organism population community ecosystem biosphere Population Ecology AP
organism population community ecosystem biosphere Population Ecology AP Biology
Why Population Ecology? § Scientific goal u understanding the factors that influence the size of populations § Practical goal u management of populations § increase population size w endangered species § decrease population size w pests § maintain population size w fisheries management n AP Biology maintain & maximize sustained yield
AP Biology
Life takes place in populations § Population u group of individuals of same species in same area at same time § rely on same resources § interact § interbreed AP Biology Ecology: What factors affect a population? Population
Factors that affect Population Size § Abiotic factors u u u sunlight & temperature precipitation / water soil / nutrients § Biotic factors u other living organisms § prey (food) § competitors § predators, parasites, disease § Intrinsic factors u AP Biology adaptations
Characterizing a Population § Describing a population range u pattern of spacing u § density u size of population 1970 1966 1964 1960 1965 1961 Equator 1958 1951 1943 1937 1956 1970 Immigration from Africa ~1900 range AP Biology density
Population Spacing § Population spacing: Dispersal patterns within a population Provides insight into the environmental associations & social interactions of individuals in population clumped random AP Biology uniform
Clumped Pattern AP Biology (most common)
Population Size § Changes to population size u adding & removing individuals from a population § § AP Biology birth death immigration emigration
Survivorship curves § Generalized strategies Survival per thousand 1000 Human (type I) Hydra (type II) 100 1 0 AP Biology 25 I. High death rate in post-reproductive years II. Constant mortality rate throughout life span Oyster (type III) 10 What do these graphs tell about survival & strategy of a species? 50 75 Percent of maximum life span 100 III. Very high early mortality but the few survivors then live long (stay reproductive)
Reproductive strategies § K-selected u u u late reproduction few offspring invest a lot in raising offspring § primates § coconut § r-selected u u u K-selected early reproduction many offspring little parental care § insects § many plants AP Biology r-selected
Trade-offs: survival vs. reproduction § The cost of reproduction u increase reproduction may decrease survival § age at first reproduction § investment per offspring § number of reproductive cycles per lifetime AP Biology Natural selection favors a life history that maximizes lifetime reproductive success
Trade offs Number & size of offspring vs. Survival of offspring or parent r-selected K-selected “Of course, long before you mature, AP Biology most of you will be eaten. ”
Population Growth Curves AP Biology
Exponential growth rate § Characteristic of populations without limiting factors u introduced to a new environment or rebounding from a catastrophe Whooping crane coming back from near extinction AP Biology African elephant protected from hunting
J- Shaped Curves § Exponential growth AP Biology
S-shaped Curve § shows logistic growth, illustrates a populations carrying capacity Carrying capacity – the number of organisms the environment can support over a period of time Limiting factors (food, disease, predators, or lack of space) will cause population growth to slow over time AP Biology
Predator-Prey Relationships § As the # of prey , the # of predators § As the # of predators the # of prey AP Biology
Boom and Bust Population Growth § Occurs when a population maintains a constant § number, but experiences a brief, sudden increase in population growth Usually due to season change – mosquitoes in warm & muggy weather AP Biology
Regulation of population size marking territory = competition § Limiting factors u density dependent § competition: food, mates, nesting sites § predators, parasites, pathogens u density independent § abiotic factors w sunlight (energy) w temperature w rainfall APcompetition Biology for nesting sites swarming locusts
Any Questions? AP Biology
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