Understanding the Diversity of LifePart 2

EVOLUTION & SPECIATION1

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MODERN EVOLUTIONARY THEORY

•By combining the work of Charles Darwin with modern genetics, evolutionary biologists have a much better understanding of how evolution works

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MODERN EVOLUTIONARY THEORY

•What is a population?

•What is a gene pool?

• Group of individuals of the same species that interbreed

• All of the genes that a population has in common

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MODERN EVOLUTIONARY THEORY

•What is relative frequency?

• In genetic terms, evolution is…

• How often an allele occurs in a gene pool

• any change in relative frequency of alleles in a population

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MODERN EVOLUTIONARY THEORY

• What are the 2 main sources of genetic variation

1. Mutations

2. Gene Shuffling

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MODERN EVOLUTIONARY THEORY

•What is a mutation ?•Why does a

mutation occur?

• Change in DNA sequence

•Mistakes in replication • Exposure to

radiation • Chemicals in the

environment 6

MODERN EVOLUTIONARY THEORY

•What is gene shuffling?

•What happens during gene shuffling?

• Distribution of different alleles during meiosis

• Each new gamete gets a different set of alleles

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BEYOND MUTATIONS & GENE SHUFFLING

• Non-random mating is…

• Examples:

• Results:

• Some members of the population have more opportunity to mate than others

• Fighting (lions & walrus)• Dances/songs (birds)

• Better fighters/dancers mate with more females

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BEYOND MUTATIONS & GENE SHUFFLING

• Gene flow is…

• Gene flow has…

• Why?

• Gain or loss of genes as organisms move in and out of populations

• Less effect on large populations

• Genes are diluted by large pool

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BEYOND MUTATIONS & GENE SHUFFLING

• Genetic Drift is…

• Occurs more often in…

•Why?

• Random change in allele frequency causes an allele to become more common

• Small populations

• Fewer alleles to counteract affects

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BEYOND MUTATIONS & GENE SHUFFLING• Types of genetic drift:1. Bottleneck effect –

happens due to…

Examples:

• Catastrophic events• Random survivors whose

genes do not reflect original population

• Bald Eagle• American Bison

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BEYOND MUTATIONS & GENE SHUFFLING

1963 – 417 mating pairsDDT Buildup

1890’s – 750 animalsOverhunting

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BEYOND MUTATIONS & GENE SHUFFLING

• Types of genetic drift:2. Founder effect -

happens when…

Examples:

• A few organisms from a larger population are transferred to another location

• Darwin’s Finches• Seeds carried by

wind/water13

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SPECIATION15

SPECIATION• What is a species?

• What is speciation?

• A group of organisms capable of interbreeding and producing fertile offspring

• A change in organisms that leads to new species

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SPECIATION• How does speciation

happen?• Organisms from a

population must be reproductively isolated from each other

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SPECIATION• Geographic isolation

leads to speciation because…

• Examples:

• It puts a physical barrier between members of a population

• Earthquakes• Mountain ranges• Human activity

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SPECIATION• Behavioral isolation

leads to speciation because…

• Geographically isolated members of a population develop new mating behaviors

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SPECIATION• Temporal isolation

leads to speciation because…

• Members of a population start to reproduce at different times

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PATTERNS OF EVOLUTION

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MACROEVOLUTION• What is

macroevolution?• Large-scale history of

life on earth

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MACROEVOLUTION

1. Extinction is…

• Extinction happens because…

• The complete loss of a species from Earth• Organisms are unable

to adapt to changes in the environment

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MACROEVOLUTION

2. Adaptive radiation is…• Adaptive radiation

happens when…• Example:

• Evolution of one species into several species• A species moves into a

new, unoccupied region• Darwin’s Finches

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MACROEVOLUTION

3. Coevolution is…

• Examples:

• The evolution of 2 different species due to their interactions with each other• Mutualism• Predator-Prey• Parasitism

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MACROEVOLUTION

4. Convergent evolution is…

• These structures are called…

• Convergent evolution happens because…

• The development of body structures with similar functions that are structurally different• Analogous structures

• Vastly different organisms face similar environmental demands

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MACROEVOLUTION• Examples of

convergent evolution in organisms:• Birds• Bats• Bugs

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MACROEVOLUTION

5. What are Hox genes?

• Where are Hox genes found?

• Why are Hox genes important?

• A specific sequence of nucleotides about 180 units long• In the DNA of most

animals• They are the master

genes that control embryological development of body plans 28

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MACROEVOLUTION6. Punctuated equilibrium is…

• Punctuated equilibrium occurs after…

• Example…

• Rapid period of speciation between long periods of stability

• A catastrophic event• Some sort of massive

mutation occurs in a gene pool• Cambrian Explosion

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MACROEVOLUTIONCatastrophic Event Massive Mutation in Gene Pool

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