Population Dynamics Human Population 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: population density- the number of organisms in an area (44 deer/square mile) spatial distribution growth rate

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

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

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

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

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

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

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

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

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

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

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

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

Age Structure

Biodiversity and Conservation

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

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?

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!

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

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)

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

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

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

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)

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

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

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

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

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

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