
A problem may be encountered when counting the amount of mobile individuals within a species as
they can immigrate/emigrate out of the sample area
This is solved by marking all the individuals within the area, allowing them to roam free and interact
with other individuals outside the same area, and then another sample is taken. The proportion of
individuals in the new sample that are marked can be used to estimate the size of the population using
the formula:
m2 = n1 n1 = # of marked individuals in first sample(all of them)
n2 N n2 = # of individuals in the second sample
m2 = # of marked individuals in the second sample
N = The estimated size of the population
This method has its faults, however. This method can only be accurate if it assumes that the populations
of tagged and untagged individuals randomly mix. Also it would be inaccurate if the individuals learn to
avoid traps or become trap-happy (because of the free meals)
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