Anthropology

Human origin is one of the most debated topics in anthropology. Currently there are two major propositions for the origin of anatomically modern Humans: the multiregional hypothesis and the “out of Africa”/ replacement hypothesis. Yet, these theories fail to explain the variations in skin color among human populations. What is the explanation Sean Carroll provides in chapter 7?  Does Dr. Carroll’s theory on skin color weakens or strenghtens both hypotheses’ claim that our hominid ancestors originated from a small population in Africa? How So? Do you think that skin color simply reflects relatedness among humans or that people of different origins can develop the same skin tone once they migrate to a certain area due to selection pressure?

Pax-6 and Eye Structure

Different eyes have developed in different species. The Pax-6 gene plays a role in the eye development of many organisms such as the mouse, human, squid, and ribbon worm. What is Pax-6 and what is its function? What would occur if there was a disruption in the Pax-6 gene of a human? Why would a mouse Pax-6 gene be able to also "induce fly eye tissue" (196)?

The structure of the eye differs in complexity even if we just examine the phylum of mollusks. What factors would induce such a difference? One could address the information we learned about mollusks in the invertebrate unit. 

Yeast and Pathogens

M. leprae is a microbe that is responsible for the disease leprosy. The microbe is "closely related to M. tuberculosis, the species responsible for pulmonary tuberculosis" (131). M. leprae contains a vast number of fossil genes: almost 1100 fossil genes out of 1600 functional genes. However, M. tuberculosis only has 4000 intact genes and only 6 fossil genes. Why is there such a difference in fossil genes between the two closely related species?

Compare and contrast M. leprae with S. kudriavzevii, the only yeast that cannot utilize glucose. What does the pattern of the genes of the S. kudriavzevii reveal about natural selection? One could relate their response to fermentation. How would fermentation (if fermentation changes) differ in the S. kudriavzevii when compared to other yeasts that can utilize galactose? (What would happen if the glucose supply ran out?)

What do the accumulation of fossil genes in both of the organisms reveal about the environment of the organisms? One should remember to address the themes of biology: for example, heritable information and evolution. 

LINES and SINES and other fun things

Explain what LINES and SINES are. Why do LINES and SINES survive from generation to generation? How can we use LINES and SINES to determine ancestral relationships between species, and why does a similarity in LINES and SINES indicate a relationship between species? Use an example of a relationship between a human and another species found using LINES and SINES. Have a nice last day of Spring Break!

Natural Selection: Change Is Not Necessarily Progess

"Natural selection cannot preserve what is not being used, and it cannot plan for the future." -Carroll pg. 136. Both in "Making of the Fittest" and in AP Biology class, it is always reinforced that evolution doesn't think ahead, or really think at all; natural selection only acts to select what is best for whatever the present situation of a species may be. Using a specific species example, show an instance in shich natural selection has caused a species to move in a direction that could be considered "unprogressive."

Technology's effect Nature

Today's technology allows for scientists to sequence a child's DNA before he/she is even born. This knowledge allows the scientists to find any mutations that exist in the unborn child’s DNA. The existence of these mutations can give parents a look into how “normal” their child will be. However, scientists are unaware of how all these mutations will effect the child since the outcome of all the different mutations are unknown. This information can cause the termination of a pregnancy. How does this process affect nature and what are the positive and negative effects of it? In your explanation use Carroll’s ideas about natural selection and immortal genes.

Sexual Selection and Ultraviolet Light

In many cases, the forces of evolution have been shaped by sexual selection. In the book, Carroll mentions that "many birds have tuned an opsin to detect ultraviolet light" (110). What mutation(s) occur in birds for the birds to see in the ultraviolet range? How does this ability to detect ultraviolet light connect to how the females select mates? How would the different characteristics (relating to ultraviolet light) of the male be a measure of his fitness? One could relate this phenomenon to the courtship behavior we have learned about in the ecology unit (Campbell 1141). Please examine how sexual selection pertains to the themes of evolution or heritable information. 

Fossil Genes

On page 118, Carroll starts talking about a unique fish, Latimeria chalumnae, that was found many years ago but was preserved for the years to come. This fish has been labeled as a "living fossil" because the chances of finding and studying another one like it is very slim. Carroll compares this "living fossil" to the idea of "fossil genes". Why are fossil genes so important and how can they help us understand the behaviors and lifestyles of the species that are present in our world today?

Genealogic Trees

Explain the various genealogic trees that have been made, focusing on the more recent trees that have been approved by the scientific community. In doing so, explain the major differences between the trees and note the scientific reasoning behind the changes. Is there one tree that is more accurate than another? Why or why not? Why bother spending times on creating genealogic trees, especially when it will most likely be made obsolete in a few years? And of course, as this is AP Bio, use scientific terms and reasoning in your responses.

Cancer and Cancer Treatment

Cancer is a leading cause of death worldwide, predicted to become the number one cause of death in the year 2010. Certain types of cancers are always associated with specific gene mutations, such as the chronic myelogenous leukemia (CML). According to Carroll, CML is caused by the fusion of genes that "[disrupt] the normal control of a potent regulatory protein called the ABL kinase" (183). The ABL kinase signals the induction of apoptosis. How would the disruption of the ABL kinase promote cancer? How does the disruption relate to the cellular checkpoints that regulate the cell cycle? Please relate your response to the theme of regulation. 

The drug Gleevec targets the ABL kinase in the CML tumors. How do the CML cells become resistant to Gleevec? Also, how does the change in the ABL protein relate to the concept of the substrate-enzyme model? Please relate the response to the theme of structure vs. function. What methods should be pursued to avoid and/or treat resistant CML cells?

On the subject of ABL kinase, this online journal suggests that the kinase induces apoptosis: 

http://www.pnas.org/content/94/4/1437.full

Junk DNA

In chapter three, Sean Carroll discusses the structure and layout of DNA, noting the sequences known as introns, or non-coding segments. He refers to these sequences as "junk" DNA, saying that this DNA is merely an accumulation of informationless sequences; as such, he chooses mostly to ignore introns. However, many would protest such an abjection. Having thouroughly studied the mechanisms of DNA in Campbell chapter 17, do you agree with Carroll's assertation? Or, as some scientists now feel, do you believe there is a purpose to these seemingly useless sequences? Explain your opinion.

Archaea vs. Bacteria

Tom Brock found what he thought to be another kind of bacteria living in the hot springs of Yellowstone National Park. However, further analysis revealed that these oragnisms were actually as different from bacteria as eukaryotes. We now call these organisms Archaea. Using your understanding of the diversity of life, compare and contrast the two traits of bacteria and archaea (preferably one compare, one contrast), how these are selective advantages, and how these difference might have arisen.

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