Types of Selection
Changes the average value of a trait. It favors one of the more extreme phenotypes.
Directional Selection
It increases fitness and increases frequency
Beneficial alleles
This type of selection violates the Hardy-Weinberg equilibrium with potential non-random mating
Sexual selection
Biological fitness is best defined as...
the ability of an individual to produce offspring that survive and reproduce, relative to other
individuals in the population
A sudden decrease in population size in large populations. Caused by a catastrophic effect
Bottleneck effect
Maintains trait variation. All phenotypes are favored
Balancing selection
Mutations do not create new combinations of alleles. Instead, they create what?
New alleles
Hardy-Weinberg
Over long periods of time, many cave-dwelling organisms have lost their eyes. Tapeworms
have lost their digestive systems. Whales have lost their hind limbs. How can natural selection
account for these losses?
Under particular circumstances that persisted for long periods, each of these structures
presented greater costs than benefits.
A barrier to gene flow. it isolates 2 populations within species
Genetic isolation
Disadvantageous. Causes alleles to decline in frequency
Purifying selection
A change in a single base pair
Point mutation
Who stated that some traits are heritable
Darwin
What must be TRUE of any organ described as vestigial?
It must be homologous to some feature in an ancestor.
Biological system of naming organisms
Binomial nomenclature
Prefers certain characteristics in a mate rather than in other potential mates
Sexual selection
Natural selection does what to alleles
It can favor beneficial alleles
Who crossbred pigeons to see how traits were passed down, demonstrating artificial selection
Darwin
When can genetic variation occur?
In a population before natural selection can occur on the population
Decrease in allele frequency when a small subset of a large population establishes a colony in a new location
Founder effect
Increases trait variation. Prefers both extremes over the intermediate phenotype
Disruptive selection
Down's syndrome, for example, is an example of this type of mutation
Chromosomal level mutations
The equation:
p2+2pq+q2=1 is derived from who's postulates/principles?
Hardy-Weinberg
The recessive allele that causes sickle cell anemia in humans is harmful to homozygous
individuals. What maintains the presence of this allele in a population's gene pool?
Heterozygous advantage
Individuals leave one population, join another, and breed
Gene flow