5 populations
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Chapter 5
Populations
5.1 How Populations Grow
3 Important Characteristics of a population: Geographic Distribution Density Growth Rate
Population Density
The number of individuals per unit area Example: Cactus in Desert vs. Other plants
Population Growth
3 factors affect population growth: Number of Births Number of Deaths Number of individuals that enter or leave a certain
area
Population Growth
Population growth can be positive or negative.
Example: Penguins
Example: Penguins
At the beginning of the year there were 1200 penguins and 1600 at the end of the year.
What was the population growth? An increase of 400 penguins.
Example: Penguins
Suppose 250 chicks died during the year. What is the population growth?
A net increase of 150 penguins
Example: Penguin
Suppose that 200 adults died during the year. What is the populations growth?
A net decrease- or negative growth- of 50 penguins.
Population Growth
Immigration: Movement into an area This can increase a populations growth
Population Growth
Emigration: Movement out of an area This can decrease the populations growth Food shortages can lead to emigration
Exponential Growth
Individuals in a population reproduce at a constant rate
At first the growth is slow, then it becomes larger and larger
Logistic Growth
Population’s growth slows or stops following a period of exponential growth
Less resources available, less growth
Logistic Growth
Follows a general S-shaped curve
Carrying Capacity: Largest number of individuals an
environment can
support
Analyzing Data Activity
Turn to page 123 Follow the directions and answer the
questions that deal with graphing for Exponential Growth and Logistic Growth
5.2 Limits to Growth
Limiting Factor: Factors that cause a population growth to
decrease. Examples:
Competition, Predation, Parasitism and disease, Drought and other climate extremes, and Human Disturbances
Density Dependent Factors
Limiting factor that depends on population size.
Includes: Competition Predation Parasitism and
Disease
Density Independent Factors
Limiting factor that does not depend on population size.
Include: Unusual Weather Natural Disasters Seasonal Cycles Certain Human Factors
5.3 Human Population Growth
Human population tends to increase with time.
Patterns of Population Growth: Demographic Transition Age Structure
Demographic Transition
Change in a population from high birth and death rates to low birth and death rates. What are some reasons why some countries have
a high growth rate and others do not? Nutrition Sanitation Medicine
Age Structure
Population growth depends on how many people make up different ages in a population.
Age Structure Diagram