Chapter 2: evolution via natural selection Flashcards
What two processes produce genetic variation?
Mutation and sexual reproduction
What is the term for all alleles for all genes of all individuals in a population
Gene pool
Variation in genotype leads to variation in phenotype.
- but not all phenotypes are heritable, why is that?
What is genotype
What is phenotype
Some genotypes doesn’t appear in phenotype, what happens because of this
Genotype is the genetic makeup (What you carry in your genes)
Phenotype is the physical expression of the genotype (what you show)
- not all phenotypes are heritable because some of them are like physical fitness or if you gained a scar.
if genotypes don’t appear then it doesn’t affect the organism, but they will still carry said genotype thus can pass it down to their offsprings.
(a) Genetic Variation WITHIN a population has two levels, what are they?
- Gene variability
- Nucleotide variability
what is a level of genetic variation within population can be measured as Average heterozygosity
- which measures average percent of loci that are heterozygous in a population
(different alleles at a given locus)
- Genetic variability
A level of genetic variation within population that is measured by comparing DNA sequences of two individuals in a population then averaging the data from comparisons.
- Nucleotide Variability
genetic variations between populations exists due to geographic variations
ex: populations are isolate = can’t mate = evolving independently from each other
Genetic Variation BETWEEN populations
In variations between populations why can’t mutations be passed around from a population to another?
variations can’t be passed around because of geographic isolation
what are changes in sequence of DNA that results in new alleles in a population?
Mutations
Where should mutations be produced so they can be passed to an offspring?
Gametes (in gonads = testes/ovary)
Why are most mutations lost when an individual dies?
because most mutations occur in somatic cells so they can’t be passed on
Why are mutation rates in animals and plants low but higher in viruses and bacteria?
due to viruses and bacterias’ short generation time
2 types of Mutations
- Point Mutations
- Chromosomal Mutations
type of mutation where there is a change of one base gene.
Point Mutations
What are the 3 ways point mutations can affect an organism and how?
Neutral: eye color (doesn’t affect protein production bc of silent mutation so it’s neutral)
- silent mutation is when a letter in genetic code is changed but still makes the same intended protein
Harmful: gives diseases/disability (change in protein production)
Positive: lactose tolerance (can increase fit between organism and environment)
mutations that occur by altering gene number and sequence
> may lead to deletions, insertions, translocations, and duplications of Chromosomes (mostly harmful)
- Chromosomal Mutations
what shuffles existing alleles that happen during cross over that results in new combinations
> independent assortment and random fertilization
Sexual Reproduction
what are the three major factors that are responsible for genetic variation and altering it that makes evolution take place?
- Natural selection
- Genetic drift
- Gene flow
What is the major factor responsible for genetic variation where individuals with better adapted traits tend to produce more offspring than those who dont?
Natural selection
What is the major factor responsible for genetic variation where there is an sudden change in allele frequencies from one generation to the next?
this has 2 types
Genetic Drift
2 types: Founder effect and Bottleneck effect
Type of genetic drift when few individuals (with either reduced genetic variation or a non-random sample of genes) become isolated from original population
Founder effect
Type of genetic drift that is a sudden reduction in population size dues to change in environment (like climate change, natural disasters, etc.)
Bottleneck effect
What is the major factor responsible for genetic variation where there is a transfer of alleles among populations by movement of fertile individuals from one region to another.
- this tends to reduce differences between populations and is more likely to alter allele frequencies than mutation
- also depending on the genes involved can increase or decrease the fitness of a population
Gene flow
How does gene flow decrease fitness of a population
if the alleles being transferred between populations are unfavorable (not fit for environment or harmful to organisms)
How does gene flow increase the fitness of a population?
if alleles being transferred are alleles that give organisms better chance at survival
What Mechanism consistently causes adaptive evolution?
Natural selection because environments can change and adaptive evolution is a continuous process
What two mechanisms can lead to adaptive evolution but not consistenly?
genetic drift and gene flow
Natural selection uses 3 modes that acts on phenotypes of certain favored genotypes.
What are the three modes?
- Directional selection
- Disruptive selection
- Stabilizing selection
Natural selection mode that favors individuals a one end of phenotypic range
> White V.S. Black (white is favored)
Directional selection
Natural selection mode that favors individuals at both extremes of phenotypic range
> White AND Black (Both is favored)
Disruptive selection
Natural selection mode that favors intermediate variants
> Brown is favored (kind of middle of white and black)
Stabilizing selection
Form of natural selection where organisms with specific heritable characteristics more likely to obtain mates
- makes organisms go to extreme lengths for sex
has two types, what are they?
Sexual Selection
has two types: Intrasexual and Intersexual
Sexual selection where there is competition (mostly same sex) between organisms to prove worthy of mating with opposite sex
Intrasexual selection
Sexual selection called mate choice where individuals are really choosy when selecting mates for sex
Intersexual selection
sexual selection can lead to ______ _______ which is when females and males have different physical characteristics
Sexual dimorphism
How can sexual selection be harmful to individual’s survival?
- usually things like extravagant and colorful feather or fins attract the opposite sex more but they also leave the organisms vulnerable to predators
Why preserve Genetic Variation?
Natural selection wants to eliminate genetic variation by promoting “best fit” traits and lets the weaker ones die out
If natural selection succeeds in making the most fit organisms with no genetic variation, it can lead to extinction when environments change where said organism is not fit enough to survive.
Mechanisms that help preserve genetic variation in population
Diploid, Balancing selection, Neutral Variation
Mechanisms that help preserve genetic variation by preserving them in form of hidden recessive alleles.
Diploidy
Mechanisms that help preserve genetic variation that has two types
Balancing selection
two types:
Heterozygote advantage and frequency-dependent selection
Type of balancing selection where heterozygotes have higher fitness that do both homozygotes
Heterozygote advantage
type of balancing selection where it is hypothesized that a phenotype becomes more commons when it becomes more vulnerable to a predator
> thus natural selection will favor less common phenotype
Frequency-dependent selection
Mechanisms that help preserve genetic variation where some genetic variation does no benefit/ harm
- it only exists in noncoding regions of DNA so it remains only in Genotype
- if it exists as phenotype then it has no harm or benefit to organism (ex: eye color or fingerprints)
Neutral variation
