4.1, 4.2 Biodiversity and Endemism Flashcards
4.1 Know that over time the variety of life has become extensive but is now being threatened by human activity. 4.2 i) Understand the terms biodiversity and endemism. ii) Know how biodiversity can be measured within a habitat using species richness and within a species using genetic diversity by calculating the heterozygosity index (H): iii) Understand how biodiversity can be compared in different habitats using a formula to calculate an index of diversity (D):
How has biodiversity on Earth increased over time?
natural selection leading to adaptation and evolution has increased variation within and between species and ecosystems
What has caused a decrease in biodiversity?
human activity (such as farming and deforestation) is reducing species diversity as a growing number of species are threatened with extinction
What is biodiversity?
the measure of the variation among living organisms, including variation within a species, between species, and within and between ecosystems
What is species diversity?
the number of different species and the abundance of each species in an area
What is genetic diversity?
the variation of alleles within a species or a population of a species
What is endemism?
when a species is unique to a single place (isn’t naturally found anywhere else in the world)
Give an example of endemism:
the giant tortoise is endemic to the Galapagos Islands (it is only found there)
How can biodiversity be measured within a habitat?
- by measuring species diversity:
- do this by counting the number of species present in the given habitat - this is know as species richness
- the higher the number of species, the greater the species richness
What is a problem of using species richness to measure biodiversity?
it gives no indication of the abundance of each species
How can biodiversity be measured within a species?
- by measuring the genetic diversity
Explain genetic diversity in more detail than just the definition:
- individuals of the same species vary because they have different alleles
- the greater the variety of alleles, the greater the genetic diversity
Give an example of genetic diversity:
humans have three alleles for blood group, but gorillas have only one, so humans show greater genetic diversity for blood group than gorillas
What is a gene pool and how does it relate to genetic diversity?
- a gene pool is all the alleles present in a species or population
- the greater the variety of alleles in the gene pool, the greater the genetic diversity
How can genetic diversity be measured using phenotype?
- the larger the number of different phenotypes, the greater the genetic diversity
- this is because different alleles code for different versions of the same characteristics (different observable characteristics will be produced)
- therefore diversity of phenotypes indicates diversity of alleles
How can genetic diversity be measured using genotype?
- by sampling DNA of individuals of the same species or population and analysing the sequence of base pairs
- this determines which alleles are present as the order of bases in different alleles is slightly different
- the similarities and differences in the alleles within a species can be identified
- the number of different alleles can be measured to indicate genetic diversity
What is the heterozygosity index (H)?
H = number of heterozygotes / number of individuals in the population
How does the heterozygosity index measure diversity?
- heterozygotes have two different alleles at a particular locus (the position of a gene on a chromosome)
- the higher the proportion of heterozygotes in a population, the greater the genetic diversity
- an average value for H at many loci can be used to estimate genetic diversity in the whole genome of the population
How can biodiversity of different habitats be compared?
- by calculating the index of diversity (D) of each habitat and comparing the species diversity in different habitats
- the greater D is, the more diverse the area is
- if there is no species diversity (all individuals are of the same species) the index is 1
What is the index of diversity (D)?
D= N(N-1) / Σn(n-1)
N = total number of organisms of all species
n = total number of organisms of one species
Σ = ‘sum of’
What is a strength of using the index of diversity?
it takes into account both the number of species (species richness) and the abundance of each species
