EcologyBioObjectives.docx - Outline how population size is...

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Outline how population size is affected by natality, immigration, mortality and emigration. Natality: Increases population Birth rate, more organisms brought into a population Reproductive rates, over a variety of time periods Immigration: Increases population Organisms migrating into a habitat Mortality: Decreases population Death rate, more organisms dying out of a population Emigration : Decreases population Organisms migrating away from a habitat Draw and label a graph showing a sigmoid (S-shaped) population growth curve (How detailed?) Explain the reasons for the exponential growth phase, the plateau phase and the transitional phases between these phases. Exponential growth phase Population growth is fastest Birth rate & immigration exceeds death rates & emigration Transitional phase Disease spreads faster as populations get larger Reduces number of individuals to reproduce Predators can hunt more successfully as prey population increases Increases population of predators in negative feedback Competition set limits to population increase Resources become scarce when population is larger Increases competition Plateau phase Stabilized by available resources Population growth hits zero, as it reaches its carrying capacity Max pop size that environment can support Birth rate = death rate Populations tend to produce more offspring than can be supported by environment Extreme competition for resources Distinguish between the various types of survivorship curves and explain what certain species have that type of survivorship curve.
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Type I: Humans Have high probability of surviving through early/middle life Rapid decline in number of individuals surviving into late life Most will make it to adulthood, proportion surviving into old age greatly decreased Convex curve Type II: Songbirds Constant mortality rate for species throughout Chance of dying independent of age Diagonal decreasing line Type III: Frogs Few individuals live to adulthood, die as they get older Greatest mortality experienced early in life Concave curve List three factors that set limits to population size. (How detailed) Shortage of resources (e.g. food) Increase in predators Increase in diseases and parasites Distinguish between r-strategies and K-strategies.* R-Strategists Increase the number of offspring in an unpredictable environment Require little energy investment for each offspring Even if a lot of offspring are eliminated, there are still some left to pass on genes Early age at first reproduction Short lifespan Short maturation time Often high mortality time Few number of reproductions per lifetime No parental care Small size of offspring/eggs Ex) Invertebrates Lots of eggs and larvae Few survive to produce mature, reproductive adults K-Strategists
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