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Population Ecology

Population Ecology. Population Dynamics Human Population. Population Characteristics. A population is a group of organisms of the same species that live in the same area. Characteristics of populations include: p opulation density- the number of organisms in an area (44 deer/square mile)

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Population Ecology

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  1. 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

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

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

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

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

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

  11. 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

  12. 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

  13. 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

  14. Trends • Developed countries have a lower birth rate and a later death rate • USA (1850) 50/1000 death @ 38.8 • USA (2009) 13.9/1000 death @78.11 • Why? • Zero population growth • Birthrate + Immigration rate = death rate + emigration rate

  15. Age Structure

  16. Biodiversity and Conservation

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

  18. 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?

  19. 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!

  20. 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

  21. 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)

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

  23. 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

  24. 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

  25. 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)

  26. 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

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

  28. 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

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

  30. 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

  31. 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

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