Bio 242 Laboratory Module 2 Theme: Evolution shapes the flow and pattern of information through phylogenetic lineages, evident in the linkage between form and function Objectives -we will track the effects of natural selection on the lineages of life as they adapt to life on land -we will compare the different adaptations of homologous features among lineages -we will use the variation among homologous loci to reconstruct the phylogeny of the lineages of life Bio 242 Lab 6 Understanding Biological Diversity: Systematic Theory and Practice Brief introduction to Kingdom Animalia Examine form and function of Mollusca morphology, especially features that enabled life on land. Use computer software (Mesquite) to assemble a phylogeny of the molluscs and test hypotheses of evolution What is an animal? Without looking at your notes, any thoughts? 1
What is an animal? Multicellular heterotrophs: feed by ingestion. How does this differ from plants, fungi, protists? What is an animal? Carbohydrates stored as glycogen Polysaccharide of glucose (no, you do not need to know this structure) What is an animal? No cell walls Cells supported by structural proteins: collagen Extracellular matrix, supports tissues, gives cells structure from outside Triple-helix structural protein 2
What is an animal? Nerve and muscle tissue Impulse & movement Complex Embryo Egg + Sperm Zygote cleavage Blastula Gastrula Larva or juvenile Adult What is an animal? Note the two layers of tissue at the gastrula stage (Ectoderm and Endoderm) The complex embryo and germ layer development Diploblastic: Animals with only ectoderm and endoderm Cnidaria (jellies) and Ctenophora (comb jellies) 3
All bilateral animals have a third germ layer, the mesoderm Forms muscles and most organs between digestive tract and the outer covering. Triploblastic Gastrulation Body Cavity: The Coelom Most triploblastic animals have a body cavity Fluid- or air-filled space separating the digestive tract from the outer body wall. This is the coelom Body Cavity: The Coelom The coelom forms from tissue derived from mesoderm COELOMATES: Mesoderm connects dorsally and ventrally and provides a complete lining of the coelom 4
Body Cavity: The Coelom The coelom forms from tissue derived from mesoderm PSEUDO- COELOMATES: Coelom is lined with mesoderm (outside) and endoderm (inside) Body Cavity: The Coelom The coelom forms from tissue derived from mesoderm ACOELOMATES: No true body cavity Often soft-bodied organisms. Morphological Trends Tissues Porifera or Parazoa (sponges) lack true tissues (this is a unique development) 5
Morphological Trends Symmetry Radial vs bilateral Radial Top and bottom only-- no left or right Likely ancestral trait: Cnidarians, Ctenophores Multicellular; heterotrophic; complex embryo; no cell wall True tissues; diploblastic; radial symmetry ANCESTRAL PROTIST Metazoa Eumetazoa 770 million years ago 680 million years ago Bilateral symmetry; cephalization; triploblastic; body cavities (coelom) Cellular level/no tissues; asymmetric; skeleton of spicules and spongin Bilateria 670 million years ago Trends in the evolution of Animalia Deuterostomia Lophotrochozo a Ecdysozoa Porifera Ctenophora Cnidaria Acoela Hemichordata Echinodermata Chordata Platyhelminthes Syndermata Ectoprocta Brachiopoda Mollusca Annelida Nematoda Arthropoda The Molluscs >100,000 species (second only to the arthropods in numbers) Mostly marine, but 8,000 in freshwater 28,000 spp. of snails and slugs live on land reduced coelom Similar body plan, but modified in various ways: foot, visceral mass, mantle, shell, and radula 6
The lineages of Mollusca Gastropods (snails and slugs) Polyplacophorans (chitons) Bivalves (clams, scallops, mussels) Cephalopods (octopus, squid, nautilus) Scaphopods (tooth or tusk shells) Gastropods Bivalves 7
Polyplacophorans Scaphopods Cephalopods 8
Visceral mass Clam dissection details 9
Mouth? Anus? Scallops anyone? 10
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