A population is a group of organisms of the same species that live in the same area. Population size is determined by births, deaths, immigration, and emigration. If births and immigration exceed deaths and emigration, the population increases. Under ideal conditions without limitations, a population would experience exponential growth. However, limiting factors like resource availability typically cause logistic growth, where the population levels off at the carrying capacity of the environment.
1. Population Dynamics
A group of organisms of the same
species that occupy an area.
One of the characteristics of living
things is the ability to reproduce.
If environmental conditions are
“favorable” then the number of
individuals in population should
increase from one generation to the
next.
2. 3 Characteristics of
Populations
1) Geographic Distribution
2) Density
3) Growth Rate
3. 4 Factors Effecting Population
Size
Births-
individuals born each year
Deaths-
that die each year
individuals
Immigration –
Movement of individuals INTO a population
Emigration-
Movement of individuals OUT of a
population
4. Population Size-Growth Rate
Birth
rate- # individuals born
Death rate- # individuals die
Immigration- # of individuals move in
Emigration- # of individuals move out
IF:
BR + I = DR + E Equilibrium
BR + I > DR + E Increasing
BR + I < DR + E Decreasing
5. Biotic Potential
Under “favorable” conditions, a species may reach
its biotic potential.
Highest reproduction rate possible for a species
under “ideal” conditions.
Ex) Houseflies:
Lay over 100 eggs
Can reproduce
at 1 month
After 7 generations,
1 fly =15 billion flies!!!
6. Exponential Growth
Populations size
increases
dramatically over
time.
Occurs: when
resources (food) are
abundant
Shape: J
7. Logistic Growth A population begins with
a period of slow growth
followed by a brief
period of exponential
growth before leveling
off at a stable size
Occurs: because
resources are limited
Shape: S
Environmental resistance
limits size of a population.
Real population growth
looks like this.
3 Phases: lagging, exponential, equilibrium
8. Factors Effect Growth Rate Size
of Population
factors” stop population
“limiting
from reaching biotic potential.
(keeping the population in check)
The number of individuals in a
population for a certain area is
called population density.
9. Carrying Capacity
Max # of individuals of a species
that the environment can
normally &
consistently support.
Changes as the
environment
changes.