Guided Notes: Origins of Life - Weebly



Name: _____________________________________________________ Date: _____________ Period: ____

Guided Notes: Population Genetics and Speciation

Misconception Alert!

• ___________________________________

• Individuals _________________________ ______________________________________________________________________

• _____________________ are acted upon by ________________________________, where _____________________________ are less likely to pass on their ___________

• This causes a ________________________ ______________________________________________________________________

Genetic Variation within Populations

• A healthy population is one with ________ _________________________________________________________________________________________________________

• A wide range of genetic diversity causes there to be __________________________ ___________________________________

• The greater the variation in phenotypes, _________________________________________________________________________________________________________

• Genetic variation is stored in a population’s ________________ - _________________ ______________________________________________________________________

• An allele frequency is a measure of ______ ______________________________________________________________________

Gene Change within Populations

• Genetic change can occur ______________ ___________________________________

• Genetic change causes a shift in the ______ ___________________________________

• Genetic change within populations over time can occur in several ways…

Mechanisms of Genetic Change Over Time (Evolution)

1. Natural selection

o Occurs when __________________ _____________________________

2. Gene Flow

o When genes are ________________ _____________________________

o Caused by ____________________ _____________________________

3. Genetic Drift

o _________________________________________________________________________________________________________________________________________________

o Can be caused by ______________ ______________ such as ________ _____________________________

o Why?

4. Non-Random Mating

o The cost of reproduction between males and females ______________

o Males produce many sperm __________________, while females are born with ___________ _____________________________

o This allows females to be more __________________________________________________________

o Non-random mating occurs because certain traits in males ___________ _____________________________

5. Mutations

o A ________________________ can add a new allele to a population

Patterns of Natural Selection

• When natural selection is NOT occurring, most populations have a _______________ distribution

• When natural selection DOES occur, populations can respond in three major ways…

• In directional selection, _______________ ______________________________________________________________________

• In this case, selection acts to ____________ ______________________________________________________________________

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• In stabilizing selection, the bell-curve shape ______________________________

• In this case, selection _________________ ______________________________________________________________________

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• In disruptive selection, the bell-curve is ___________________________________

• In this case, selection acts to ____________ ___________________________________

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Speciation through Isolation

• A species is defined as ________________ ______________________________________________________________________

• It is important to remember that species are NOT ______________________________

• If gene flow between two populations stops for some reason, _____________________ ___________________________________

• As these populations adapt to their environments, _______________________ ___________________________________

• All of these changes __________________ ___________________________________

• With time, the isolated populations become more and more ______________________ from each other and may no longer ______ ___________________________________ (they become _______________________)

• Reproductive isolation between populations is the ______________________________ ___________________________________

• The rise of two or more species from one existing species is called _______________

• There are three ways in which a population may become isolated…

1. Behavioral isolation: __________ __________________________________________________________

2. Geographic isolation: __________ _______________________________________________________________________________________

3. Temporal isolation: ____________ __________________________________________________________

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Which isolation is this?

Convergent vs. Divergent Evolution

• Convergent evolution

o Occurs when __________________ __________________________________________________________

o When this occurs, the different species often evolve ____________ _____________________________

o These traits are said to be _____________________________

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• Divergent evolution

o Occurs when closely related species __________________________________________________________

o When this occurs, the similar species evolve _________________ _____________________________

o These traits are said to be _____________________________

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Circle the homologous structures

Coevolution

• The process by which two or more species ______________________________________________________________________

• Species that involve __________________ or ____________________ relationships often develop _______________________ ___________________________________

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