BSC2010 Unit 3 - Lecture 2

What is the origin of genetic variation?

Mutation

What is natural selection?

A non-random process of evolution that favors individuals that survive and reproduce

What is fitness?

Relative contribution of an individual to the gene pool of the next generation

What is fitness measure?

Relative reproductive success; relative number of offspring that survive and reproduce (always measured relative to other individuals in same population)

How can we measure evolutionary change?

Calculating and following the frequencies of phenotypes, genotypes, and alleles across generations

What is adaptation?

A favored trait that evolves through natural selection; individuals with beneficial mutations that were adaptive were more likely to survive, reproduce, and pass their alleles on to the next generation

What does it mean to be heritable?

Imagine a population of plants that exhibit discrete variation in floral color due to different genotypes at one locus. All of the floral color variation in this population is due to differences among individuals in their genotype.

What is the difference between qualitative traits and quantitative traits?

Qualitative traits may be influenced by alleles at one locus and have discrete phenotypic characters (ABO blood groups, eye color), while quantitative traits are usually influenced by a larger group of genes that show continuous variation

What is the equation for total phenotypic variance?

V_P=V_G+V_E

What is h²?

Heritability

What is heritability?

The proportion of total phenotypic variance that is due to measurable genetic factors

What is the equation for heritability?

h²=V_G/V_P

What does it mean for a trait to have a genetic basis?

Heritability is high; however all traits have a genetic bias, including phenotypic plasticity in response to environment

What does it mean when h² is close to 1?

Most phenotypic variance is due to genetics; trait will not change much within the lifetime of individual

What does it mean if h² is near 0?

Most phenotypic variation is due to plasticity, so a trait may change within lifetime of individual

What is the slope of a parent-offspring regression?

The measure of heritability

What event in the Galapagos caused selection to occur?

A severe drought caused the supply of small, soft seeds to decrease. There was a shift to harder, larger seeds. As a result, 80% of medium ground finches died.

What is the difference between evolution and natural selection?

Natural selection is one mechanism by which evolution can occur

What are the 5 evolutionary processes?

Mutation, selection, gene flow, genetic drift, and nonrandom mating

What is gene flow?

The migration of individuals or movement of gametes (ex: pollen) between populations, changing allele frequencies; increases genetic diversity and tends to equalize allele frequencies between populations

What is genetic drift?

An effect of random variation in which alleles are passed to offspring, tends to eliminate genetic variation

What is the effect of genetic drift?

Unless counteracted, it will result in fixation of a single allele

What is fixation?

Occurs when there is only one allele present and its frequency is 1.0

What counteracts drift?

Migration, mutation, and, in large populations, natural selection (slightly beneficial alleles can increase rapidly in frequency)

How does genetic drift affect small populations?

Can quickly change allele frequencies and overcome natural selection. Harmful alleles may increase in frequency or rare advantageous alleles may be lost

What is population bottleneck?

An environmental event resulting in the survival of only a few individuals. Causes loss of genetic diversity and intensifies genetic drift

What is founder effect?

When a few individuals from a population colonize a new area and become isolated, genetic drift changes allele frequencies

What does the founder effect have the same effect as?

Bottleneck

What are the three important mathematical truths about genetic drift?

An allele’s probability of fixation due to drift is equal to its frequency; the larger the population, the more generations it takes for a given allele to either drift to fixation or be lost, and in a finite population, drift will remove all but one allele eventually. Diversity comes from selection, mutation, or migration.

How do the various forces of evolution act on a population all at once?

Mutation is the ultimate source of variation, drift acts mostly on neutral variation, and selection acts on beneficial and deleterious variation