BIOLOGY
Class Notes
10-1
Aim: What affects population growth?
(A) CHARACTERISTICS OF POPULATIONS
 What is a population?
o A population is a group of organisms of the same species
that live in a given area
 Three characteristics of populations are:
o Geographic distribution—term that describes the area
inhabited by a population. Another word for geographic
distribution is range.
o Population density—the number of individuals per unit area
o Population growth—how large or small a population gets. It
is affected by 3 factors:
 Number of births
 Number of deaths
 Number of individuals that enter or leave the
population—through immigration or emigration
 Immigration—entering a population
 Emigration—leaving a population
(B) TYPES OF POPULATION GROWTH
1. Exponential—occurs when the individuals in a
population reproduce at a constant rate; under ideal
condition with unlimited resources
2. Logistic—occurs when population growth slows or stops
following a period of exponential growth; usually
occurs when resources become limited, the number of
predators increase or diseases kill individuals
 Carrying capacity—the number that represents the
largest number of individuals that a given
environment can support