The Age Old Question of Race

"Because Europeans are so variable, and lighter-skinned, we might also ask whether this is due to selection for light skin or the relaxation of selection in melanin production...it is possible that lighter skin is an adaptation to lower levels of sunlight. No matter which is the case, the evolution of human skin color and the MC1R gene demonstrates that as humans spread out across the globe, the conditions of selection varied in different regions, the amount and quality of sunlight being just one obvious variable," (Carroll 173).

Human skin color has always been a battle of debate. As evolutionary theorists and biologists come to explain the idea of natural selection as the perceived driving force upon skin color, new findings are beginning to occur. How have mutations and natural selection acted upon the specific gene MC1R? Weigh and consider the benefits/costs to each race. Is the MC1R gene the only contributing factor to variation within skin color? What other conditions of selection affect the evolution of human skin color? Finally, what do you think is the cause of the evolution of skin color: Natural Selection, Relaxation of Natural Selection, or Both? Please delineate the reasons for your though process. Again, as always, I urge responders to connect to the various themes of Biology: Structure/Function, Heritable Information, Interaction with the Environment, and Evolution. Please discuss the relationship(s) with mutations and natural selection.

The Great Compromise

"'Bad' mutations such as the sickle cell and G6PD mutations and the irreversible fossilization of genes can be favored in meeting the imperatives imposed by conditions of selection. It is all a matter of the immediate benefits outweighing the immediate costs, if only by a slim margin," (Carroll 186).

Of the many examples Carroll provides, one which is most intriguing is that of the sickle-cell disease that can provide greater protection from malaria. Malaria has had a great effect as a driving force upon the genetics of human populations. Carroll cites the evolution of the sickle cell gene as "the classic textbook example of natural selection in humans," (176). Although the sickle-cell gene may provide an advantage in protection from malaria, it provides a disadvantage as to the amount of oxygen a red blood cell (RBC) can carry (on the hemoglobin molecule). With such a disease, humans who carry/suffer from the disease have chronic pain and fatigue*. With such inadvertent effects, are the benefits with the development of the disease worth the costs (protection from malaria)? Applying this ideology to other diseases that could possibly develop or changes in the genome, are the benefits greater, or are the costs greater? If natural selection favors humans who carry the sickle-cell gene, could natural selection at one point favor the return of normal hemoglobin and RBCs? Under what conditions would this occur? Relate all answers to mutations and themes of genetic disorders, evolution/natural selection, mutations, and inheritance.


*Please take time to review this website as to inform yourself of sickle-cell anemia: http://www.nhlbi.nih.gov/health/dci/Diseases/Sca/SCA_WhatIs.html

Fishing in Hot Springs

If you were to go "fishing" (see pg. 70) at Yellowstone National Park hot springs (assuming it was legal), what species might you find- list at least two species examples? What characteristics would those species have? What domain of species would you have found? What are the different types (those that live in hot water, in salt, etc.) and name a specific species of each type. Discuss the conditions of the Earth that would lead to these types of species and their characteristics. How have the conditions of the Earth changed so that other species are born and relate to the theme of evolution. Finally, how have these species helped us discover new information?

Immortal genes

What are 'immortal' genes? Why have these genes been able to stay the same through a large amount of time without being altered by mutations? Name two functions of immortal genes, and explain why the genes serving those functions have survived in many different species.

Mutations

Describe the difference between synonymous and nonsynonymous mutations. Mathematically, which type of mutation is more common? In nature, which type of mutation do we see more often, and why is this so?

Selective Pressures

For every organism in every ecosystem, there are selective pressures that influence what traits are passed on and what traits die out based on selective advantages/disadvantages. Sometimes this selective pressure is simply due to competition for resources; one trait gives an individual an advantage in collecting food or water, for example. More often, the selective pressure is applied by "agents of natural selection," organisms that act to literally determine which trait is the fittest for survival; these agents are usually predators that consume less well adapted prey.
Cite an instance of selective pressure; state the nature of the pressures; discuss the effects of this pressure in the context of the fifth theme of biology, interaction with the environment, or the sixth theme of biology, regulation.

Natural Selection based from Mutations

The pigeon example mentioned through pages 53-54 helps to show how a mutation can actually help the selection of a certain species over another. The example illustrated is that some pigeons have a white rump that helps in maneuvering so as to evade falcons. What are two other examples through the book where a mutation has actually helped an organism's chance at survival? Also, Sean Carroll states that natural selection picks out the winners and losers of mutated organisms, please add in your response how a mutation, or lack thereof, has determined the status, whether a winner or loser, of that organism.