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Chapter 22 notes (has all information on 2011 exam)

7 Pages
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Department
Biological Sciences
Course Code
BIOA02H3
Professor
Kamini Persaud

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Chapter 22: Mechanisms of Evolution
22.1 What facts form the base of our understanding of evolution
Charles Darwin: father of evolution-population has exponential growth
Species are not immutable (they change over time) caused by natural selection
Natural selection: differential contribution of off spring to the next generation by
various genetic types belonging to the same population mechanisms by which
evolution occurs (individuals do not evolve, populations do)=variation in a population
Adaptation (allows organism to better able to survive/reproduce): an organism is
adapted to an environment when a slightly different organism survives and
reproduces less well in that environment or processes by which characteristics
appear to be more useful to their bearers evolve=phenotypic characteristic that has
helped an organism to adjust to conditions in its environment
Genotype: genetic makeup of an organism (coding)
Phenotype: physical expression of an organisms genes
Character: particular expression of an organisms genes, trait=specific form of a
character
Allele: different forms of genes, may exist at a particular locus-at any particular
locus, a single individual has only some of the alleles found in the population to
which it belongs
For a characteristic to evolve, the variation must be heritable (partly genetic
component)
Evolutionary changes based on two things: a) species change over time b) changes
produced by nature=must possess heritable genetic variation
Population: group of individuals of a single species that selectively live together and
interbreed in a particular geographic region at the same time
For a population to evolve it needs heritable genetic variation and different forms of
genes=alleles
Nearly all populations have genetic variation for many characters
www.notesolution.com
Genetic pool: sum of all the copies of all alleles at all loci found in a population :
contains the genetic variation that produces the phenotypic traits on which natural
selection acts
Heritable trait: a characteristic of an organism that is at least partly determined by
its genes i.e. genotype
Populations evolve when individuals with different genotypes survive or reproduce at
different rates
Population Genetics: explains the origin an maintenance of genetic variation,
explains patterns and organization of genetic variation, helps to understand the
mechanisms that cause changes in allele frequencies in populations
22.2 Mechanisms of Evolutionary Change
Evolutionary mechanisms are forces that change the genetic structure of a
population
1.Mutation: Origin of genetic variation (change in DNA), appears to be random with
respect to adaptive needs of organisms
Most are harmful or neutral, but if conditions change it can be advantageous
Can also restore to populations alleles that other evolutionary processes have
removed
Rates are low=1/million zygote results in only minor deviations from
equilibrium
Help maintain genetic variation within populations
2.Gene Flow: from migration of individuals and movements of gametes between
populations
New alleles can be added to the gene pool or allele frequencies change
If the arriving individuals or gametes survive and reproduce, they may add
new alleles to the gene pool of the population or they may change the
frequencies of alleles already present if they come from populations with
different allele frequencies
3.Gene Drift: From random changes in allele frequencies
www.notesolution.com

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Description
Chapter 22: Mechanisms of Evolution 22.1 What facts form the base of our understanding of evolution Charles Darwin: father of evolution-population has exponential growth Species are not immutable (they change over time) caused by natural selection Natural selection: differential contribution of off spring to the next generation by various genetic types belonging to the same population mechanisms by which evolution occurs (individuals do not evolve, populations do)=variation in a population Adaptation (allows organism to better able to survivereproduce): an organism is adapted to an environment when a slightly different organism survives and reproduces less well in that environment or processes by which characteristics appear to be more useful to their bearers evolve=phenotypic characteristic that has helped an organism to adjust to conditions in its environment Genotype: genetic makeup of an organism (coding) Phenotype: physical expression of an organisms genes Character: particular expression of an organisms genes, trait=specific form of a character Allele: different forms of genes, may exist at a particular locus-at any particular locus, a single individual has only some of the alleles found in the population to which it belongs For a characteristic to evolve, the variation must be heritable (partly genetic component) Evolutionary changes based on two things: a) species change over time b) changes produced by nature=must possess heritable genetic variation Population: group of individuals of a single species that selectively live together and interbreed in a particular geographic region at the same time For a population to evolve it needs heritable genetic variation and different forms of genes=alleles Nearly all populations have genetic variation for many characters www.notesolution.com
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