ECOSYSTEMS AND HUMAN POPULATIONS Earth Science Ecology: Human Populations Notes 1-3

Populations Biotic and abiotic factors determine the size of the population. To grow: enough biotic and abiotic factors and no major disasters To shrink: not enough biotic and abiotic factors, disease, increase in predators, loss of habitat Carrying Capacity The largest number of individuals that a habitat can support When birth rate equals death rate Can go up if there is an increase of abiotic and biotic factors Goes down if there are less abiotic and biotic factors

Populations Limiting factors The factors that limit the growth of a population Controls the size of the population or determines the carrying capacity Nutrients Space Water Predators Can be biotic or abiotic Some factors depend on population density and others affect population no matter how many organisms live there.

Human Population Overpopulation: Too many people for the resources that are available Carrying capacity has been reached and surpassed Human population may have reached its carrying capacity Farming (pesticides and fertilizers) have improved crops and increased food sources Agricultural machinery has improved crop harvest and uses 17% of US’s total energy. 70% of earth’s freshwater is used for agriculture Scientifically improved crops that have been genetically altered for drought, size and general productivity.

Populations Predator vs Prey Moose and wolf relationship on Isle Royale As wolf population goes up = moose population goes down As moose population goes down = wolf population goes down As wolf population goes down = moose population goes up As moose population goes up = wolf population goes up Density-dependent limiting factor: Depends on population size

CPV virus outbreak Changes in Food Supply

Populations Herbivores: Moose affect the balsam fir population because it is the moose’s food Plants will go up and down in number also, depending on population of herbivores. Parasites and Disease: 1980 the wolf population went down because of viral disease Competition: Overcrowding causes limited resources, lower birth rates, higher death rates and stress Stress causes a body to have to fighter harder to get rid of disease Causes mothers to kill their offspring Increases the rates of emigration

Populations Overpopulation and over-consumption Habitat destruction Farming and cities take over natural habitats Destruction of resources Using too much water Over hunting and over fishing Eating more and more…needing more and more food Invasive species Introducing exotic species to an area African Land snail introduced to US; eating crops Grow to size of rat Australian Brown Tree Snake Kills off native species of birds on Guam

homeowners

Populations Keystone species: One that affects all other species in a community If this species goes extinct, the whole ecosystem will die Producers (autotrophs) are all keystone species of their ecosystems.

Sustainable Development Using natural resources without causing long-term environmental damage Soil, water or climate Use little energy and materials as possible Be able to withstand droughts, floods and heat waves Most work well enough to improve people’s standard of living Goals: Help people out of poverty Protect the environment Use resources no faster than the rate at which they are regenerated

Succession Primary Succession Occurs in area that has never before been colonized EX: lava flows create a new volcanic island EX: glacier retreats and leaves behind bare rock First species to colonize the area is a pioneer species They change the environment and pave the way for all other species