Systematics and Taxonomy PDF

Chapter 2 Systematics and Taxonomy a. Scope and aims of Systematics b. History of systematics and taxonomy c. Theories of Taxonomy d. Contributions to other filed of Biology         ...

Chapter 2 Systematics and Taxonomy a. Scope and aims of Systematics b. History of systematics and taxonomy c. Theories of Taxonomy d. Contributions to other filed of Biology          Criteria for Grouping Fig. 1. Systematics includes taxonomy and evolution     Parts of a cladogram     1. To name and describe the world’s organisms, thus completing our inventory of earth’s biota. 2. To provide a classification of these organisms that expresses evolutionary relationships among them. 3. To understand the patterns and processes of evolution that have created this enormous diversity of organisms. 4. To provide an integrating and unifying focus, a means of communication, for all fields of biology by safeguarding and disseminating this knowledge. 1. Alpha taxonomy: -The classical or alpha taxonomy relies mainly upon morphology and is descriptive. It is concerned with the collection, identification and description of taxa. The term was coined by Turrill (1935). 2. Beta taxonomy: - The beta taxonomy focuses on arrangement of taxa into taxonomic groups or categories of classification. It is concerned with the identification of natural groups based on certain similarities and differences and uses this information for the purpose of classification. The term was coined by Ernst Mayr (1969). 3. Gamma taxonomy: - The gamma taxonomy includes study of intraspecific populations, speciation, and evolutionary rates and trends. The purpose of this type of study is to interpret the biological diversity. 4. Omega taxonomy: -The omega or modern taxonomy uses the data obtained from various biological disciplines like cytology, palynology, phytochemistry, etc. and gives information about the relationships among organisms. It is often referred to as a ‘perfected taxonomy’ as it focuses on having a broad information base for interpreting the relationships. The term was coined by Turrill (1938).  The term biosystematics was introduced by Camp and Gilly (1943) to understand the natural relationships of plants, particularly those of the rank of genus and below. Biosystematics studies include a thorough sampling of the taxon and its populations, and counting of chromosomes of many populations within geographic races, species, and genera.  The major objective of the biosystematics studies is to delimit the natural biotic units and to apply to these units a system of nomenclature adequate to the task of conveying precise information regarding their defined limits, relationships, variability, and dynamic structure. The four most widely accepted biosystematics categories are: ecotype, ecospecies, cenospecies (or coenospecies) and comparium.  Ecotype is the basic unit in biosystematics. It is adapted to a particular environment but capable of producing fully fertile hybrids with other ecotypes of the same ecospecies. Ecospecies is a group of plants comprised of one or more ecotypes. Cenospecies (Coenospecies) is a group of plants representing one or more ecospecies. Comparium is the biosystematic unit that often is comparable to the genus.  Biosystematics is considered as the taxonomic application of the disciplines known as genecology. ▪ It is the study of the genotypic and phenotypic variation of species in relation to the environments in which they occur.  A multisource approach that takes advantage of complementarity among disciplines, i.e., different fields of study, has been called combined, multidisciplinary, multidimensional, collaborative, or integrative taxonomy. Using multiple disciplines to solve taxonomic problems helps avoid failure inherent to single disciplines and increases rigor in species delimitation.  DNA TAXONOMY DNA taxonomy is defined as the analysis of genetic variation for the circumscription and delineation of species. It uses the evolutionary species concept and provides a new scaffold for the accumulation of taxonomic knowledge. In simple words, it is the use of DNA to delineate species. It is a convenient tool for species identification and rapid assessment of biodiversity.  CYBER TAXONOMY (E-TAXONOMY) Taxonomic data is enormous and hence is being widely digitized to make it convenient for people to access this information globally. Cyber taxonomy involves the use of standardized electronic tools to access information (databases, e-publications). The internet is being used as the primary medium for taxonomic teaching and research. It has provided more accessible and universal platform for the deposition and retrieval of taxonomic information.  REVERSE TAXONOMY DNA analysis and naming of the organism without studying its morphology is termed as reverse taxonomy. In this method, the molecular data is analysed first and based on it the taxon is assigned to a particular group and then described at genus/species level. It is helpful in cases where a taxon cannot be clearly defined to any taxonomic group by using traditional methods.  Integrative Taxonomy: -Combines data from various disciplines to classify organisms. DNA Taxonomy: -Uses genetic information for species identification and classification. Cyber Taxonomy: - Utilizes digital tools and the internet for managing and accessing taxonomic information. Reverse Taxonomy: -Uses DNA data first for classification, then describes physical traits.  RELEVANCE TO SCIENCE AND SOCIETY The greatest contribution of taxonomy to science and humanity is that taxonomists have discovered, described and classified over 2 million species and the process is still continuing. Understanding the biological richness, their variability and protecting them is vital to human survival. Systematics plays a vital role in society for the identification of organisms which is important for proper assessment and characterization of biodiversity  RELEVANCE TO SCIENCE AND SOCIETY Taxonomists identify species in the wild, notice the risk of extinction or the arrival of invasive species and follow the changes in biodiversity over time. They undertake inventories to survey the flora and fauna of various areas and provide advice for their protection.  RELEVANCE TO SCIENCE AND SOCIETY Systematics helps in delineating taxa and establishes the correct relationship among organisms. It not only provides an insight into the origin of life on earth but also preserves the information about existing biodiversity through proper storage and documentation. It provides an effective means of dealing with the large amount of information that exists on the earth  RELEVANCE TO SCIENCE AND SOCIETY With the increasing threat of climate change and global warming, the biotic flora is also under extreme pressure of extinction. The increased competition among species for resources is making their survival difficult. Activities like deforestation and cultivation pose a constant threat to various undescribed species. Systematics thus plays a vital role in conservation biology. It helps in identifying the rare and endangered taxa, thereby enabling us to develop strategies for their conservation.  RELEVANCE TO SCIENCE AND SOCIETY Systematic studies also give an overview of the incredible diversity of life on earth. Biogeography data help in understanding the distribution of species on the planet and the ecological interactions among the species. It also aids in identification of the biodiversity hotspots and help in making strategies for their preservation in the natural condition (in situ) or in artificially created habitats (ex situ). In areas with high risk of destruction, the floristic biota can be collected and inventoried.  RELEVANCE TO SCIENCE AND SOCIETY Systematics is also important for the correct utilization of economic resources. Understanding the wild species that are closely related to economically important crop plants can help to improve the available germplasm and develop resistant varieties. Land use pattern can also be improved through the knowledge of ecological impact on the organisms  RELEVANCE TO SCIENCE AND SOCIETY Proper identification of taxa can help reduce pest infestation and damage due to increased population of weeds. It also advances our understanding of important processes like coevolution of pests–pathogens and plants–pollinators. Dispersal mechanisms, ecological shifts in the plants due to change in climatic conditions and habitat preferences can be easily understood with the assistance of systematic studies.  RELEVANCE TO SCIENCE AND SOCIETY Systematics also helps in understanding the process of speciation and thus provides insights into the evolutionary pathways. This provides data about the ancestral – descendent relationship and the changes that occur over time. These phylogenetic studies provide insight into the evolutionary path for the origin of organisms on earth.  SUMMARY Systematics is the study of biological diversity that exists on earth and its evolutionary history. Taxonomy is that branch of science which deals with the principles and practices of classification. Taxonomy mainly comprises of four components: Description, Identification, Nomenclature and Classification. When multiple disciplines are used to solve taxonomic problems, it is called integrative taxonomy. Systematics is crucial in conservation biology as it helps in identifying the rare and endangered taxa, thereby enabling us to develop strategies for their conservation. Systematics helps in understanding the process of speciation and thus provides insights into the evolutionary pathways.