Unit 7: Evolution and Natural Selection Flashcards
Define
Evolution
A change to a population’s gene pool
Compare
Microevolution & Macroevolution
Microevolution: Small scale; on the level of populations
Macroevolution: Large scale; on the level of whole-species
Define
Genetic equilibrium
No changes to allele frequencies and/or distribution of a population’s phenotypes
Define
Gene pool
All versions of the genes from all members of a population that are capable of reproducing
Define
Allele Frequency
Prevalence of a certain allele within a gene pool
List
Five conditions for Hardy-Weinberg Equilibrium
Population is/has:
- infinitely large
- no mutations
- no migration
- random mating
- all alleles equally likely to be passed into subsequent generation
In terms of Hardy-Weinberg, what happens if:
population is small
Genetic drift may occur
In terms of Hardy-Weinberg, what happens if:
mutations occur
new alleles affect overall allele frequencies AND may increase chances of other conditions of H-W
In terms of Hardy-Weinberg, what happens if:
populations mix / migration occurs
New alleles may be introduced into population
In terms of Hardy-Weinberg, what happens if:
sexual selection occurs
individuals with preferred phenotypes are more likely to pass on their alleles
In terms of Hardy-Weinberg, what happens if:
natural selection occurs
favorable alleles/traits have increased allele frequencies
Define
Genetic drift
Random fluctuations in allele frequencies in a population
List two common types of
Genetic drift
Bottleneck Effect
and
Founder Effect
Describe
The Bottleneck Effect
Random decrease in population size, which changes allele frequencies purely due to chance
Describe
The Founder Effect
Migration of part of a population, whose allele frequencies do not reflect the population as a whole
Both the original population and new population have different allele frequencies from the original
In Hardy-Weinberg Equation:
What do the terms p and q refer to?
Allele frequencies of two alleles in a population
Reminder: All individuals carry two copies of all autosomal genes, therefore
(total # of alleles) = (population size) X 2
In Hardy-Weinberg Equation:
What does the term 2pq refer to?
The expected frequency of individuals in a population that are heterozygous
In Hardy-Weinberg Equation:
What does the term q2 refer to?
The expected frequency of individuals in a population that are homozygous for the recessive allele
In Hardy-Weinberg Equation:
What does the term p2 refer to?
The expected frequency of individuals in a population that are homozygous for the dominant allele
Define
Selection
Any phenomenon that preferentially leads to higher fitness in one allele over another
Define
Fitness
Reproductive success
List
Conditions necessary for natural selection
- The population must have heritable variations
- Some of those variations convey a selective advantage
- Competition or other factors limit population size
Define
Adaptation
A variant for a particular trait that allows individuals with that variant to survive and reproduce more than those without the variant
Define
Adapt
The process where a population / species becomes better-suited to survive and reproduce in their environment
List and define
The two types of characters
Discrete: Controlled by one or a few genes, producing a finite number of phenotypes
Quantitative: Controlled by many genes (polygenic) and influenced by environment, producing a range of phenotypes
How is evolution measured for each character?
Discrete: Change in allele frequencies
Quantitative: Changes in distribution of phenotypes
List
Three types of selection in quantitative characters
- Directional
- Stabilizing
- Disruptive
Define
Artificial selection
Humans are the selective pressure; desired or useful traits are selected for
AKA “Breeding”
List examples of
Artificial selection
Crops with highest sugar content, most starch, least chewy, and/or various pest or weather resistances are cultivated and become most common
Farm animals that produce the most milk, eggs, and/or meat are bred most
Dogs have been domesticated into separate breeds, each by artificial selection
What is the source of all genetic variation in a population?
Mutation
How does sexual reproduction affect genetic variability?
Increases it by mixing existing alleles (originally from mutations) during meiosis (crossing over, random assortment) and fertilization
