Transcript Document

Population
3 Important Characteristics of a Population
1. Geographic Distribution (Range)
- the area inhabited by a population
- example: whales occupy millions of square kilometers in the
Pacific Ocean when migrating
2. Population Density
-
the number of individuals per unit area
-
Example: the population of saquaro cactus have a low
density
3. Growth Rate
3 factors:
a. Number of births
-
population can grow when its birthrate is greater than its
death rate
b. Number of deaths
c. Number that enter or leave
-
immigration – movement of individuals into an area
-
emigration – movement of individuals out of an area
animals tend to do this in search of mates or food
If a population has abundant space and food, and is
protected from predators and disease, then organisms will
multiply.
Exponential growth – individuals in a population reproduce
at a constant rate; under ideal conditions with unlimited
resources, a population will grow exponentially
exponential growth
is represented by a
J curve
# of bacteria
Time(hours)
Carrying capacity – the largest number of individuals that a
given environment can support
Things that could limit population size would include:
competition, predation, parasitism, disease, climate
conditions, and human disturbances