Learning Objectives. The Animal Kingdom: An Introduction to Animal Diversity. Sexual Reproduction

Transcription

1 Learning Objectives The Animal Kingdom: An Introduction to Animal Diversity Chapter 29 What characters are common to most animals? Advantages and disadvantages of different environments Searching for relationships (phylogeny) Phylum Protista Phylum Cnidaria Phylum Ctenophora 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 Sexual Reproduction Sperm and egg unite (zygote) Zygote undergoes cleavage cell divisions produce hollow ball of cells (blastula) Blastula undergoes gastrulation forms embryonic tissues Marine Environments Animals live in diverse Environments Provide relatively stable temperatures buoyancy readily available food Fluid and salt balance more easily maintained than in fresh water 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

2 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

3 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 (from ectoderm) Pseudocoelom Muscle layer (from mesoderm) Mesenchyme (gelatin-like tissue) Epithelium (from endoderm) (a) Acoelomate flatworm (liver fluke). (from ectoderm) Muscle layer (from mesoderm) Epithelium (from endoderm) (b) Pseudocoelomate nematode. Fig. 29-4a, p. 624 Fig. 29-4b, p. 624 (from ectoderm) Muscle layer (from mesoderm) Peritoneum (from mesoderm) Coelom Bilateral Animals Two major evolutionary branches: Protostomia Epithelium (from endoderm) Mesentery (from mesoderm) (c) True coelomate vertebrate. Deuterostomia Fig. 29-4c, p

4 Coelom Formation Blastopore Opening from embryonic gut to outside In protostomes develops into the mouth In deuterostomes becomes the anus Cleavage Protostomes undergo spiral cleavage early cell divisions diagonal to polar axis Deuterostomes undergo radial cleavage early cell divisions either parallel or at right angles to polar axis cells lie directly above or below one another Spiral and Radial Cleavage Protostomes Dueterostomes Cleavage Relationships Based on Structure (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

5 Porifera 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 Radiata Bilateria Acoelomates Pseudocoelomates Protostomia Coelomates Deuterostomia Pseudocoelom Deuterostome development Radial symmetry True coelom Choanoflagellate ancestor Protostome development Three tissue layers (mesoderm) Bilateral symmetry Tissues (ectoderm and endoderm) Multicellularity Fig. 29-7, p. 627 Phylum: Porifera (Sponges) 10,000 species, mainly marine Sponges animals characterized by flagellate collar cells (choanocytes) Phylum Porifera 5

6 Water movement Porifera Cnidaria 4/2/2012 Sponge Structure Sponge body 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 Porifera (Sponges) to have pores Primitive animals- Lack symmetry - some radial No tissues No gut - intracellular digestion Flagellum Incurrent pores Osculum Spongocoel Epidermal cell Porocyte Spicule Microvillus Nucleus Collar cell Amoeboid cell in mesohyl Porifera Life? Gas exchange? Food? Waste? Sex? - Asexual - Sexual (most are hermaphrodites) - amoeboid cells develop into gametes - cross fertilize Collar Fig. 29-9b, p. 630 Porifera (Sponges) Parazoa Eumetazoa Radiata Bilateria Acoelomates Pseudocoelomates Protostomia Coelomates Deuterostomia Absorb food through cell No nervous system Skeletal system of spicules Swimming larvae Gas exchange by diffusion es.hp/zool250/animations/porifera.sw f Radial symmetry Choanoflagellate ancestor Pseudocoelom Deuterostome development True coelom Protostome development Three tissue layers (mesoderm) Bilateral symmetry Tissues (ectoderm and endoderm) Multicellularity Fig. 29-7, p

7 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

8 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 Polyp body form Fresh water Sessile Asexual/Sexual Class Hydrozoa Mouth Mesoglea Gastrodermis Gastrovascular cavity Class Hydrozoa (polyp) Fig a, p. 633 Class: Schyphozoa (Jellyfish) Mouth Mesoglea Gastrodermis Gastrovascular cavity Sexes separate Males release sperm through mouth!! Class Scyphozoa (medusa) 8

9 _YIM Feeding polyp Mouth Tentacle Medusa bud Reproductive polyp Medusae Egg Sperm. Class Cubozoa ( box jellyfish ) have complex eyes that form blurred images 4 tentacles Fast! Active Hunters Gastrovascular cavity Planula larva Polyp colony Young polyp colony (b) Life cycle of Obelia. Fig b, p. 635 Mouth Class: Anthozoa (sea anemones + coral) Mesoglea Gastrodermis Gastrovascular cavity Class Anthozoa (polyp) Fig c, 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

10 Porifera Cnidaria Ctenophora Choanoflagellates Porifera Cnidaria Ctenophora Platyhelminthes Nemertea Nematoda Rotifera Tardigrada Onychophora Arthropoda Annelida Mollusca Echinodermata Hemichordata Chordata 4/2/ Do not post photos on Internet Fig Parazoa Eumetazoa Radiata Bilateria Acoelomates Pseudocoelomates Protostomia Coelomates Deuterostomia Phylum Ctenophora (comb jellies) (100 spp.) Radial symetry, Medusa body form - NO Cnidocytes, Cilia like combs on tenticles Radial symmetry Choanoflagellate ancestor Pseudocoelom Deuterostome development True coelom Protostome development Three tissue layers (mesoderm) Bilateral symmetry Tissues (ectoderm and endoderm) Multicellularity Fig. 29-7, p. 627 fragile, luminescent marine predators eight rows of cilia that resemble combs tentacles with adhesive glue cells Comb Jelly Parazoa Eumetazoa Radiata Bilateria Acoelomates Pseudocoelomates Protostomia Coelomates Deuterostomia Pseudocoelom Deuterostome development Radial symmetry True coelom Choanoflagellate ancestor Protostome development Three tissue layers (mesoderm) Bilateral symmetry Tissues (ectoderm and endoderm) Multicellularity Fig. 29-7, p

11 Choanoflagellates Porifera Cnidaria Ctenophora Platyhelminthes Nemertea Mollusca Annelida Lophophorate phyla Rotifera Nematoda Tardigrada Onychophora Arthropoda Echinodermata Hemichordata Chordata 4/2/2012 Parazoa Radiata Eumetazoa Bilateria Protostomia Lophotrochozoa Ecdysozoa Deuterostomia 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