Population Genetics & Patterns of Evolution. Are these organisms the same species?. Same column, same species! The same species can be born different colors, depending on the season they were born. Can we use appearances to determine whether organisms are the same species?.
Same column, same species! The same species can be born different colors, depending on the season they were born.
Can we use appearances to determine whether organisms are the same species?
A donkey & horse can produce offspring (a mule), but mules are NOT fertile! So, donkeys & horses are considered separate species!
Individuals do NOT evolve; a population evolves!
True or False – individuals within a population can evolve.
That’s Lamarck’s theory & it’s wrong!
We study evolution as genetic changein a population!
Individuals cannot change their genes & therefore cannot evolve!
With natural selection, only the giraffes that have the beneficial genes get to reproduce & pass on the good genes.
The giraffes with bad genes do not reproduce & the bad genes disappear over time.
That’s genetic change in a population over time!
In order for evolution to occur, there has to be some genetic variation within the population.
In this population of rabbits, there is a wide variety of fur color.
There are several different alleles for fur color in this population of rabbits!
We can figure out what the frequency of a particular allele is by calculating the number of times that the allele appears in a population compared to others in the entire gene pool.
Basically, we are trying to answer this question:
What percentage of the time does the brown allele occur in a population compared the black allele?
The gene pool here consists of 20 alleles!
13/20 (65%) carry the “A” allele.
7/20 (35%) carry the “a” allele.
This gene pool consists of 72 alleles. beneficial genes get to reproduce & pass on the good genes.
What is the frequency of A?
24/72 = .33 or 33%
What is the frequency of a?
48/72 = .67 or 67%
20 out of 50, or 40%
30 out of 50, or 60%
In this sample population, is the most common allele the dominant one?
The most common allele does NOT have to be the dominant allele!
What do you think would happen if polydactyly became an advantage?
In order for that genetic change to occur, there has to be some genetic variation within the population.
Blue eyes is caused by a mutation that originally occurred 6-10 thousand years ago!
There’s not a change of frequency when genes are shuffled, but that’s why there is so much variation.
Meiosis can produce egg/sperm that carry many different combinations of alleles!