selection speciation taxa phylogenies evolution darwin
selection speciation taxa phylogenies evolution darwin
Why Study evolution? (5 points)
Diseases, agriculture and industry, species and divesity, conservation.
Darwin's 3 propositions for theory of evolution through natural selection
1. species change over time, 2. dif species may have common ancestor. 3. Species change because of natural selection.
3 things required for natural selection
a. population must have variation in a trait. b. said trait must be heritable. c. trait must impact individual's reproductive success.
T/F: evolution and natural selection are synonymous
FALSE FALSE FALSE!
blue brown is to ______ as eye color is to ______.
Fixed action pattern
an instinctive response triggered by simple stimuli.
4 OTHER points to dawins theory
1. without variation, natural selection can't occur.; 2. natural selection only acts on heritable traits. 3. heritable traits may be more or les beneficial depending on circumstances at hand (i.e. changes in environment) 4. only populations evolve. individuals do NOT .
5 assumptions of HW eq
1. no mutations. 2. no selection. 3. infinitely large population 4. no gene flow (migration) between the populations. 5. no random mating.
What did darwin note about individuals and their parents?
More individuals are born than can surivive to reproduce, & iindividuals resemble their parents but are not exactly the same.
If an average phenotype is most fit _______ will occur
if one extreme phenotype is most fit________ selection will ocur
If both extreme phenotypes are most fit, _________ selection will occur.
gene flow can _______ genetic variation but it CANNOT create it from scratch
This occurs when one allele is lost and the other becomes the only one present in the population
Refers to genetic additions to or substractions from a population resulting from the movement of fertile individuals or gametes
two factors that impact gene flow:
number of migrants
size of population
occurs when individuals are more likely to maet when they have traits in common
this type of mating causes heterozygous genotypes to decrease in f and homozygous to iincrease in frequency
this kind of mating is the basis for sexual selection
this type of selection involves the selection for advantageous traits that make individuals of one sex more atractive to that of the other
male competition between members of the same sex over acces to mates
types of adaptations that result from intrasexual selection
sneaker males and mate guarding.
Females tend to choose males based on 3 observable traits
1. direct benefits. 2. indicia of health or longevity aka 'good genes'. 3. arbitrary signs of male quality (penis preference)
a condition in which males and females have gametes of different sizes (e.g. egg and sperm)
this is a type of selection that occurs when a phenotype's fitness depends on how common it is in the population
two types of frequency dependent selection
positive and negative
this occurs when most common pheotype is favored in the population.
positive frequency dependent selection
this type of selection occurs when rare phenotypes are favored in the population
negative frequency dependent selection.
different kinds of mutations (2)
synonymous and nonsynonymous substitutions
when rate of NSS > rate of SS
positive selection and the resulting amino scid residue changes
when rate of NSS = ate of SS
neutral selection genetic drift is randomly changing
When NSS < SS
purifying selection. weeding out harmful alleles and resisting changes in corresponding amino acid residues.
disadvantages of sexual reproduction (3)
1. recombintion can separate adaptive gene combinations. 2. sex reproeduction reduces reproductive rates. 3. reduces rate of gene transfer between females and offspring
Some potential advantages that could have driven the evolution of sexual reproduction
-recombination could separate deleterious gene combinations and eventually make them disappear. - can repair damaged DNA - new combinations of alleles on which selection can act
A key disadvantage for asexual reproduction (muller's ratchet)
no way to elimiate deleterious mutations
in this type of gene transfer, bacteria pick up fragments of dna directly from the environment
in this type of gene transfer, DNA fragments are transferred from one bacterium to another by a virus.
In this type of gene transfer, DNA is passed from one bacterium to another via a physical connection, such as a sex pilu.
When is directional selection most likely
when a gene has duplicated. this way, the original gene is free to serve its original function. when the entire genome is duplicated, there are massive opportunities.
This is a group of homologous genes that have related functions
2 problems with morphological series concept
members of same species may not look alike, members of different sepecies may look alike
3 problems with biological sepcies concept
does not apply to asexual organisms, cannot be applied to extinct organisms, not clear what 'potentially interbreed' really means
According to this model, something happens to subdivide a population into two isolated groups that evolve independently
two major causes of sympatric selection
disruptive selection and polyploidy
This type of species refer to species that are in the process of diverging into seperate species but can currently interbreed
When this happens, populations may interbreed to a point that the formely separate sppecies become a single parent species again