Mod 4 Chap 11: Biodiversity Flashcards
Describe how biodiversity can be studied / measured at different levels.
- closer a region is to equator = more biodiversity
- biodiversity plays important role in conservation, informs scientists of species present
- this provides baseline for level of biodiversity in an area
- so, effect of any changes to environment can be measured from this info (e.g. effect of human activity, disease, climate change etc)
- Biodiversity can be studied at diff levels, of:
Habitat biodiversity, Species biodiversity, and Genetic biodiversity
Describe the study of habitat biodiversity, and give examples of habitats.
- reefers to no. of diff habitats found in an area
- each habitat can support a no. of diff species, so, greater the habitat biodiversity = greater the species biodiversity in that area
Examples: meadow, woodland, streams, wild grassland
Describe the study of species biodiversity, and define species.
Species: a group of similar organisms able to reproduce to give fertile offspring.
Two components of species biodiversity:
- species richness: no. of diff species living in a particular area
- species evenness: a comparison of no.’s of individuals of each species living in a community
Describe the study of genetic biodiversity.
- refers to variety of genes that make up a species
- many of genes making up organisms are same for all individuals in a species, but, for many genes, diff versions (alleles) exist
- this then leads to genetic biodiversity in a species which can mean quite diff characteristics are exhibited
- greater genetic biodiversity in a species = better adaption to changing environment, + is more likely to result in disease-resistant individuals
- when population of an organism has a large ‘gene pool’, it has greater chance of surviving than a pop w/ limited genetic variability
- so genetic biodiversity = important
Define biodiversity, community and gene pool.
Biodiversity: The variety of living organisms present in an area
Community: All the populations of living organisms in a particular habitat
Gene pool: The variety of genetics of the individuals in a population (so large gene pool = significantly varying genetics in individuals of a pop)
Describe how genetic biodiversity can be assessed.
- measuring polymorphism
- polymorphic genes have more than one allele
- but most genes are monomorphic (only have a single allele that exists for them)
- this ensures basic structure of individuals in a species remains consistent
- proportion of polymorphic genes can be measured w/ formula:
Proportion of polymorphic gene loci = no. of polymorphic gene loci / total no. of loci
(Where locus of a gene refers to position of a gene on a chromosome)
- greater proportion of polymorphic gene loci = greater genetic biodiversity in a population
Describe the importance of sampling, and define sampling.
Sampling: taking measurements of a limited no. of individual organisms present in a particular area.
- can be used to estimate no. of organisms in an area, without counting them all. (No. of individuals of a species present in an area = abundance of the organism)
- can also be used to measure a particular characteristic of an organism
- after measuring sample, can use results to make generalisations / estimates about no. of organisms, distribution of species, or measured characteristic throughout entire habitat
- sampling can be done in two ways: random + non random
Describe random sampling.
- means selecting individuals by chance
- each individual in pop has equal likelihood of selection
- random number tables / computers can be used to decide, you have no involvement in the choice of what is studied
Describe a practical investigation into collecting a random sample in the field.
E.g. Taking a random sample at a grass verge:
- mark a grid on grass w/ two tape measures at right angles
- use random numbers to determine x and y coordinates on grid
- take sample at each of coordinate pairs generated
Describe non random sampling.
- alternative method where samples is not chosen at random
- divided into three main Non Random sampling techniques:
Opportunistic, Stratified, Systematic
Describe Opportunistic Non Random Sampling.
- weakest form of sampling as may not be representative of population
- uses organisms that are conveniently available at the time
Describe Stratified Non Random Sampling.
- Some populations can be divided into a no. of strata (subgroups) based on a particular characteristic
- random sample then taken from each strata proportional to its size
Describe Systematic Non Random Sampling, and how it is carried out.
- when diff areas in an overall habitat are identified + then sampled separately
- often carried out using a line / belt transect
Line transect: marking a line between 2 placed poles (one at one end of chosen site + one at other), then taking samples at specified points between two points, e.g. all organisms that touch the line
Belt transect: provides more information. Two parallel lines are marked in ground, + samples are taken of area between two lines (e.g. by placing quadrants)
Describe a practical investigation into collecting a non random sample in the field.
E.g. With stratified, on a heathland
- heathland may have patches of gorse on it
- so Heath + gorse areas would be sampled separately according to how much of each there was in the habitat
Describe the issues with the reliability of sampling.
- a sample = never entirely representative of organisms present in a habitat
- this may be due to:
Sampling Bias
Chance
Describe Sampling Bias as an issue with the reliability of sampling.
- selection process may be biased, may be by accident / on deliberate
- effects of sampling bias can be reduced using random sampling (as human involvement in choosing sample is removed)
Describe Chance as an issue with the reliability of sampling.
- organisms selected may, by chance, not be representative of whole pop
- chance can never be completely removed from process, but it’s effect can be minimised w/ a large sample size
- as, greater no. of individuals studied = lower probability that chance will influence result
- so, larger sample size = more reliable result
Describe some methods used to collect living animals to sample.
- Pooter: catches small insects, person sucks on mouthpiece + insect drawn into holding chamber via inlet tube, filter before mouthpiece stops insect being sucked into person’s mouth
- Sweep Nets: catch insects in areas of long grass
- Pitfall Traps: catch small crawling invertebrates, a deep hole in ground covered w/ roof structure to prevent filling w/ rain water, left overnight to collect nocturnal species too
- Tullgren Funnel: device to cope t small animals from sample of soil / leaf litter, sample placed on sieve fixed across wide end of funnel, light bulb above funnel to dry + warm sample, so animals move down through sieve into funnel + collecting dish, (which may contain water / alcohol to prevent escape)
- White Sheets: placed on ground below bushes branches, bush shaken so invertebrates fall onto white sheet, can then remove from sheet w/ pooter
- Light Traps: collects insects by confusing them + intercepting chosen flight path, most commonly effective for night-flying insects
Describe some other methods used to sample plants.
Quadrats, two main types:
- Point quadrat: frame w/ a horizontal bar, long pins pushes through bar at set intervals to reach ground, each species of plant pin touches is recorded
- Frame quadrat: square frame divided into a grid of equal sections. Type + no. of species in each section of quadrat is recorded
Describe how quadrats can be used to collect the most valid representative sample of an area.
- sample = most valid + representative when quadrats used following a random sampling technique
- but, can be placed systematically to study how presence + distribution of organisms across an area of land varies
Describe how to measure species richness.
- identification keys used to accurately identify all species present in a habitat (I.e. images to identify them / questions to classify them into particular species, based on identifiable characteristics they have)
- a list should be complied of each species identified
- total no. of species can then be calculated
Describe how to measure species evenness.
- take random samples of a habitat
- count no. of individuals of each diff species
Describe the overall general method to estimate biodiversity using samples.
- choose a site to sample (via random / non random)
- record no. of diff species / count no. of individuals of each species
- repeat process; take as many samples as possible to give better indication of whole habitat
- estimate no. of individuals for whole habitat by calculating mean for data collected in each sample + multiplying it by size of whole habitat
Describe how to calculate the biodiversity of a habitat using Simpsons index of diversity (D).
- Simpsons index if diversity (D) = better measure of biodiversity than simple way of just species richness, as takes into account both species richness + evenness
Formula:
D = 1 - ☪ (n / N)^2
Where
☪ (see notes for actual symbol) = sum of (total)
N = total no. of organisms of all species
n = total no. of organisms of a particular species
Simpsons index always results in values between 0 and 1. Higher the value = more diverse the habitat.
Practice questions.