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ETD59: Why are echinoderms thought to be close relatives to chordates?
March 15, 2013 at 3:33pm


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Courtney S.
March 26, 2013 at 7:00pm

I found it very interesting how two things that look so different could be so similar. It is also very interesting to me that one thing that determines how similar two organisms are is what is determined by what is formed first, the mouth or anus. ---------- This was fairly easy to explain to my father although he had a lot of questions. This made me really have to look at my notes to accurately answer his questions but it really challenged me to know the material.

Adilah M.
May 12, 2013 at 6:42pm

Adilah taught me about echinoderms and chordates. Before she discussed this with me I has no idea what these two terms meant. I found it interesting how organisms that differ so greatly in appearance are actually closely related. I learned a lot from this discussion. --------------------------------------- Discussing echinoderms and chordates with my mother helped solidify in my memory the concepts that we learned in class as well as expand my understanding on them. Teaching this to my mother required me to think deeper about the similarities between echinoderms and chordates.

Sophie Wulfing
April 27, 2014 at 9:12pm

Both are known as deutrostomes (second mouth).  Anus forms first, mouth forms second.  Coelom is a cavity which is surrounded by the mesoderm.  Echinoderms and chordates have radial cleavage during the 8 cell stage, meaning cells can be swapped (indeterminate development) and will still grow normally (cells branch to unique functions later than 8 cell).  Different from protostomes, (first mouth) and they have spiral cleavage.

Sophie- I had to review that the coelom was a cavity within the mesoderm and that there were different types of it. These became the organs as meso means middle. Also, radial cleavage indicates that the cells are interchangeable at this stage while the sprial cleavage of a protostome meanis it is not interchangeable.

MacKenzie Dress
June 03, 2014 at 5:44pm

Not being a scientific person I found this information interesting.  I had never heard of the these so learning about their differences and similarities was informative and make me wonder how scientist figure out such tidbits.


"Wow," is apparently what she can come up with in response to this particular ETD. It was difficult, somewhat, to explain to her the difference between Radial and Spiral cleavage, because I had forgotten it. I am glad we are reviewing this because of the upcoming test... She asked what exactly determines which opening develops first, and I was unable to answer. Possible the maternal effect? Well, then what started it as organisms evolved? Freak mutation?

Madison Neyers
April 12, 2015 at 7:23pm

Student: This was really fun to teach to my mom because I felt like I knew a lot of fancy AP words that she didn't seem to understand at first. I went over the words a second time explaining what they mean and breaking them down to the latin words and meanings to make a better connection. While doing this it also helped me to understand the words better. I still wonder why deuterostomes evolved to develop an anus first and  what advantages it created. Maybe this allowed more time to be spent on the mouth to create complex structures like vocal chords and an esophagus.

Parent: I learned that humans are closely related to echinoderms (seastars) because they develop the same way during embryo development. It was interesting to know that based on whether a mouth or anus is formed first depends on if you are a protostome or deuterostome.

Lauren Masters
April 30, 2016 at 2:47pm

Student: I tried to teach my mom about protostomes and deuterostomes. This was difficult because I wanted to use biology terms that she did not know. Explaining spiral and radial cleavage was also kind of hard because she did not quite understand what cleavage was but I explained it to her. I also taught her that the embryonic development of echinoderms (starfish) and chordates (humans) is the same because the anus is formed first and the mouth is formed second. Protostomes are formed with their mouth first and anus second.

Parent: This was a difficult lesson. The terms Lauren used were not familiar to me. I had forgotten what cellular cleavage was. After she explained that again it was easier to understand. What I took from this is that humans are closely related to sea stars due to their development. They are both deuterostomes because their mouth was formed second to their anus. Protostomes developed their mouth first.

Calista Moore
May 01, 2016 at 3:50pm

Student: This helped me review the vocabulary and understand what they meant. I explained the difference between determinate and indeterminate development and why those were connected with spiral or radial cleavage. I broke down protostomes and deuterostomes into parts to explain what they meant.

Parent: I learned that protostomes have determined cells, rather than undetermined as humans have.  It was interesting that starfish were related closer to humans than other creatures.

Zach Holtz
March 12, 2020 at 11:13pm

Student:   Echinoderms and chordates are both under the category of Deutoerostomes.  Deuterostomes mean 2nd mouth.   A type of echinoderm is a starfish and a chordate is human.  The reasons why we are similar are by there being radial cleavage and indeterminate cells.  Along with that, the anus forms first and the mouth forms second.  Finally, the thing that shows our similarity is a closely related DNA sequence.

Parent:   Wow.  It is amazing how we can show that humans and starfish are related by our DNA sequence.  I had never heard about deuterostomes and protostomes.  It's cool that one forms their mouth first while the other forms their anus first.  

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