Ecology_Exam 2.docx - Ecology Lecture 13 Ch.8 Introduction...

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Ecology Lecture 13 Ch.8 Introduction Ecologists usually define a population as a group of individuals of a single species inhabiting a specific area. o Characterized by the number of individuals and their density. Additional characteristics of a population include age distributions (longevity reproduction), growth rates (Generation time), distribution, and abundance (Can be a measure of rarity). Age distribution= longevity and reproduction Growth rate is also called generation time Abundance can be a measure of rarity Individuals and populations Typically, an individual is derived from a zygote o Identified by its morphological parts For example, individuals are such Moose or Bear are easy to identify and count o Can also be identified by individuals genotypic traits However, what about cryptic or covert individuals or species? o Unitary: Forming a single or uniform entity Typical of free standing or free ranging individuals, but see… Genets - produced from sexual reproduction Ramets - produced from asexual reproduction o Clone- an individual (ramet) or group of ramets arising from the same genet make up individual Basically a copy of the previous individuals o Modular Plants connected by the same root structure For example, plant stems may be connected by the same root structure Each stem is a module of the whole Metapopulations
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Most population are not continuous… Rather they are: o Spatially disjunct populations the act of disjoining or the state of being disjoined o Distributed in patches across a heterogeneous landscape o Demes exist in discrete patches of breeding habitat in a matrix of unsuitable habitat Deme: (sub-populations) a subdivision of a population consisting of closely related plants, animals, or people, typically breeding mainly within the group. Reasons due to demes being in discrete patches: Dispersal Green Flow Corridor Type of Metapopulations : Classic Model Classic Model (RichardLevins,1969) o Each deme has its own birth & death rate independent of other nearby demes o Limited dispersal links the demes o Individual demes have a finite lifetime o All habitat patches are similar in size & shape, continuously favorable, & equally accessible o Some suitable habitat patches must remain empty for colonization o The pattern of habitat occupancy changes with local extinctions and recolonizations o Extinction and colonization go hand in hand If the organisms go extinct, but the habitats still there, then the habitat can still be colonized again. Type of Metapopulation: Mainland-island Model o adapted from Island Theory of Island Biogeography by MacArthur and Wilson o Island populations are maintained by continuous immigration from large, extinction-resistant mainland populations.
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