where adults are more likely to survive to breed again and where competition

Where adults are more likely to survive to breed

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where adults are more likely to survive to breed again and where competition for resource is intense K selection (density dependent selection): selection for traits that are sensitive to population density and are favored in hig=h densities o Operates near carrying capacity where competition is stronger R selection (density independent selection): selection for traits that are maximize reproductive success in uncrowded environments o Operates well below carrying capacity facing little competition o Maximize “r” per capita rate of increase Many factors that regulate population growth are density dependent Density independent: a birth rate or death rate that does not change with population density. o Ex: dune fescue grass dies because of a drought stress that happens when the roots of this plant are uncovered Density dependent: a death rate that rises or a birth rate that falls as population density rises o Ex: as population density increases, birth rate decreases because there are less resources for dune fescue grass o Mechanisms of Density Dependent Regulation: Competition for Resources Increasing population density intensifies competition for resources which reduces reproductive rates Toxic Wastes Increased toxic wastes regulates population Predation Predator captures more food as the population density of the prey increases Intrinsic Factors In some species high density causes a decrease in birth rate and increase in death rate. Territoriality Can limit population density when space becomes a resource for which organisms compete Disease Can limit population density when the transmission rate of a particular disease depends on a certain level of crowding in a population
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o Highest growth rate in age structure pyramids is one that is bottom heave on the bottom and thins out o One that is relatively uniform and evenly spaced out is the second highest growth rate o One that is thin on the bottom thick in the middle and thin on the top shows negative growth rate/no growth rate Community Ecology Community: a group of populations od different species living close enough to interact Interspecific interactions: interactions with individuals of other species o Competition (-/-): occurs when individuals compete for a resource that limits their growth and survival Two species competing for the same limiting resource cannot coexist permanently in a community if their niches are identical Competitive exclusion: a slight reproductive advantage will eventually lead to local elimination of the inferior organism Ecological niche: the sum of a species use of the biotic and abiotic resources in its environment Resource partitioning: the differentiation of niches that enables similar species to coexist in community Fundamental niche potentially occupied by that species Realized niche: portion of its fundamental niche that ir actually occupies
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