Learning Objectives The Animal Kingdom: An Introduction to Animal Diversity
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4/2/2012 Learning Objectives The Animal Kingdom: An Introduction to Animal Diversity Chapter 29 Kingdom Animalia Animal Characteristics: • Multicellular Eukaryotic • Heterotrophic • Cells specialized for specific functions Charecteristics that most animals have • Most are capable of locomotion at some time during life cycle • Most can respond to external stimuli • Most can reproduce sexually Animals live inEnvironments diverse Environments Marine • Provide • relatively stable temperatures • buoyancy • readily available food • Fluid and salt balance • more easily maintained than in fresh water • What characters are common to most animals? • Advantages and disadvantages of different environments • Searching for relationships (phylogeny) • Phylum Protista • Phylum Cnidaria • Phylum Ctenophora Sexual Reproduction • Sperm and egg unite (zygote) • Zygote undergoes cleavage • cell divisions produce hollow ball of cells (blastula) • • Blastula undergoes gastrulation • forms embryonic tissues Fresh Water Environments • Provides • less constant environment • less food • Animals must osmoregulate • fresh water is hypotonic to tissue fluid • Disadvantages: • currents and other water movements 1 4/2/2012 Terrestrial Environments • Have adaptations that: • protect them from drying out • protect them from temperature changes • protect their gametes and embryos Animall Fossils • Earliest Known animal fossils 600 mya– 540 mya Small simple critters Suggests sponges, jelly fish were present • Molecular evidence indicates: - genes that control development, rna, other molecules similar among all animal groups - suggests a common ancestor - monophyletic Relationships Based on Structure (True tissues) • How do we determine relationships among animal phyla? • Genetics • Structure Radial and Bilateral Symmetry 2. Body Cavity • What is it? - The space between the body wall and the digestive tube • “Coelom” (pronounced: see lome) • 3 types of body cavities - Acoelomates (no cavity) - Psuedocoelomates (false cavity) - Coelomates (true cavity) 2 4/2/2012 Germ layers: embryonic tissue layers Endoderm Ectoderm Mesoderm Ectoderm - epidermis and nervous tissue Endoderm - lining of gut and some digestive organs Mesoderm - most body structures (bones, muscles, circulatory system) Triploblastic vs Diploblastic Body Cavities in Triploblastic critters Epidermis (from ectoderm) Pseudocoelom Muscle layer (from mesoderm) Epidermis (from ectoderm) Muscle layer (from mesoderm) Mesenchyme (gelatin-like tissue) (a) Acoelomate—flatworm (liver fluke). Epithelium (from endoderm) Epithelium (from endoderm) (b) Pseudocoelomate—nematode. Fig. 29-4a, p. 624 Fig. 29-4b, p. 624 Bilateral Animals Coelom • Two major evolutionary branches: Epidermis (from ectoderm) Muscle layer (from mesoderm) Peritoneum (from mesoderm) • Protostomia Epithelium (from endoderm) Mesentery (from mesoderm) • Deuterostomia (c) True coelomate—vertebrate. Fig. 29-4c, p. 624 3 4/2/2012 Coelom Formation Blastopore • Opening from embryonic gut to outside • In protostomes • develops into the mouth • In deuterostomes • becomes the anus Cleavage Spiral and Radial Cleavage • Protostomes • undergo spiral cleavage • early cell divisions diagonal to polar axis Protostomes • Deuterostomes • undergo radial cleavage • early cell divisions either parallel or at right angles to polar axis • cells lie directly above or below one another Dueterostomes Relationships Based on Structure Cleavage (True tissues) • Protostomes • undergo determinate cleavage • fate of each embryonic cell is fixed very early • Deuterostomes • undergo indeterminate cleavage • fate of each embryonic cell is more flexible 4 4/2/2012 Molecular Systematics Take home message • Biologists classify animals based on their body plan and features of their early development • Confirmed much of animal phylogeny based on structural characters • including axiom that animal body plans usually evolved from simple to complex Parazoa Eumetazoa Bilateria Radiata Acoelomates Coelomates Pseudocoelomates Protostomia Porifera Deuterostomia Segmentation Segmentation Pseudocoelom Deuterostome development True coelom Radial symmetry Protostome development Three tissue layers (mesoderm) Bilateral symmetry Tissues (ectoderm and endoderm) Multicellularity Choanoflagellate ancestor Fig. 29-7, p. 627 Phylum Porifera Phylum: Porifera (Sponges) • 10,000 species, mainly marine • Sponges • animals characterized by flagellate collar cells (choanocytes) 5 4/2/2012 Sponge Structure Porifera (Sponges) “to have pores” • Sponge body • Primitive animalsLack symmetry - some radial • No tissues • No gut - intracellular digestion • sac with tiny openings for water to enter • central cavity (spongocoel) • open end (osculum) for water to exit • • Sponge cells • loosely associated • do not form true tissues Osculum Porifera Life? Water movement Incurrent pores Spongocoel • • • • Epidermal cell Porocyte Spicule Flagellum Microvillus Nucleus Collar cell Amoeboid cell in mesohyl Collar Gas exchange? Food? Waste? Sex? - Asexual - Sexual (most are hermaphrodites) - amoeboid cells develop into gametes - cross fertilize Fig. 29-9b, p. 630 Parazoa Radiata • • • • • • Absorb food through cell No nervous system Skeletal system of spicules Swimming larvae Gas exchange by diffusion http://www.biology.ualberta.ca/cours es.hp/zool250/animations/Porifera.sw f Eumetazoa Bilateria Coelomates Pseudocoelomates Porifera Protostomia Deuterostomia Cnidaria Porifera (Sponges) Acoelomates Segmentation Segmentation Pseudocoelom Deuterostome development True coelom Radial symmetry Protostome development Three tissue layers (mesoderm) Bilateral symmetry Tissues (ectoderm and endoderm) Multicellularity Choanoflagellate ancestor Fig. 29-7, p. 627 6 4/2/2012 Phylum: Cnidaria - ~10,000 spp. •Jelly fish •Anemones •Coral Phylum: Cnidaria • • • • • • • Body radially symmetrical Body a hollow sac Mouth serves to ingest food and expel wastes Two tissue layers - Diploblastic - ectoderm - epidermis - endoderm - gastrodermis (digestion) separated by the mesoglea Digestion is extracellular!!! Sexual and asexual Cnidocytes that contain Nematocysts! - Two types of body forms Radial Symmetry 7 4/2/2012 Nematocysts Phylum Cnidaria • Gastrovascular cavity – with single opening for mouth and anus – Forms a hydrostatic skeleton • Nerve cells (not really) form irregular nerve nets – sensory cells with contractile ability Mouth Class Hydrozoa Epidermis •Polyp body form •Fresh water •Sessile •Asexual/Sexual Mesoglea Gastrodermis Gastrovascular cavity Class Hydrozoa (polyp) Mouth Class: Schyphozoa (Jellyfish) Fig. 29-10a, p. 633 Mesoglea Gastrodermis Epidermis Gastrovascular cavity Sexes separate Males release sperm through mouth!! Class Scyphozoa (medusa) 8 4/2/2012 http://www.youtube.com/watch?v=oHiVA9J _YIM Mouth Tentacle Medusae . Class Cubozoa (“box jellyfish”) Feeding polyp – have complex eyes that form blurred images – 4 tentacles – Fast! Active Hunters Medusa bud Reproductive polyp Gastrovascular cavity Egg Sperm Planula larva Polyp colony Young polyp colony (b) Life cycle of Obelia. Fig. 29-13b, p. 635 Mouth Class: Anthozoa (sea anemones + coral) Epidermis Mesoglea Gastrodermis Gastrovascular cavity Class Anthozoa (polyp) Fig. 29-10c, p. 633 Class: Anthozoa (sea anemones + coral) • Individual and colonial forms • No free swimming medusa stage • Coral - Colonies - Symbiotic relationship with algae (Zooxanthellae) - Secrete a matrix on which calcium carbonate is deposited - Tremendous biodiversity - “Bleaching” (bacteria? Temp.? Ph.) 9 4/2/2012 http://www.archipelago.co.uk/project/whatis-coral-bleaching-animation/ Do not post photos on Internet Fig. 28.11 Parazoa Radiata Ctenophora Porifera Cnidaria Acoelomates Eumetazoa Bilateria Phylum Ctenophora (comb jellies) (100 spp.) Coelomates Pseudocoelomates Protostomia Deuterostomia • Radial symetry, Medusa body form - NO Cnidocytes, Cilia like combs on tenticles Segmentation Segmentation •fragile, luminescent marine predators •eight rows of cilia that resemble combs True coelom Radial symmetry •tentacles with adhesive glue cells Protostome development Three tissue layers (mesoderm) Bilateral symmetry Tissues (ectoderm and endoderm) Multicellularity Fig. 29-7, p. 627 Parazoa Eumetazoa Bilateria Hemichordata Chordata Echinodermata Mollusca Annelida Deuterostomia Arthropoda Tardigrada Nematoda Nemertea Platyhelminthes Cnidaria Ctenophora http://www.youtube.com/watch?v=G7WT81ukHZE Coelomates Acoelomates Pseudocoelomates Protostomia Porifera Comb Jelly Choanoflagellates Radiata Onychophora Choanoflagellate ancestor Rotifera Pseudocoelom Deuterostome development Segmentation Segmentation Pseudocoelom Deuterostome development True coelom Radial symmetry Protostome development Three tissue layers (mesoderm) Bilateral symmetry Tissues (ectoderm and endoderm) Multicellularity Choanoflagellate ancestor Fig. 29-7, p. 627 10 4/2/2012 Parazoa Eumetazoa Bilateria Chordata Hemichordata Arthropoda Onychophora Tardigrada Nematoda Rotifera Annelida Lophophorate phyla Mollusca Nemertea Platyhelminthes Cnidaria Ctenophora Ecdysozoa Lophotrochozoa Echinodermata Deuterostomia Protostomia Porifera Choanoflagellates Radiata Segmentation Segmentation Segmentation Protostome pattern of development Radial symmetry Deuterostome pattern of development Bilateral symmetry, three tissue layers, body cavity Tissues Multicellularity Choanoflagellate ancestor Fig. 29-8a, p. 629 11
