This preview shows pages 1–3. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: A group of taxa is said to be paraphyletic if the group contains its last common ancestor but does not contain all the descendants of that ancestor. Monophyletic means common descent form a single ancestor. Coelomates (also known as eucoelomates "true coelom") have a fluid filled body cavity called a coelom (pronounced / si l m/ ) with a complete lining called peritoneum derived from mesoderm (one of the three primary tissue layers ). The complete mesoderm lining allows organs to be attached to each other so that they can be suspended in a particular order while still being able to move freely within the cavity. Most bilateral animals, including all the vertebrates , are coelomates. Pseudocoelomate animals have a pseudocoel (literally false cavity), which is a fully functional body cavity. Tissue derived from mesoderm only partly lines the fluid filled body cavity of these animals. Thus, although organs are held in place loosely, they are not as well organized as in a coelomate. All pseudocoelomates are protostomes ; however, not all protostomes are pseudocoelomates. An example of a Pseudocoelomate is the roundworm. Pseudocoelomate animals are also referred to as Hemocoel and Blastocoelomate . Acoelomate animals , like flatworms , have no body cavity at all. Organs have direct contact with the epithelium . Semi-solid mesodermal tissues between the gut and body wall hold their organs in place. 1) Animal Diversity Animals in the eukaryotic tree are A protist taxon, the Choanoflagellates, are our sister group Among the two other multicelluar groups, were more closely related to the fungi than plants Characteristics of animals Heterotrophs that ingest their food Plants are autotrophs Fungi are heterotrophs Lack structural support of cell walls Animal cell are held together by structural proteins, foremost of which is collagen Reproduction Most animal reproduce sexually and the diploid stage is the dominant one Very characteristic form of early development Development is largely regulated by a set of genes called Hox genes Early Beginnings (A brief History) Molecular clock data suggest that animals might go back as far as 875 million years First good fossil though appeared about 575 million years ago Known as the Ediacaran biota, contains a lot of weird soft bodied things unlike anything we see today. But also see some familiars like sponges and cnidarians Between 535 and 525 million years ago, most of the modern phyla suddenly appeared in the fossil record in forms wed recognize today. Almost all modern phyla arose only 10 million years ago Animal Sister group Morphologically choanoflagellates cells and collar cells (choancytes) are almost indistinguishable Collar cells have been seen in other animals but never in the other eukaryotes Phylogenies from DNA sequence data supports relationship Animal body Plans Symmetry Asymmetric...
View Full Document
This note was uploaded on 10/23/2010 for the course BIOL 2308 taught by Professor Boxer during the Spring '10 term at University of Houston - Downtown.
- Spring '10