Lecture 2 Flashcards
Mutations can change allele frequencies. A typical gene mutates once every ____________ (number) cell divisions.
one hundred thousand
How are mutations and evolution related?
mutations are the genetic mechanism that allows evolution to occur.
What is the definition of gene flow?
the movements of alleles from one population to another
Why is gene flow important?
it allows diversity in populations
What is the definition of assortative mating?
type of non-random mating
What does assortative mating result in phenotypically?
Mating occurs between two very similar looking birds
What is the definition of disassortative mating?
choosing a random mating partner
What does disassortative mating result in phenotypically?
Will lead to an excess of heterozygotes
What is the definition of genetic drift
Pure chance, random, frequencies of a particular allele change drastically by chance alone
How can genetic drift change the genetic frequencies of a small or large population?
can change the allele frequencies
According to the video Genetic Drift, what is the difference between genetic drift and natural selection?
Genetic Drift is random
Organisms that have traits that result in high fitness are able to pass those alleles to their offspring
Which statement describes a bottleneck effect?
occurs because so few individuals form the next generation
How can a bottleneck effect change the alleles of a population?
it can completely change them and make some disappear
According to the video Speciation, how can natural selection bring about speciation
its a mechanism of evolution that changes over time and can lead to new species
According to the video Speciation, which statement accurately describes (a) allopatric speciation or (b) sympatric speciation?
(a) In allopatric speciation, there is a geographic barrier that separates the populations. So while natural selection is acting on these populations, there is also some big geographical barrier (like rivers, mountains, etc.) that keeps them from being able to interbreed and share the same gene pool. Eventually over a period of time, there can be change over time in the separated populations in their separated areas from mechanisms like natural selection or genetic drift. Over time, these populations can have significant genetic differences that may not allow them to interbreed even if they were brought together. Populations separated geographically can form different species
(b) You might think you would always need a geographic boundary to separate populations, but in sympatric speciation, the speciation happens in the same area. Yet, there’s something else isolating them. It can be a lot of things. Like prezygotic barriers– that means– barriers that occur before you can even make a zygote. A zygote is a fertilized egg so a prezygotic barrier is not even allowing fertilization to happen. So of these prezygotic barriers, the first one here is behavioral isolation. This is when species can have different behaviors, even very slight differences, that can isolate them (like birds having different songs– some only having very slight differences– can prevent males from attracting females of other populations and these birds can look very similar, appearances are deceiving)
