UNIT 8 MODERN TRENDS IN ANIMAL TAXONOMY Structure 8.1 Introduction Objectives 8.2 Taxonomists as Synthesisers 8.3 Taxonomy, Systematics and Biosystematics 8.4 Stages in Taxonomic Procedures 8.4.1 Alpha Taxonomy 8.4.2 Beta Taxonomy 8.4.3 Gamma Taxonomy 8.5 Neotaxonomy 8.6 Electron Microscopy in Taxonomy 8,7 Embryological Approach in Taxonomy 8.8 Ecological Approach in Taxonomy 8.9 Ethological Approach in Taxonomy 8.10 Cytological Approach in Taxonomy 8.10.1 DNA Hybridisation 8.10.2 Karyological 8.11 Biochemical Approach in Taxonomy 8.11.1 Chromatography 8.1 1.2 Electrophoresis 8.11.3 Immunological Technique or Immunotaxonomy 8.12 Numerical Taxonomy 8.13 Summary 8.14 Terminal Questions 8.15 Answers 8.1 INTRODUCTION In Unit 6, you learnt how taxonomy is interrelated to other biological fields. You also learnt how information is used from other fields of biology along with morphological data in the identification of a large number of plant species. Similarly, in this unit you will see how often morphological observations are not sufficient for accurately identifying or classifying animals and taxonomists have to, supplement their information from other scientific fields such as electron microscopy, embryology, ethology, cytology, biochemistry and computer analysis. Furthermore, you will learn that the use of such data has given taxonomy a much wider dimension. It is now no longer limited to just classifying animals but is also involved in working out the phylogenetic relationship between species. As a result taxonomy is now a part of systematics or biosystematics on which it relies heavily for its theories and concepts. Biosystematics has a broad base as it not only includes the function of identification but also the comparative study of all and every aspect of the organism and also the interpretation of the evolutionary history. After you have gone through this unit, you will be able to: differentiate between taxonomy, systematics and biosystematics, e explain the alpha, beta, gamma phases of taxonomy, 64 o define neotaxonomy and enumerate the various approaches used in this field, Modern Trends in Plant Taxonomy I 0 describe and explain the techniques, and importance of various approaches used in I heotaxonomy-electron microscopy, embryology, ecology, ethology, cytblogy f biochemistry and numerical taxonomy. I Your study of the earlier units of taxonomy, in particular its history must have made you aware that the"field of taxonomy has changed considerably. Nowadays, it is a very dynamic and broad field and no longer deserves the reputation that persists even today,among some biologists of being a dry and static field. It is no longer limited to just preserving and cataloguing organisms. After going through this unit you will realise fhat taxonomists today do not depend on morphological data alone, but use ;long with it, relevant information and techniques from the scientific field of physics, chemistry, biochemistry, cell biology, ethology, mathematics etc. The present day taxonomists thus try to use whenever possible or wherever available a synthesis.of relevant data and iechniques from other scientific fields for identifying organisms and so can aptly be called 'synthesisers' oflbiological knowledge and techniques. 8.3 TAXONOMY, SYSTEMATICS AND BIOSYSTEMATICS The three terms taxonomy, systematics and biosystematics are often used interchangeably and may confuse you, especially since they are not synonymous. Each has a specific meaning as you will see below. Taxonomy The term taxonomy which is derived from the Greek word 'taxis', meaning order or arrangement and 'nbmos' meaning law, deals with the study of 'principles of classification'; It is concerned with the grouping and classification of organisnls. This involves recognition, description, naming (nomenclature) and classification of the organisms. Taxonomy is a part of systematics and biosystematics on both of which it relies heavily for its theory and concepts. Systematics Systematics is defined as the study of relationship among organisms which means reconstruction of phylogenies. It is that branch of biology which qmploys the techniques of other branches of biological knowledge like biochemistry, genetics. biophysics etc, for the comparative study of the interrelationships df groups of organisms. In other words, thcrc are two parts of systematics. The first part is taxonomy which is concerned with identifying, describing and naming the various kinds of organisms. The second part is evolution which is concerned with understanding the origin of organisms in nature and the processes which tend to change or maintain them. In systematics four types of relationships are studied and thcy are: 1) Relationships of phylogeny (evolutionary descent) or the degree to which two organisms are thought to be related to a common ancestor. 2) Relationships of similarity in morphology (appearance and structure) physiology, cytology etc. 3) Spatial or geographical relationships 4) Trophic or nutritimal relationships, which study the extent to which two or more organisms depend upon each other or compete with each other for food. rmls and Trends in Tnxmomy Biosystematics Biosystematics is basically synonymous with systematics, though it places more emphasis upon genetic (concerning inheritance) and cytologi'cal data (concerning cell function and structure) rather than upon morphological, anatomical physiological or spatial information, alone. It tries to infer evolutionary relationships with the study of reproductive compatibility and gene flow. Biosystematists assess the genetic variation in population and among species. Using information from their genetic studies, biosystematists make inference about the ancestral hisfory of a species and thus study speciation (the evolution of one species into two). They collect data on variation in a population of organisms and then analyse the data in order to construct a model of genetics of the population. For example, in Winconsin, a single population of fly maggots has begun to feed, mature and then reproduce near either apple or cherry trees. Since these two types of trees bear fruits at different time of the year, the apple eating maggots and the cheery eating maggot may at one point of time become reproductively isolated from one another. A biosystematist might infer that in this case speciation is occurring. SAQ 1 Fill in the blanks choosing appropriate words from the list given below: a) A scientist who studies the comparative characters of the species of frog (genus Rana) with respect to their morphology, ecology, distribution and genotype and works out their interrelationship on basis of speciation is more appropriately called a ................................ b) A scientist who studies the comparative characteristics of the species of the cat family with respect to their morphology, e'cology and ethology and works out their interrelationships is more appropriately a ........................... ..... .., .. c) A scientist who identifies the various species of Rana on the basis of their morphological characteristics is more appropriately called a (biosystematist, taxonomist, systematists) 8.4 STAGES IN TAXONOMIC PROCEDURES The taxonomic procedures used in the study of a given group of organisms can be divided into three levels or phases: 1) Alpha (a) phase, 2) Beta (P) phase, 3 Gamma (y) phase. 8.4.1 Alpha Taxonomy The alpha phase of taxonomy is analytical. At the level of alpha taxonomy, the organisms are identified, named and characterised. 8.4.2 Beta Taxonomy This stage is also known as macro taxonomy or synthesis taxonomy. At this level the species are arranged or classified into a natural system of higher and lower categories. At first this arrangement is constructed from the maximum number of available characters i.e. it is a purely phenetic classification. 8.4.3 Gamma Taxonomy This phase of taxonomy is also called biological taxonomy and is concerned with the study of speciation. It is involved primarily with the analysis of intra specific variations which leads to the study of origin, evolution and determination of biological species and its subspecies. These three phases of taxonomy have been explained to you separately though in practice they are not that clearly demarcated as they tend to overlap and intergrade. Systematic studies in most of the groups of animals have not yet progressed beyond the alpha and beta taxonomy. It is only among a few insec! ordcrs such as Modern Trends in Animal Taxonomy Lepidoptera (months and butterflies) and vertebrates especially birds that any real progress have been made at the gamma level of taxonomy. SAQ 2 Fill in the blanks with apprc8:lriate words from the list given below: a) A biologist who examines, identifies, describes and names a species of birds is working at the level of ............................... taxonomy. b) A biologist who identifies a species of bird and places it in its scheme of classification, modifying the classification if necessary, is working at the level of ............................. taxonomy. c) A biologist who studies a group of birds for the purpose of working out their phylogenetic relationship is working at the level of ................................. taxonomy. [beta (PI,'alpha (a),gamma (y] 8.5 NEOTAXONOMY In earlier units, you have learnt that most taxonomists use comparative morphology in identifying organisms. However, morphological features themselves are often npt sufficient for identification and sb taxonomists nowadays use data from various