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Lecture 5

Biology Lecture 5 Article 1 & 2.docx

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Scott Browning

BIOLOGY LECTURE #5 ARTICLE #1 + #2 Population Ecology - POP ECO: The study of factors affecting pop + how + why a pop changes over time - Roots in the study of: pop growth, regulation, dynamics, demography - Human pop growth = IMP MODEL FOR MOST ENVIRO ISSUES - Org’s life history = record of major events relating to growth, development, R + S = Varies from one species to next Population Limiting Factors Population Growth Limitation: - Pops grow @ geometric/exponential rates if unlimited resources - Geometric pop grow through pulsed repro (annual repro) - Exponential pop grow continuously (repro @ any time) - All populations begin in exponential growth in favorable enviro + low pop densities - May apply to pops establishing in new enviro - G + E growth can’t continue indefinitely, must eventually slow + stop - Resources depleted = pop growth rate slows and eventually stops = LOGISTIC GROWTH - Pop size where growth stops = Carrying Capacity - # OF INDIVIDUALS OF A PARTICULAR POP THE ENVIRO CAN SUPPORT - POP = CONSTANT HERE, so BR = DR = PG = 0 Pop Can’t Grow Without Limit - Pop can’t increase without limits - Pops increase/decrease in response to changes in factors that restrict growth - Factors influence growth + density = oscillations in pop size over time - Difficult to determine exact factor limiting growth Ex) Lemmings are small rodents that are food for @ of predators, single most important factor limiting lemming pop size was predation pressure affecting pops. Other predators switched to lemming predation as lemming @s increased, preventing rapid pop growth Ex) Stoat got more food from lemmings = reproductive success increased = increase in pop that overran lemming pop, lemming pop collapsed so stoat’s did too REPEATING CYCLE Density Dependent Limitation: - Limits to growth are whether den
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