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Karen Ing (49)
Lecture 11

ENV 200 Feb 28 lecture 11.docx

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School of Environment
Karen Ing

ENV 200 Feb 28 lecture 11  Evolution: o Imagine a situation where 2 species of warblers “compete” for insects on a spruce tree (ex: spending time and energy chasing each other from a certain place in the tree) o Now imagine a behavioural change (likely driven by a random mutation) by which some individuals move to a unique area of the tree to feed o Now the warbler neither has to chase away others (or be chased) it has more time to gather insects than individuals who are still competing o With more energy available to devote to reproduction, it raises more chicks than the individuals who are still competing o Overtime, long time, the population will come to be dominated by the individuals with the unique feeding behaviour o Over time in reasonable stable/predictable envs populations are expected to exhibit progressively narrower realized niches ex: to become more specialized  In the early days of life on earth... o Resources would have been abundant o Populations would have grown rapidly o But as populations began to approach carrying capacity, competition for resources would have increased o Any heritable adaptation or element that would confer an adv with respect to obtaining/using resources would have been selected for (adaptive)  Evolution: natural selection o This is a simple concept, but astonishingly powerful o All the organism on Earth (living or fossil) came about through evolution o Individuals with various traits that promote reproduction (and the number of offspring produced) will come to dominate the population over time o Individuals w/o these adaptations will disappear (eventually) o This is what we mean by survival of the fittest  Where fitness is defined by the number of offspring particular individuals put into the next generation o Since fitness is defined as the number of offspring a particular individual produces any adaptation that improves fitness will be selected for as long as it is not accompanied by negative implications  Ex: we also see adaptations to attract a mate for animals or attract pollinator and disperse seeds in plants  Role of Genetics o Adaptations had to be heritable (passed on to the next generation) o The mechanism how “heritability” worked was not understood until the 1950s when Watson and crick proposed the structure for Dna o Since adaptation have to be heritable they have to be coded for by dna  DNA: deoxyribonucleic acid is double stranded  Two strands are held together by bonds between the nucleic acid rungs  There are only four nuc
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