Animal Diversity Introduction

BLY102 (GENERAL BIOLOGY II) ANIMAL DIVERSITY INTRODUCTION • Animal diversity deals with natural history, classification, characteristics ,conservation and distribution information on thousands of animal species. • About 1.3million living species have been identified. • With this large variety of animals scientists must find a meaningful way of classifying, identifying and naming them. Olatubi I.V 2 CLASSIFICATION • Generally, all animals are grouped into these ranks. • Kingdom • Phylum • Class • Order • Family • Genus • Species Olatubi I.V 3 IDENTIFICATION • All animals are given two names termed ‘Binomial Nomenclature’ • First name is from the Genus the animal belongs • Second name is the name of the Species to which it belongs • For example; Homo sapiens Olatubi I.V 4 FEATURES OF ANIMALS • Some features common to all animals are highlighted below: • Mode of Nutrition: Heterotrophic. • Cell structure (Eukaryotes, no cell wall, body held together by structural proteins such as collagen) • Nervous and muscle tissues are unique to animals. • Reproduction is sexual with diploid stage dominating life cycle: • Cleavage: either spiral in Protostome or radial/ intermediate in Deuterostome. • Possess at least one larval stage Olatubi I.V 5 FEATURES OF ANIMALS cont’d • Hox genes (unique to animals): regulates the development of body forms. • Body plan (radial/bilateral, cephalization (head)). • Tissues: ectoderm(embryo surface), endoderm (archenteron),mesoderm. • *diploblastic, triploblastic • Body cavity: true coelom(derived from the mesoderm),pseudo: derived from the mesoderm and endoderm. Olatubi I.V 6 THE PROTOZOA • Derived from the greek word protos=first, zoon=animal. • They are the first assemblage of eukaryotic unicellular organisms with animal like features. • protozoans are the simplest forms of animal life Characteristics They are unicellular organisms but some are with multicellular stages in their life cycle. They show an amazing degree of differentiation at their protoplasmic level of organization. They are mostly microscopic. Many have no body axis no plane of symmetry and bodies are not divided into cells no tissues no organ. They posses functional units termed organelles. Olatubi I.V 7 THE PROTOZOA ‘xtics cont’d Locomotion is by any of the three organelles; pseudopodia, flagella and cilia. Nutrition is either autotrophic or heterotrophic. Heterotrophic forms may also be saprozoic taking in dissolved substances in their surrounding by diffusion active transport or pinacytosis. Reproduction is by Asexual and Sexual means. asexual reproduction is by binary fission, multiple fission or schizogony and budding. In sexual reproduction when nuclear material is exchanged between mates the sexual reproduction is called conjugation. Embryonic development does not occur some protozoans. occur in colonies and certain colonials 2 types of vacuoles are present food vacuole Into which food accumulates. contractile vacuole or water expulsion vesicles(wev) which function principally in osmoregulation Olatubi I.V 8 CLASSIFICATION It is difficult to classify protozoans particularly on the account of numerous modification of their life cycle but has been classified into four classes based on its locomotary organs 1. Class Rhizopoda - Locomotary organ: pseudopodia Mostly free living, some are parasitic Examples: Amoeba, Entamoeba 2. Class Mastigophora/ Flagellata - Locomotory organ: Flagella Free living or parasite. Body covered with cellulose, chitin or silica. Examples: Giardia, Euglena, Trypanosoma Olatubi I.V 9 CLASSIFICATION cont’d 3. Class Sporozoa - Locomotory organ: Absent Exclusively endoparasites Examples: Plasmodium, Monocystis 4. Class Ciliata - Locomotary organ: Cillia Nuclei two types i.e. Macronucleus and Micronucleus. Examples: Paramecium, Voricella, Blantidium 0 Olatubi I.V 1 PHYLUM PORIFERA Derived from Latin words “porus”= pore and “Ferre” = bear Characteristics Sponges are multicellular organisms having a variety of shapes. Some form crusts, some are simple tubes, some are vase shape while others can be cup shaped, massive clumps, fan shaped, finger like bulges, treelike or even bushy. They maybe soft, brittle or hard and asymmetrical but some are radially symmetrical. They posses Spicules which forms the skeletal structure where they interlock to form a delicate framework of tubes inside and outside the body and on this basis they are classified. False body cavity and all the cells and tissues surround a water filled space. 1 Ol atubi I.V 1 PHYLUM PORIFERA cont’d Members also possess: a few tissues with no organs. Three main layers of their body structure are: a layer of flattened epidermal cells, a semi fluid matrix and a layer of flagellated collar cell. Numerous pores by means of which water and other plankton enter the sponge body. Also used to control water flow through the spongocoel (body cavity). Flagellated cells to circulate water through a unique system of water canals. No proper digestive, nervous or circulatory system. Unique water canal system which are of three types – Asconoid, Syconoid and Leuconoid. 2 Olatubi I.V 1 PHYLUM PORIFERA cont’d The power of cell aggregation is tremendous in sponges. If cut into a million minute pieces, they can still come together and re-form into a fully functional sponge. Excretion and respiratory (gas exchange) occurs by simple diffusion Most cells of freshwater sponges contain contractile vacuoles for osmoregulation. Reproduction can be asexual or sexual; Asexual reproduction is either by fragmentation or budding Sexual reproduction is by the production of sperms from the choanocytes and eggs in the mesohyl. Sponges are generally hermaphroditic, but can be only one gender at a time, being either male or female 3 Olatubi I.V 1 CLASSIFICATION 1. Class Calcarea: This class consists of members with calcareous spicules occuring in shallow waters. Examples are Caltrina, Schypha, Leucosolenia. 2. Class Hexactinelida: members are the ‘glass sponges’ with siliceous spicules. They consist of a small group in the deep sea; their growth is orientated to the constant water currents there. Their tissues are 75% syncitial (lacking cell boundaries). Even the choanocytes are not separate cells. There are no pinacocytes and no cells with any contractility. The skeleton is a lattice made from six-rayed spicules of silica. Examples are Hyalonema(glass rope sponge), Euplectella (venus flower basket) 4 Olatubi I.V 1 CLASSIFICATION CONT’D 3. Class Demospongiae: Some are with siliceous spicules (Examples are Halichondria, the breadcrumb sponge) and others without spicules but only protein fibres (an example is the Spongia, the once commonly used bath sponge). Venus flower basket 5 bath sponge Olatubi I.V 1 PHYLUM CNIDARIA Characteristics • They are mostly marine except for hydra which is the fresh water form. • They may be sedentary or free swimming. • They are radially symmetrical and their body has two or three layers a gastrovascular cavity and • a single opening that serves as both mouth and anus which is usually surrounded by tentacles. • They possess special stinging cells called cnidocytes or cnidoblasts which helps in food capture defence mechanism and adhesion in the case of sessile cnidarian 6 Olatubi I.V 1 PHYLUM CNIDARIA cont’d • They are carnivorous and exhibit both extracellular digestion i.e. inside the nutritive cells of the endodermis. • process such as respiration and excretion occur by simple diffusion. • The nervous system is primitive and consist of a diffused net of nerve cells. • The soft body of cnidarians may be naked or supported by calcareous exoskeleton or endoskeleton. 7 Olatubi I.V 1 PHYLUM CNIDARIA cont’d • Many cnidarians exhibit polymorphism i.e. they exist in 2 different forms • ---a polyp: a tubular body form usually sessile- • ---a medusa: an umbrella shaped free swimming body form. • Polyp represent the asexual phase while the medusa represent the sexual phase of the lifecycle • a polyp give rise to medusa asexually by budding and a medusa produces polyps by sexual reproduction in which fertilized eggs develop into a ciliated free swimming planula larva. This process is termed alternation of generations/metagenesis 8 Olatubi I.V 1 CLASSIFICATION 1. Class Anthozoa • Anemones and most corals belongs to this class members are Polyps with vertical divisions(mesenteries) in the coelenteron. • They have no medusa forms. They are grouped into 2 ---alyconaria: polyps with eight mesenteries and typically eight branched tentacles Examples are Sea pens, Branching corals, Soft corals ---zoantharia: typically with six or twelve mesenteries and variable numbers of simple tentacles Examples are Anemones and True oceanic reef-buildingcorals 9 Olatubi I.V 1 CLASSIFICATION CONT’D 2. Class Scyphozoa: • In this class the medusa form is dominant but may develop from a transient polyp-like sessile stage. • Jellyfish are very common in all oceans; they may penetrate shallow seas or be washed ashore. 3. Class Cubozoa: • Their Medusae is with four sides and a marginal shelf • Found in tropical seas, e.g. Australia, where they are known as ‘sea wasps’ and can be poisonous to humans. • They are very different from scyphozoa by having elaborate eyes Examples include Box jellies 0 Olatubi I.V 2 CLASSIFICATION CONT’D 4. Class hydrozoa: • Typically with both polyp and medusa stages in the life cycle. • The polyps are small, without mesenteries in the coelenteron, and the medusa may have a shelf Examples are Hydra, Physalia,Obelia, Tubularia • Hydra lives

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