Animal Diversity Lecture 2 PDF

Animal Diversity Leslie_s_flatworm Lecture 2 “Radiata” vs. Bilateria “Radiata” e.g. Phylum Cnidaria Dr. Serena Sgarzi School of Biology Bilateria – the coelom...

Animal Diversity Leslie_s_flatworm Lecture 2 “Radiata” vs. Bilateria “Radiata” e.g. Phylum Cnidaria Dr. Serena Sgarzi School of Biology Bilateria – the coelom & Environmental Science – Phylum Platyhelminthes Classes Turbellaria, Trematoda Slides by Prof. Tasman Crowe  Body Symmetry oral Radial aboral dorsal Bilateral posterior anterior ventral  Ectoderm Endoderm In some animals there are two germ layers (as above) - such animals are DIPLOBLASTIC.  Ectoderm Endoderm Mesoderm In most multicellular animals a third layer of cells develops between the outer and inner layer - these are TRIPLOBLASTIC ANIMALS Major groups of Eumetazoa “Radiata” Lopho- Deutero trochozoa - stomia diploblastic, Porifera Cnidaria Ecdysozoa radial symmetry e.g. cnidaria Bilateria Bilateria triploblastic, bilateral Eumetazoa symmetry Metazoa Ancestral Protist  “Radiata” e.g. Phylum Cnidaria  Phlylum Cnidaria Hydras and colonial hydroids  Phylum Cnidaria Jelly-fish & box jellies Phylum Cnidaria Anemones Phylum Cnidaria Corals  Phylum Cnidaria Eumetazoa (multicellular with tissues) radial symmetry diploblastic – 2 embryonic layers Ectoderm - epidermis of adult Endoderm - gastrodermis of adult + Mesoglea - jelly-like cementing layer – No Mesoderm no complex organs no head or centralised nervous system. Cnidaria have two body forms Polyp - sac-shaped, mouth directed upwards, surrounded by tentacles Medusa - flattened sac, mouth directed downwards.  Cnidarians are carnivores that use their tentacles to catch prey. Food enters the gastrovascular cavity via the mouth/anus BUT undigested food also exits via the mouth/anus. i.e. there is only one body opening  Cnidarians have nematocysts stinging or sticky cells for capture of prey or self defence 30 different kinds (spiky toxic and sticky) When triggered, evert at 2 m/s, acceleration of 40,000G! Among the fastest intracellular processes known. “Radiata” diploblastic, radial symmetry e.g. cnidaria Bilateria triploblastic, bilateral symmetry  Bilateria Three clades based on molecular analysis: LOPHOTROCHOZOA – Platyhelminthes, Annelida, Mollusca, etc. ECDYSOZOA – Nematoda, Arthropoda DEUTEROSTOMIA – Echinodermata, Chordates (including vertebrates e.g. man) see Campbell, Chapter 32 A biological basis for classification: body plans of the Bilateria Ectoderm Endoderm Mesoderm  The mesoderm may be either a solid layer or is split by a cavity or inner space. The body cavity is called a COELOM  Body cavities are a key feature of Bilaterian biology and are the basis for their classification into 3 major Body Plans. Campbell Chapter 32 BODY PLANS OF THE BILATERIA ACOELOMATE e.g. flatworm PSEUDOCOELOMATE Cavity between mesoderm & endoderm COELOMATE True coelom – develops within mesoderm  Acoelomate body plan e.g. Phylum Platyhelminthes  Phylum Platyhelminthes - flatworms MAJOR DEVELOPMENTAL ADVANCES bilateral symmetry – unidirectional movement moderate cephalization (i.e. head development) triploblastic condition - mesoderm gives rise to muscle tissue for movement some organs present (esp. excretory organs – protonephridia)  Phylum Platyhelminthes mostly marine free-living and parasitic species dorso-ventrally flattened …or parasitic acoelomate - no body cavity one body opening acts as mouth & anus  Phylum Platyhelminthes 3 Classes: Turbellaria – free living flatworms Trematoda – parasitic flukes Cestoda – parasitic tapeworms Class Turbellaria live in marine and free-living freshwater habitats flatworms head with light sensitive eyespots plus primitive “brain” mouth at tip of pharynx carnivorous: pharynx is muscular - sucks in prey gut has 3 blind-ending branches e.g. Dugesia - a freshwater species Class Trematoda - flukes endoparasites (pathogens humans & livestock) leaf-shaped anterior suckers – oral (surrounds mouth) – ventral gut similar to the free- living flatworms complex life cycle - one to many hosts, several larval forms Class Trematoda reproduction adults reproduce sexually each contains both male & female organs - hermaphrodite in copulation each individual fertilizes the other  Adults in Class primary host - Trematoda sheep life cycle eggs released in faeces e.g. Fasciola hepatica metacercaria infect primary host hatch into miracidium larva release cercarian larva Infect secondary host – snail - sporocyst develops into redia  Lancet flukes and zombie ants flukes have ants as tertiary host cercaria afflict ant nervous system behaviour changes so more ‘zombie ants’ likely to be eaten climb grass by sheep & attach to tips http://molluscs.at/gastropoda/index.html?/gastropoda/parasites/dicrocoelium.html SUMMARY: MAJOR GROUPS OF EUMETAZOA “Radiata”: diploblastic, radial symmetry e.g. Phylum Cnidaria (jelly fish, corals, etc.) Bilateria: triploblastic, bilateral symmetry - 3 clades: Lophotrochozoa, Ecdysozoa, Deuterostomia - 3 major body plans: acoelomate – e.g. Phylum Platyhelminthes (flatworms, flukes & tapeworms) pseudocoelomate – e.g. Phylum Nematoda (roundworms) coelomate – all other true multicellular animals  Further reading Campbell – relevant parts of Chapters 32 & 33 for more detail: Brusca and Brusca, Invertebrates Chapters 8 & 10. held in UCD main library (skim read only - for clarification and interest) remember to construct glossary of terms  Sample MCQs Assessments include MCQ questions on animal diversity – from lectures and pracs Which of the following is true of a fluke (Class: Trematoda) Free-living Diploblastic Coelomate Unicellular Dorsoventrally flattened  The diagram represents a TS of which of the following: Amoeba Dugesia Hydra Trypanosoma mesoderm Paramecium