Lecture 2 – Biodiversity Classification Systems
Classification refers to the grouping and subgrouping of organisms based on taxa (a taxonomic group of any rank, such as a species, family, or class)
• It is important because:
o it provides logical, universal names for different species o allows for scientists to communicate across language barriers o allows us to deduce relationships between species
• The rank order of taxa commonly used today is:
o Kingdom o Phylum o Class o Order o Family o Genus o Species
Handy Acronym: King Phillip Came Over For Good Soup Kingdoms
• Major groups of life are classified into 6 kingdoms
• The 5 kingdom system recognise Monera (prokaryotes), Protista, Fungi, Plantae and Animalia
• The 6 kingdom system further breaks down prokaryotes into bacteria and archaea, grouping the remaining four kingdoms as ‘eukarya’
• Major differences between prokaryotes and eukaryotes: pro are uni-cellular whereas eukaryotes are multicellular
Diversity of Life on Earth
• Approx. 1.2 million named species on Earth
• An estimated 86% of terrestrial species are unnamed and 91% of marine species
• Difficult to quantify the diversity of life on Earth (i.e. count species) due to:
o Inaccessible habitats
o Difficulties in ‘defining’ a species o Cryptic species
o Complex life cycles
o Advances in technology create new criteria (e.g. genetic differences between sub-species of giraffe)
o Sampling bias
Relative Abundance
• Most of the world’ biodiversity are insects
• Mammals comprise the smallest portion of biodiversity Biodiversity Indices
• Simpson’s Diversity Index takes into account both the number of species and their abundances
• It gives the probability that two organisms selected from the community at random would belong to two different taxas
• It ranges from 1-0, 0 being a community made up of a single organism, and 1 being a community made up of many species present in equal proportions
• The formula is as follows:
n being the total number of organisms of a particular taxon N being the total number of organisms in all taxa
Note that (n/N) is also called ‘relative abundance’
• To calculate the relative abundance of each species:
Relative abundance of taxon A = !"#$%& () *!+*,*+"-./ *! 0-1(! 2 (!) 0(0-. !"#$%& () *!+*,*+"-./ () -.. 0-1- (5)
• i.e. Simpson’s Diversity Index = 1- relative abundance squared
• A low D value indicates low species diversity, whereas a high value indicates high species diversity Different Types of Diversity
• Alpha Diversity: number of species within a chosen area or community (local diversity)
• Beta Diversity: the ratio between regional and local species diversity
• Gamma Diversity: the diversity of the entire landscape
"Imagine that you have a landscape containing of a number of separate sites and habitats. Alpha diversity is just the diversity of each site (local species pool). Beta diversity represents the differences in species composition among sites. Gamma
diversity is the diversity of the entire landscape (regional species pool)."
D = 1 − Σ 9!
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