Environmental Sciences Module 09 Animal Diversity: Origin and Classification

Paper No: 03 Biodiversity and Conservation Module:09 Animal Diversity: Origin and Classification Development Team Prof. R.K. Kohli Principal Investigator & Prof. V.K. Garg & Prof. Ashok Dhawan Co- Principal Investigator Central University of Punjab, Bathinda Dr Sunil Mittal Paper Coordinator Central University of Punjab, Bathinda Dr R.K. Chaitanya Content Writer Central University of Punjab, Bathinda Dr. Sunil Mittal Content Reviewer Central University of Punjab, Bathinda Anchor Institute Central University of Punjab Paper 03 Biodiversity and Conservation Environmental Sciences Module 09 Animal Diversity: Origin and Classification Description of Module Subject Name Environmental Sciences Paper Name Biodiversity and Conservation Module Animal Diversity: Origin and Classification Name/Title Module Id EVS/BC-III/09 Pre-requisites Objectives To learn about Animal Diversity, its origin and classification Keywords Ectodermic, endodermic, diploblastic, triploblastic Paper 03 Biodiversity and Conservation Environmental Sciences Module 09 Animal Diversity: Origin and Classification Module 09: Animal Diversity: Origin and Classification 1. Introduction 2. Evolutionary origin of animals 3. Animal Classification 3.1. Carolus Linnaeus classification 3.2. Five kingdom classification 3.3. Three domain classification: Tree of Life 3.4. Other animal classification systems 4. Description of animal phyla 5. Salient features of different phyla in the animal kingdom 6. Animal germ layers and their derivatives 7. Larval forms of various animals 8. State animals and birds Paper 03 Biodiversity and Conservation Environmental Sciences Module 09 Animal Diversity: Origin and Classification 1. Introduction Among the 5 major kingdoms of biodiversity, the KindomAnimalia is one of the important one. All the members of this kingdom are multicellular, eukaryotes and heterotrophs. Most of the members can move independently and are regarded as motile. As per estimates, there are around 9 to 10 million species of animals and among these about 8 lakh species have been identified. India has only 2.4% of global land area but contains 7-8% of globally recorded species. Over 46,000 species of plants and 96,000 species of animals are recorded in India. Animals may lack symmetry or may have radial or bilateral symmetry. Bilaterally symmetrical animals have dorsal and ventral sides, as well as anterior and posterior ends. There are three major clades of bilaterian animals: Deuterostomia, Lophotrochozoa, and Ecdysozoa. With one exception, the phyla in these clades consist entirely of invertebrates, animals that lack a backbone; Chordata is the only phylum that includes vertebrates, animals with a backbone. They have been classified/subdivided into many categories on different basis as discussed in this module. The module discusses the evolutionary origin of animals, different animal classification systems, animal germ layers and their derivatives, State animals and birds etc. 2. Evolutionary origin of animals The history of animals spans more than half a billion years. Fossil biochemical evidence and molecular clock analyses indicate that animals arose over 700 million years ago. Genomic analyses suggest that key steps in the origin of animals involved new ways of using proteins that were encoded by genes found in choanoflagellates. This table provides an overview of how animals evolved from their distant common ancestor over four geologic eras. Era Period Age (Millions Important Events of years ago) Neoproterozoic Ediacaran 560-542 soft-bodied; radially symmetric invertebrate animals appear (fossils: Mawsonitesspriggi, Sprigginafloundersi, Cloudina, Paper 03 Biodiversity and Conservation Environmental Sciences Module 09 Animal Diversity: Origin and Classification Dickinsoniacostata) Paleozoic Cambrian 542-488 Sudden increase in diversity of many animal phyla (Cambrian explosion) (fossils: Pikaia(eel-like chordate, Marella (small arthropod, Anomalocaris(large animal with grasping limbs and a circular mouth), and Hallucigenia(animals with toothpick-like spikes Ordovician 488-444 Colonization of land by animals; invertebrates dominated Silurian 444-416 Radiation of crinoids; a continued proliferation and expansion of the brachiopods, and the oldest known fossils of coral reefs; also marks the wide and rapid spread of jawless fish Devonian 416-359 Diversification of bony fishes; first tetrapods and insects appear (Fossils: Coccosteuscuspidatus, Tiktaalik) Carbonifero 359-299 Origin of reptiles; amphibians dominant us Permian 299-251 Radiation of reptiles; origin of most present-day groups of insects; extinction of many marine and terrestrial organisms at end of period (Fossils: Dimetrodon, the largest known carnivore of its day) Paper 03 Biodiversity and Conservation Environmental Sciences Module 09 Animal Diversity: Origin and Classification Mesozoic Triassic 251-199.6 Dinosaurs evolve and radiate; origin of mammals Jurassic 199.6-145.5 Dinosaurs abundant and diverse (Fossil: Rhomaleosaurus victor, a plesiosaur) Cretaceous 145.5-65.5 Dinosaurs become extinct at end of period Cenozoic Paleogene 65.5-23 Major radiation of mammals, birds, and pollinating insects; Origins of many primate groups Neogene 23-2.6 Continued radiation of mammals; Appearance of bipedal human ancestors Quaternary 2.6-0.01 Ice ages; origin of genus Homo 3. Animal Classification 3.1.Carolus Linnaeus classification All modern classification systems have their roots in the Carolus Linnaeus classification system. His two most important contributions to taxonomy were: i) A hierarchical classification system: species are grouped in increasingly broad taxa: Related genera are placed in the same family, families in orders, orders in classes, classes in phyla, phyla in kingdoms; ii) The system of binomial nomenclature (a 2-part naming method): Genus: The first part of the binomial to which the species belongs. The first letter of the genus is always capitalized, Specific epithet: The second part of binomial, is unique for each species within the genus, Entire binomial is italicized and scientific names are in Latin 3.2. Five kingdom classification Many biologists including R.H. Whittaker recognized five kingdoms:Monera (prokaryotes), Protista (a diverse kingdom consisting (mostly of unicellular organisms), Plantae, Fungi, andAnimalia.However, phylogenies based on genetic data soon began toreveal a problem Paper 03 Biodiversity and Conservation Environmental Sciences Module 09 Animal Diversity: Origin and Classification with this system: Some prokaryotes differ asmuch from each other as they do from eukaryotes. Such difficultieshave led biologists to adopt a three-domain system. 3.3.Three domain classification: Tree of life The three-domain system is a biological classification introduced by Carl Woese et al. in 1977 that divides cellular life forms into archaea, bacteria, and eukaryote domains. Tree of life is based in part on sequence comparisons of rRNA genes or rDNA 3.4. Other animal classification systems Paper 03 Biodiversity and Conservation Environmental Sciences Module 09 Animal Diversity: Origin and Classification i) Animal classification based on level of organization: a) Cellular level of organisation: Animal kingdom is divided into two subkingdoms- protozoa and metazoa. Protozoa are defined as single-celled eukaryotic organisms and metazoa are multicellular eukaryotic organisms. The sub-kingdom metazoa is further sub-divided into two branches: parazoa and eumetazoa. Parazoa: Cells are arranged as loose cell aggregates, i.e., they exhibit cellular level of organisation; absence of tissue or organ system level of organisation. Eg. Phylum porifera Eumetazoa: Clade comprising all major animal phyla except porifera. Embryo gets layered during gastrulation. Exhibit either tissue or organ system level of organisation. b) Tissue level of organisation: In phylum Cnidaria and Ctenophora, the arrangement of cells is more complex. Here the cells performing the same function are arranged into tissues. c) Organ level of organization: Organ level is exhibited by members of Platyhelminthes and other higher phyla where tissues are grouped together to form organs, each specialised for a particular function. ii) Animal classification based on symmetry a) Symmetry: Animals can be categorised on the basis of their symmetry. b) Asymmetry: Sponges are mostly asymmetrical, i.e., any plane that passes through the centre does not divide them into equal halves. c) Radial symmetry: When any plane passing through the central axis of the body divides the organism into two identical halves, it is called radial symmetry. Cnidarians, ctenophores and echinoderms have this kind of body plan. In phylum Echinodermata, larval stages are bilaterally symmetrical and adult stages are radially symmetric. Paper 03 Biodiversity and Conservation Environmental Sciences Module 09 Animal Diversity: Origin and Classification d) Bilateral symmetry: Animals like annelids, arthropods, etc., where the body can be divided into identical left and right halves in only one plane, exhibit bilateral symmetry iii) Animal classification based on Number of germ layers: In all the animals except sponges, the embryo becomes layered during gastrulation. As development progresses, these layers, called germ layers, form the various tissues and organs of the body. a) Diploblastic animals: Animals in which the cells are arranged in two embryonic layers, an external ectoderm and an internal endoderm, are called diploblastic animals, e.g., Cnidarians and Ctenophores.

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