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Chapter 22

Chapter 22

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Department
Biological Sciences
Course Code
BIOA02H3
Professor
Kamini Persaud

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Chapter 22 Introduction To Evolution
Charles Darwin
-interested in science and became a companion of scientists, especially the botanist John Henslow, and went
on a voyage in 1831 in the H.M.S. Beagle
-explored the Galapagos Islands to study rocks and to observe and collect specimens of plants and animals
-Theory for Evolutionary Change
Species are not immutable; they change over time.
The process that produces these changes is NATURAL SELECTION.
-(1) asserted that evolution is a historical fact that can be demonstrated to have taken place; (2) natural selection is
the cause of evolution
-Alfred Russel Wallace was also studying the theory of natural selection; although both Darwin and Wallace
articulated the idea of natural selection, Darwin developed the idea first and concepts of natural selection are more
closely associated with Darwin (The Origin of Species)
-(3) recognized that populations of all species have the potential for rapid increases in numbers; (4) reasoned that
death rates in nature must also be high without high death rates, species would reach enormous population
sizes
-(5) observed that although offspring tend to resemble their parents, the offspring of most organisms are not
identical to one another or to their parents; (6) suggested that slight variations among individuals affect the
chance that a given individual will survive and reproduce (NATURAL SELECTION the differential contribution
of offspring to the next generation by various genetic types belonging to the same population)
-Darwin was a pigeon breeder and was familiar with ARTIFICIAL SELECTION the selection by plant and
animal breeders of individuals with certain desirable traits
-individuals do not evolve; populations do (a POPULATION is a group of individuals of a single species that live
and interbreed in a particular geographic area at the same time)
Adaptation
-in evolutionary biology, a particular structure, physiological process, or behaviour that makes an organism better
able to survive and reproduce; the evolutionary process that leads to the development or persistence of such a trait
ex: chemical defences of the newt
Genetics
-POPULATION GENETICS, the study of genetic variations and its causes within populations, has three main
goals:
To explain the origin and maintenance of genetic variation
To explain the patterns and organization of genetic variation
To understand the mechanisms that cause changes in allele frequencies in populations
-different forms of a gene, called ALLELES, are contained in a GENE POOL; it contains the genetic variation that
produces the phenotypic traits on which natural selection acts
-nearly all populations have genetic variation for many characters; however, the study of the genetic basis of
natural selection is difficult because genotypes alone do not uniquely determine all phenotypes (dominance and
recessive); similarly different phenotypes can be produced by a given genotype, depending on the environment
encountered during development
-MENDELIAN POPULATIONS a local population of individuals belonging to the same species and exchanging
genes with one another
-FREQUENCY means proportion, so the frequency of a given allele or genotype is simply the proportion of the
gene pool at that locus; the frequencies of different alleles at each locus and the frequencies of different genotypes
in a Mendelian population describe that populations GENETIC STRUCTURE
-HARDY-WEINBERG EQUILIBRIUM the allele frequency at a given locus in a sexually reproducing population
that is not being acted on by agents of evolution; the conditions that would result in no evolution in a population;
several conditions must be met for a population to be at H-W equilibrium:
Mating is random : individuals do not preferentially choose mates with certain genotypes
Population size is infinite : the larger a population, the smaller will be the effect of genetic drift
There is no gene flow : there is no migration either into or out of the population
There is no mutation : there is no change to alleles A and a, and no new alleles are added to change
the gene pool
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Description
Chapter 22 Introduction To Evolution Charles Darwin - interested in science and became a companion of scientists, especially the botanist John Henslow, and went on a voyage in 1831 in the H.M.S. Beagle - explored the Galapagos Islands to study rocks and to observe and collect specimens of plants and animals - Theory for Evolutionary Change Species are not immutable; they change over time. The process that produces these changes is NATURAL SELECTION. - (1) asserted that evolution is a historical fact that can be demonstrated to have taken place; (2) natural selection is the cause of evolution - Alfred Russel Wallace was also studying the theory of natural selection; although both Darwin and Wallace articulated the idea of natural selection, Darwin developed the idea first and concepts of natural selection are more closely associated with Darwin (The Origin of Species) - (3) recognized that populations of all species have the potential for rapid increases in numbers; (4) reasoned that death rates in nature must also be high without high death rates, species would reach enormous population sizes - (5) observed that although offspring tend to resemble their parents, the offspring of most organisms are not identical to one another or to their parents; (6) suggested that slight variations among individuals affect the chance that a given individual will survive and reproduce (NATURAL SELECTION the differential contribution of offspring to the next generation by various genetic types belonging to the same population) - Darwin was a pigeon breeder and was familiar with ARTIFICIAL SELECTION the selection by plant and animal breeders of individuals with certain desirable traits - individuals do not evolve; populations do (a POPULATION is a group of individuals of a single species that live and interbreed in a particular geographic area at the same time) Adaptation - in evolutionary biology, a particular structure, physiological process, or behaviour that makes an organism better able to survive and reproduce; the evolutionary process that leads to the development or persistence of such a trait e
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