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Population Size - Coggle Diagram
Population Size
It is the total number of individuals in a population
Which is one Part of
Demographics
The statistical characteristics that can be
used to describe a population
.
The
sampling techniques
are used to estimate
population size
Plot sampling
A method of estimating the total number of individuals in an area based on data from direct counts in some portion of the area.
Mark–recapture sampling
Method of estimating population size of mobile animals by marking individuals, releasing them, then checking the proportion of marks among individuals recaptured at a later time
It is continually change
Individuals are added to a population by
Births
Immigration
Movement of individuals into a population
If their effect set aside, we will have
Zero Population Growth
Interval during which the number of births equals the number of deaths.
Used to measure
per capita growth rate (r)
Of a population, per capita (per individual) birth rate minus per capita death rate
As long as
r
remains constant and greater than zero,
exponential growth
will occur.
A population grows by a fixed percentage in successive time intervals; the size of each increase is determined by the current population size.
Can be calculated for each interval based on the number of individuals (N) and the per capita growth rate (r): N x r = G
Graphing the increases against time results in a
J-shaped curve
It is a characteristic of exponential population growth
The number of new individuals increases in each generation
Individuals are removed from it by
Deaths
Emigration
Movement of individuals out of a population
Biotic potential
Maximum possible population growth rate under optimal conditions
Factors that affect biotic potential include
The age at which reproduction typically begins
How long individuals remain reproductive
The number of offspring that are produced each time an individual reproduces.
Limits on Population Growth
Density-dependent limiting factors
Factors that limits population growth and has a greater effect in denser populations
These factors include
Predation,
Parasitism
Disease
Competition for a limited resource
Such as
Intraspecific competition
Competition for resources among members of the same species.
When they affect population size over time,
logistic growth
occurs
A population grows exponentially at first, then growth slows as population size approaches the environment’s
carrying capacity
for that species
Carrying capacity (K)
is the maximum number of individuals of a species that a particular environment can sustain; can change over time
Density-independent limiting factor
Factor that limits population growth and arises regardless of population size.
Volcanic eruption
Hurricane
Flood
Human-caused events such as oil spills
A population’s growth rate is affected by its members’
life history
Schedule of how resources are allocated to growth, survival, and reproduction over a lifetime
One way to investigate life history traits is to focus on a
cohort
Group of individuals born during the same interval.