1. Populations Interdependence in Nature
Chapter 5

2. Describing Populations
Group of organisms of a single species that lives in a given area
Studied by
Geographic range
Density and distribution
Growth rate
Age structure

3. Describing Populations
Geographic range
The area inhabited by a population (where they live)
Native (natural) range vs. introduced range
Hydrilla
Zebra mussels
Density and distribution
Number of individuals per unit area
Three general types
Random
Uniform
clumped

4. Describing Populations
Growth Rate
Determines whether the size of a population increases, decreases or stays the same
Age structure
The number of males and females of each age a population contains

5. Population Growth Birthrate vs. death rate Immigration vs. emigration
Higher birthrate – population grows
Higher death rate – population shrinks
Equal rates – zero growth
Immigration vs. emigration
Imm- growth caused by moving in from elsewhere
Em- decline caused by leaving a population range

6. Types of Growth Exponential Growth Logistic Growth
The larger a population, the faster it grows
Under ideal conditions with unlimited resources, populations will grown exponentially
Causes a J-shaped curve when graphed
Logistic Growth
Phases of growth
Exponential
Growth slows
Growth stops
Causes an S-shaped when graphed
Carrying capacity – the maximum number of individuals of a particular species a particular environment can support

7. Limits to Growth
Limiting factors – controls the growth of a population
Determine the carrying capacity of an environment

8. Two types of limiting factors
Density-dependent
Competition
Predation
Herbivory
Parasitism
Disease
Stress from overcrowding
Density-independent
Unusual weather
Natural disaster

9. Human Population Growth
Tends to increase
Rate of increase has changed over time
Causes of increase – advance of civilization

10. Patterns of Human Population Growth
Demography – study of human populations
Looks at the characteristics of human population
Tries to explain how populations will change over time