Biodiversity

Biodiversity

the variety and variation of ecosystems and species in an area/ habitat and the genetic diversity within each species. This variaiton and variety is considered at 3 levels: variation in ecosystems, no.of species + relative abundance, and genetic variation within a species.

Species

A group of closely related organisms that are capable of interbreeding to produce fertile offspring.

Ecosystem

A functional, self contained community of living organisms in an area and their interactions with each other and the biotic and abiotic elements

Population

No. Of individuals of the same species that live in the same habitat at the same time

Habitat

Natural environment of an organism. Characterised by physical features/ dominant producer and land that’s occupied by a pop or organism

Abiotic Factors

Non-living, chemical and physical components of the ecosystems

Community

All organisms of all diff species living in a habitat

Ecological niche

Match of a species to a specific environment condition. The position.role of an organism in its environment

Species richness

Measure of the no. Of diff species that are present in a habitat.

Producer

Organism that synthesises its own food from inorganic compounds into organic compounds

Consumer

Organism that obtains food in its organism form from other species

Genetic diversity

Measure of genetic variation found in a particular species- no. Of alleles in a gene pool. Diversity of the alleles within the genes in the genome of a single species. Assesses what proportion of genes have diff alleles and how many alleles there are per gene

Trophic level

Organisms position in a food chain/web/pyramid

Decomposers

Organism that obtains food by breaking down dead organisms

Food web

Group of interlinking food chains that shows in feeding relationships between them and the direction of energy flow

SIMPSONS INDEX OF DIVERSITY (D)

Represents that probability that 2 individuals randomly selected from a sample will belong to a diff species. Takes into account species richness of and species evenness.

FORMULA: D

D= 1- (SUM OF (n/N)²)

N= total no. Of organisms of all species, n= total no. Of organisms of a particular species

Value of D- ranges between 0 and 1

Near 0= low species density

Species Diversity

All the species in an ecosystem. Ecosystem with high species diversity r more stable to change. Variety of species and their relative abundance. As a species richness and evenness increases the species diversity also increases.

% cover

% of quadrat area that is covered by species. Used when organisms grow over surfaces forming a covering

Species frequency

The probability that a species will be found within a single quadrat

%F= no of quadrants in which species is found/ total no. Of quadrats * 100

Species density

Measure of the no.of individuals there are per unit area.

Measuring species density

In each quadrat make a list of species present and use identification key to identify the species. Do this 20-30 quadrats and find the avg no. Of individuals per m².

Formula: no of individuals counted/ total area of all quadrat

Random sampling

Used in areas that appear uniform and have no visible environmental gradient

Systematic sampling

Method of sampling where transects are used. Used when there are changes in the physical conditions of the environment

Line transect

Uses a tape measure stretched across the ground in a straight line. Any species touching the line is recorded

Belt transect

Uses 2 lines and all species between the 2 lines is recorded or quadrat is placed at regular sample points.

Mark-release- recapture

A sample of species is captured and marked then released back into the area from where they were captured. After a certain period of time another sample pf the species is captured and the no. Of marked organisms r counted. Uses Lincoln index. Used for estimating pop size and for motile organisms

Lincoln index

Estimated pop size= (total no. Of individuals in first sample * total no. Of individuals in second sample)/ no of marked individuals in second sample.

(N1*N2*)/ M2

Assumptions made for mark release recapture

Marked individuals distribute evenly. Mark does not come off. No migration in/out of pop. Few births/ deaths. Method of marking doesn’t affect survival

Pearsons linear correlation

Statistical test that determines whether there is a linear correlation between 2 variables.

Pearsons linear correlation equation

r= (Exy- n(mean of xy)/ (n-1)SxSy

r= correlation coefficient

X= no of species (A)

Y= no of species (B)

N= no of readings

Sx= standard deviation of A

Sy= standard deviation of b

Spearman’s rank correlation

Analyses the relationship between 2 variables but the data doesn’t show normal distribution.

Spearman’s rank- equation

Rs= 1- ((6 *ED²)/ n³-n)

R=r= spearman’s rank coefficient

D= sum of the diff in ranks between the 2 samples

n= no of samples