Monday, April 13, 2009
Unmaking the fittest
On page 252 Carroll reminds us that "the 'fittest' is a conditional, if not precarious status," and that over time the ideal 'fit' changes as the climate does. He uses fossil remains of ancient palm trees in Wyoming as an example of this. What changes exactly happened in Wyoming that sparked their "unmaking?" (252) How is this mode of species decline compare to the "unnatural mode of human selection," and how has our role as the "managing director of the biggest business of all" (254) affected the shape of evolution and direction of the fittest today? (What happened with those cod fish?) Also, find another species (extinct or existing) who's evolutionary course has been changed by human intervening. Is all unnatural selection harmful in the end, or can some intervening have a positive effect?
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The changes that occurred in Wyoming had to do with climate changes. The temperatures increased and less rainfall occurred. This caused the rainforests to dry out. Along with the rainforests many species disappeared. When the rainforests turned into deserts, many animals like “crocodiles, turtles, birds, bats, and horses” (252) disappeared from Wyoming. In Wyoming it said that the species had an “unmaking”, which means the decline of species.
ReplyDeleteEven though the environment has a huge impact on the extinction of species, humans may have an even bigger role. When humans hunt and fish, they kill species and many become extinct. When humans abuse nature for their own benefits, the consequence is that they are causing an “unnatural mode of section” (253). When humans are careless about evolution, many species will continue dying out along with those people that are dependent on them.
An example of this is seen with the cod fish. The population of northern cod dropped 99.9 percent due to over fishing. When cod fishermen selected the largest fish, the fish began favoring smaller maturing fish. Also fish that tended to mature at a larger size and greater age were more likely to be caught before they could reproduce. So since they could not reproduce they could not make more fish, and the fish population declined almost to extinction.
Another example of what human involvement can do to a species can be seen with the bighored rams. Because hunters desire rams with big horns, , rams have started to select against the faster growing horns and started to favor shorter horns. The average size of many species has gone down as a result to hunting and unnatural selection and because the prized parts of the species' gene pools are simply no longer there.
http://en.wikinews.org/wiki/Climate_change_impacts_Wyoming
http://www.nature.com/nature/journal/v457/n7231/full/457803a.html
The changes that occurred, the "unmaking of the fittest", were a result of drastic temperature changes 40 to 50 million years ago. Because these climate changes were so rapid, the flora and fauna, including the palm tree, was not allowed any time to evolve and adapt to the conditions, leading to a number of extinctions.
ReplyDeleteThe role of humans as it relates to the onset of global warming has been well-documented. The world has seen a steady rise in atmospheric carbon dioxide, due mainly to the fact that humans have consumed a great amount of energy, an amount that is only increasing (+2.3% per year). Something that has been keeping this situation in relative check is the presence of the oceans, and its ability to absorb the carbon dioxide. However, as the overall temperature of the water continues to rise, less carbon dioxide can be absorbed, meaning that we will see an even heavier rise in atmospheric carbon dioxide.
The result of this is increased temperature due to the greenhouse effect. It is caused by the presence of greenhouse gases (which include carbon dioxide), which absorb the thermal infrared radiation emitted from the Earth's surface, the atmosphere itself, and the clouds. The gases then re-emit the infrared radiation back to the surface of the earth, resulting in an increased temperature, something we have seen since the 1970's.
Because of the increase in temperature, we may be seeing the gradual extinction of the polar bear before our eyes, as their habitat is being whittled down to nothing. The sea ice from which polar bears fish has been melting, with two consequences. One is that with the ice melting earlier in the year, the bears are forced to return to the mainland before they have enough reserves stored to last them through their hibernation. The second is that polar bears now have to swim across longer distances, something which requires more energy. But because there is less time for fishing, and thus have less energy stored up, this may result in drowning. Another problem to polar bears also caused by humans but unrelated to global warming is the risk of poisoning. Because they are at the top of the food chain (they consume a certain species, which consumes other species, and so on), the amount of poison in their bodies the most concentrated.
http://en.wikipedia.org/wiki/File:Instrumental_Temperature_Record.png
http://upload.wikimedia.org/wikipedia/commons/8/88/Mauna_Loa_Carbon_Dioxide.png
http://en.wikipedia.org/wiki/Fossil_fuels
http://www.naturalnews.com/001398.html
http://maps.grida.no/go/graphic/graphicid/156EC22F-9DC2-4D6E-A355-A4E7D82C47C9
http://en.wikipedia.org/wiki/Greenhouse_effect
http://en.wikipedia.org/wiki/Polar_bears#Global_warming
Carroll discusses in the book that the “fittest” is conditional and shifted based on the accordance to surrounding environmental factors and other species. Even changing these factors are outside changes such as in the weather or climate.
ReplyDeleteCarroll uses Wyoming and the fossils found on the site to convey his theory that the “fittest” is only conditional. Wyoming is of now a place where climate is rather dry and evaporation takes place at a fairly quick rate. This puts a limitation on natural vegetation for the state. It is hard to believe that in this same area there was once a tropical forest that covered the ground. In the fossils that were uncovered in Wyoming, there was shown to be a variety of different species including fish, stingrays, turtles, crocodiles, and even a small horse (251). Beyond just the presence of these species was the identification of a palm tree that was also in the fossil. A palm tree requires a moist and warm tropical climate in order to survive. They are so fragile in fact that some palm trees can be injured by just one night in cold temperatures and with lack of moisture. With the identification of palm tress in the fossil it can be seen that Wyoming was once a tropical area and that being a palm tree was an advantage in that current environment. This climate change is most likely due to the Paleocene-Eocene Thermal Maximum. This was a time period where the temperature rose to about 10 degrees higher than before and created an environment to support what is now known as the “Age of Mammals.” This is the time period in which some of the first primates were seen. This climate change did not only affect the diversity of animals in creating numerous mammals, but it also had an affect on the environment which supported the growth and development of these new mammals. With higher temperatures and a higher humidity tropical areas flourished, even in areas such as Wyoming. The global warming that occurred at the time allowed for animals to migrate to northern areas and across northern land bridges. The loss of palm trees in Wyoming is seen as a natural “unmaking” as Carroll puts it. The decrease in temperatures and humidity caused for the environment to not be suitable for the palm tress and other life forms that were once prevalent in Wyoming. The climate gradually changes and with it the advantage of being a palm tree decreased until other plant forms took their place as the “fittest”.
Beyond the change in Wyoming there are now unnatural “unmaking” in the process. With the presence of the human race there is a turn of Mother Nature having the power of evolution to mankind affecting these changes. This can be seen in many different aspects throughout the entire book that Carroll has written. In the beginning Carroll discussed on page 53 the melanic moths and the change of their color in accordance to the air quality in their environment. Because of human pollution air quality had become poor and the moths took on a darker color. This change was due to the addition of pollution. Because of compromised air quality, the moths had found an advantage to a darker color for camouflage. In this way humans had stepped in and caused change in a species because of their doing.
In another example that is very relevant to the present is the fishing industry. There is growing demand in the area of the fish market and fish products causing more fishermen to go out in search for a larger catch. Because larger fish bring in more money, the fishermen target large fish in order to make a living. This has changed the characteristics that are perceived as advantageous to fish. Fishermen, desperate to catch fish in a time where fish catch is greater than rate of fish reproduction, are catching maturing fish and leaving the smaller less developed fish to reproduce. This is changing the advantages of size in the fish community. Because larger fish are caught at a higher rate, a smaller fish has a greater chance to survive and reproduce. This was the case in Cape Cod where fishermen over fished the cod population till 99.9% was gone (256). Due to this over fishing laws were placed to stop fishing in order to allow for the Cod population to occur. Unfortunately that option was unable to occur because of the upset in the ecosystem that the humans had brought. While population of cod had been declining the prey that they had once fed off expanded in inhabitants. Since the cod had become smaller in size and fewer in numbers, even after the cease of fishing they were unable to survive due to these once prey that have now become predators and competitors in their environment. Since the population of these smaller fish and crustaceans increased they now fed on the cod eggs and larvae, decreasing the survival of the cod and keeping their population to a minimum. Due to the affect of the human race, an entire ecosystem was placed off balance and seems to be unable to recover.
The fishing industry is having a large effect on all fish populations. The numbers of fish are declining at alarming rates due to new technologies such as trolling where large nets are dragged on the ocean floor. This affects not only the fish being caught but also those species that inhabit the ocean floor that is being destroyed. Another large concern is by catch, fish that are not sold and are dragged in on accident by large nets or long lining. These by catch are thrown back into the ocean and majorities are already dead or injured due to the nets and long lining. The destruction of these marine ecosystems and populations by mankind has caused a change in the course of evolution for different species.
Another example of human affected evolution is that of the bighorn ram that inhabits in Wyoming. Their distinctly large horns have been a selective advantage in the course of their history because they aid in battles and mating. The large horns provide a weapon when fighting other rams and many fights occur over a mate. The larger horned rams are more likely to find a mate because of the size of their horn and with a higher dominance rank they have a higher success in mating. Yet this advantage has been compromised due to the human population. Hunting has become avid and hunters are looking for a trophy ram to display, preferably with the largest horns. Because there is a decline in the number of large horned rams it is seen that the population is now taking a turn to having smaller horns and a smaller body size as the selective advantage. Because a smaller horn length and body size increase the chances of survival from human hunting, these rams are more likely and reproduce, passing on their genetic characteristics. With human confrontation, the evolutionary path of the bighorn ram has been changed to be “fittest” in the environment given.
http://www.wrcc.dri.edu/narratives/WYOMING.htm
http://news.mongabay.com/2005/1111-science.html
http://en.wikipedia.org/wiki/Arecaceae#Range_and_Habitat
http://overfishing.org/
In Wyoming, evolutionary changes came due to a massive climate change. Around 40 to 50 million years ago, the area had a distinct tropical climate. This led to the selection of plants that did not have excessive water saving mechanisms. For example, few, if any, plants developed cam 3 adaptations (where co2 is collected and stored as a solid at night, and the stomata close during the day to prevent water loss), thicker cuticles (a waxy layer on the leaf to prevent water loss) were not chosen for, etc. However when the climate changed so dramatically and became a desert region, for plants to survive extensive water saving measures had to be applied. This meant that plants such as the palm tree referenced either evolved to fit the new definition of evolutionarily fit and evolved water saving mechanisms, or died off, as was the case with the palm trees.
ReplyDeleteHuman interference changing the definition of evolutionary fitness is similar to environmental changes redefining evolutionary fitness, though there are some differences between the two. They are similar in that they can radically and rapidly change the environment, and therefore the adaptations needed for survival in that region. Whether it be the Lampsilis higginsii mussel that was driven into endangerment due to industrial and urban pollution, or the aforementioned palm tree that became extinct in that region, the extinctions/endangerments were caused by environmental changes, the only differences were in the sources of the environmental change. However differences are present between environmental changes redefining fitness and “unnatural selection” redefining fitness. The primary difference is that oftentimes, humans hunt for animals that are near physically perfect. For example, hunters pride themselves on killing the physically fittest bighorn rams with the largest horns. This leads to the selection for weaker rams, which are less able to cope with the rigors of life. This can be very harmful to a population. This contrasts natural redefinitions of fitness, which randomly select traits to select for.
http://www.int-res.com/articles/esr2007/3/n003p229.pdf
http://animals.about.com/od/esstatelists/a/esa_wisconsin.htm
Organisms can become extinct through various means of human intervention. Predation, competition, disease, environmental changes, and the introduction (purposefully or not) of a new species can all lead a decrease in the population of a species, or rendering them incapable of survival. The classic example of extinction is predation or hunting. The passenger pigeon, one of hundreds of extinct birds, was hunted to extinction over only a period of around 20 years. The population decrease led to a decline in the pigeon’s ability to survive and reproduce.
ReplyDeleteA rather indirect cause of extinction is population genetics. Obviously, species with smaller populations are more vulnerable, and a limited geographic range is also an important determinant of extinction. If a mutation were to spread throughout a small population that alters the genetic make-up, fatality will spread resulting in extinction.
Humans have a habit of overexploitation. Unrestricting whaling brought the whale species nearly to extinction and even caused a change in the migration pattern of gray whales as a result. All of these causes relate to the alteration or change in either the population or environment in which the organisms live. One of the greatest changes that humans have made in the environment that has impacted organisms around the world is global warming. The Antarctic Emperor penguin, who has experienced a 9% decline in adult survival for a .26*C warming, is only one of those organisms effected. Warming negatively affects both the breeding successes and adult survival of this seabird. Also, the warming has changed the eating habits of the penguins, which usually dine on krill and other small crustaceans, which live within the oceans warming waters. As warmer temperatures reduce the abundance of sea ice, there is less food for the penguins. This, in turn, could cause a need for the penguins to develop a new, more prolonged means of fat storage, a change in geographic location, or a more effective way of breeding.
http://en.wikipedia.org/wiki/Greenhouse_effect
http://news.mongabay.com/2008/0211-penguins.html