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Welcome to the discussion group for Making of the Fittest by Sean Carroll. Prompts and posts are student generated. This is a collective effort to engage in discussions that connect the theory of evolution with the biological concepts and themes discussed in our course throughout the year.
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- Can evolution expain all traits?
- Detrimental Diseases helping Life pg. 174
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Sea anemones, scorpions, marine cone shell snails, and black mambas all have venom that contains potassium channel blockers. When the potassium channels are blocked there is a lack of communication in the neurons and therefore the nerves and muscles are unable to work properly. This will cause the death of the organism that had been injected with the venom. However, close relatives of each of these organisms does not contain the potassium channel blocker venom. Therefore, each of these organisms evolved to have this venom individually. This is proven on page 153 where the different DNA codes are shown which produce the venom. They are all very different and no similarities are evident. This also proves that they each evolved individually. Each of these organisms live in very different environments and are approached by different natural pressures in their environments. Because each organism is so different, it is likely that the evolution of the venom occurred for different reasons in each organism. Some organisms may have needed the venom to fight off predators while others may have needed it to kill their prey.
ReplyDeleteThe most similarities between a variety of species is the genetic code. No matter what species one is referring to, CUU, CUC, CUA, and CUG as mRNA codons will always code for leucine, GGU, GGC, GGA, GGG will always code for glycine (the chart is on pg. 308 of campbell).
ReplyDeleteHowler monkeys are a species of New World monkeys. Howler monkeys were found to have full color vision. Also, Old world primates also have full color vision. These two different groups of species share the same trait and Carroll explains why (142-145). Because the howler is more so related to other New World species (who do not possess full color vision), Carroll uses the "simpler explanation...the howler evolved from a dichromatic ancestor and gained full color vision on its own" (143).
Gene duplications allow for a gene to be cloned once and the two identical genes can then go separate ways and change. The more time that passes after duplication, the more different the two once equal genes will be.
In Becca's response, she talked about the venom with potassium channel blockers that is present in sea anemones, scorpions, marine cone shell snails, and black mambas. The lack of potassium channel blocker venom in close relatives of the organisms with the venom could be due to a gene duplication. The gene for the potassium channel blocker in the venom could have been duplicated and each duplicate ends up being different over time.
One example of convergent evolution (the type of evolution described in the prompt where one similar adaptation occurs in different species) is the evolution of hinged jaws in the phylum arthropoda and the phylum chordata. Originally, neither of these phyla were characterized by hinged jaws; in fact, they were more similar in body plan to mollusks or echinoderms. However, as many years passed (on the order of geological), both arthropods and chordates began to develop hinged jaws. Hinged jaws then evolved over time, but are slightly different between both phyla. In phylum arthropoda, the hinged jaw is called a mandible and consists of two separate hinged structures that function in mechanical digestion as well as pushing food into the arthropod’s mouth. In the higher level chordates such as cartilaginous fish, reptiles, amphibians, boney fish, and mammals, the hinged jaw is a single, non divided structure that functions mainly in mechanical digestion as well as closure of the opening to the digestive lumen. Even though slightly different in structure, the hinged jaws that convergently evolved in these two phylum serve basically the same purpose. They both function in mechanical digestion, which would give the organism a selective advantage because the “chewing of food” increases the surface area of the food which in turn allows the enzymes of the digestive system to work more efficiently and break food down into more monomer units. This would lead to more cellular respiration resulting in higher energy levels which would usually mean that the organism has a better chance at survival and reproduction. Another important function of the hinged jaw is the control of substances entering the mouth. A hinged jaw allows an organism to choose what substances to place in its mouth, unlike organisms without jaws which have no way of isolating the beginning of the digestive tract, which ultimately results in digestion of dangerous or unnecessary substances. Unnecessarily spending energy on digestion or the ingestion of dangerous substances such as toxins from bacteria is definitely a selective disadvantage because either of these actions lowers fitness. The most important idea to get from this example of convergent evolution is the idea that similar selective pressure produced similar adaptations. This without a doubt shows that natural selection worked to produce similar body plans of hinged jaws because there is very little variation other than the mandible or hinged lower jaw plan. It is obvious that any other mutation that produced a different sort of mouth adaptation was not as effective as the hinged jaw, so natural selection eliminated those mutations from the population while at the same time favoring the hinged jaw mutations so much so that two entirely different phyla of animals developed essentially the same body structure.
ReplyDeleteConvergent evolution takes place due to similar environmental facets of both organisms' surroundings, prompting natural selection to take place in a similar fashion in both organisms over time.
ReplyDeleteA prime example of this is found between camels and squirrels; the similar trait in both organisms is thickness of the organism's outer layer.
The Australian feral camel and the Bactrian camel are both of the same genus: Camelus. The Australian feral camel is native to the fiery deserts of inland Australia, while the Bactrian camel is native to the relatively cooler steppes of Northeastern Asia. The Bactrian camel possess a much thicker outer coat than the Australian feral camel.
In a similar case, the California Ground Squirrel and the Yellow-bellied Marmot are both members of the same family: Sciuridae. The California Ground Squirrel lives in the lower elevated, warmers regions of California, while the yellow-bellied marmot lives generally in the relatively cooler Rockey Mountains and the Sierra Nevada. The yellow-bellied marmot possesses a much thicker outer coat than the California ground squirrel.
Squirrels and camels are remotely related, however both organisms displayed an increased thickness of their outer coat in the presence of colder weather. The process by which this specific change of trait came about is what we call natural selection. Organisms that DID NOT have thicker outer coats in cold climates perished, and offspring bearing genetic mutations causing thicker coating survived. The presence of the trait was amplified by the continued existence of thicker coated organisms, so much so that the thick outer coat became a common trait.
Sources:
http://en.wikipedia.org/wiki/Yellow-bellied_Marmot
http://en.wikipedia.org/wiki/California_ground_squirrel
http://en.wikipedia.org/wiki/Australian_feral_camel
http://en.wikipedia.org/wiki/Bactrian_camel
Species could adapt to the same environment using two methods: similar means to similar ends and different means to similar ends. The latter of these two methods is more noteworthy because it shows that evolution, on some level occurs by design as well as by chance. Arctic fish and Antarctic fish are separated by thousands of miles of ocean, yet their antifreeze proteins are both “made up of repeating sequences of threonine-alanine-alanine or threonine-proline-alanine” (Carroll 151). Despite the protein's similar appearances “the arctic fish antifreeze evolved in a different way and at a different time from the Antarctic fish antifreeze” (Carroll 152). How can fish of two different orders develop the same antifreeze protein? To better understand this phenomenon, we should consider the 4th theme of biology: structure and function. Remember that all things in this universe are government by the laws of physics. These laws naturally put restrictions on what is workable and what is not. In the case antifreeze protein, the laws of physics dictates that only the threonine-alanine-alanine or threonine-proline-alanine primary sequence will give rise to a tertiary structure that could effectively function as an antifreeze protein. It is imaginable that initially the population of Arctic and Antarctic fish developed may different variations of antifreeze. However, the most effective antifreeze protein had the threonine-alanine-alanine or threonine-proline-alanine sequence. Fish with these kinds of antifreeze would be at a selective advantage to those fish with faulty antifreeze. Thus only the gene for the “fittest” antifreeze would be left in the gene pool of the Arctic and Antarctic fish population. The antifreeze protein is just one example of convergent evolution. Other example include Sea anemones, scorpions, marine cone shell snails, and black mambas (Becca), color vision (Erin), hinged jaw (Aaron) and ground squirrels (Vissagan).
ReplyDeleteOne example of convergent evolution is the body types/shapes of the icthyosaur (reptile), whale, and fish. All of these organisms have sleek, smooth bodies with a muscular tail that allows them to travel quickly and efficiently through water. All of these organisms also have a pair of flippers and many of them also have a dorsal fin along their backs. Although the icthyosaur, whale, and fish are completely different organisms, they all have similar bodily features which allow them to survive and reproduce successfully in their environment.
ReplyDeleteAnother example of convergent evolution is between bats and birds, which both have wings. Although both organisms come from different species, their wings allow them to travel and go after prey and/or run from predators. Bats and birds did not develop wings at the same time; selective pressure pushed each group to evolve wings at different times. Over time the wings became known as a selective advantage was passed through reproduction.