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13 - biology of animals - BIOLOGY 325 Biology of animals...

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BIOLOGY 325 Biology of animals 2/15/08 Several branches on the tree of life have evolved species with a multicellular body plans, including animals, plants, and fungi. In the next few weeks we will primarily focus on the biology of animals, although from time to time we will compare and contrast the evolutionary trajectory of animals with those of the other groups. Today we will focus on certain characteristics of animals. First and foremost is the fact that animals are heterotrophs (more specifically, “chemoheterotophs”) and must acquire organic compounds both as their source of carbon and their source of energy. Thus, all animals consume organic compounds produced by other living creatures, and many do so by actively killing and eating other organisms. This creates something of an arms race, with predator and prey animals evolving ever more effective adaptations to capture or escape one another. Another important feature of animals (and other multicellular organisms) has to do with the tissue organization of the body, which is often refered to as the ‘body plan’. An important goal of today’s lecture is to understand the evolution of body symmetry among animals, the geometric significance of the surface area:volume ratio, and the ways in which animal body plans have been shaped by physiological limitations resulting from that ratio. Learning goals 1. Animals ingest organic macromolecules in order to meet two distinct biochemical needs. What are these two biochemical pathways, and why does the animal need both? 2. What four types of tissue are found in animals, and what are their general features? 3. You should appreciate that nerve and muscle tissue are unique to animals. How does the presence of these two tissues relate to the behavior and motility of animals compared to other multicellular organisms? 4. What is the distinction between radial symmetry and bilateral symmetry? Which of these body plans is thought to have evolved more recently? You need to become well acquainted with the anatomical axes of the bilaterian body plan. What is cephalization, and why is it adaptive?
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