2. Porifera - This course will focus on the This Metazoa -...

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Unformatted text preview: This course will focus on the This Metazoa - multicellular life Metazoa multicellular life We will be talking about Grades of Construction Body Architecture Development Origins and Diversity Morphological, Molecular Phylogenetics Morphological, Phylogenetics Fossil Evidence Ediacaria Cambrian Explosion Burgess Shale Fauna Direct vs Indirect Development Direct Direct = no free living larval stage mini-adult formed Indirect = Larval stage – Larval not similar to adult Free living Metamorphosis radical change to adult form Cell Fate - Will come back to this later Cell Developmental Patterns Regulative (Indeterminate) = Cell fate not set at 4 cell stage separate at 4 cell stage 4 identical individuals Patterns of cell division = Cleavage Patterns Cleavage Radial = regular, equal regular, (e.g., echinoderms) Spiral = unequal, oblique unequal, (e.g., molluscs) Mosaic (Determinate) = Cell fate set very early separate at 4 cell stage no development of complete animal Types of larvae: Benthic - bottom living Pelagic - in water column Planktotrophic - feeding in water column (plank = water column troph = feed) Invertebrates represent the vast majority of animal diversity on Earth Some will be familiar Many will not! Lecithotrophic - non-feeding feeding use stored yolk use (lecith = yolk) 1 Phylum Porifera (pore-bearers) Sponges Phylum Cnidaria Phylum Cnidaria Phylum Platyhelminthes Phylum Platyhelminthes flatworms Free Living and Parasitic Create habitat for a huge diversity of species Phylum Rotifera Phylum Rotifera wheel animals exhibit Cryptobiosis exhibit Cryptobiosis Phylum Annelida Phylum Annelida Polychaeta Oligochaeta Hirudinea 2 Phylum Arthropoda Phylum Arthropoda greatest # species described huge diversity of life styles, body structures, and morphologies Phylum Onychophora Only phylum found presently only on land Phylum Mollusca snails, clams, squids, octopus, etc. 2nd largest phylum Radula 3 Derived Marine Gastropods – Lost shell, many with chemical and structural defenses Phylum Brachiopoda Phylum Brachiopoda Primarily fossil species marine Phylum Bryozoa moss animals Phylum Echinodermata Phylum Echinodermata sea stars, urchins, sand dollars, cucumbers Phylum Chordata Phylum Chordata Phylum Phylum Hemichordata Hemichordata Solitary – each from single larva Social – asexual budding, not physiologically integrated 4 Simplest Animals - Protozoa Single Celled “Protista” - not a taxon. Is Polyphyletic. We will not use this term. It is a general term for unrelated groups that have small bodied taxa - also includes Giant Kelp! Very Diverse Know little about most species Some free living Some parasitic Good fossil record of those with skeletons Study these in lab this week. Phylum Porifera (pore-bearers) Sponges Important systems for : Hydrodynamics Symbiosis Chemical Biology Immunology (self-non self recognition, non immune memory) immune Called sponges - but are not!! Called PHYLUM PORIFERA ( = pore-bearer) bearer) Sponges Sponges Cellular grade Loose aggregation of cells Cells fairly independent Can reaggregate Major Features: Determined to be animals ~200 years ago ~8- 10,000 species Cellular grade of construction All aquatic – mostly marine All Sessile – can move some Size – 1-2cm ! >1m Size 2cm Symmetry – most have none, some ~radial some Early in fossil record, but don’t give rise to others Early “dead-end” phylum – but very successful phylum Unique Water Canal System OSTIA: water goes in OSCULA: water exits important for feeding, respiration, reproduction and excretion All processes depend on DIFFUSION All DIFFUSION No nervous system Poor development of contractile system 5 Water goes OUT the Osculum Water OUT Cell Types 1) EPITHELIAL = PINACOCYTES epidermis forms PINACODERM cover outside and inside of canals not firmly attached capable of feeding sometimes participates in skeletal secretion 2) Several types of AMOEBOCYTES in fluid layer inside pinacocytes in the mesoglia, secret skeleton, transport food from feeding cells a) archeocytes: form other cell types as they are needed, form gametes b) phagocytes: transport food c) collencytes: fixed, anchor d) sclerocytes: secrete skeletal spicules e) lophocytes: secrete spongin and IN the Ostia and IN Spongocoel = space within the sponge SKELETAL SECRETIONS: SPICULES: CaCO3 or SiO2 sclerocyte – divides into 2 cells – one begins formation and lengthens, other thickens spicule three basic shapes: monaxon, triaxon, hexaxon Siliceous Siliceous microfossils microfossils Most are calcium carbonate but some are made of silica Even though they are loose rods in goo - they give structural strength in and stiffness to sponges Biomechanical work by MAR Koehl Biomechanical Koehl (1982) Mechanical design of (1982) spicule-reinforced connective tissues: spicule reinforced Stiffness. J. Exp. Biol. 98: 239-268. 98 268. SPONGIN: Protein secreted by lophocytes tough – resistant scleroprotein – bath sponges – Endangered in most parts of the world due to over harvesting Massive CaCO3 secreted outside of the body probably secreted by epithelium has silicious spicules as well 6 3) POROCYTES (surround OSTIA) guard ostia not in all sponges 4) No Nerve or Sensory Cells but can receive sensory input by cell-cell communication 5) CONTRACTILE = MYOCYTES in mesoglia have contractile elements contact each other by filopodia - can result in coordinated behavior 6) CHOANOCYTES and FEEDING COLLAR CELLS read Sherman & Sherman & Brusca and Brusca have flagella inside collar made of pseudopodia creating microvilli flagellum creates water current food trapped in microvilli, phagocytized no coordination or coordinated movement among choanocytes choanocytes show up in other groups as well 7) MESOHYL Between outer epithelial cells and collar cells Filled with organic jellylike EXTRACELLULAR MATRIX, supports delicate cells Polysaccharide with fine fibrils 7 ...
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