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Biology 112- Evolution by Natural Selection

by: Alexa Hanley

Biology 112- Evolution by Natural Selection Biology 1120

Marketplace > College of Charleston > Biological Sciences > Biology 1120 > Biology 112 Evolution by Natural Selection
Alexa Hanley
C of C
GPA 3.5

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Chapter 25 notes
General Biology
Kathleen E. Janech
Class Notes
Biology, evolution, natural selection
25 ?




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This 4 page Class Notes was uploaded by Alexa Hanley on Sunday January 17, 2016. The Class Notes belongs to Biology 1120 at College of Charleston taught by Kathleen E. Janech in Spring 2016. Since its upload, it has received 28 views. For similar materials see General Biology in Biological Sciences at College of Charleston.

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Date Created: 01/17/16
 The evolution of evolutionary thought (25.1)  Plato and typological thinking   Plato believed that every organism was an example of a perfect  essence created by God  Typological­the idea that species are unchanging types and that  variations within species are unimportant or even misleading   Aristotle and the great chain of being   Great Chain of Being   Aristotle’s linear scheme of organisms ordered by increased  size and complexity (humans are at the top)  His central claims  Species are fixed types   Some species are higher or more complex than others   Lamarck and the idea of evolution as change through time   Lamarck’s theory of evolution was that species ARE NOT static,  but that they change through time  They change through time because of the inheritance of  acquired characteristics   Darwin and Wallace and evolution by natural selection   Darwin claimed that instead of being unimportant or an illusion,  variation among individuals in a population was the key to  understanding the nature of species (population thinking)  This type of thinking changed many things   It overturned the idea that species are static and unchanging   It replaced typological thinking with population thinking  It was scientific   The pattern of evolution: have species changed, and are they related? (25.2)   Descent with modification­species that lived in the past are the  ancestors of the species existing today, and that species change  over time   Evidence for change through time   In order to find out more about evolution they looked at fossils   The vastness of geologic time   Based on layers of sedimentary rocks, scientists placed fossils in  order of age   Earth is about 4.6 billion years old and life is bout 3.4­3.8 billion  years old   Extinction changes the species present over time   Recent analyses of the fossil record show that over 99 percent of  all the species that have ever lived are now extinct   Transitional features link older and younger species   Law of succession­ extinct species were being succeeded in the  same region by similar species  Transitional feature­ a trait in a fossil species that is intermediate  between those of ancestral (older) and derived (younger) species  Vestigial traits are evidence of change through time   Vestigial trait­ a reduced or incompletely developed structure that  has no function, or reduced function, but is clearly similar to  functioning organs or structures in closely related species   Example: monkey tail and human coccyx (tailbone)   Current examples of change through time   Species are dynamic –not static, unchanging and fixed types   Similar species are found in the same geographic area   Darwin’s realization that mocking jays from various islands are  closely related  Similar species share homologies  Homology­ a similarity that exists in species because they  inherited the trait from a common ancestor   Example: human hair and dog fur—we are connected  somewhere  Homology can be recognized and studied at three levels   Genetic homology­ occurs in DNA nucleotide sequences, RNA nucleotide sequences, or amino acid sequences   Developmental homology­ is recognized in embryos   Gill pouches is an example of multiple species having them  in the embryos but eventually losing them   Structural homology­ is a similarity in adult morphology, or  form   Example­ we use our hands for grasping, moles use theirs  for digging, yet they are structure similarly   Evolution’s “internal consistency”—the importance of independent  date sets  Internal consistency­ the observation that data from independent  sources agree in supporting predictions made by a theory  The process of evolution: how does natural selection work?  (25.3)  Darwin’s Inspiration   Artificial selection­ choosing certain individuals with desirable  traits to reproduce, thus manipulating the composition of the  population  Darwin did this when cross breeding pigeons   Darwin’s idea of natural selection arose from his reading of  Malthus’ idea of “struggle for existence”  Darwin’s four postulates (of evolution by natural selection)  The individual organisms that make up a population vary in the  traits they possess   Some of the trait differences are heritable   In each generation, many more offspring are produced than can  possibly survive   Individuals with certain heritable traits are more likely to  survive and reproduce. Natural selection occurs when  individuals with certain characteristics produce more offspring  than individuals without those characteristics do  The outcome of evolution by natural selection is a change in allele  frequencies in a population over time  The biological definitions of fitness, adaptation, and selection  Darwin referred to individuals as “more fit” than others  Fitness is the ability of an individual to produce surviving,  fertile offspring relative to that ability in other individuals in the population  Adaptation is a heritable trait that increases the fitness of an  individual in a particular environment relative to individuals  lacking the trait  Common misconceptions about natural selection and  adaptation (25.5)  Selection acts on individuals, but evolutionary change occurs in  populations   Individuals do not change, only the population does  Natural selection is not “Lamarckian” inheritance   Lamarck thought that individuals are changed when they find a  desirable trait, however, Darwin found that those with “bad” traits  just produce less offspring and those with the desirable traits  produce more offspring  Acclimation is not adaption   Acclimation­ a change in an individual’s phenotype that occurs in  response to a change in natural environmental conditions   These traits are not passed on   Evolution is not goal directed   Evolution by natural selection is not goal directed  Mutations randomly occur and if they help a species to survive  better, they become more common  Evolution is not progressive   Evolution is not progressive, this means that organisms don’t  necessarily get bigger and better   There is no such thing as a higher or lower organism  Organisms do not act for the good of the species   Individuals with self sacrificing alleles die and do not produce  offspring, but individuals with selfish, cheater alleles survive and  produce offspring  Genetic constraints   Genetic correlations occur because of pleiotropy, in which a  single allele affects multiple traits


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