Chapter 16
Population Genetics and Speciation
Section 1 Vocabulary Pretest
1. Population Genetics
2. Microevolution
3. Gene Pool
4. Allele Frequency
5. Phenotype Frequency
Population Genetics
 _________________________ is the study of evolution from a genetic point of view (it
is the study of microevolution)
 _______________________—a change in the collective genetic material of a population
 ___________________–members of the same species that can interbreed. It is
the smallest unit in which evolution occurs.
Variation
 Populations show ________________________________________.
 Many quantitative traits (height and weight etc.) follow a ______________
_________________________.
Causes of Variation
 ______________________________—amount of food, quality of food, etc.
 __________________________
 ______________________—random changes in genes
 ______________________—reshuffling of genes
 ______________________ of gametes
Gene Pool
 __________________ —total genetic information available in a population
Allele and Phenotypic Frequency
 ____________________________—expressed as a percent: it is determined by
________________________________________________
_____________________________________ of all types in the population
 _____________________________—expressed as a percent: it is the number of
individual with a particular _________________ divided by the total number of
individuals in the population.
Hardy-Weinberg Genetic Equilibrium
 Developed by ____________________German physician) and
________________________________(British mathematician)
 States that genetic frequencies in a population tend to ________________
____________________from generation to generation ________________
___________________________________________
 It is based on a “hypothetical population” that is ____________________.
Conditions of Hardy-Weinberg Equilibrium
 In Genetic Equilibrium:
 ____________________________ occur
 Population size remains __________________
 The population is _______________________
 Individuals ____________________________
 Selection _____________________________
 It is ______________________ that all five of the conditions in the Hardy-Weinberg
Model will happen in the real world.
 Therefore, Genetic Equilibrium is _________________________________.
 It is a theoretical state that allows us to consider what forces could disrupt such balance
(equilibrium).
Section 2 Vocabulary Pretest
1. Immigration
2. Emigration
3. Gene Flow
4. Genetic Drift
5.
6.
7.
8.
Sexual Selection
Stabilizing Selection
Disruptive Selection
Directional Selection
Disruption of Genetic Equilibrium
 Disruptions to the Hardy-Weinberg equilibrium can ___________________
_________________________.
 The five requirements for genetic equilibrium can be disrupted by the following outside
forces:
 __________________________
 __________________________
 __________________________
 __________________________
 __________________________
Requirement #1: No Net Mutations Occur
 Mutations _______________________ at very low rates under normal conditions.
 Exposure to __________________ (mutation-causing agents, i.e. radiation and
chemicals) can increase mutations rates.
 Mutations produce new alleles for a trait
 They can be __________________________________________
 Helpful mutations are a vital part of evolution.
Requirement #2: Population Size Remains Constant
 Individuals enter and leave populations constantly. Their “genes” move with them. This
is called __________________________.
 Factors influencing gene flow include:
 ___________________—movement of individuals into a population
 __________________—movement of individuals out of a population
 ____________________________________ can also influence the movement of
individuals into new populations
 ___________________________________ also remove or add genes from
individuals to a population.
Requirement #3 Population is Infinitely Large
 In nature, population sizes are restricted rather than infinitely large.
 _______________________ can occur in small populations of organisms
 ________________________—the random change in allele frequency in a
population
 Significant changes can happen in small populations if even a single organism
either fails to reproduce or reproduces too much.
 If the frequency of an ________________________ in a population, then
(assuming you started with two alleles), there is only one left.
 All individuals will be ______________________ for that trait---__________
_________________________________
 This __________________________
 Ex: Northern Elephant Seal
Bottleneck Effect
 Genetic Drift can lead to a _____________________________in which variations are
reduced overtime.
Requirement #4: Random Matings
 Organisms ____________________________________ in nature.
 Mate selection is influence by:
 _______________________________—choose mates nearby: can result in
kinship mating
 _______________________________—choose mates with similar traits: reduces
variation
 ______________________________—choose mates based on favorable traits
Requirement #5: Selection Does Not Occur
 ___________________________—organisms with favorable traits are more likely to
survive and reproduce, passing on their favorable genes to the next generation.
 It is an ongoing process in nature and an important disruption to equilibrium.
 _____________________ of Natural Selection:
 __________________________: individuals with the average form of a trait have
the highest fitness.
 Ex: Lizard body size
 __________________________: individuals with either extreme variation of a
trait have the highest fitness.
 Ex: Shell Color of Limpets
 _____________________________: individuals with one extreme of a trait have
the highest fitness
 Ex: Nose and tongue lengths of anteaters
Section 3 Vocabulary Pretest
1. Speciation
2. Geographic Isolation
3. Allopatric Speciation
4. Reproductive Isolation
5. Sympatric Speciation
6. Gradualism
7. Punctuated Equilibrium
Speciation
 ______________________—formation of a new species
 _______________: a single kind of organism whose members are
________________________________________ to produce fully fertile offspring.
 Two types of speciation: _____________________________________________
Allopatric Speciation
 ____________________________: species arise as a result of geographic isolation.
(Allopatric = different homelands)
 ___________________________—physical separation of members of a population
 Gene flow between the new subpopulations stops and the two begin to diverge
 Eventually, the become incompatible for mating, creating new species.
 Debate exists as to whether or not allopatric species are different enough to be
considered new species.
Sympatric Speciation
 _____________________________ —occurs when two subpopulations become
reproductively isolated within the same geographic area.
 ___________________________—the inability of members of the same species to mate
 Can be caused by disruptive selection
 Two types: ____________________________________________
 ___________________________: (different mating seasons, different mating calls, etc.)
 ______________________________: offspring do not fully develop, die, or are infertile.
Rates of Speciation
 Two Theories:
 __________________ —slow change over millions of years
 ____________________________—short bursts of rapid change
 Evidence exists that suggests that both have taken place over time.
The Hardy-Weinberg Equation
 Hardy and Weinberg went on to develop an equation that can be used to discover the
probable genotype frequencies in a population and to track their changes from one
generation to another.
 The equation is: ________________________________
p= frequency of the dominant allele
q = frequency of the recessive allele
Significance of the Hardy-Weinberg Equation
 ___________________________ allow geneticists to predict the probability of offspring
genotypes for particular traits based on the known genotypes of their two parents
 The Hardy-Weinberg equation essentially allowed geneticists to do the _____________
___________________________________.
 Before Hardy and Weinberg, it was thought that dominant alleles must, over time, wipe
out recessive alleles _________________________________
 According to this wrong idea, dominant alleles always increase in frequency from
generation to generation.
 Hardy and Weinberg demonstrated that _______________________________________
________________________________________________________________________