In Chapter 6, Shubin explains the relationship between our body plans and the body plans of other organisms. Specifically, he compares our body plan with a sea anemone’s. But how is it possible for these to be even remotely similar considering that we have bilateral symmetry while a sea anemone has radial symmetry? Explain by using what is said in Your Inner Fish and what we have learned in class.
Matt Micucci (coochqbk@sbcglobal.net)
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ReplyDeleteSea anemones display radial symmetry. An organism with radial symmetry exhibits no left or right sides. They have a top and a bottom (dorsal and ventral surface) only.
ReplyDeleteMost radially symmetric animals are symmetrical about an axis extending from the center of the oral surface, which contains the mouth, to the center of the opposite, or aboral, end. This type of symmetry is especially suitable for sessile animals such as the sea anemone, floating animals such as jellyfish, and slow moving organisms such as starfish.
Humans exhibit bilateral symmetry. In bilateral symmetry, only one plane, called the sagittal plane, will divide an organism into roughly mirror image halves. Thus there is approximate reflection symmetry. Often the two halves can meaningfully be referred to as the right and left halves, and this form of symmetry is found in most active animals.
Shubin say that it was discovered that early versions of our deuterostome genes (anus to mouth formation) are present in sea anemones. These genes are found in the oral-aboral axis of the sea anemone which is similar to the human head to anus axis. There is also another axis of symmetry that leads us to believe that humans and sea anemone’s are similar.The directive axis which is found when cutting an organism in half. The Noggin gene is turned on in places that will develop back structure in humans. It was found in sea anemones that a version of this gene is turned on at the end of the directive axis. When tested in an experiment with frogs, the gene in the anemones proved to be similar to that of the gene in humans.
“One of the big surprises of the anemone genome, says Swalla, is the discovery of blocks of DNA that have the same complement of genes as in the human genome. Individual genes may have swapped places, but often they have remained linked together despite hundreds of millions of years of evolution along separate paths, Putnam, Rokhsar, and their colleagues report.” (http://www.uncommondescent.com/intelligent-design/where-did-sea-anemones-get-human-genes/) It also says the the sea anemone’s genes are vertebrate-like, and that 80% of the anemone introns are in the same places in humans, which leads us to believe they had a common ancestor.
-Adnan Jahan
(adnanjahan@gmail.com)