Understanding the Diversity of Life Part 2 EVOLUTION & SPECIATION 1 1

MODERN EVOLUTIONARY THEORY By combining the work of Charles Darwin with modern genetics, evolutionary biologists have a much better understanding of how evolution works 2

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 3

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 4

MODERN EVOLUTIONARY THEORY What are the 2 main sources of genetic variation 1.Mutations 2.Gene Shuffling 5

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 7

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 8

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 9

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 10

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 11

BEYOND MUTATIONS & GENE SHUFFLING 1963 – 417 mating pairs DDT Buildup 1890’s – 750 animals Overhunting 12

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/water 13

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SPECIATION 15

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 16

SPECIATION How does speciation happen? Organisms from a population must be reproductively isolated from each other 17

SPECIATION Geographic isolation leads to speciation because… Examples: It puts a physical barrier between members of a population Earthquakes Mountain ranges Human activity 18

SPECIATION Behavioral isolation leads to speciation because… Geographically isolated members of a population develop new mating behaviors 19

SPECIATION Temporal isolation leads to speciation because… Members of a population start to reproduce at different times 20

PATTERNS OF EVOLUTION 21

MACROEVOLUTION What is macroevolution? Large-scale history of life on earth 22

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 23

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 24

MACROEVOLUTION 3. Coevolution is… Examples: The evolution of 2 different species due to their interactions with each other Mutualism Predator-Prey Parasitism 25

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 26

MACROEVOLUTION Examples of convergent evolution in organisms: Birds Bats Bugs 27

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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MACROEVOLUTION 6. 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 30

MACROEVOLUTION Catastrophic Event Massive Mutation in Gene Pool 31

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