1. Population Dynamics Human Population
Population Ecology
Population Dynamics
Human Population

2. Population Characteristics
A population is a group of organisms of the same species that live in the same area.
Characteristics of populations include:
population density- the number of organisms in an area (44 deer/square mile)
spatial distribution
growth rate

3. Dispersion Patterns Uniformed (Solitary) Members are evenly spaced
Members often don’t want to be near each other
Competition
Limited resources
Territorial

4. Clumped (Herds) Usually clumped around important resources
Members are usually social
Defense
Mating behaviors
Offspring

5. Random (Groups) Some members are social and some are not
Not centered around or influenced by certain resources

7. Limiting Factors Keep populations from growing indefinitely
Can be abiotic or biotic
Rainfall
Temperature
Hiding places
Food
Predators
Disease

8. Limiting Factors Density Independent Density Dependent
Does not depend on population density
Usually abiotic
Weather: floods, droughts, hurricanes, temperature
Human activities: dams, pollution
Depends on population density
Usually biotic
Disease
Competition
Parasites
Predators

9. Population Growth
Population Growth Rate- a measure of how fast a population grows
Birth and immigration increase populations
Death and emigration decrease populations

10. Exponential Growth Growth without limiting factors
All the young survive and breed
Population increases rapidly
J shaped

11. Logistic Growth Rapid population growth will strain resources
Population’s growth slows or stops at carrying capacity
S shaped curve

12. Carrying Capacity
The maximum number of individuals in a species that an environment can support for the long term
Limited by resources
Water
Oxygen
Nutrients

13. Reproductive Strategies
r-strategists (rate)
Small organisms
Usually have short lives
Reproduce quickly
Produce many offspring
Don’t nurture offspring
k-selected (carrying capacity)
Large organisms
Usually have long lives
Mature late
Produce few offspring
Parental care and nurturing

14. Human Population
Humans change their environment to increase the carrying capacity
Technology reduces death rate
Medicine
Shelter construction
Increase of 70 million people each year
Population to double in 53 years
Growth rate has slowed
Diseases (AIDS)
Voluntary population control

15. Trends
Developed countries have a lower birth rate and a later death rate
USA (1850) 50/
USA (2009) 13.9/1000
Why?
Zero population growth
Birthrate + Immigration rate = death rate + emigration rate

16. Age Structure

17. Biodiversity and Conservation

18. Biodiversity Biodiversity- variety of life in one area
Extinction- no more members of a species exists

19. The variety of genes in a population
Genetic Diversity
The variety of genes in a population
Higher diversity offers a better chance to survive during a disaster (environmental change, disease outbreak, disappearance of food)
Species Diversity
Number of different species and the abundance in a community
What biomes have a higher diversity?

20. Why Preserve Biodiversity
Wild species might someday be needed to create better crops
Scientists continue to find new medicines in nature
Aspirin- Willow
Penicillin- Bread mold
Many organisms haven’t been identified yet
It’s beautiful!

21. Extinction Rates
Background Extinction: gradual process of a species going extinct
Always present
Caused by natural processes (Climate change, natural disasters, activity of other organisms)
Mass Extinction: a large percentage of all living species become extinct in a short period of time
Dinosaurs 65 million years ago

22. Extinctions
73% of mammals that have become extinct in the last 500 years were island species.
Why?
Evolved without natural predators
Don’t have ability to protect themselves
When predators are introduced
they can harm native species
bring diseases (natives populations don’t have resistances to)

23. Extinctions Hawaiian birds In danger of extinction: Amphibians I’iwi
African penguins Panamanian Golden Frog

24. Threats: Humans
Change natural conditions faster than organisms can adapt
Overexploitation- excessive use of a species that has economic value
50 million bison dwindled to 1000 in 1889 (overhunting)
Overexploitation may lead to extinction
Passenger pigeon (hunted)
Habitat loss
Have to move or they will die

25. Habitat Disruption
Changing one thing can lead to huge loss of biodiversity
Whales disappear then plankton bloom
Habitat Fragmentation- separating an ecosystem into small areas (can’t support large numbers, decrease in genetic diversity)
Edge Effect- temperature, humidity, wind and species are different at edges than interiors

26. Biomagnification Pollutants build up to high levels in carnivores
DDT-kills mosquitoes and other insects; accumulates in birds affecting eggs shells
Mercury- accumulates in humans causing problems in nervous system (vision, hearing, speech)

27. Acid Precipitation
Caused by burning fossil fuels- forms sulfuric and nitric acid
Acid rain falls back as rain, snow, fog or sleet
Acid rain removes nutrients in the soil and kills fish and other organisms
Eutrophication: pollution increases nitrogen and phosphorous in water causing algae to grow
Depletes oxygen suffocating other organisms

28. Invasive Species Organisms moved to new habitat
Populations are not controlled by natural means (predators, parasites)
Cane Toads
Fire ants
African honey bees
Kudzu

30. Conservation Industrialized countries use more resources
Renewable resource- replaced by natural processes faster than they are consumed
Nonrenewable resource- replaced slower than they are consumed (limited)
Which are renewable and which are not?
Fossil fuels Water Metals
Timber Species
Solar radiation Hydropower

31. Sustainable Use
Using resources at a rate in which they can be replaced
All resources need to be used in a sustainable manner

32. Hot Spots Areas that have a high number of endemic species
only exist in that location
70% of the original habitat was lost
1/3 of all plant and animal species are found in hot spots
Originally covered 15% of the Earth but only about 1/10 of that remains

33. Restoring Ecosystems How should we do it?
Bioremediation- using living organisms to remove toxins from polluted areas (bacteria, fungi)
Biological augmentation- adding natural predators to a degraded ecosystem
Ladybugs- control insect populations