Test 3, Deck 2 Flashcards
Can all causes of death be explained by natural selection? Justify your response.
No. Accidental deaths or diseases that take effect after production of offspring would not be acted upon by natural selection.
Each island in the Galapagos Archipelago has its own form of giant tortoise. They are very similar but not identical. Explain why. (why similar? why not identical?)
They are similar because all the tortoises probably evolved from same ancestral species.
They are different probably because each island is isolated and has a different environment and therefore different selection pressures, the ancestral tortoises diverged differently from the original progenitor.
Huntington’s Disease is a genetic disorder caused by a dominant allele and followed by death. However, the condition usually does not manifest until victims are in their 40’s or 50’s, and by then have already produced children, half of whom are likely to receive the allele for Huntington’s disease and be doomed to the same fate as their affected parent.
a. Can selection act against such a late-acting genetic trait? Explain.
No, Huntington’s disease has no effect on fitness because it has no effect on the ability to produce viable offspring.
Huntington’s Disease is a genetic disorder caused by a dominant allele and followed by death. However, the condition usually does not manifest until victims are in their 40’s or 50’s, and by then have already produced children, half of whom are likely to receive the allele for Huntington’s disease and be doomed to the same fate as their affected parent.
b. Suppose you discovered that individuals carrying the allele for Huntington’s disease leave, on average 22% more children than non-carriers. What effect does the allele for this disease appear to have on fitness now?
It appears that Huntington’s disease increases fitness
How do each of the following factors affect genetic variability and why? mutation polymorphism natural selection increase in population size
mutation: although new alleles are created, it is unlikely to observe a change in the population
polymorphism: maintains variation, if there is ni selection pressure to eliminate these variations, they will continue to accumulate.
natural selection: depends on the type of selection. stabilizing or directional will decrease variation
increase in pop. size: more combinations of alleles, more variations
How do each of the following factors affect genetic variability and why? sexual reproduction decrease in population size emigration immigration
Sexual reproduction: creates new combinations of alleles (increases)
decrease in pop. size: removes alleles, decreases variations
emigration: removes alleles (less variations)
immigration: adds alleles (more variations)
L. hoffmeisteri individuals from unpolluted environments are killed or severely stressed when placed in an environment with toxic cadmium levels. Only the worms from Foundry Cove show cadmium tolerance. In general, tolerance to toxic environments is a genetically complex mechanism.
a. Suppose the cadmium tolerance is heritable and you decide to relocate some worms from a non-polluted area to a cadmium-polluted area. You expected all of the worms to die but found that about 1% of them managed to just barely survive. How would you explain these results?
Because variation exists within the population of aquatic worms, it is conceivable that some worms had a phenotype that was capable of surviving toxic levels of cadmium.
L. hoffmeisteri individuals from unpolluted environments are killed or severely stressed when placed in an environment with toxic cadmium levels. Only the worms from Foundry Cove show cadmium tolerance. In general, tolerance to toxic environments is a genetically complex mechanism.
b. If the Foundry Cove worms were relocated to a non-polluted area where no other worms were living (and therefore, no competition) would cadmium tolerance remain in the population? Explain.
it depends
If maintaining the tolerance alleles makes the Foundry Cove worms less fit in the new environment, then the tolerance alleles are likely to decrease in frequency. This is often the case with resistance/tolerance because it usually requires the production of specific elements. This extra “work” usually makes resistant individuals less fit in an environment free of toxins, thus there would be a selection against tolerance.
However, if there is no selection pressure against tolerance, (i.e. it does not make the worms less fit) then the resistance alleles will remain in the population and their frequency would not change.
L. hoffmeisteri individuals from unpolluted environments are killed or severely stressed when placed in an environment with toxic cadmium levels. Only the worms from Foundry Cove show cadmium tolerance. In general, tolerance to toxic environments is a genetically complex mechanism.
c. Would your answer to (b) be different if the Foundry Cove worms were relocated to a non-polluted area that was already populated by non-cadmium tolerant worms with which they could freely interbreed?
In addition to the considerations mentioned in the response to part (b), we must now consider competition. If the non-tolerant worms can out-compete the tolerant variety, then the tolerance alleles will decrease in the population. If tolerance has no adverse effects on a worm’s ability to compete, then the allele frequency would only change for the original population (due to gene flow because new alleles were introduced into the population). In this case, the allele frequency is likely to remain constant for all future generations.
Why do male peacocks have large, brightly colored tail feathers if this feature makes them more vulnerable to predation?
The large tail increases the chances of mating, thus making a male peacock with large, elaborate tail feathers more fit than male peacocks with smaller, less colorful tails. Display of ornaments
Are humans in the future likely to have an appendix? Justify your response.
Currently, having an appendix has no effect on fitness, therefore it can not be eliminated by natural selection. The probability that a random mechanism would eliminate the human appendix is highly unlikely. The exception to this would be if a new selection pressure arose that favored smaller appendices.
In 1870, Thomas Henry Huxley proposed for the first time, that modern birds are closely related to the theropod group of dinosaurs. This idea however, was not widely accepted for over 100 years. Name three types of evidence of evolution that could be used today and explain how they could be used to support this theory.
comparative anatomy (compare anatomy of birds and theropod dinosaurs) (Same ancestors) comparative embryology (assuming a theropod dinosaur egg containing a fossilized embryo were available to compare with a modern bird embryo) other possibilities (though less likely) biochemistry/molecular biology (compare protein or DNA sequences of birds and dinosaurs, assuming dinosaur DNA and protein is available)
See Question Table in Question 8 Speciation problems:
a. What do you suppose is the disadvantage to a starling of laying a very small clutch of eggs?. Explain.
The probability of survival is lower than the number of hatchlings.
See Question Table in Question 8 Speciation problems:
b. What do you suppose is the disadvantage to a starling of laying a very large clutch of eggs?. Explain.
There are not enough resources to keep the hatchlings alive
See Question Table in Question 8 Speciation problems:
c. Which brood size seems to b the most advantageous? Does the most frequent brood size correspond to the most recoveries. What type of selection is it?
Brood sizes of 4 or 5 are most advantageous.
The most frequent brood size is 5
Broods of 4 are less common but just as advantageous as broods of
This is an example of stabilizing selection.
