WELCOME TO THE DISCUSSION GROUP FOR THE BOOK "YOUR INNER FISH" BY NEIL SHUBIN. PROMPTS AND POSTS ARE STUDENT GENERATED. THIS IS A COLLECTIVE EFFORT TO ENGAGE IN DISCUSSIONS THAT CONNECT THE THEORY OF EVOLUTION WITH THE BIOLOGICAL CONCEPTS AND THEMES DISCUSSED IN OUR COURSE THROUGHOUT THE YEAR.
Thursday, March 31, 2011
Amphioxus
On page 94, Shubin describes Amphioxus, which is an invertebrate. Describe the evolutionary significance of Amphioxus and how it and others like it provide a window into our past. Include how it is unique and why it is studied.
Even though Amphioxus is an invertebrate, it contains many features similar to that of many vertebrates. The Amphioxus contains a nerve cord that runs along its back as well as a notochord (Shubin 94). The notochord is "filled with a jelly-like substance and provides support for the body," according to Shubin. While the notochord in the Amphioxus remains parallel to the nerve cord, the notochord that humans are born with will eventually become the disks that lie between the vertebrae in our spine. Amphioxus also has gill arches, but no cephalization. The gill arches in this organism "pumps water through them to filter out little particles of food" (Shubin 96).
Amphioxus is unique because they were the earliest organisms that displayed notochords and nerve chords, which shows us how the human body originated. According to the Encyclopedia Britannica, "growing evidence suggests that the vertebrate brain evolved from a portion of the nerve cord in a lancet like ancestor" (http://www.britannica.com/EBchecked/topic/21580/amphioxus). Knowing this, we can trace the evolution of Amphioxus into more developed species, and eventually trace those species to the development of humans. Because Amphioxus did not have a developed head or brain, their gill arches provided primitive development, but nevertheless provided a basis for cephalization. Being one of the first organisms with gill arches shows scientists the time and organism in which head structures began to form. As the animals evolved with more developed forms of gill arches, structures such as jaws, ear bones, facial muscles, and the throat would appear. These structures are all selective advantages to survival, and all began with the gill arches of the Amphioxus.
Amphioxus is a unique invertebrate because it has a nerve cord and a notochord for support, which are two characteristics of all vertebrates. As vertebrates, humans have both of these except our notochord “breaks up and ultimately becomes part of the disks that lie between our vertebrae” (Shubin 94). Amphixous’s close connection with vertebrates(but still being an invertebrate) shows that it was the first organism to develop a notochord and a nerve cord, and it is the bridge between vertebrates and invertebrates. Further supporting this is the fact that Amphioxus also has gill arches composed of cartilage, used to filter out little particles of food through water. The cartilage from gill arches is used to make up many parts of the head in certain vertebrates.
Through organisms like Amphioxus, Tiktaalik, and other animals with evolutionary milestones, we can learn about how and why organisms may have started to develop certain characteristics. For example, Amphioxus’s notochord and nerve cord showed us the beginnings of vertebrates, and Tiktaalik showed connections between aquatic and terrestrial animals through its jointed limbs and neck - key features of terrestrial animals. The discovery of Tiktaalik gives us an idea of when the Earth was able to provide resources for life on land. Amphioxus evolved from worms and Tiktaalik evolved from fish, but both had selective advantages that allowed them to survive and pass on their traits to future generations, influencing us. Often times, humans are influenced by the past because each part of our bodies came from a different organism in the past. Our jointed limbs and necks are from Tiktaalik, while the disks in our backbones are derived from Amphioxus. Our research of these animals isn’t only to learn about them, but also to learn about the building blocks that put us together.
As Austin had mentioned, organisms such as Tiktaalik or Amphioxus provide an insight into how we, as humans, came to be. These organisms provide a bridge between invertebrates and vertebrates and the advancement of our species. Shubin describes Amphioxus as an invertebrate worm that shares similar features to vertebrates or backboned creatures (Shubin, 94). He goes on to explain that while Amphioxus does not have a backbone, it has a nerve cord along its back called the notochord (Shubin, 94). The notochord, he says, provides support for the body as a jelly-like substance (Shubin, 94). However, current research defines the notochord as an “embryonic midline structure” common to all in the phylum Chordata (“Structure and function of the notochord: an essential organ for chordate development”, Gene Tools, LLC). This is important because, in our bodies, as humans and other “higher” vertebrates, the notochord is transient and simply becomes a disk lying between our vertebrae as Claire had explained. Therefore, as far as evolution goes, we can see that Amphioxus is incredibly significant because the organism provided initial insight to the beginnings of the backbone. Once organisms evolved to have more advanced and supportive structures such as the backbone, the notochord simplified to become a temporary structure only crucial in our developmental stages for support. Amphioxus, like other worms, have gill arches common to more advanced mammals, like humans. For Amphioxus, gills are used to pump water through them and filter out food (Shubin, 96). Shubin shares that these “headless” worms contained the basic beginnings of the structures that would eventually evolve into our own heads. The arches each have a bar of cartilage that we now use as part of our voice box and ear bones (Shubin, 96). In general, Ampioxus contained the beginnings of structures that allow us to be the advanced vertebrates that we are today. The notochords and gill arches are a few of the structures that have evolved in our species as our backbones and heads. In agreement with Austin and Claire, Amphioxus is unique as one of the first organisms to display a nerve cord or a notochord. Gill arches were common to many early worms, but the notochord was truly significant in our evolutionary pathway. Different types of the amphioxus species give us greater knowledge and insight into our own bodies. For example, amphioxus Branchiostoma belcheri, in a study involving zebrafish Danio rerio Hsd17b10, was discovered to be utilized as a model for human developmental disorders using mutations of the HSD17B10 gene (“Comments on 'Significance of developmental expression of amphioxus Branchiostoma belcheri and zebrafish Danio rerio Hsd17b10 in biological and medical research’ ”, U.S. National Library of Medicine and National Institutes of Health). The International Journal of Biological Sciences claims, “the cephalochordate amphioxus, described in 1778 as a mollusk has been regarded as the closest invertebrate relative to the vertebrates, possessing a vertebrate-like body plan, with notochord, hollow dorsal nerve cord, segmented muscle blocks, perforated pharyngeal region and post anal tail” (“Amphioxus: a peaceful anchovy fillet to illuminate Chordate Evolution I”, International Journal of Biological Sciences). With this vertebrate-like body plan, Amphioxus is crucial to continuing studies because it provides that gap between invertebrates and vertebrates as far as structure and function go. For this reason, Shubin like other college professors use Amphioxus to begin their curriculums while teaching comparative anatomy.
It's a long way from amphioxus It's a long way to us… It's a long way from amphioxus To the meanest human cuss. It's good-bye, fins and gill slits, Hello, lungs and hair! It's a long, long way from amphioxus, But we all came from there!
A fish-like thing appeared among the annelids one day; It hadn't any parapods or setae to display. It hadn't any eyes or jaws, or ventral nervous chord, But it had a lot of gill slits and it had a notochord.
(chorus)
It wasn't much to look at, and it scarce knew how to swim. And Nereis was very sure it hadn't come from him. The molluscs wouldn't own it, and the arthropods got sore, So the poor thing had to burrow in the sand along the shore.
He burrowed in the sand before a crab could nip his tail. He said "Gill slits and myotomes are all to no avail. I've grown some metapleural folds, and sport an oral hood. And all these fine new characters don't do me any good!"
(chorus)
He sulked a while down in the sand without a bit of pep. Then he stiffened up his notochord and said "I'll beat 'em yet! Let 'em laugh and show their ignorance; I don't mind their jeers! Just wait until they see me in a hundred million years!"
"My notochord shall turn into a chain of vertebrae; As fins, my metapleural folds will agitate the sea. My tiny dorsal nervous chord shall be a mighty brain And the vertebrates will dominate the animal domain!" (chorus)
Even though Amphioxus is an invertebrate, it contains many features similar to that of many vertebrates. The Amphioxus contains a nerve cord that runs along its back as well as a notochord (Shubin 94). The notochord is "filled with a jelly-like substance and provides support for the body," according to Shubin. While the notochord in the Amphioxus remains parallel to the nerve cord, the notochord that humans are born with will eventually become the disks that lie between the vertebrae in our spine. Amphioxus also has gill arches, but no cephalization. The gill arches in this organism "pumps water through them to filter out little particles of food" (Shubin 96).
ReplyDeleteAmphioxus is unique because they were the earliest organisms that displayed notochords and nerve chords, which shows us how the human body originated. According to the Encyclopedia Britannica, "growing evidence suggests that the vertebrate brain evolved from a portion of the nerve cord in a lancet like ancestor" (http://www.britannica.com/EBchecked/topic/21580/amphioxus). Knowing this, we can trace the evolution of Amphioxus into more developed species, and eventually trace those species to the development of humans. Because Amphioxus did not have a developed head or brain, their gill arches provided primitive development, but nevertheless provided a basis for cephalization. Being one of the first organisms with gill arches shows scientists the time and organism in which head structures began to form. As the animals evolved with more developed forms of gill arches, structures such as jaws, ear bones, facial muscles, and the throat would appear. These structures are all selective advantages to survival, and all began with the gill arches of the Amphioxus.
Claire Yao (claire.yao521@gmail.com)
This comment has been removed by the author.
ReplyDeleteThis comment has been removed by the author.
ReplyDeleteAmphioxus is a unique invertebrate because it has a nerve cord and a notochord for support, which are two characteristics of all vertebrates. As vertebrates, humans have both of these except our notochord “breaks up and ultimately becomes part of the disks that lie between our vertebrae” (Shubin 94). Amphixous’s close connection with vertebrates(but still being an invertebrate) shows that it was the first organism to develop a notochord and a nerve cord, and it is the bridge between vertebrates and invertebrates. Further supporting this is the fact that Amphioxus also has gill arches composed of cartilage, used to filter out little particles of food through water. The cartilage from gill arches is used to make up many parts of the head in certain vertebrates.
ReplyDeleteThrough organisms like Amphioxus, Tiktaalik, and other animals with evolutionary milestones, we can learn about how and why organisms may have started to develop certain characteristics. For example, Amphioxus’s notochord and nerve cord showed us the beginnings of vertebrates, and Tiktaalik showed connections between aquatic and terrestrial animals through its jointed limbs and neck - key features of terrestrial animals. The discovery of Tiktaalik gives us an idea of when the Earth was able to provide resources for life on land. Amphioxus evolved from worms and Tiktaalik evolved from fish, but both had selective advantages that allowed them to survive and pass on their traits to future generations, influencing us. Often times, humans are influenced by the past because each part of our bodies came from a different organism in the past. Our jointed limbs and necks are from Tiktaalik, while the disks in our backbones are derived from Amphioxus. Our research of these animals isn’t only to learn about them, but also to learn about the building blocks that put us together.
Sources:
Your Inner Fish
http://en.wikipedia.org/wiki/Lancelet
http://www.ucmp.berkeley.edu/chordata/cephalo.html
As Austin had mentioned, organisms such as Tiktaalik or Amphioxus provide an insight into how we, as humans, came to be. These organisms provide a bridge between invertebrates and vertebrates and the advancement of our species. Shubin describes Amphioxus as an invertebrate worm that shares similar features to vertebrates or backboned creatures (Shubin, 94). He goes on to explain that while Amphioxus does not have a backbone, it has a nerve cord along its back called the notochord (Shubin, 94). The notochord, he says, provides support for the body as a jelly-like substance (Shubin, 94). However, current research defines the notochord as an “embryonic midline structure” common to all in the phylum Chordata (“Structure and function of the notochord: an essential organ for chordate development”, Gene Tools, LLC). This is important because, in our bodies, as humans and other “higher” vertebrates, the notochord is transient and simply becomes a disk lying between our vertebrae as Claire had explained. Therefore, as far as evolution goes, we can see that Amphioxus is incredibly significant because the organism provided initial insight to the beginnings of the backbone. Once organisms evolved to have more advanced and supportive structures such as the backbone, the notochord simplified to become a temporary structure only crucial in our developmental stages for support. Amphioxus, like other worms, have gill arches common to more advanced mammals, like humans. For Amphioxus, gills are used to pump water through them and filter out food (Shubin, 96). Shubin shares that these “headless” worms contained the basic beginnings of the structures that would eventually evolve into our own heads. The arches each have a bar of cartilage that we now use as part of our voice box and ear bones (Shubin, 96). In general, Ampioxus contained the beginnings of structures that allow us to be the advanced vertebrates that we are today. The notochords and gill arches are a few of the structures that have evolved in our species as our backbones and heads.
ReplyDeleteIn agreement with Austin and Claire, Amphioxus is unique as one of the first organisms to display a nerve cord or a notochord. Gill arches were common to many early worms, but the notochord was truly significant in our evolutionary pathway. Different types of the amphioxus species give us greater knowledge and insight into our own bodies. For example, amphioxus Branchiostoma belcheri, in a study involving zebrafish Danio rerio Hsd17b10, was discovered to be utilized as a model for human developmental disorders using mutations of the HSD17B10 gene (“Comments on 'Significance of developmental expression of amphioxus Branchiostoma belcheri and zebrafish Danio rerio Hsd17b10 in biological and medical research’ ”, U.S. National Library of Medicine and National Institutes of Health). The International Journal of Biological Sciences claims, “the cephalochordate amphioxus, described in 1778 as a mollusk has been regarded as the closest invertebrate relative to the vertebrates, possessing a vertebrate-like body plan, with notochord, hollow dorsal nerve cord, segmented muscle blocks, perforated pharyngeal region and post anal tail” (“Amphioxus: a peaceful anchovy fillet to illuminate Chordate Evolution I”, International Journal of Biological Sciences). With this vertebrate-like body plan, Amphioxus is crucial to continuing studies because it provides that gap between invertebrates and vertebrates as far as structure and function go. For this reason, Shubin like other college professors use Amphioxus to begin their curriculums while teaching comparative anatomy.
Sonia Doshi (soniadoshi7@gmail.com)
Also, here's a song involving Amphioxus! Enjoy :)
ReplyDeletechorus:
It's a long way from amphioxus
It's a long way to us…
It's a long way from amphioxus
To the meanest human cuss.
It's good-bye, fins and gill slits,
Hello, lungs and hair!
It's a long, long way from amphioxus,
But we all came from there!
A fish-like thing appeared among the annelids one day;
It hadn't any parapods or setae to display.
It hadn't any eyes or jaws, or ventral nervous chord,
But it had a lot of gill slits and it had a notochord.
(chorus)
It wasn't much to look at, and it scarce knew how to swim.
And Nereis was very sure it hadn't come from him.
The molluscs wouldn't own it, and the arthropods got sore,
So the poor thing had to burrow in the sand along the shore.
He burrowed in the sand before a crab could nip his tail.
He said "Gill slits and myotomes are all to no avail.
I've grown some metapleural folds, and sport an oral hood.
And all these fine new characters don't do me any good!"
(chorus)
He sulked a while down in the sand without a bit of pep.
Then he stiffened up his notochord and said "I'll beat 'em yet!
Let 'em laugh and show their ignorance; I don't mind their jeers!
Just wait until they see me in a hundred million years!"
"My notochord shall turn into a chain of vertebrae;
As fins, my metapleural folds will agitate the sea.
My tiny dorsal nervous chord shall be a mighty brain
And the vertebrates will dominate the animal domain!"
(chorus)