Chapter 31 - Textbook

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Biological Sciences
Kamini Persaud

Chapter 31 Animal Origins & the Evolution of Body Plans 31.1 What Evidence Indicates the Animals Are Monophyletic Traits that distinguish animals from other groups: - Unlike bacteria, archae, and most microbial eukaryotes, all animals are multicellular. Animals develop from single- celled zygote into a multicellular adult. - All animals are heterotrophs. - Fungi are also heterotrophs, but unlike fungi, animals use internal processes to break down materials from environment into organic molecules they need most. - They can move. Animal Monophyly: - may have resembled modern choanoflagellates, protists that are closest living relatives of animals Proof of Animal Monophyly: - Gene sequence, such as the ribosomal RNA genes. - Organization and function of Hox genes that are present in all animals. - Types of junctions between cells that are present in all animals. - Animals have a common set of extracellular matrix molecules, ex. Collagen & proteoglycans Embryonic develop wrt phylogeny: - First few cell division of zygote = cleavage (# of cells doubles) - Different cleavage patterns exist amongst different animals. - During early development of animals, distinct cell layers form, which later develop into organs and organ systems. - The embryos of diploblastic animals have 2 of the cell layer outer (called ectoderm) and inner (called endoderm). rd - The embryos of triploblastic animals have above 2 and a 3 layer (called mesoderm) which lies between the other 2. - During early development, a hollow ball indents to form a cup-shaped structure, process = gastrulation. - The opening of the cavity formed by this indentation is called the blastopore. The pattern of formation after the appearance of the bastopore divides the triploblastic animals into 2 main groups: protostomes and deuterostomes.
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