Sunday, March 22, 2009

Timeline of Icefish Evolution

On page 28, there is a timeline of icefish evolution, along with events happening in their habitat. Discuss each adaptation and relate it to what happened in the habitat. Discuss why each adaptation occurred, and why it would be a selective advantage to the icefish.
Posted by at

3 comments:

  1. Chris ChenMarch 24, 2009 at 4:33 PM

    This comment has been removed by the author.

    ReplyDelete
  2. Chris ChenMarch 25, 2009 at 2:55 PM

    To begin, we see that the existence of the Antarctic notothenioid fish first rooted almost 25 million years ago, and according to the chart, they adapted genes that make “antifreeze” proteins. University of Illinois animal biology professor Arthur DeVries discovered in the late 1960s that some notothenioids manufacture their own "antifreeze proteins." These proteins bind to ice crystals in the blood to prevent the fish from freezing. Furthermore, it's been shown that warm water fishes have no signs in their DNA that would indicate that they had this gene at one time as well, meaning that the Antarctic notothenioid fish "invented" this gene in response to the cold environment they were faced in, which can be seen as one of the countless evidence that could be used to prove the reality of evolution. 



    Later on, at about 7 million years ago, the Southern oceans underwent a rapid cooling phase, and the temperature dropped from 50 degrees F to about 30 degrees F. During this time, the Antarctic notothenioid fish evolved into the icefishes we know of today. At this time, they lost the globin genes and their red blood count drastically decreased. This is an adaptation made to cope with the difficulties of pumping body fluids in the subfreezing surrounding water temperatures, which caused the viscosity of the body fluids to increase. But to counter the lack of red blood cells, which leads to the difficulties of supplying oxygen to the body, the icefishes developed larger gills and evolved a scaleless skin with large capillaries that can be used to absorb the oxygen-rich waters. 


    In short, looking at a biological stand point, the icefish's evolution of getting rid of red blood cells and developing methods of directly absorbing O2 from the environment is advantageous because it allows them to survive in such cold temperatures, which gives them protection from some predators and allow them to make home of a hostile habitat so that they can survive and reproduce.

    During further research, I found that the Antarctic notothenioid fish all lack a swim bladder, which is an internal gas-filled organ that contributes to the ability of a fish to control its buoyancy, allowing them to stay at certain water depth without having to waste energy. This is interesting because that means they either abandoned this characteristic during evolutionary stages or they had never found reasons to evolve swim bladders since they are benthic in nature. In turn, this is another example of how evolution can slowly perfect a species over time.

    ReplyDelete
  3. Kimberly KenyonApril 15, 2009 at 9:15 PM

    In the book Antarctica splits from South America and 25 million years ago from now, the Antarctic notothenioid fish were in existence and we had not yet seen the icefish. These notothenioid fish had a version of the “antifreeze” we see in artic and Antarctic fish today. The “antifreeze” they used would produce proteins to bind to ice crystals in the blood. This would prevent the blood from freezing and furthermore prevent the fish from freezing. This gene was most likely produced by a mutation and a selective advantage to spread the “antifreeze” to generations.
    Then there was a rapid cooling phase (dropped from 50 – 30 degrees Fahrenheit) and the number of red blood cells seen in fish was decreasing. There were many changes in ocean currents and continental drifts that isolated Antarctica, these made it very hard for fish the migrate, therefore they had to adapt to the cold in order to survive. The development of icefish finished and notothenioid fish left. Icefish do not have any red blood cells. The icefish faced freezing temperatures and could not use the “traditional” or passed on “antifreeze” from the notothenioid fish. Without red blood cells, it is very difficult for oxygen and other nutrients to be supplied to the rest of the body. The icefish then evolved so they may absorb oxygen from its environment. The icefish’s physical features include large gills, scaleless skin, and large capillaries. All these physical features make it more suitable to obtain oxygen from the fish’s environment. These features occurred throughout evolution and sective advantages allowed them to be passed on and develop to become more efficient in their functions. Over time, the fish near Antarctica also developed cold adaptive tubulins and lost all of its globin genes. For instance, the Myoglobin gene has been inactivated by the insertion of an additional TATAAAA that blocks transcription from occurring.

    The cold environment is a major reason the icefish developed and evolved. The adaptations they developed allow them to survive and reproduce in extreme cold.

    http://74.125.95.132/search?q=cache:O4PFwXMvz9oJ:student.ccbcmd.edu/~sschmit4/BIOL%2520111/Evolution/The%2520Ice%2520Fish%2520of%2520Anarctica.ppt+icefish+tubulin&cd=2&hl=en&ct=clnk&gl=us

    ReplyDelete

Subscribe to: Post Comments (Atom)