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Community Characteristics, Types of Biodiversity, Diversity Index, Abundance, Species Richness, Vertical and Horizontal Stratification: Part II

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Paper No. : 12 Principles of Ecology Module : 18 Community: Community characteristics, types of biodiversity, diversity index, abundance, species richness, vertical and horizontal stratification: Part II Development Team Principal Investigator: Prof. Neeta Sehgal Head, Department of Zoology, University of Delhi Co-Principal Investigator: Prof. D.K. Singh Department of Zoology, University of Delhi Paper Coordinator: Prof. D.K. Singh Department of Zoology, University of Delhi Content Writer: Dr. Haren Ram Chiary and Dr. Kapinder Kirori Mal College, University of Delhi Content Reviewer: Prof. K.S. Rao Department of Botany, University of Delhi 1 Principles of Ecology ZOOLOGY Community: Community characteristics, types of biodiversity, diversity index, abundance, species richness, vertical and horizontal stratification: Part II Description of Module Subject Name ZOOLOGY Paper Name Zool 12, Principles of Ecology Module Name/Title Community Module Id M18, Community characteristics, types of biodiversity, diversity index, abundance, species richness, vertical and horizontal stratification: Part-II Keywords Biodiversity, Species diversity, genetic diversity, community/Ecosystem diversity, alpha-, beta- and gamma diversity, biogeography Contents 1. Learning Objectives 2. Introduction to Biodiversity 3. Types of Biodiversity a. Species Diversity b. Genetic Diversity c. Community or Ecosystem Diversity i. Alpha Diversity ii. Beta Diversity iii. Gamma Diversity 4. Evolution of Biodiversity 5. Factors that Promotes High Diversity 6. Measurement of Biodiversity 7. Biogeography 8. Summary 2 Principles of Ecology ZOOLOGY Community: Community characteristics, types of biodiversity, diversity index, abundance, species richness, vertical and horizontal stratification: Part II 1. Learning Outcomes After studying this module, you shall be able to • Understand the meaning of Biodiversity • Briefly study the types of biodiversity • Learn about the different types of community or ecosystem diversity • Evaluate how biodiversity has evolved and the factors affecting biodiversity • Understand the theory of biogeography 2. Introduction As per CBD (Conventional on Biological Diversity (1992)), living organisms from all the sources show variability among themselves called as Biological diversity. The sources of living organisms can be marine, terrestrial or aquatic ecosystem and the ecological complexes in which they have participated such as diversity between species, within species and of ecosystem. The biodiversity not only include plant and animals and other living organisms (species) but also the variety of ecosystem they inhabiat and their varied genes. The species richness accounting for the total number of species in a community is called as biodiversity. The numbers of species differ in different ecological communities and provide an active area for the current research. The animal and plant life are more varied and abundant in the tropic regions than other part of the world, stated by Alfred Wallace (1878). MacArthur and Wilson (1967) suggested that islands exhibit different patterns of variation; more species in large and nearer continents than remote and small islands. Conservation biology involves the measurement of biodiversity as its important integral part. To detect and understand the cause of formation of large patterns in groups of species, a community based approach is employed. In 1988, Norman Myers, a British biologist coined the term Biodiversity Hotspot. It is an irreplaceable biogeographic area that is threatened with destruction and act as a significant reservoir of biodiversity. The area must be threatened to a limit of at least 30 percent of its original vegetation must be lost or must be irreplaceable due to the presence of high endemic species. Around the world, there are specifically 35 areas that are biologically rich and have lost nearly 70% of their original habitat. The biosphere provides life support system to all living organisms and the presence of biological diversity (innumerable organism) makes the complex life pleasant. In 1985, Walter and Rosen coined the term biodiversity as an abbreviated form of Biological Diversity. It 3 Principles of Ecology ZOOLOGY Community: Community characteristics, types of biodiversity, diversity index, abundance, species richness, vertical and horizontal stratification: Part II took more than four billion years to originate life on earth and almost one billion year to develop this complex and wide spectrum of life. In 1988, Wilson believed that almost 10 to 80 million of total number of species are present on earth, out of which only 1.4 million is known to us. However, we are losing the diversity in life forms that can result into grave consequences. The total varieties of species on earth i.e. different types of plants, animals and microbes constitute the Biodiversity. The variety can be in any of the life forms, combinations and levels. The Biological diversity encompasses diversity within species termed as species diversity, genetic diversity (between species) and ecosystem diversity. 3. Types of Biodiversity The biological diversity is broadly categorized into three different levels —Species diversity, Genetic diversity and Community or Ecosystem diversity. (i) Species Diversity: Species are a group of similar organisms that share a common lineage, interbreed and produce offspring and called as basic unit of classification. Species diversity is commonly used as a synonym for Biodiversity. The species diversity has evolved attributing to the diversity in habitat of living organisms and defined as variety of species within a habitat. Thus, based on the number of species within an area the diversity of that region can be measured. In a given area, the species diversity is comprised of the total number of plant and animal species in that area. Although some regions are have fewer species than others but both type of ecosystems, agricultural and natural, have diversity. Moreover, agricultural 4 Principles of Ecology ZOOLOGY Community: Community characteristics, types of biodiversity, diversity index, abundance, species richness, vertical and horizontal stratification: Part II ecosystem has fewer varieties in species than the undisturbed natural system such as tropical forests showing higher species richness (number of species in given habitat). Hotspots are the areas rich in species diversity. India is among the 15 nations of the world encompassing exceptionally rich in species diversity. The total number of species belonging to different taxonomic groups is measured as Global Diversity. Species diversity is studied at different levels: alpha, beta, gamma, delta and omega species diversity. The number of species habituating at the same region is the measure of alpha diversity. The difference in species between patches is defined as beta diversity. The number of different species in different geographical locations is called gamma diversity. The diversity in species of biomes is measured as delta diversity. Biomes also referred to as ecosystem, are geographically and climatically defined ecological regions. The number of species measured for the entire biosphere is called omega diversity. In a given area, the measurement of variety of taxa (at the genus and family taxonomical levels) is referred to as taxon or taxic diversity, that when studied at species level called as species diversity. (ii) Genetic Diversity: Every single organism obtains special characteristics encoded by the broad range of possible combinations in the genes. Thus, every individual of plant or animal species vary from each other in their genetic makeup. Even a slight variation in the genetic makeup provides differences within a species where each individual slightly differ from each other representing different strains, forms (variation in single morphological characteristic), varieties and subspecies. This diversity within the species or different species due to different genetic make-up is called as genetic diversity. Large number of strains and varieties within a species is considered as diverse and rich in genetic organization. Chromosomal or gene mutations cause the genetic variations in single individuals of a species. These genetic variations are an important aspect and an integral part of biodiversity and considered as prerequisite for adaptation and evolution. Genetic variations are studied at population level and expressed in terms of alleles. PCR (polymerase chain reaction), DNA fingerprinting, allozyme analysis, DNA sequencing and restriction site mapping are the currently employed different techniques used to measure the Genetic variations. (iii) Ecosystem or Community Diversity: On earth large variety of different ecosystems, based on the differences in the habitat, have their own complement of distinctive inter linked species. India is an outstandingly prosperous in ecosystem diversity. Distinctive natural ecosystems include aquatic ecosystems like the sea, lakes, and rivers and as well as landscapes like mountains forests, deserts, grasslands etc. Different land-forms may exist in ecosystem, each of which supports specific and different vegetation. Natural ecosystems become degraded and less productive when misused or 5 Principles of Ecology ZOOLOGY Community: Community characteristics, types of biodiversity, diversity index, abundance, species richness, vertical and horizontal stratification: Part II overused. Various sub-ecosystems are constituted and separated by the boundaries of the communities
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