exam 1.docx - Edward Piscopo 1 Describe the process of...

Info icon This preview shows pages 1–3. Sign up to view the full content.

Edward Piscopo 1. Describe the process of gastrulation in all animals. Include the distinguishing hallmarks of the two major groups of bilateral metazoans: the Protostomia and the Deuterostomia. The basic process of Gastrulation is a phase that occurs in the early development of animals. It is where cells divide and multiply forming the ectoderm, the mesoderm and the endoderm. Gastrulation starts with the fertilization of the cell forming a Zygote. The zygote then cleaves multiple times into an morula (8 cell stage), then forming into a Blastula. The Blastula is many cells surrounding a fluid filled space called the Blastocoel. From this point a dimple forms on the outside of the blastula and extends into the blastocoel. This space protruding into the blastocoel is called a gastrocoel. The blastula has now been transformed into a gastrula in which there is a defined ectoderm and endoderm that has formed. From this point the gastrocoel continues to extend into the blostocoel till it pierces through the other side of the gastrula, forming a complete gut. One end of this gut is the mouth and the other is the anus. At this point one of 3 forms develops: a. Pseudocoelomate body where the mesoderm lines only the outer edge of the blastocoel. b. Acoelomate body where mesoderm completely fills the blastocoel. c. Coelomate body where coelom cavity forms inside the mesoderm. Going back to the zygote, cells cleave in 2 different manners, according to whether it is a Protostome or a Deuterostome. A Protostome cleaves spirally forming a mosaic embryo. If one cell splits off this embryo, development of the organism is arrested; otherwise the embryo continues to form. At this stage a blastopore forms that will be the mouth of the animal. In other words in Protostomes, the mouth forms first. In contrast to the Protostome the Deuterostomes, of which humans belong, cleave radially and if one of the cells split off it will just begin forming another embryo, with the original continuing to develop. Also in the process of gastrulation for Deuterostomes, the blastopore that forms will become the anus, with the mouth forming secondarily.
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

2. What is the difference between a cladogram and a phylogenetic tree? Given a cladogram for a group of species, what additional information is needed to construct a phylogenetic tree? What is the benefit of using one as opposed to the other? There are only slight differences between the two. The phylogenetic tree, unlike a cladogram, involves evolutionary time. Length of the arms of the tree is used to depict evolutionary time. Phylogenetic trees are based on common descent, clades emphasize it. Another difference is in the relationships of the taxonomic groups, while phylogenetic trees can show relationships as monophyletic or paraphyletic, cladistics only considers monophyletic relationships.
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.
  • Fall '16
  • Professor York
  • Zoology, Cnidaria, recent common ancestor, gastrovascular cavity, medusa form, polyp form

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern