CHAPTER 12
what are the requirements for natural selection to happen?
1. members of a population have inheritable variations 2. populations have the capability of producing more offspring than the environment can support 3. only certain members of a population can survive and reproduce
how long has life on earth been around?
3.5-3.8 billion years
earth is approximately how old?
4.6 billion years old
what is an example of genetic drift?
A man steps on a group of beetles, randomly killing most of the green ones but leaving most of the brown ones alive, resulting in fewer green beetles being produced in the population
what is an example of the bottleneck effect?
An example of the founder effect comes from the Afrikaner population of Dutch settlers in South Africa. This population has an abnormally high count of Huntington's Disease (nerve cells in brain degenerate) because the original Dutch settlers carried the gene with a higher frequency that the rest of the Dutch population.
Describe what is meant by "survival of the fittest."
Fitness: organism's genetic contribution to the next generation. Survival is NOT enough: must have the ability to survive UNTIL the reproduction has taken place. Fitness also takes into consideration how many of the OFFSPRING make it to the reproductive age.
what is an example of directional selection?
Giraffes having long necks
what was the name of the ship that Darwin travelled on?
HMS Beagle
what is an example of stabilizing selection?
In humans, birth weight is an example of stabilizing selection. Babies that are born too small can lose heat too easily and may die, whereas babies being born too large can lead to complications during childbirth and the death of the mother or the baby
what is an example of sexual selection?
Many plants have flowers that are pretty and brightly colored. This is because the brightest colors attract bees, butterflies, and other pollinators, which enable the plant to reproduce. If a flower is dully colored, it does not reproduce, and the dull color genes disappear from the population, whereas the plants with brightly colored flowers reproduce, so they gradually make up more and more of the population.
what is an example of the founder effect?
Northern elephant seals have reduced genetic variation most likely due to being hunted. Hunting reduced their population size to as few as 20 individuals at the end of the 19th century. Since then their population has rebounded to over 30,000 but the genes still carry the marks of their bottleneck. They have much less variation than a population of Southern Elephant seals that have not been hunted.
what was the name of Darwin's publication?
On the Origin of Species
what is an example of disruptive selection?
One of the most studied examples of disruptive selection is the case of London's peppered moths. In rural areas, the peppered moths were almost all a very light color. However, these same moths were very dark in color in industrial areas. Very few medium colored moths were seen in either location. It seems that the darker colored moths survived predators in the industrial areas by blending in with the polluted surroundings. The lighter moths were seen easily by predators in industrial areas and were eaten.
Founder Effect
Small group leaves home population and establishes a new, isolated settlement; new group of alleles does NOT represent the frequency in the original population
Sexual Selection
a differential change in the relative frequencies of genes due to differences between individuals in their ability to mate
Bottleneck Effect
a sudden reduction in a population's genetic diversity due to a sudden decrease in a population
what is an example of non-random mating?
all mating on this planet is non random mating. We don't just go up to someone and say "let's have a baby."
Genetic Drift
allele frequencies in a population change as a random result of random events or chance
Gene flow
alleles move between populations
Sexual dimorphism
any difference between the sexes of a species
Mutation
are the raw material for evolution. Genes contribute to phenotypes. Natural selection acts on phenotypes
Microevolution
change in gene frequencies
what is evolution?
changes in a population over time due to accumulation of inherited differences "descent with modification"
pq= ___?
frequency of heterozygous
p^2 =___?
frequency of homo. Dominant
q^2=___?
frequency of homo. Recessive
what are the requirements for Hardy-Weinberg equilibrium?
gene frequencies will remain unchanged under the following conditions: -no mutation -no natural selection -no migration -large population size -random mating.
what is an example of sexual dimorphism?
in some species, including many mammals, the male is larger than the female. In others, such as some spiders, the female is larger than the male.
what is an example of gene flow?
migration
Macroevolution
much larger scale; appearance of a new species
Does Hardy-Weinberg equilibrium typically occur in most natural populations?
no
Non-random Mating
occurs when the probability that two individuals in a population will mate is not the same for all possible pairs of individuals
B=____?
p
what is the Hardy-Weinberg equilibrium equation?
p^2 + 2pq + q^2 = 1
Natural Selection
process of organisms with variations are better able to survive in their environment longer, compete better, and reproduce (Random)
b=____?
q
Stabilizing Selection
selection against extreme phenotypes
Disruptive Selection
selection against intermediate phenotypes
Artificial Selection
the breeding of plants and animals by humans to produce desirable traits
Directional Selection
trait is moving in one direction
