Transcript How can populations evolve to form new species or to

How can populations
evolve to form new
species or to eliminate a
species?
What causes a
population’s gene pool to
change?
Evolution
Karen A. Robinson
Evolution Topics Covered:
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Genes and evolution
Changes in a population’s gene pool
Formation of new species
Genes tell evolutionary history
What is evolution
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Evolution is defined as a change in the
frequency of alleles in a population over time.
I. Genes and Evolution
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Heredity is controlled by genes
Genes are carried on the chromosomes
Changes in genes or chromosomes create
variation
Genetic variation is the cause for evolution
Evidence shows how evolution occurs
Evidence shows why evolution occurs
II. Populations and Gene Pools
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Genetic variation and evolution studied
Population: a group of species that interbreed
Interbreeding produces a common gene pool
Genes can have different alleles or versions of that
gene
Dominant and recessive alleles
Allelic frequency is studied
Evolution and Allelic Frequency
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Evolution has occurred if change in allelic frequency
occurs.
Example- population contains:
48% heterozygous black mice Bb
36% homozygous brown mice bb
16% homozygous black mice BB
B is the dominant allele (black) and is shown more
frequently (36% + 16%= 52%)
If the B allele drops to 30%, the population is
evolving.
How can we predict evolution
will occur?
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Hardy-Weinberg Principle states:
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Allele frequencies in a population should remain
constant
Factors cause those frequencies to change
Makes predictions for populations
p squared + 2pq + q squared=1
Ex: p is dominant and q is recessive
www.pearsonsuccessnet.com will give more
information regarding the Hardy-Weinberg
Principle
III. Formation of a New Species
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Speciation: formation of a new species
Typically speciation is due to reproductive
isolation
Reproductive Isolation
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Population will evolve into two separate
species
Due to:
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Behavioral Isolation Ex: differences in mating
rituals
Geographic Isolation: two populations separated
by geographic barriers
Temporal Isolation: Two or more species
reproduce at different times
Evolution in a Nutshell
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Evolution is a continuous process
Evolutions is evident through fossil records
Evolution can be calculated using the HardyWeinberg Principle
Evolution is typically caused by environmental
factors
www.biologyjunction.com choose evolution
for information regarding evolution
Questions????