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
 Evolution is defined as a change in the frequency of alleles in a population over time.

I.
Genes and Evolution
 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
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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?
 Hardy-Weinberg Principle states:
 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
 Speciation: formation of a new species
 Typically speciation is due to reproductive isolation

Reproductive Isolation
 Population will evolve into two separate species
 Due to:
 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
 Evolution is a continuous process
 Evolutions is evident through fossil records
 Evolution can be calculated using the Hardy-
Weinberg Principle
 Evolution is typically caused by environmental factors
 www.biologyjunction.com
choose evolution for information regarding evolution

Questions????