1. Properties of Populations
Homework
Read Pages
Answer Questions1-6 on p. 202

2. Population Ecology Practical Goal Management of Populations
Increase Population Size
Endangered species
Decrease Population Size
Pests
Maintain Population Size
Fisheries Management
Maintain and maximize sustained yeild

3. Properties of Populations
Size
Total # of individuals
Density
# of individual per unit area or volume
Dispersion
Arrangement of individual in space.
EVEN
CLUMPED
RANDOM

5. How Does a Population Grow?

6. We will finish our graphs AFTER Lecture!
Pop Ecology Files
You will compare graphs of different populations over time to gain an understanding of both the nature of that growth and ecology of the species being studied.
We will finish our graphs AFTER Lecture!

7. How Fast Can a Population Grow?
A species’ biotic potential is the fastest rate at which its populations can grow. This rate is limited by the maximum number of off spring that each member of the population can produce, which is called its reproductive potential.
REPRODUCTIVE POTENTIAL HIGH WHEN:
Individuals produce more than one offspring at a time.
Reproduce more often.
Reproduce earlier in life.

8. Exponential Growth
Populations sometimes undergo exponential growth, which means they grow faster and faster.
Human Population Growth: Video

9. When Does Exponential Growth Happen?
Only when populations have:
Plenty of food and space
Little or no competition or predators

10. Because natural conditions are neither ideal nor constant, populations cannot grow forever and rarely grow at their reproductive potential.
Eventually resources are used up or the environment changes.
Carrying Capacity is the population size where birth rates and death rates are equal. It is also the maximum population that its ecosystem can support indefinitely.

11. Forecasting Population Size
How will your community change in the next 20 years?
Will it need more schools or retirement centers?
Will more people move in and create demand for more roads and utility services?
Demographers look at many properties of populations to predict such changes.

12. Population Characteristics
Different populations of same species have specific characteristics that distinguish them from one another.
Natality (birth rate)
Mortality (death rate)
Sex Ratio
Age Distribution
Growth Rates
Density
Spatial Distribution

13. Natality and Mortality
# of individuals added to population through reproduction over a period of time.
Asexual (i.e. bacteria)
Sexual (i.e. humans)
How is Natality Reported:
# of individuals born per 1000 individuals
Most populations produce more offspring than are necessary to replace the parents.

14. Natality and Mortality
Population growth also depends on mortality rate!
Mortality
# of deaths in a population over a period of time.
How is Mortality Rate Reported:
# of people who die per 1000 individuals
Death Rates:
Most Organisms- very high (i.e. seeds)
Humans- very, very low!

15. On the Double
Effect of Population Birth Rate and Death Rate on Population Size
Growing?
Shrinking?

16. Sex Ratio and Age Distribution Examples

17. Sex Ratio Relative numbers of males and females.
# of females important as they determine # of offspring produced in a population.
Polygamous Communities
Can survive w/ few males, b/c they are capable of fertilizing several offspring.
Monogamous Communities
Unpaired females may not be fertilized and produce young.
Therefore female #’s are more important that male #’s.
If you’re an earthworm, sex ratio doesn’t matter. Why?

18. Sex Ratio Statistics Most Species 1:1 Game Species
Males are shot more frequently than females.
Insect Populations (bees, ants, wasps)
# of females greatly exceeds # of males at all times
Human Populations
105 males born for every 100 females
People reach mid-twenties and higher death rate equalizes the sex ratio
Higher death rate for males extends into old age, then females out number males.

19. High Population Density
Individuals Injured
Competition for resources.
Plant Population
Water
Soil nutrients
Sunlight
Animal Population
Food
Shelter
Nesting sites
Fix
Dispersal= migration to new areas

20. Species Interactions Interaction Species A Species B Description
Competition
Harmed
Each species negatively affects the other
Predation and Parasitism
Benefited
Species A feeds on species B
Mutualism
Each species is helpful to the other
Commensalism
Unaffected
Species A benefits from species B, but B is unaffected.

21. Graphing Species Interactions

22. Dispersal Emigration:
Seasonal reproduction leading to rapid increase in population size.
Environmental changes intensify competition among members of same species.
Water holes dry up, desert birds emigrate to areas where water is available.

23. Dispersal Immigration Implications
Organisms leave one population and become members of a different population.
Implications
Alter gene pool
Introduce disease

24. Why Do Humans Emigrate? How do countries cope with the large influx of new inhabitants?
Droughts
Wars
Political Persecution
Estimated 11.5 million refugees world wide!
Facts and Figures about Refugees

26. Carrying Capacity & Environmental Resistance
Number of individuals of a species that can survive in an area over time.
Combination of factors that sets the carrying capacity for an area.

27. Limiting Factors Key component that limits size of a population.
Availability of raw materials
Availability of energy
Accumulation of waste products
Interactions among organisms

28. K-Strategists Long lives Produce few offspring
Provide care for offspring.
Populations stabilize at carrying capacity
Invest a great deal of energy into producing a few offspring that have a good chance of living.
Populations controlled by density dependent limiting factors.
Competition for resources.

29. R-strategists Short lives Produce many offspring
Don’t care for offspring.
Populations do not reach carrying capacity
Invest a great deal of energy into producing many offspring in hopes that a few will live.
Populations controlled by density independent limiting factors.
Weather
Destruction of habitat

31. 1 Earth

32. 7 Billion People

33. Are You Typical?