Evolution - Ch 23 - Evolutionary Processes Flashcards
How do we know whether evolution or biased mating is occurring?
Hardy-Weinberg Principle
What are the 4 modes of natural selection?
directional selection, balancing selection, stabilizing selection, disruptive selection
Which sex is more affected by sexual selection, and why?
sexual selection acts more strongly on males than females since any allele that increases a male’s attractiveness or success in intrasexual competition should quickly pop up in a population
What is the Hardy-Weinberg equilibrium equation (for two traits, p and q)
p^2 + 2pq + q^2 = 1
[p + q = 1]
What is purifying selection, and what mode of selection does it fall under?
disadvantageous alleles tend to decrease in frequency, and fall to 0 frequency (while favoured alleles become fixed)
What is a gene pool?
all the alleles of all the genes of a certain population
What is genetic variation?
the number and relative frequency of alleles present in a population
What does stabilizing selection do? How does it affect genetic variation?
selects against both extremes
-decrease in genetic variation
What does disruptive selection do? How does it affect genetic variation?
What can it lead to?
(opposite of stabilizing) the middle is selected against
- increases genetic diversity
- can lead to speciation
What does balancing selection do? How does it affect genetic variation?
no alleles have a distinguishable advantage, at all times
-genetic variation stays the same
What can cause balancing selection?
- heterozygote advantage
- frequency-dependent selection
What is frequency-dependent selection?
when specific alleles are favoured when rare, but disadvantageous when common
What is genetic drift? What populations are most affected by it?
the change in allele frequency in a population, by chance
-is significant in smaller populations
What is genetic drift? What populations are most affected by it?
the change in allele frequency in a population, by chance
-is more significant in smaller populations
What is genetic drift? What populations are most affected by it?
the change in allele frequency in a population, by chance
-is more significant in smaller populations
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What is genetic drift? What populations are most affected by it?
the change in allele frequency in a population, by chance
-is more significant in smaller populations (more prone to fixation/loss of alleles)
How is the genetic variation of a population affected by natural selection, genetic drift, genetic flow, and mutations?
- natural selection: depends on mode
- genetic drift: neutral
- genetic flow: increase or decrease
- mutations: increase
How is the genetic variation of a population affected by natural selection, genetic drift, genetic flow, and mutations?
- natural selection: depends on mode
- genetic drift: neutral
- genetic flow: increase or decrease
- mutations: increase
What is a founder event, and what is the founder effect?
- founder event: when a group of individuals immigrate to a new geographical area to start a new population
- founder effect: when a founder event occurs that causes a change in allele frequencies (compared to the original population) due to sampling error of small population
What is a population bottleneck, and what is a genetic bottleneck?
- population bottleneck: when a large population suddenly loses a high number of individuals
- genetic bottleneck: when a great amount of alleles decrease in number, which by chance likely changes the allele frequency of the population and decreases genetic variation
What is gene flow?
the movement of alleles between populations when an individual migrates between them
What is the ultimate source of genetic variation?
mutations
What is a chromosome-level mutation?
the change in number of composition of chromosomes, which can duplicate genes, leading to loss of function or new alleles
What is a lateral gene transfer?
the movement of genes from one species to another
