Drift and Selection Flashcards
(26 cards)
What is evolution?
Evolution is the change over time in the proportion of individuals in a population differing in
one or more inherited traits
During evolution, how does changes in allele frequency occur?
It occurs through the non-random processes of
natural selection and sexual selection, and the random process of genetic drift
Natural selection acts on…
…genetic variation in a population
Populations produce more offspring than…
…the environment can support
Individuals with variations that are better suited to their environment tend to survive longer and…
…produce more offspring, breeding to pass on those alleles that conferred an advantage
to the next generation
What is sexual selection?
Sexual selection is the non-random process involving the selection of alleles that increase
the individual’s chances of mating and producing offspring
What may sexual selection lead to?
Sexual dimorphism
What can sexual selection be due to?
Male-male rivalry and female choice
When does genetic drift occur?
Genetic drift occurs when chance events cause unpredictable fluctuations in allele
frequencies from one generation to the next
Why is genetic drift more important in small populations?
As alleles are more likely to be lost
from the gene pool
The Hardy-Weinberg (HW) principle states that…
…in the absence of evolutionary influences,
allele and genotype frequencies in a population will remain constant over the generations
Where selection pressures are strong…
…the rate of evolution can be rapid
What can the HW principle be used to determine?
The HW principle can be used to determine whether a change in allele frequency is
occurring in a population over time
Changes suggest…
…evolution is occurning.
Variation in traits arises as a result of…
…mutation
Mutation is the original source of…
…new sequences of DNA (These new
sequences can be novel alleles)
Most mutations are…
…harmful or neutral, but in rare cases they may be beneficial to the fitness of an individual
What does selection result in?
Selection results in the non-random increase in the frequency of advantageous alleles and the non-random decrease in the frequency of deleterious alleles
What is male-male rivalry?
Male-male rivalry: large size or weaponry
increases access to females through conflict
Female choice involves…
…females assessing
the fitness of males
When do population bottlenecks occur?
Population bottlenecks occur when a
population size is reduced for at least one
generation
When do founder effects occur?
Founder effects occur through the isolation of a few members of a population from a larger population. The gene pool of the new population is not representative of that in the original gene pool.
What are selection pressures?
Selection pressures are the environmental
factors that influence which individuals in a
population pass on their alleles
What are some biotic selection pressures?
Competition, predation, disease, parasitism
