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Both artificial and natural selection lead to a shift in the genes that are most prevalent, however, artificial selection occurs when humans are the cause of the shift and natural selection occurs in wild population due to a factor other than direct human actions. D devoted much of On the Origins to examples to further explain his ideas and show specifically how evolution could have happened. GSD’s are the result of artificial selection as humans began breeding them for service work in 1899.
In discussions of the evolution of agricultural pests’ development of resistance to human-made pesticides on p 7, your authors bring up the concept of an (evolutionary) arms race between humans and these pests. Look up the definition of coevolution in the Glossary and then explain how such arms races are one form of coevolution. Be able to give an example of a coevolutionary arms race occurring in nature that doesn’t involve our species.
An arms race is an example of coevolution because two species are evolving to better survive from one another. An example is that of cheetahs and gazelles where they are both adapting to become faster with each generation. If a cheetah doesn’t catch a gazelle then it might die, and if a gazelle is caught by the cheetah it dies which leaves the fastest of the two species living to reproduce.
How does the goal of conservationists who want to preserve phylogenetic diversity differ from the goal of conservationists who want to preserve species diversity? In Fig 1.8, which type of conservationist would favor pouring resources into saving the species in blue? Why?
The people in blue would want to preserve phylogenetic diversity because it is looking at a phylogeny rather than just the extant species.
Fig 1.12 presents the results of an empirical study of the karyotypes of humans, chimpanzees, gorillas and orangutans. What do I mean by saying this is an empirical study? Based on this figure alone, we might hypothesize that humans are the most recently evolved of these four species. How so?
This is an empirical study because it is based on facts(genetics) rather than observations (phenotypes). We could hypothesize that humans are the most recently evolved because for chromosome 2 humans only have one while the other species have pairs. This suggests that the human chromosome two fused at some point.
On pp 18-19, we learn that the enormous phenotypic differences between humans and chimps may be more about differences in gene expression than differences in the DNA composition of their genes. Explain.
The differences in DNA in chimps and humans is very small, but only certain genes are expressed in each and while there are fewer differences the differences as well as what is expressed and what is not is very important phenotypically.
On the other hand, a comparison of gene expression in the brains of humans and chimps by Khairovich, et al. (2006), showed surprisingly few differences in gene expression. This seems curious since it’s obvious that human and chimp brains operate quite differently. What do your authors suggest as a possible solution to this initially unexpected finding?
They suggest that the small differences in gene expression have a large effect on both species and that they were made due to natural selection in humans.
On p 106, we read that “Both the process of reconstructing trees, and the process of mapping evolutionary events onto trees, generate hypotheses.” In what sense are these hypotheses?
The hypotheses are about evolutionary relationships and how evolutionary history has unfolded.
Both phylogenetic trees in Fig 4.5 indicate two examples of interior nodes. Exterior nodes (not defined in your text) would be either existing taxa or extinct taxa (if shown) at the ends of branches. What do the interior nodes represent?
The interior nodes represent the possibility of the two having a common ancestor.
With Fig 4.9.A and B, the authors are illustrating the concept of competing phylogenetic hypotheses. Fig A presents the currently most widely accepted phylogeny, but earlier in the last century, before the advent of DNA sequencing as a taxonomic tool, the phylogeny of Fig B also had its proponents. The polytomy in Fig C, however, is not a hypothetical phylogeny. What then does it represent?
Aristotle was the first to say that their beliefs and principles needed to be based on facts and logic rather than on supernatural reasoning. Scala naturae leaves out the ability to change and the ability to share a degree of complexity. This means that the entire evolutionary history would have to be linear which is not so.
Many of Darwin’s critics (to this day) have relied on William Paley’s “God as watchmaker” argument in his Natural Theology. Why was the argument so effective? Interestingly, Darwin admired much of Paley’s work, especially his emphasis on the adaptations of living organisms. Even more interesting, Darwin actually occupied the same dormitory room when he was a student at Christ’s College, Cambridge as Paley did a half-century before.
The argument was effective because it mixed theology with science which gave people a sense of peace. If God were not hand crafting everything to happen perfectly it would not happen and everything would fall apart. Darwin admired that Paley had noticed that the structure on organisms were functional means of survival (adaptations).
· Erasmus Darwin’s thoughts on the “struggle for existence” in his Zoonomia
· He proposed the idea of evolution, but was missing the connection between the struggle for existence and the changes he saw in the species around him. He also believed that the adaptations occurred throughout the life of the organism
· Jean-Baptiste Lamarck’s “transformationist hypothesis on the inheritance of acquired characteristics” in his Zoological Philosophy
· Lamarck thought that species adapted and passed those on through generations, but he thought that the adaptations occurred in the species lifetime
· Robert Chambers’ “principle of progressive development” and population thinking in his Vestiges
· He noted that species gradually changed over time however he looked at the evolution of individuals rather than the evolution of populations
· Patrick Matthews’ “circumstance-adaptive law” in his On Natural Timber and Arboriculture
· He proposed the same theory that Darwin did, but published it in an obscure place in a book that scientists were not likely to read so the idea did not catch on.
Your authors argue (p. 41) that you can boil D’s work down to two major themes: evolution by “natural selection” and the common ancestry of all living things (referred to elsewhere as “descent with modification” How do these two concepts differ? By the way, “descent with modification” was D’s phrase for “evolution,” a term that he carefully avoided using. Any ideas why? (This isn’t discussed in your text.)
Natural selection is that the fittest survive and those who are not fit enough die while descent with modification is that the adaptations are passed down through generations. Darwin avoided evolution because of the terminology. At that time evolution meant to unfold which would lead people to think of something else at that time.
Darwin understood that a major flaw in his hypothesis was that scientists had a very poor understanding of where variation among individuals within populations came from.
a. On p 49, D’s theory of evolutionary change is described as a “variational process” because
variation within a population is critical to the concept of natural selection. Why?
There have to be differences within the population for there to be anything to select from. Otherwise everyone is equal.
. Like most other scientists of the day, D thought information was passed from one generation to the next by a process known as “blending inheritance” (p 55). Why was that a problem for his concept of natural selection?
Gregor Mendel published his hypothesis on “particulate inheritance” (essentially inheritance by genes, although the word "gene" wasn’t coined until decades later) just a few years after D published On the Origin of Species. D, however, apparently never found out about Mendel’s work. If he had, how might this have helped with this problem?
He would have understood allele and genetics more which would have solved his problem of blending.
What happened during the evolutionary synthesis that brought the theory of natural selection back into prominence?
During the evolutionary synthesis genetics came about and showed that change could happen slowly
Consider the various color morphs of oldfield mice depicted in Fig 3.6. How did Hoekstra’s research strongly suggest that there is a genetic component to the observed variability in pelage color? On the other hand, why would it be wrong to conclude from her studies that pelage color in oldfield mice is “genetically determined?”
One of the most commonly heard criticisms of natural selection from many non-biologists is that they can’t believe that the world’s species “evolved just by chance.” But most evolutionists would argue that natural selection is essentially the opposite of chance—a non-random process. How is it non-random? Why, then, do so many non-biologists think natural selection is a random process?
It is a non-random process because the traits that are passed on are being selected for in terms of whether or not the person reproduces and has successful offspring. They believe it is a random process because of the link with mutation, but mutation is not essential for natural selection to occur.
What was the role of gene duplication in the eventual evolution of the aldosterone-M receptor pairing presented in Fig 3.33?
Gene duplication allowed for the diversity of the receptor so that one could mutate without being detrimental to the function of the organism
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