Chapter 4: Flashcards
(28 cards)
What idea did Gould and Lewontin put forward?
Too often scientists assumed the EVERY trait must be an adaptation
What did Gould and Lewontin publish to explain their idea and what is their main argument?
-Series of “Just-so-stories” to explain how that trait evolved
-Adaptation exists, but not every trait comes from adaptation
What metaphor did Gould and Lewontin use to explain their idea and how?
The spandrels in the San Marco Basilica in Venice
How did Gould and Lewontin use the spandrels of San Marco as a metaphor of their idea?
-Asked the question “did they make spandrels because they wanted to make paintings” or “did they make arches and used the resulting spandrels for paintings”?
-Argued that spandrels are a consequence of the architecture (it’s what happens when you create an arch). Once the spandrels were there, they could be used for paintings.
What genera idea do Gould and Lewontin put to light?
Natural selection is not the only mechanism of evolution
What is the Hardy-Weinberg equilibrium?
It is an equation we can use to predict the frequency of genotypes from one generation to the next
What is it called when there is a pair of two different alleles?
heterozygous
What is it called when you have a pair of two of the same alleles?
homozygous
What do we predict genetics wise if there is no evolution ?
The genetics of the population will not change from one generation to the next.
This means the frequency of the alleles will be the same from generation to generation
What can the Hardy-Weinberg equilibrium predict?
The frequency of genotypes of a population in the next generation.
Under what assumption does the Hardy-Weinberg equilibrium predict the frequency of genotypes of a population for future generations?
-No mutation: genetic code doesn’t change
-No selection: No natural selection or adaptations.
-No genetic drift: infinitely large population
-No gene flow: no one with a new genotype immigrates
-Random mating of individuals: no sexual selection
Why would we calculate the Hardy-Weinberg equilibrium if we know that not all the assumptions can hold?
-Study evolution: compare the predicted frequency and the actual frequency to determine whether the population is evolving.
-Medicine: Can also use the equation to estimate the frequency of “carriers” (heterozygotes) of rare recessive diseases.
What are the two key points about genetic drift?
-Effects are random
-Effects of drift are stronger in small populations
What is the genetic bottleneck?
An extreme example of drift where an event results in a big decrease in population size and genetic diversity
What is the founder effect?
-Similar to a genetic bottleneck except event is that a few individuals “found” a new population somewhere new, like on an island.
-Like the genetic bottleneck it results in a decrease in population size, genetic diversity.
What do we know from Wallace and Darwin that serves for the Founder effect?
-Natural barriers can serve to separate species
-They prevent gene flow between populations
-Island provide a good example of this.
What happens after a few individuals move to a separate piece of land?
Natural and sexual selection occurs
What is speciation?
occurs when gene pools are separated, gene flow is restricted and populations diverge genetically over time
What is a species?
A population whose members can interbreed to produce offspring that are
-viable (they survive after birth)
-fertile (they can reproduce)
What are examples of animals tartare different species?
Donkey and horse
-offspring is mule
-viable but not fertile
What mechanism is needed to form a new species?
reproductive isolation:
-mechanisms that prevent gene flow between members of different species
-can be prezygotic or post-zygotic
what is a zygote?
-cell formed by joining of two gametes
-pre-zygotic, post-zygotic mechanismes (in reproductive isolation)
What does pre-zygotic mechanisms do?
-prevent formation of a zygote
-do so by preventing interactions, mating or the actual union of gametes
What are examples of pre-zygotic isolation?
-Habitat isolation: the species don’t live in the same environment
-Temporal isolation: the species don’t mate at the same time of the year
-Behavioral Isolation: the species aren’t attracted to each other because they don’t have the same attraction displays
-Mechanical Isolation: the species mechanisms of mating aren’t the same
-Gametic Isolation: gametes cannot unite
