Posted by Kate on Monday, August 16, 2010 at 10:48pm.
I know my english is crap any corrections suggestions cirtisims etc. would greatly be apreciated... if you know any biology and find anything that is biologically wrong that would be great as well but don't worry if you don't THANK YOU!!!
im putting my initals just in case my teacher googles my response... it's happened before... no teacher that was me @_@... lol... D.H.
C. 1. A. Mutation can be a source of variation for a species gene pool by creating new alleles through a change in nucleotide sequence of an organism’s DNA. “Point mutations”, a change in one base in a gene, may have a very significant impact on the phenotype of the infected species, such as sickle-cell disease, or have very little to no effect at all on the infected species.
In meiosis, during the process of sexual reproduction, homologous chromosomes are inherited from each parent and both contribute alleles by crossing over and are distributed at random into gametes that ensure variation into the gene pool of the species. If a transposable element inserts itself into a regulatory sequence, increased or decreased production of one or more protein may occur, introducing variation into the species gene pool as a result, which may either be harmful or beneficial in the long run for the individual that may result in some sort of survival advantage.
C. 1. B. Natural selection has a huge ability to change the composition of a gene pool over long periods of time. For example, a population of a certain species must reproduce in order to maintain its population. Even though offspring look like their parents, the process of reproduction is not a perfect replication process. For example, individuals may have longer claws, a longer neck, or a better since of smell then their parents allowing for a greater variation within a population allowing evolution to occur within a large population with ease. These different phenotypes within a species may either be harmful or beneficial for the organism. A variation within a species that has a better phenotype may allow it to live longer than the individuals without it giving it a better chance to live long enough to reproduce and pass on its genes. With time this process may repeat itself and thereby allow for natural selection to set in, allowing the string of individuals within the population with the beneficial phenotype to become so drastically different from their original species that speciation may even eventually occur, as a result the individuals without the specific phenotype may die off eventually because of a lower reproductive success.
Genetic drift, events that happen by chance that can cause allele frequencies to change unpredictably from each generation to the next, has the ability to change the composition of a species gene pool, especially in cases of small populations. Individuals of a population may become separated into two separate populations, which would force the two separate populations to reproduce from two separate gene pools that will eventually become drastically different from each other because genes could no longer flow from all individuals within the population as a result of geographical isolation, such as a body of water, a canyon, or other barriers. This effect is called the founder effect and may be caused from a natural occurrence as a storm that may have blown a small group of individuals onto a separate island from the rest of the population or by other causes. The founder effect is often blamed for the occurrence of relatively high frequencies of inherited disorders among human population because of repetitive reproduction with a small gene pool to choose from if it’s infected with alleles that may cause the disorder even if it’s not physically present in the current population if an individual has the recessive allele for the disease.
C. 2. A. The theory of evolution, descent with modification, by natural selection, the process in which organisms with certain inherited phenotypes are more likely to survive and reproduce than organisms with less favorable characteristics, as presented by Charles Darwin stressed the idea that the process of evolution was one which took time, and several generations to occur and to observe. He was able to infer from his observations of nature that the unequal ability of individuals to survive and reproduce within their environment lead to the accumulation of a higher frequency of the more favorable traits within the population. Darwin reasoned that if artificial selection, modifying species over many generations by selection and breeding individuals that possessed desired traits, can bring about dramatic change in relatively short periods of time, then natural selection should be capable of substantial modification of species over hundreds of generations.
In order for a species to exist, for a substantial amount of time, it must be able to reproduce through the process of sexual reproduction, in which it’ll inherit traits from both the mother and the father. Sexual reproduction however is not a perfect replication process, despite individuals looking very similar to their parents. An individual may have sharper teeth than their parents; a thicker coat of fur, better eyesight, longer arms, etc., allowing for a large variety of phenotypes to occur within a population promoting evolution to occur. Individuals that inherit certain phenotypes over others may be able to have greater reproductive success. For example, a bird with a sharper longer beak than the rest of the individuals within its population might allow it to crack shells of certain nuts that other individuals within its population couldn’t consume. This may allow the bird with the phenotype of a longer and sharper beak to live longer and have a greater reproductive success than those without the phenotype, which may eventually die out, especially in the case over reproduction.
Darwin made the important connection between natural selection and the capacity of organism’s ability to “overreproduce” after reading work by Thomas Malthus, who connected over reproduction and suffering-famine and disease-was the consequence of the species ability to increase in population size faster than food supplies and other resources could keep up. For example say that our bird from earlier overpopulated a region, making their normal source of food a very limited resource, while the bird with the sharper and longer beak might have access to another type of food that’s in abundance in the region that other phenotypes wouldn’t have access to. This might allow the bird to live long enough to reproduce more than other individuals, giving it a higher reproductive success than other individuals.
C. 2. B. II. Through the process sexual reproduction offspring often look strikingly very similar to their parents because genes are inherited through this process from both parents. This replication process however is not perfect and many different phenotypes within a population allow for great variation within a species promoting evolution to take place. If one of these variations allows an insect to become resistant to the normally fatal effects of pesticide it will gain a larger reproductive success than those individuals without it because it’ll most likely live longer to reproduce more frequently and pass on their genes to offspring than others. Overtime natural selection will eventually set in and this beneficial trait will appear more frequently within the species population than it once did while the inheritable trait of not being resistant to pesticide will become less common.
C. 2. B. III. When a species is divided into two separate isolated populations and are not able to reproduce with each other, as a result of barriers like oceans or such, may become so drastically different from each other, through natural selection, that they become two completely separate species with time and are no longer able to reproduce with each other despite possibly looking striking similar to each other. Natural selection may modify the two isolated populations differently as a result of different environments that may favor different variations and with time become so drastically different can no longer reproduce with each other.
C. 2. B. V. Heterozygote advantage is exhibited when individuals who are heterozygous at a particular locus have greater fitness then do homozygotes. For example in the case of malaria natural selection favors the heterozygote individual over both the homozygotes because they are more resistant to malaria making it more likely for them to live long enough to produce fertile offspring over homozygotes who are less likely to create fertile offspring as a result of a more likely possible death as a result of catching the disease.
D. 1. Darwin’s evolutionary premise was that plants that used the strategy of self-fertization for the process of sexual reproduction was poor for its health and the population’s long-term survival.
D. 2. Darwin based this premise of off the idea that the offspring of plants that used self-fertilization would carry only the genes of their single parent making it nearly an exact replication, allowing for very little variation within the populations for evolutionary flexibility in the face of a changing environment.
D. 3. The panda’s “thumb” is an enlarged and elongated bone called the radial sesamoid that is normally a small component of the wrist. The radial sesamoid underlies a pad on the panda’s forepaw while the other fingers underlie another. The furrow between these two pads allow panda’s to use it as a channelway for bamboo stalks. Two short muscles run between the radial sesamoid and the pollex, the abductor of the radial sesamoid, pull the sesamoid towards the true digits.
D. 4. Davis argued that the musculature for operating the panda’s “thumb” required no intrinsic change from conditions already present in the panda’s closest relatives. He argued that the whole apparatus arose as a mechanical response to growth of the radial sesamoid itself that resulted in the muscles shifting as a result because the enlarged bone blocked them of their original locations. Davis claims that the increase size in the bones was a response to natural selection, reflecting some kind of genetic change or a single mutation affecting the timing and rate of growth of the bone itself.
D. 5. Gould’s theme within this piece of work is that evolution has created such a diverse collection of species, each created from very raw materials. Species function very well despite being made up of a collection of parts that would seem to be fashioned for other purposes and were jury-rigged together.
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