biol notes for final

biol notes for final - Population Growth and Regulation...

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Population Growth and Regulation Ecology o The study of the interrelationships among living things and their nonliving environment Population o Members of a particular species within an ecosystem o Actually or potentially interacting How does Population size change? o Biotic potential Maximal growth rate given ideal conditions Produces exponential growth if not restrained o Environmental resistance Factors that limit populations growth Examples: food availability , space, access to mates, environmental factors o Populations growth = Biotic potential – Environmental resistance Exponential Growth o Population change = (births –deaths) + (immigrations – emigrations) o If we ignore migration then, Growth rate (r) = birth rate (b) – death rate (d) o To determine the number of individuals asses to a populations in a given time period, the growth rate (r) is multiplied by the current population size o Exponential Growth Curve is characterized by the J shaped curve o Effect of Death Rates on Populations Growth Death rate is less than birth rate you get exponential growth Just takes longer o Death rate is greater than the growth rate then there is a decline in population numbers Populations Can’t Grow Exponentially forever o Finite amount of resources available o Once they are limiting, population growth stops Can reach equilibrium or population may crash o Lemming Population Cycles Conditions good there is a boom If they are bad there is a bust Environmental Resistance Limits Populations Growth o Decreases birth rate, increases death rate o Density-dependent factors
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Predation Parasitism Competition (inter- and intraspecific) o Density-independent factors Weather, natural disasters, pesticides, pollutants o Causes populations to stabilize at or below carrying capacity Maximum populations size an area can support long term o Population growth has an S curve o The effects of Exceeding Carrying Capacity When there were no predators or environmental resistance; reindeers ate all of the food and the population crashed Predators Help Control Prey Populations o Density- dependent control More prey, easier for predators to find and capture o Works both ways Well fed predators make more offspring o Population in predators and prey Population pf one determined the population of other Staggered growth, decline of populations Prey Populations May grow unchecked in the absence of predators, competitors o Rabbits in Australia o Giant African Snails seized from Florida schools o Survivorship Curves Human Population o Growing exponentially Exponential growth will continue du to age structure We continue to overcome environmental resistance Medical advances: agriculture advances Developed countries with more stable populations o US population Growing faster than other developed countries (greater
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biol notes for final - Population Growth and Regulation...

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