1. Population Growth Increase in population = population growth
Population Growth Rate = the change in the number of individuals in a population over time
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2. Population Dispersion
The way in which individuals of a population are spread in an area
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3. Clumped vs. Uniform Dispersion
Live in close proximity for mating, protection, and/or food access
Due to territoriality and intraspecific competition
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4. Spread randomly within an area
Random Dispersion
Spread randomly within an area
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5. Survivorship Curves

6. Survivorship Curve
Shows the number of surviving members over time from a measured set of births.
Type I—low level of infant mortality and will survive until old age (mammals and humans)
Type II—survivorship rate is equal at all stages of life (birds, mammals, reptiles)
Type III—very high birth rate, very high infant mortality (inverts, amphibians, plants)
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7. Population Studies
CHECK YOUR NEIGHBOR
A population is a group of individuals belonging to a single species that occupies a certain area.
What are some ecological populations we could find outside? Discuss with your neighbor.

8. Population Studies
Population size over time depends on four variables—birth rate, death rate, the rate of immigration into the population, and the rate of emigration out of the population.

9. Population Studies
Exponential growth occurs when a population grows at a rate that is proportional to its size.

10. Population Studies
Logistic growth occurs when population growth slows as it reaches the habitat’s carrying capacity, the maximum number of individuals or maximum population density the habitat can support.

11. Population Studies Organisms have different life history strategies.
r-selected organisms produce a lot of offspring and invest little in each offspring. For example, they provide little parental care. Few of the offspring reach adulthood.
K-selected organisms produce a few offspring and provide a great deal of investment in each. For example, they provide a lot of parental care. Most of their offspring reach adulthood.
These are two extremes along a continuum.

12. Population Studies

13. Population Growth Biotic Potential
The rate at which a population will grow if all individuals in a population survive and reproduce at maximum capacity
This is the ideal environment
Unlimited resources
No hazards
Does not exist in real world
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14. Population Growth Four factors can affect the size of a population:
Immigration
Births
Emigration
Deaths
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15. Growth Curves
Graphs showing the number of individual in a population over time
2 types
Exponential (J shaped curve)
Logistic curve (S shaped curve)
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16. Exponential Growth Exponential Growth Due to an increase in resources
J shaped curve
2 phases
Lag phase – little or no increase in population growth
Exponential phase – rapid population growth
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18. Logistic Growth Logistic Growth S shaped curve
Represents the Carrying Capacity
Carrying Capacity = the max number of individuals the ecosystem is capable of supporting
Just enough resources
Sudden drop in population causes a population crash.
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20. Limits to Growth Density Dependent Factors Density Independent Factors
Limiting factors are factors that cause population growth to decrease.
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21. Limits to Growth Density Dependent Factors
Factors that affect populations depending on population density
Competition
Food
Water
Space
Shelter
Predation
Availability of mates
Availability of parasites and disease
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23. Limits to Growth Density Independent Factors
Factors that affect populations regardless of population size
Generally abiotic factors
Ex: weather changes
Ex: natural disasters
Ex: human activities
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24. Human Population Growth
Some human populations have undergone a demographic transition, a shift from high birth and death rates to low birth and death rates.
Usually, death rate decreases first, due to medical and public health advances. Later, birth rate also declines.
During the period between the fall in death rate and the fall in birth rate, the combination of low death rate and high birth rate causes the population to grow very rapidly.

25. Human Population Growth
A pyramid-shaped age structure diagram, such as that of Kenya, is a sign of a rapidly growing population. Most of the population is young and therefore at or approaching reproductive age.
The United States has an age structure that is much more even—its population is growing slowly.
In Italy, much of the population is older, and there are relatively few children. Italy’s population is stable or even declining.

26. Human Population Growth

27. Human Population Growth
AIDS has affected world population more than any other disease since the bubonic plague of the Middle Ages.
AIDS strikes primarily adults of reproductive age.
Some of the countries struck hardest by AIDS, including Botswana and South Africa, are expected to experience population declines as a result of the disease.

28. Human Population Growth
Human population is currently about 6.5 billion.
Although world population continues to grow rapidly, the rate of growth has slowed, so that growth is no longer exponential.
Scientists now believe that if present trends continue, the global human population will peak at around 10 billion soon after 2050.

29. Human Population
From 6000 BC to 1800 AD the number of people increased slowly
Mid 1800’s human population began to grow exponentially
Why?
Agricultural revolution
Industrial revolution
Advances in medicine
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30. Human Population In 1650 – 500 million people
In 1930 (about 300 years later) – 2 billion people
Today (about 70 years later) – over 6 billion people
By 2050 – between 7.8 and 12.5 billion
This is based on population growth in China and India
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31. Human Population
Humans have been able to push the carrying capacity of the Earth past what it really should be
Ability to cultivate crops
Ability to domesticate animals
Ability to cure diseases
Eventually we will run out of space and possibly resources
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