Lab 08 Animal Diversity I 2008

Lab 08 Animal Diversity I 2008 - Exercise 8: Survey of...

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1 Exercise 8: Survey of Animal Diversity Sponges, Cnidarians, Flatworms, and Roundworms Week of March 17, 2008 OBJECTIVES List the distinguishing characteristics of the Kingdom Animalia. Describe the types of features that determine an animal’s “body plan” (e.g., type of symmetry; diploblastic vs. triploblastic; types of body cavity; incomplete gut vs. complete gut; type of skeleton, etc). Identify members of the four phyla covered in today’s lab: Porifera, Cnidaria, Platyhelminthes, and Nematoda. Identify members of the three major classes of the Platyhelminthes: the Turbellaria, Trematoda, and Cestoda. Describe the distinguishing characteristics of each phylum and how those features relate to the biology of phylum members. List the types of habitats inhabited by members of each phylum (marine, freshwater, terrestrial, or parasitic). I. Introduction Most of us identify animals as motile, non-photosynthetic creatures. Indeed, most animals do have some mode of locomotion and all are heterotrophic , mostly with ingestive nutrition (eat other organisms or their parts and digest them internally). Animals have eukaryotic cells , and, like many algae, most fungi and all plants, they are multicellular . Individual animal cells lack a rigid, layered cell wall, but the body is typically supported internally by a unique kind of extracellular matrix rich in hydrated carbohydrates and structural proteins, including collagen . C ollagen is a glycoprotein (a protein with a covalently attached carbohydrate) that is unique to animals. Most of it is arranged into minute, stretch-resistant fibers, that form a three-dimensional scaffolding upon which the various cells of the body are arranged. In humans, collagen composes up to 50% of total protein. Also unique to animals (but not necessarily present in all cells or tissues) are specific kinds of cell junctions . These are complexes of structural proteins that join adjacent cells and allow the cells to function as a coordinated tissue (see Fig. 6.31 in your text). Animals probably evolved from colonial protozoan ancestors, which exhibited some division of labor amongst cells (e.g., somatic cells vs. reproductive cells). Animals carry the division of labor to new extremes. For example, humans contain 200 different cell types. Similar types of cells are typically grouped together to form functional assemblages called tissues and different types of tissues are arranged into larger functional units, the organs and organ systems . Animals have a diploid dominant life cycle – the unicellular gametes are the only haploid stage. Typically, animals are oogamous, producing a large non-motile egg (or eggs) and small, swimming sperm. Following fertilization, the zygote undergoes cleavage to form a spherical blastula . In the simplest animals, the sponges, this blastula develops directly into a swimming larval stage, which metamorphoses into an adult sponge. In all other animals, one side of the blastula invaginates to form a gastrula and the embryo begins to
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Lab 08 Animal Diversity I 2008 - Exercise 8: Survey of...

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