Biodiversity

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33 Terms

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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.

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Species

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

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Ecosystem

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

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Population

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

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Habitat

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

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Abiotic Factors

Non-living, chemical and physical components of the ecosystems

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Community

All organisms of all diff species living in a habitat

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Ecological niche

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

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Species richness

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

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Producer

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

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Consumer

Organism that obtains food in its organism form from other species

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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

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Trophic level

Organisms position in a food chain/web/pyramid

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Decomposers

Organism that obtains food by breaking down dead organisms

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Food web

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

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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.

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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

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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.

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% cover

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

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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

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Species density

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

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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

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Random sampling

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

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Systematic sampling

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

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Line transect

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

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Belt transect

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

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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

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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

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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

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Pearsons linear correlation

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

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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

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Spearman’s rank correlation

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

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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