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BIOL 121 (72)
Chapter

Natural Selection

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Department
Biology
Course
BIOL 121
Professor
Robert Adamson
Semester
Winter

Description
Chapter 24-Evolution through Natural Selection Pattern-how things are in nature/statement summarizing observations eg. For special creation: species created independently of one another, don’t change Process-produces that pattern/set of observations eg. For special creation: instantaneous and independent creation of orgs. by God 24.1 Typological thinking-species are unchanging, variations not important -Plato claimed organisms made perfect by God, unchanging -Aristotle ordered organisms into ladder of life/chain of being-more big & complex at top Population thinking-overturned typological thinking -Lamarck: species change, evolve from lower ladder species to higher “better” ones -Darwin & Wallace: variation among individuals very imp, not linear like ladder idea 24.2-Pattern of Evolution -Theory of evolution’s pattern claimed: 1) Species change thru time 2) related Species Change through Time Fossil-any trace of an organism that lived in the past (eg. bones, shells, tracks, dung) Extinction: Darwin said because array of species has changed through time Transitional Form-fossil species with traits intermediate btwn old & younger species -law of succession: extinct species succeeded by similar species (they’re related) eg. fossils show whales used to be land/H20 creatures w/ limbs, now H20 & no limbs Vestigial Trait-incompletely developed structure w/ no or little function -similar to functioning structures in closely related species -inconsistent with perfectness of special creation eg. whales & boas have tiny hip bones, ostrich has tiny wings (can’t fly), our tail Species are Related Geography: similar species in same area means share ancestor who lived in same region -Galapagos island mockingbirds have different beak size and shapes -Darwin said: similar b/c descended from same ancestor (same phylogenetic tree) -birds that went to different islands changed and formed new species thru time Homology-species have similarity b/c come from common ancestor eg. human hair & dog fur are homologous b/c common mammal ancestor w/ hair 3 levels of homology: a) Genetic-different species have similar DNA sequence b) Developmental-similar embryonic traits, homologies seen in morphologies/forms eg. human, chick, cat embryos similar (have gill pouches and tails) -gills vestigial (lost) in chicks, humans, cats; tails vestigial for humans -b/c pouch & tail existed in fishlike common ancestor of fish, birds, mammals c) Structural-dvlpmental homos due to homo genes, give rise to structural homology eg. common structure in limbs of vertebrates (turtle paddles, human hands, horse legs, bat wing all have same bones in relatively same positions) 24.3-Process of Evolution Darwin’s 4 steps of natural selection: 1. Individuals in population [must] have varying traits (eg
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