Secret option
4 misconceptions of evolution
INDIVIDUALS EVOLVE
ORGANISMS ‘WANT’ OR ‘NEED’ TO EVOLVE
ORGANISMS ARE PERFECTLY ADAPTED
TO THEIR ENVIRONMENT
HUMANS ARE THE MOST EVOLVED SPECIES
Prebiotic soup model
Complex organic molecules
formed from inorganic gases in the atmosphere,
condensed with rain and then fell into oceans
What do neutralists and selectionists agree upon?
What are the three general modes of selection?
directional, stabilizing, disruptive
What is a species according to the biological species concept? What are some weaknesses of this concept?
GROUPS OF INDIVIDUALS THAT CAN INTERBREED AND PRODUCE VIABLE, FERTILE OFFSPRING
-weaknesses: Cannot accommodate asexual organisms, Cannot elucidate fossil species, Many “good” species hybridize
4 mechanisms of evolution
1. Mutation
2. Migration
3. Drift
4. Selection
RNA world hypothesis
Earliest living cells were liposomes containing RNA
Synonymous versus non-synonymous mutation
Non-synonymous (replacement) substitution: a nucleotide change in a coding region that produces an amino acid change
Synonymous (silent) substitution: a nucleotide change in a coding region that DOES NOT produce an amino acid change (often at 3rd position of a codon)
What trait values are favored in disruptive selection? Does the mean change? Does the variance change?
Extreme values favored, mean stays the same, variance increases
Describe allopatric speciation by dispersal
dispersal: geographic subdivision in which individuals move from original population and colonize a new habitat.
What do neutralists and selectionists agree on? (in terms of mutation)
Most mutations are deleterious. These do not comprise “observable” genetic variation because they are
removed from the population immediately, by
negative, or purifying, selection.
Are organisms PERFECTLY ADAPTED
TO THEIR ENVIRONMENT? Explain why or why not.
NO—SOME TRAITS ARE NEUTRAL, MALADAPTIVE, OR CONSTRAINED
-vestigial traits
-fitness trade offs
What are the three postulates of natural selection?
1. Individuals vary
2. This variation is heritable
3. Fitness correlates with heritable variation
There are two geographically isolated populations of lizards. On the east side, females prefer males with red coloration and most males are red. In the west population, females prefer orange males and most males are orange. What type of reproductive barrier is evolving?
behavioral isolation
Provide an example of hybrid inviability and hybrid sterility. Which of the three general types of reproductive barriers to gene flow do these barriers fall under?
darter example, certain hybrids between species don't live past certain stage in embryonic development
mules often sterile - hybrid sterility
these are post-zygotic barriers
What is a species according to the morphological species concept? What are some weaknesses of this concept?
A group of individuals that looks more like each other than like any other individuals
weaknesses: sexual dimorphism, cryptic species, features used to identify species can be arbitrary
What is the difference between natural selection in the broad vs narrow sense?
Natural selection (broad sense): change in allele frequency due to dis/advantage in relative fitness
Natural selection (narrow sense): change in allele frequency due to dis/advantage in competition for survival or fecundity
Define altruism
Would a ground squirrel be more likely to risk it's life to protect a cousin or a sibling? Explain.
BEHAVIOR THAT DECREASES THE FITNESS OF THE ACTOR AND INCREASES THE FITNESS OF THE RECIPIENT
A ground squirrel would be more likely to protect a sibling since a sibling carries more of it's own alleles compared to a cousin.
Explain the two postmating-prezygotic reproductive barriers to gene flow that were mentioned in lecture.
Gametic incompatibility: sperm (pollen) cannot fertilize the egg (ovule) of another species
Conspecific gamete preference: sperm (pollen) of conspecifics outcompetes sperm (pollen) of heterospecifics
What is a species according to the phylogenetic species concept?
A monophyletic group of individuals that share uniquely evolved (“derived”) trait(s)
Explain some asymmetries in the cost of reproduction. Do males or females benefit more from increased mating success? How does this lead to the evolution of sexually dimorphic traits?
Females tend to spend more time caring for progeny compared to men. Eggs require more energy input to be produced in comparison to sperm. Sperm are more plentiful.
Asymmetries in the cost of reproduction --> males benefit more from increased mating success --> greater intensity for selection in males for traits that increase mating success --> sexual dimorphism
In a mountain range, there is an interbreeding population of birds. These birds are flightless, but one day a storm blew a pregnant bird over the mountain range, and this bird laid her eggs on the opposite side of the range. This led to a distinct population forming with different allele frequencies than the original population. What type of geographic subdivision is this?
Dispersal