Big Ideas 1 (the process of evolution drives the diversity and unity of life) and 3 (living systems store, retrieve, transmit, and respond to information essential to life processes). On pages 189-191, Sharon Moalem talks about the correlation between size and life expectancy. He states that “the bigger you are, the longer you live.” Explain what he means by that. What does bigger refer to (being fat or larger)? How may this help a species survive? Dr. Moalem says that repairing DNA is how species live longer. Describe how a cell replicates DNA and the enzymes it needs to complete the process. Explain the process of repairing DNA. How does the cell repair, damaged or mutated DNA?
What is planned obsolescence (pg. 190-191)? How does is affect species and thus populations? Provide two examples of planned obsolescence: one must be relating to a species, one that relates to the human lifestyle. The biogenic obsolescence is the biology version of planned obsolescence. How does the biogenic obsolescence drive evolution? Explain what Dr. Moalem means by “a species gets upgraded.” What variations lead to adaptations that over a long period of time cause evolution (hint: the natural selection flow chart)?
Sigal Sasson (ssasson3@students.d125.org)
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ReplyDeletePlanned obsolescence is "the often denied but never disproved notion that manufactures of everything from refrigerators to cars build a shelf life into their products, guaranteeing that they wear out after a limited number of years" (190). It affects species and populations because it creates room for change or evolution.
ReplyDeleteOne example with humans is with Apple products. Consumers accused apple of manufacturing ipods with batteries that only lasted about 18 months and could not be replaced. This would force consumers to buy a new ipod when the battery died. However, for a small fee, they would send you a new or refurbished equivalent.
One example relating with species is rodents developing a resistance to posions quickly. Rodents have a greater risk of being eaten and therefore evolve to live shorter lives. So because there's a shorter length of time between generations, it helps them deal with the many different environmental threats.
Biological obsolescence drives evolution through aging. Aging helps make way for new models, which creates room for change or evolution. Also aging can protect a group by ridding of the individuals with parasites and preventing them from infecting future generations.
Dr. Moalem is referring to selective advantage when he talks about "upgrading species". If there is a variation that is beneficial for the population, it will be selected by the environment. So variation in skin tone is an example. As early humans moved into hot, open environments in search of food and water, one big challenge was keeping cool. The adaptation that was favored involved an increase in the number of sweat glands on the skin while at the same time reducing the amount of body hair. With less hair, perspiration could evaporate more easily and cool the body more efficiently. But this less-hairy skin was a problem because it was exposed to a very strong sun. Since strong sun exposure damages the body, the solution was to evolve skin that was permanently dark so as to protect against the sun’s more damaging rays. Melanin, the skin's brown pigment, is a natural sunscreen that protects tropical peoples from the many harmful effects of ultraviolet (UV) rays.
Dr. Moalem describes biogenic obsolescence, or "programmed aging" (190), as when biological organisms have a section of code in their genome deliberately cause the eventual aging and death of the organism. Biogenic obsolescence aids in evolution by increasing the overall reproductive fitness of the population. The requirement for a population to survive is to survive and reproduce, but after reproducing, it may be more advantageous to the population for the organism to die to avoid competition for resources with younger members who are yet to reproduce. This is where biogenic obsolescence comes into play, clearing the way for future generations. Another way that it can be advantageous that Dr. Moalem mentioned is that "aging can protect the groups by eliminating individuals that have become laden with parasites, preventing them from infecting the next generation" (191).
ReplyDeleteOne example in animals is the planned obsolescence of sockeye salmon. Adult salmon make an annual migration up the streams they were born. Upon reaching the fresh water of the stream, they will stop feeding and their stomachs will start disintegrating. This may seem detrimental at first, but it allows for more room in the adult salmon for sperm and eggs, resulting in more fertility and offspring, which is advantageous for the population as a whole. After swimming upstream and spawning, sockeye salmon will grow weaker and weaker over a course of a few weeks until they eventually die. This kind of annual migratory behavior is programmed into the genetic code, which connects it with programmed obsolescence.
In humans, planned obsolescence manifests itself in the gradual aging of humans. One of the symptoms of this is the shortening of telomeres, which occurs during mitosis in body cells. Connecting back to the DNA unit, in copying DNA on the lagging strand, Okazaki fragments are created and RNA primers are added. These are eventually removed and replaced with DNA by RNA nuclease and DNA ligase. However, at the very ends of the DNA molecule on the lagging strand, the RNA primer is unable to be replaced. It is then degraded and the end result is that the telomere is shortened. Once the telomeres are shortened enough, which goes along with aging, signals will be sent that lead to apoptosis (cell death). Similar to sockeye salmon, this is advantageous to the population because after reproductive age planned obsolescence helps avoid overpopulation, which would threaten the survival of the younger population.
All this relates to Big Idea 1 (The process of evolution drives the diversity and unity of life). One way they drive the diversity of life is by "upgrading" species. The increased reproductive fitness leads to a higher rate of offspring production, which means that populations are more likely to acquire variations in alleles. If these variations are positive for a given environment, they will cause an allele shift in the population by being selected for by environmental factors, leading to the diversity of life. Planned obsolescence is a process that aids in all of this.
Sources:
http://www.marinebio.net/marinescience/05nekton/sarepro.htm
http://www.nmfs.noaa.gov/pr/species/fish/sockeyesalmon.htm
http://www.news-medical.net/health/Telomere-Shortening.aspx
Austin Hua (auhua4@students.d125.org)