1. What is the theory of endosymbiosis as it relates to the formation of the fir
ID: 50415 • Letter: 1
Question
1. What is the theory of endosymbiosis as it relates to the formation of the first eukaryotes ?
2. What is the physiological explanation for differences in skin color? What is the selective advantage of light skin in northern latitudes?
3. What is the genetic evidence that supports the idea that all human are descendants of a single woman in Africa?
4. What are the selective pressures that existed in the African Rift Valley that drove human evolution? Particularly focus on the traits examined in the “Becoming Human Series”: larger brain size, hairlessness, and bipedalism. What advantages did the development of these traits give the predecessors of humans?
5. What is the relationship between Neanderthals and Humans? What advantages did humans have over Neanderthals if any?
Explanation / Answer
1. The theory of endosymbiosis states the formation of eukaryotic cell from prokaryotic cell. The theory states that the organelles such as Chloroplast and mitochondria were all present in prokaryotes such as cyanobacteria, typhus. Chloroplast convert the light energy from the sun to form chemical energy by photosynthesis. Mitochondria produce energy by aerobic respiration. During evolution, the prokaryotic cell which required crucial nutrients has engulfed the above organism by endocytosis and transformed it as a new cell in which both met the requirements. Evidence for the above theory are a) size of chloroplast and mitochondria. same as that bacteria 1 to 10 microns b) DNA, RNA, Protein synthesis of mitochondria and chloroplast are similar to that of bacteria c) Mitochondria have double walled phospholipid bilayers may be formed during engulfing by vesicular growth which could be possible only by endocytosis etc.
2. The skin colour is mainly due to two types of pigments such as eumelanin and pheomelanin. The color difference is mainly for protecting the body from UV-radiation. In places with high UV radiation the skin will be darker whereas it will be opposite when it is low. UV radiation is the main reason for causing skin burns and skin cancer etc. The selective advantage of light skin is their body efficiently aborp UV radiation which will be helpful in production of vitamin D ultimately helps in stronger bone development.
3. Cells of human contains 46 chromosomes which has 23 chromosomes inherited from mother and 23 chromosome from father. However there are also other DNA in a cell which is not inherited from both of the parents. one such organelle containing DNA is mitochondria which has come from mother not from father. During fertilization the mitochondria of the sperm has not been used whereas the mother mitochondria has been used for the formation. So the mitochondria will be identical to that of mother. They only descendant from mother to daughter without any recombination, only with slight mutation. With this they can able to predict the lineage about 200,000 years before and able to tell all the humans are from a african mother called The Mitochondrial eve. However some paleoanthropologists did not accept the theory due to method (Restriction digestion analysis )they are used to predict the sequence, inferior method of phylogenetic construction, sampling from african americans not in native africans
5. Neanderthals are believed to a subspecies of homosapiens. There are many relationship between neanderthals and humans differing in body structure such as height and size. The brain size of neanderthals is large as that of humans. When compared to neanderthals humans have the advantage of longer life, better eye sight and sense of smell. The shortlife expectancy of neanderthals, has the disadvantage of not sharing the experiences gained during their lifetime to their people rather in case of humans share the life experieces with their children. Further there are also large DNA differences found among neanderthals and humans.
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