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11.5 and 11.6.notebook
February 20, 2014
BellWork: How does genetic drift affect populations of the same species that are isolated from one another?
Isolated populations can lead to speciation. Isolated populations begin to adapt to their environment and gene pools may change. Mutations and genetic drift will contribute to these changes.
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Reproductive Isolation
­occurs when different populations can no longer mate with one another and produce fertile offspring.
­final step in becoming separate species (speciation)
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11.5 and 11.6.notebook
speciation­ the rise of 2 or more species from one existing species
Three types of barriers that cause reproductive isolation
Temporal
Behavioral Geographic
chemical scents and courtship dances/songs are sexual signals used to attract mates. Different species use different signals.
physical barriers that divide a population into 2 or more groups.
barriers that involve timing. When organisms show signs of courtship at different times of the year.
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Example
there are over 2,000 species of fireflies! They produce light patterns in order to attract a mate...different species have different patterns February 20, 2014
Examples
Rivers, Mountains, dried lake beds etc. Example Flowers bloom at different times of the year, avoids competition and prevents species interaction 3
11.5 and 11.6.notebook
February 20, 2014
FREEZE: Apply the Concepts!
Directions: Use the pictures on pages 345 & 346 to answer the following questions.
Page 345
1. Why didn't the scientists bring together flies from the original locations?
2. What type of isolation produced populations of tropical and temperate flies?
3. Why type of isolation kept lab flies from mating?
Page 346
4. How did the formation of the isthmus affect marine species?
5. How did the formation of the isthmus affect the land species of North and South America?
6. What might it mean for marine species that there is now a canal connecting the Caribbean Sea and the Pacific Ocean?
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Page 345
1. Why didn't the scientists bring together flies from the original locations?
want to be sure that the flies would be able to mate
2. What type of isolation produced populations of tropical and temperate flies?
geographic
3. Why type of isolation kept lab flies from mating?
behavioral
Page 346
4. How did the formation of the isthmus affect marine species?
become geographically isolated
5. How did the formation of the isthmus affect the land species of North and South America?
populations were no longer geographically isolated and could interact and breed.
6. What might it mean for marine species that there is now a canal connecting the Caribbean Sea and the Pacific Ocean?
some species may be able to migrate
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Natural Selection is NOT random. Individuals with traits that are better suited to their environment have a better chance of surviving and reproducing.
We've learned about directional, stabilizing, and disruptive selection. In all of these the effects of natural selection add up over several generations. Natural selection is pushing a population in an advantageous direction.
REMEMBER: the environment controls the direction of natural selection.
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Patterns in Natural Selection
Convergent Evolution
­different species adapt to similar environments.
­different ancestors but evolved to have similar characteristics.
­Examples: Analogous structures of bird and insect wings & tail fins of fish and marine mammals.
Divergent Evolution
­closely related species evolve in different directions.
­Example: Red Fox and Kit
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Patterns in Natural Selection Continued
Coevolution
­process in which 2 or more species evolve in response to changes in each other from constantly interacting with one another in their environment
­Two types: cooperation and competitive relationships
­In a competitive relationship each species responds to the other through better adaptations.
­Examples: ant and acacia tree & crab vs. snail
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Just like birth and death are natural processes in life so is the rise and fall of species through evolution.
Extinction­ the elimination of a species from Earth
­usually due to the species being unable to adapt to a change in its environment. Two types:
Background extinction­ continuously happening at a random and slow rate.
Mass extinction­ a loss of many species very quickly, thought to be caused by catostrophic events, scientists think that we have seen 5 in the last 600 million years.
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Patterns in Speciation
Scientists have noticed a repeating pattern in the history of life.
Bursts of evolutionary activity followed by long periods of stability are called punctuated equilibrium.
­This was written as a revision to Darwin's idea that new species arise through gradual transformations of ancestral species.
Adaptive radiation­ the diversification of one ancestor species into many descendent species.
­Usually found in a wide range of environments.
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