In chapter six, Schubin discusses characterisitics of sea anemones. Schubin explains how they are very primitive in that they have a single opening to eat and expel waste and also that they have a very primitive body pattern. If sea anemones are so primitive, what is the value of studying them? While thinking about the theme of evolution, what does the discovery of multiple back-to-belly genes in sea anemones tell us about our relationship to sea anemones and other similar creatures? How might this and other similarities found (such as symmetry) contribute to our understanding of why we are able to grow body parts of frogs by injecting sea anemone genes?
Marissa Lobl marissa.lobl@gmail.com
Just because Sea Anemones are primitive doesn’t mean that there isn’t value to studying them. Sea Anemones are a more basic version of other cnidarians. Anemones are a part of the polyp stages of a cnidarian their whole life. Thus, the studying of sea anemones is vital in the understanding of an abnormal cnidarian. It is abnormal because most cnidarians switch off in generations between the polyp stage and the medusa stage. However, sea anemones stay in the polyp stage. Also, learning about sea anemones allows us to understand the polyp stage a lot better. It provides us information of primitive creatures and how they were able to reproduce as well as survive in harsh conditions.
ReplyDeleteLooking at the belly to back genes, there are obviously similarities in orientation with humans. Also, as Shubin explains, the scientists also found a left and a right side to the anemone (114-115). Thus, orientation is present in a sea anemone as it contains a belly, back, left, and right side. Although other differences such as having one mouth as the opening to waste products is present too, orientation is a similar feature that has been used to compare the evolution of cnidarians to humans. The medusa stage of cnidarians is always radially symmetrical, thus there are no similarities to humans. However, as seen in sea anemones, the polyp stage contains an “obscure axis symmetry” as well as orientation. Because sea anemone genes contain the gene “Noggin” which is turned on at one end of the directive axis, it will create a larger backside to an animal. A frog can contain this gene normally and its back side will enlarge. When placing the sea anemone Noggin gene in a frog embryo, the frog’s back side will also enlarge because the gene has the same effect on the frog. Also, the noggin gene contains orientation instructions as well. Thus, it will have the same effect on the frog because the gene has the same orientation directions.
Sources:
Shubin
http://library.thinkquest.org/J001418/anemone.html
Shreeraj Patel
shreeraj.patel1@gmail.com
It is true that sea anemones are one of the most primitive creatures that currently exist on this planet. However, as Shreeraj said, just because they are primitive does not mean that they should not be studied. As Shubin said, “All animals are the same but different” (115). By studying the sea anemones, we can compare and contrast them with many other animals, including ourselves, and see how we evolved from a simple cnidarian. In the diagram in page 114 of Your Inner Fish, it can be seen that sea anemones also has hox genes of front and back end, just like humans, while lacking the central region hox genes. Since the sea anemones are cnidarians with bilateral symmetry, and with front and back end hox genes, they can be an evolutionary step into bilateral symmetrical organisms. Even though their hox genes express less than a vertebrate or an anthropod hox genes, since they overlap a lot, it is one of the first appearance of canonical hox gene arrangement (http://scienceblogs.com/pharyngula/2006/05/bilateral_symmetry_in_a_sea_an.php). Since the sea anemones, unlike other cnidarians, were bilaterally symmetrical, they had a great advantage over others, such as parts of bodies and organs able to develop in different locations, movement made more efficient with better defined direction of movement, and higher mobility (http://www.jochemnet.de/fiu/BSC1011/BSC1011_11/tsld003.htm). With these advantages, sea anemones were able to ‘survive and reproduce’ better than other organisms, later evolving to organisms with better-defined hox genes.
ReplyDeleteSea anemone genes, unlike other invertebrates, look more like a vertebrates’, as their genes contain full of introns, noncoding regions in DNA, and 80% of the intron placement are in the same place as humans (http://www.detectingdesign.com/pseudogenes.html#Anemone). As for building body parts, the noggin gene and the BMP-4 gene are present in both the sea anemone and the frog. Since the both of those genes use the on-off interactions from the top and bottom side, they can easily control the developmental process (Shubin 112). As Shreeraj also explained, the injection of sea anemone genes to a frog can lead to growing of body parts in a frog’s body, such as the enlarged backside, because of the on-off interactions of the noggin and BMP-4 genes.
John Park (wisejsm@yahoo.com)