Saturday, January 10, 2015

Biologists Map Crocodilian Genomes

URL: http://www.sciencedaily.com/releases/2014/12/141211141837.htm
Date Published: December 11, 2014
Source: Texas Tech University

      Recently scientists have succeeded in mapping the entire genomes of an American alligator, a saltwater crocodile, and an Indian gharial. By using this new information, they were able to compare the DNA of each crocodilian species with each other, as well as with the DNA of other animals.
     They found that crocodilians evolve extremely slowly. For example, an alligator and a crocodile share about 93% of the same genetic information. In comparison, that is the same percentage of identical DNA between a human and a macaque. However, the common ancestor between an alligator and a crocodile lived more than 90 million years ago, while the common ancestor between a human and a macaque is more recent, only 23 million years. This means that over the generations, crocodilians have evolved at 1/4 the speed of primates.
      Now, scientists are trying to use this data to not only to understand more about crocodilians, but to reconstruct the genomes of their ancient relatives. By finding similarities in DNA between crocodilians and birds, their closet living relatives, they have been able to piece together almost half the genome of their common ancestor. Using this new information, scientists hope not only to learn more about crocodilians, but also about evolution and the connections between different species. 

     This article relates to our current unit about evolution. By sequencing the entire genome of three crocodilians, scientists have learned that they evolve relatively slowly, barely changing over many generations. This story also brings up the idea of a common ancestor, another aspect of evolution that we are studying in class. For example, it explains that birds are the closest living relative of crocodilians, meaning that starting long ago, crocodilians and birds both stemmed from the same species.
     

4 comments:

  1. By piecing together the entire crocodilian genome, what corrections have scientists discovered between the much faster evolution of primates opposed to the slower evolution of crocodilians? Is there a reason or a benefit that they evolved at different rates of time?

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  2. Is there any available name for the name of the species that the crocodilians and birds both stemmed from? Also, does that species look like a combination of a crocodilians and birds?

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  3. Isabella,
    according to this source: http://kttz.org/post/inside-texas-tech-crocodilian-bird-evolution-focus-biologists-study , scientists believe a reason for the crocodilians' slow evolution is that they have an "ideal" phenotype and genotype for their environment. In other words, they are well-adapted and don't have any reasons to change. Using the same logic, perhaps primates (and other mammals) evolved faster to adapt to new niches.

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  4. Mitsuko,
    both birds and crocodiles belong to a group called Archosauria. I couldn't find a specific species that was their common ancestor or a picture. But here's an article: http://www.britannica.com/EBchecked/topic/33063/archosaur

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