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 ____________ ______________________________________________________________________
[pic]
• In stabilizing selection, the bell-curve shape ______________________________
• In this case, selection _________________ ______________________________________________________________________
[pic]
• In disruptive selection, the bell-curve is ___________________________________
• In this case, selection acts to ____________ ___________________________________
[pic]
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: ____________ __________________________________________________________
[pic]
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 _____________________________
[pic]
• Divergent evolution
o Occurs when closely related species __________________________________________________________
o When this occurs, the similar species evolve _________________ _____________________________
o These traits are said to be _____________________________
[pic]
Circle the homologous structures
Coevolution
• The process by which two or more species ______________________________________________________________________
• Species that involve __________________ or ____________________ relationships often develop _______________________ ___________________________________
[pic]
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