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Evolution of the Great White Shark
Transcript of Evolution of the Great White Shark
This is evidence of a common ancestor using fossil and anatomical records
The Great White Shark tooth is both long and wide combining the characteristics and adaptions seen in the Cretaceous sharks. Biogeographical Great White Shark Range Today In the Cretaceous Period, sharks range was much greater due to tropical climates.
Carbon Dioxide levels were three time what are seen today
Few ice caps/ glaciers existed during this period, as the earth was slowly cooling to modern temperatures.
Pangaea had split apart but continents were still moving
Oceans were deep with high oxygen levels (close to what is seen today) In the Devonian Period, sharks were smaller due to shallow oceans and low oxygen levels
sharks survived mass extinction caused by low oxygen levels
Pangaea was beginning to form Biochemistry Even though the Goblin and Great White shark have different physical appearances they are related.
Both are part of the Order Lamniformes.
Thanks to DNA research scientist are able to determine connections between species.
Physical appearance can be deceiving and if it were not for DNA, and anatomical study a connection between two very different sharks would not have been possible. For instance shark teeth are very important in distinguishing sharks as descending from a common ancestor, yet these sharks would not have been connected without DNA because their teeth are so different. Carcharodon carcharias Mitsukurina Owstoni Phylogenetic Tree of the Great White Shark: Using orders instead of individual species Works Cited
"450 Million Years of Sharks." Shark Savers. Shark Savers Inc., 2012. Web. 22 Oct. 2012.
Broyles, Robyn. "Shark Phylogeny, Part 2: A Phylogeny Tree for Sharks." Bright Hub Education. Ed. Donna Cosmato. IVillage, 15 Sept. 2008. Web. 22 Oct. 2012.
"The Cretaceous Period – Flowers in Bloom and Asteroid of Doom." Eonsepochsetc.com. J.E. Morris, 2010. Web. 22 Oct. 2012.
"The Devonian Period – The Age of Fishes." Eonsepochsetc.com. J.E. Morris, 2010. Web. 22 Oct. 2012. Areas of Evolutionary Study Stabilizing Disruptive Directional Coloration:
The Great White is lighter underneath and darker on top. This allows the shark to blend in with lighter water above it, and darker water below, so that prey are less likely to notice and get away. This is called counter-shading. This adaption does not favor light or dark coloration over the other. Neither extreme adaption is favored, instead the middle one is chosen. Size:
The largest carnivorous shark, the Great White's size allows it to eat much larger prey, such as seals, that other sharks may avoid. The Great White's ancestor probably had the genes to be larger and smaller, due to a change in diet, the larger could have survived better. Yet, the smaller survived better in a different area, eventually leading to the species splitting into two extremes. Speed:
The Great White's body is streamlined for its aquatic environment. Among sharks, speed would be chosen over slowness. To be able to have this burst of speed and still have the energy to catch their prey, they regulate their body temperature. By this, it allows them to conserve energy. This one extreme advantage would improve the chances of survival for the species, from catching prey, to hiding from bigger fish. Types of Selection Agents of Evolutionary Change Great Whites have sensory organs that are called electroreceptors; these receptors allow the Great Whites to sense when hidden prey have moved. The receptors are found from the Ampullae of Lorenzini; in which each ampulla is a jelly-filled canal that comes from the surface pores and clusters together in electroreceptors. Watch the first 40 seconds of this video and think about it as you learn how the Great White evolved Catistrophisim: Catastrophic events, such as hurricanes may have caused the some Great White's ancestors to be more fit in dark, murky waters if they had electroreceptors, and the others would have died off, causing the shark to evolve.
Founder effect: If a small population of sharks lacking this sense gained a member with electroreceptors, making them more fit, it could cause the species to split over time.
Bottleneck effect: If a small population of sharks with a limited gene pool (including electroreceptors) survived on its own for a long period of time, it could not change with the rest of its species resulting in a new species Different circumstances, such as the ones listed could cause the Great White to change in different ways. It could favor certain extreme phylogenetic traits and adaptions, or cause the least extreme trait to be chosen. This is our next topic. Teeth are very important characteristics to sharks as seen above the shape and size can vary from one shark to another due to the area they are inhabiting. The type of climate in which each shark lives depends greatly on its ability to adapt to changes in temperatures and the type of prey it hunts, every animal is susceptible to natural selection and as the prey changes so does the hunter, the hunter best adapted will survive to produce offspring. Now, lets watch that video again and discuss it with what we know.