A recent estimate suggests that the eukaryote species for which science has names, about 1. Species diversity is determined not only by the number of species within a biological communityi. Strictly speaking, species diversity is the number of different species in a particular area species richness weighted by some measure of abundance such as number of individuals or biomass. If an ecosystem has poor species diversity, it may not function properly or efficiently. Beginning with a practical definition of biodiversity and an overview of diversity patterns on earth, this book develops a conceptual framework that extends traditional theories of species diversity to explain both the general patterns of diversity and the apparent exceptions to these patterns. Choose from 500 different sets of species diversity biology flashcards on quizlet. Species diversity is marked by some interesting factssuch as larger areas have more species, and diversity is particularly high near the equator. Each species has adapted to its own niche, which is characterized by certain features e. Biogeographic region components of species diversity. We will then consider one measure used to compare diversity among communities, jaccard. Species diversity and community structure novel patterns.
The species diversity and richness version 4, first released in january 2006, includes the following additions and enhancements. D diversity index n total number of organisms of all species found n number of individuals of a particular species n number of individuals of a particular species. Ecologyspecies richness and diversity wikibooks, open. Pdf measuring species diversity for conservation biology. Biogeographic region biogeographic region components of species diversity. Species diversity is the measure of the diversity within an ecological community that incorporates species richness and the evenness of species abundances. Introduction the diversity of species in an ecosystem can be used to determine the health of an ecosystem. We discuss what is meant by biodiversity, and calculate an example. There are numerous reasons why species diversity is essential. A related term, evenness e, is another dimension of diversity that defines the number of individuals from each species in the same area. Species diversity is the diversity of species in a community. Species abundance refers to the number of individuals per species.
Apart from these basic indices, there are more modified approaches and newer indices used in ecological studies. However, it is common for conservation biologists to speak of species diversity even when they are actually referring to species richness. List of books and articles about biodiversity online. It also takes into account evenness, which is the variation of abundance in individuals per species in a. One of the most common indices of species diversity is the simpsons index. Simpsons index d is a measure of diversity, which takes into account both species richness, and an evenness of abundance among the species present. The proposed index incorporates an importance weight to each species of organisms found in an ecosystem. Species richness refers to the number of species in an area. All reference to questions andor pages in the book are from nelson thornes aqa as biology student book isbn 9780748782758. By not allowing one species or another to become overly dominant, a keystone species maintains species diversity and ecosystem integrity. A diversity index also called phylogenetic indices or phylogenetic metrics is a quantitative measure that reflects how many different types such as species there are in a dataset a community and that can simultaneously take into account the phylogenetic relations among the individuals distributed among those types, such as richness, divergence or evenness. Diversity definition and examples biology online dictionary. Populations and species are disappearing due to disturbances in the environment caused by human activities.
In essence it measures the probability that two individuals randomly selected from an area will belong to the same species. According to the encyclopedia of earth, species diversity is a measurement of an ecosystems species richness and species evenness. Species abundance is the number of individuals per species, and relative abundance refers to the evenness of distribution of. Feb 21, 2015 species richness the number of species that live in a certain location. The aim of this study was to evaluate the structure and diversity in the. It is sometimes incorrectly referred to as the shannon weaver index krebs, 1985. Rarefaction one of the fundamental tenants of diversity is that the number of species found in a given sample is strongly. How to calculate simpsons diversity index ap biology. The collection defines the terms species richness and species evenness as methods for measuring species diversity, and it discusses the use of species richness as a.
There are a number of other options that may be used such as species richness and shannons diversity index, but the ap biology equation and formula sheet includes simpsons, so ap biology students should be prepared to use it for the ap biology exam. The hypothesis assumes that most communities exist in a state of nonequilibrium where competitive equilibrium is prevented by periodic population reductions and. Species diversity takes into consideration species richness, which is the total number of different species in a community. Biodiversity is the variety and variability of life on earth. Difficult to define because definition consists of two distinct components. Alpha diversity refers to the diversity within a particular area or ecosystem, and is usually expressed by the number of species i. Species richness is the number of species present in a sample, ecological community, ecosystem, landscape, region, or any defined spatial unit. Species diversity in space and time examines crucial questions about species diversity, and seeks to set the agenda for research well into the next century. The effective number of species refers to the number of equally abundant species needed to obtain the same mean proportional species abundance as that observed in the dataset of interest where all species may not be equally abundant. For example, if we are monitoring the effect that british farming practices have on the. Species diversity indices take two aspects of a community into account, namely species richness and evenness or equitability the distribution of abundance among the species. Learn species diversity biology with free interactive flashcards. For example, communities with a large number of species that are evenly. May 23, 2019 brief definitions of populations, species, communities, and ecosystems are provided, with some introductory discussion of different types of species concepts.
Given, the obvious risk of loss of diversity, it is increasingly necessary to take actions concerning preservation, in which safety features are necessary for measuring the variation of diversity in space and time. Whittaker 1972 described three terms for measuring biodiversity over spatial scales. In this video we look at aqas version of an index of species diversity. Species diversity is a statistical abstraction with two components. Species diversity is an index that incorporates the number of species in an area and also their relative abundance. He also propounds that if a diversity index is to be used, then a variancebased index is preferable i. Published by the japanese society of systematic zoology 544 registered articles updated on may 08, 2020 online issn. The composition of species in a given ecosystem is the result of longlasting evolution. A widely used dominance index is simpsons diversity index. Species diversity pertains to the effective number of species represented in a data set.
Use a quadrat to measure a known are that is marked off and examine species within the squares. Biodiversity is typically a measure of variation at the genetic, species, and ecosystem level. For example, in the image below, we can see that these two communities are. An overview of plant biodiversity is provided in this chapter. Species diversity refers to species richness and how evenly species abundance is distributed.
Put simply, how many different species are there in a community. Ncert class 12 biology biodiversity and conservation. Ecosystem diversity refers to the diversity of a place at the level of ecosystems. The book highlights new developments, including innovative approaches to measuring taxonomic distinctness and estimating species richness, and evaluates these alongside traditional methods such as species abundance distributions, and diversity and evenness statistics. For each of these diversity measures we analyze the statistical accuracy of estimates of the actual diversity in a community that can be made from random samples. Despite considerable effort, knowledge of the species that inhabit the planet is limited.
Species diversity is a measurement of biological diversity to be found in a specific ecological community. Dec 10, 2012 lesson and activities for aqas as biology 17. Species diversity the number of different species in a particular area i. Terrestrial biodiversity is usually greater near the equator, which is the result of the warm climate and high primary productivity. Sdi takes both the number of species and the population size of. It represents the species richness or number of species found in an ecological community, the abundance or number of individuals per species, and the distribution or evenness of species.
A general hypothesis of species diversity the american. The diversity index values will vary between 0, which would indicate no diversity, and 1, which is very diverse. Diversity a2levellevelrevision, biology, appliedecology. It takes into account both species richness and species eveness. The most common indices of species diversity are dominance index, simpsons index and shannons index. Species richness s is a relative term that refers to the number of species in a community, and is directly associated with measuring the diversity of species in a given area. Scientists have variously estimated that there are from 3 to 30 million extant species, of which 2. Dominance indices are weighted toward the abundance of the commonest species. However, as has been recognized for decades, grassland plant species have undergone a significant amount of ecotypic variation olmsted, 1945, and the reduction in grasslands has resulted in a reduction of genetic diversity diversity losses that are not apparent in simple measures of species diversity. In environmental systems and society we use a derivative of the index with the formula. Brief outlines of the two types of diversity indices of biodiversity are discussed in this article.
Diversity, and southwood and henderson 2002, ecological methods 3rd edition. Species richness variety of species or the number of different species or genera, families, etc. In addition to issues of statistical sampling, the rather arbitrary nature of delineating an ecological community, and the difficulty of positively identifying all of the species present, species diversity itself has two separate components. Learn vocabulary, terms, and more with flashcards, games, and other study tools.
We will examine both alternatives as they are widely used in ecology. The importance of species diversity to the ecosystem sciencing. A keystone species is an organism that helps maintain species diversity within an ecosystem by keeping the numbers of other species in an ecosystem constant. A diversity index is a quantitative measure that reflects the number of different species and how evenly the individuals are distributed among those species.
Species and diversity lab report bio 153 lab report species. Simpsons diversity index sdi is one approach to quantifying biodiversity. Other factors to consider are what reduces diversity in ecologically productive places and across what scales of space and time diversity patterns hold. Species richness the number of different species in a particular area species evenness the relative abundance with which each species are represented in an area. First, it explains species diversity and the functioning of fungi in asian regions as outlined by metagenomic approaches using nextgeneration sequencing technology. A new hypothesis, based on differences in the rates at which populations of competing species approach competitive equilibrium reduction or exclusion of some species, is proposed to explain patterns of species diversity. Details of genetic diversity, species diversity and ecosystem diversity are given. This accessible and timely book provides a comprehensive overview of how to measure biodiversity. Beginning with a practical definition of biodiversity and an overview of diversity patterns on earth, this book develops a conceptual framework that extends traditional theories of species diversity to explain both the general patterns. On the other hand, species diversity is a function of the number of species present i. Species diversity is described as the number of species in a community. Species richness an index based on the number of species i.
A diverse species assemblage also contributes to ecosystem diversity. Typically, the value of a diversity index increases when the number of types increases and the evenness increases. It also takes into account evenness, which is the variation of abundance in individuals per species in a community. Species diversity refers to the measure of diversity in an ecological community. Diversity in and among grasslands biodiversity ncbi. Here, we will explore two measures of biodiversity. To study species diversity richness and evenness, index of dominance, similarity index, dissimilarity index and species diversity index in grazed and protected grassland. A new importancediversity index is proposed as an enhancement to the traditional shannons diversity index. Download ncert class 12 biology biodiversity and conservation ncert book and other cbse kvs biology latest books free in pdf format chapter wise, ncert class 12 biology biodiversity and conservation. Biology ecology diversity index lab introduction the measure of the biodiversity of organisms in a given area is known as the diversity index. Perhaps the most meaningful but seldom used index, not a diversity index sensu stricto, is pie probability of. Species diversity is a measure of diversity within an ecological community that encompasses both species richness and evenness of species abundance hamilton, 2005. Statistical properties are described for the three most commonly used nonparametric scalar measures of species diversity. Genetic diversity refers to both the vast numbers of different species as well as the diversity within a species.
Alpha, beta, and gamma diversity biology libretexts. Introduction, simpsons index and shannonweiner index. A diversity index also called phylogenetic or simpsons diversity index is a quantitative measure that reflects how many different types such as species there are in a dataset a community and that can simultaneously take into account the phylogenetic relations among the individuals distributed among those types, such as richness, divergence or evenness. Species diversity is the number of different species that are represented in a given community a dataset. According to the preprint that i examined, end material will include a guide to species, classification, glossary, a list of further reading, and an index. Both these books are recommended for further information on the methods offered by species diversity and richness. The book includes chapters on taxonomy and evolution, life stages and strategies, diet, reproduction, interactions with other species, diversity and distribution, and relationships with humans. The index independently derived by shannon and wiener from the application of information theory is known as the sharmon index of diversity. Different diversity indices apportion different relative weights to these properties, and the definition of evenness itself varies. What if there are two separate communities like this. Species diversity, functional diversity and ecosystem. Thats some rocket science, i dont really know what it is, but i dont wish to find out, and neither do you. About this book this book introduces recent progress in the study of species diversity and community structures in terrestrial organisms conducted by three groups at kyoto university. Copies of these textbooks may be downloaded and used as textbooks or for reference.
126 1275 1580 54 961 1601 1405 399 1000 879 1017 970 823 841 57 782 768 699 217 1012 949 1280 1070 1370 1417 1609 962 1136 1056 1095 483 1526 1180 395 618 204 730 15 1448 342 380 899 828 336 81 554