Module 1: lecture 4, selection and evolution Flashcards
True or False. Selection is the only driver of evolution.
False. Selection is actually not the only driver of evolution.
Is every trait an adaptation? What example is used to explain this.
NO, Not every trait is an adaptation, to explain this use the metaphor of the spandrel in the San Marco Basilica in Venice.
Explain the example of the sprandel in the San Marco Basilica in Venice
Baisilica has lots and lots of arches + domes, A spandrel is the extra space that is made when you create an arch in a rectangular space, Many of these, and all of these all have paintings on them, well which one came first?
Gould and Lewontin argue that spandrels= consequence of architecture ( what happens when you create arch) so once spandrels there, you can use them for paintings.
Short arms on Tyrannosaurus Rex is the phenomenon of what?
natural selection not the only mechanism of evolution. Selection acting directly on the arms, perhaps making them important for hunting or etc but point is that natural selection is not the only mechanism of evolution.
What does the Genetic drift and the Hardy-Weinberg Equilibrium show?
A way that we can actually show that evolution is happening
What is the Hardy-Weinberg Equilibrium ?
Equation that we can use to predict the frequency of genotypes from one generation to the next. ( don’t need to calculate)
Which is the right order? 1.Allele→Genotype→Phenotype
2.Allele→Phenotype→Genotype
3.Phenotype→Genotype→Allele
The right answer is 1.
Homozygous?
Two of the same allele
Example of Homozygous
gg or GG
Heterozygous?
Two different alleles
Example of heterozygous
Gg
No evolution = no_______?
Change; If there is no evolution, we predict that the genetics of the population will not change from one generation to the next.
Using the Hardy-Weinberg Equilibrium equation what assumptions do we make?
- General nature of it assumes that no change is going to happen so no mutation, so the genetic code will not change, no natural selection, adaptatic, no genetic drift, no sexual selection.
- So no gene flow, no individuals who will arrive from somewhere else with a new genotype to introduce ; population stays contained
- There is only random mating of individuals
If many of the assumptions we make based of the Hardy-Weinberg Equilibrium equation are unlikely to all be true, so why do we use it to calculate stuff then??
- Compare the predicted frequency and the actual frequency to determine wether the population is evolving.
– A way to study evolution - Great in medicine to study diseases : To calculate the frequency of “carrier” ( heterozygotes) of rare diseases, like how many ppl potentially have the disease gene…
What can the Hardy-Equilibrium equation tell us about our population over time;
Sometimes just by chance or by being unlucky some phenotypes get wiped out ( principle behind genetic drift)
What is genetic drift
There is no selection or particular phenotypes leading to surviving longer, there are just some individuals lucky and unlucky.
Effects are random
Genetic drift- evolution by_______
Chance
On what kind of populations does genetic drift work best? Which one sees greater effects quicker
Small populations see result quicker, larger population takes a bit more time…
Two ways that genetic drift results in big changes:
1.Genetic Bottleneck
2.Founder Effect
What is an extreme example of genetic drift?
Where an event results in a big decrease : ( Ex flood or earthquake or fire, etc)
What happens in genetic drift?
Population size (reduced) + Genetic diversity (reduced) = New population takes from the surviving population which is not necessarily representative of the original population.
