Ch 23: Evolution of Populations Flashcards
What is microevolution?
changes in gene frequencies that occur over generations in a population of organisms (Evolution on the smallest scale)
What is a genetic mutation?
a random change in the nucleotide sequences of an organism’s DNA. Must occur in gametes (transcription and translation)
What are the two sources of genetic variation?
genetic mutation (translation and transcription) and sexual reproduction (meiosis)
What is the one thing that natural selection needs to occur?
natural selection can only act on variation with a genetic component
What is a mutation?
a random change in nucleotide sequence of DNA
What is a point mutation?
change in one base in a gene
What factors can influence mutation rate?
generation time, which is how long it takes for animals to produce offsprig and how long it takes for them to produce offspring
Generation time example for plants and animals:
plants and animals have a relatively long generation time so they have a low mutation rate
Generation time example for micro organisms:
micro organisms have short generation time so they have a very high mutation rate
What is a population?
a group of individuals of the same species that occur in a defined area that reproduce with eachother and reproduce fertile offspring
What is a gene pool?
all alleles of all genes that occur in a population
What is allele frequency?
how common an allele is in a population
What is the Hardy-Weinberg equation?
p^2+2pq+q^2=1
(p+q)^2=1
What are the five Hardy-Weinberg assumptions?
- Infinite population size
- No migration (ex. gene flow)
- No mutations
- Random mating
- No natural selection
What are the five causes of microevolution?
genetic drift, mutation, gene flow, non-random mating, and natural selection
What is genetic drift?
random changes that occur in the gene pool of a generation to generation
When is genetic drift strongest?
in smaller populations and it will eventually reduce the genetic variability of the population
What is the “bottleneck” effect?
a phenomenon in which a population is reduced in size due to natural disasters, habitat loss, or overhunting. A consequence of the bottleneck effect is the loss of variation in a population caused by the reduction of allele frequencies
What is the founder effect?
genetic drift that occurs when a new habitat is colonized by a single or a few individuals
What is gene flow?
gene flow consists of the movement of alleles among populations
What is directional selection?
a mode of negative natural selection in which an extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype
What is disruptive selection?
occurs when both extreme traits are favored in an environment. Disruptive selection increases genetic and phenotypic diversity in a population, since more than one phenotype, or physical trait, is favored
What is stabilizing selection?
a form of natural selection wherein individuals with moderate or average phenotypes are more fit (more likely to survive and reproduce)
What is sexual dimorphism?
marked differences between the sexes in secondary sexual characteristics
What are the two subcategories of sexual selection?
intrasexual selection and intersexual selection
What is intrasexual selection?
competition among individuals of one sex (often males) for mates of the opposite sex
What is intersexual selection?
often called mate choice, occurs when individuals of one sex (usually females) are choosy in selectinf their mates
What is the good gene hypothesis?
if a trait is related to male genetic quality or health, both the male trait and female preference for that trait should increase in frequency
What is diploidy?
maintains genetic variation in the form of hidden recessive alleles (Rr)
What is balancing selection?
natural selection maintains stable frequencies of two or more phenotypic forms in a population
What is heterozygous advantage?
occurs when heterozygous have a higher fitness than do both homozygotes (ex sickle cell anemia)
What is frequency-dependent selection?
the fitness of a phenotype declines if it becomes too common in the population
