AQA Unit 4 (3.4.7) Investigating diversity Flashcards
Define Species Richness
number of species (in a community/habitat/ecosystem/area);
Reject number of species in a population
Define Index of Diversity
Index of diversity – the relationship between the number of species (in a community) and the number of individuals in each species;
Accept equation with N and n correctly explained
Genetic diversity in soil species was traditionally inferred by making observations after growing prokaryotes on agar plates.
However, it is estimated that less than 10% of prokaryotes found in soil will grow if spread on an agar plate in a laboratory.
In recent years, our knowledge of prokaryotic biodiversity in the soil has increased.
Suggest why.
- DNA/genome sequencing now used;
Accept RNA/amino acid sequencing
- (Now) can analyse every/more prokaryote species (in the community);
Accept ‘identify’ for analyse
- Rather than just recording measurable/observable characteristics;
Describe a method that could be used to determine the mean percentage cover of algae on a coral reef.
Do not include information on the difficulties of using your method underwater.
- Method of randomly determining position (of quadrats) e.g. random numbers
table/generator;
Ignore line/belt transect.
- Large number/sample of quadrats;
Accept many/multiple/lots but ignore several.
Ignore point quadrat.
Accept squares/frames (of a grid) for quadrats.
If a specified number is given, it must be 10 or more.
- Divide total percentage by number of quadrats/samples/readings;
Littorina littorea is a species of snail found on rocky sea shores.
A student investigated variation in snail shell height in two populations of snails.
Give two ways in which the student could ensure his samples would provide a reliable measure of the variation between individuals in each population.
- Select at random;
Accept description of random technique
- Large sample/number (of snails)/>10;
The student could determine the median, mode and range from his measurement of shell heights in these populations.
Give two other statistical values the student could calculate from his measurement of shell heights in populations.
Mean and standard deviation;
The student noticed there was a difference in shell height between these populations of snails. He wanted to investigate if the difference was significant.
Give a suitable null hypothesis to use in his investigation and name the statistical test to use with these data.
- No (significant) difference between (mean) height (in these populations);
- (Students) t-test;
The genetic diversity of species is measured by comparing differences in the base sequence of DNA or differences in the base sequence of mRNA.
Give two other ways in which genetic diversity between species is measured
1. Comparing (measurable/observable) features/characteristics;
2. Comparing amino acid sequences/primary structures (of a/named/the same protein);
Scientists investigated differences between 260 North American bird species by comparing the base sequence of a gene in mitochondrial DNA. They compared the gene base sequence of each bird with all of the other 259 species. For each comparison they calculated the percentage difference in base sequence.
(b) Figure 1 shows the base sequence for part of the gene in two species.
Figure 1
Species 1 A G C T G C C T A G A
Species 2 A T G T G G C A A G A
Calculate the percentage difference in base sequence for these base sequences.
36 to 36.4;
Bees are flying insects that feed on nectar made in flowers. There are many different species of bee.
Scientists investigated how biodiversity of bees varied in three different habitats during a year. They collected bees from eight sites of each habitat four times per year for three years.
Suggest and explain two ways in which the scientists could have improved the method used for data collection in this investigation.
- Collect at more times of the year so more points on graph/better line (of best fit) on graph;
Both suggestion and explanation is required for each mark point.
The explanation must relate to the graph.
- Counted number of individuals in each species so that they could calculate index of diversity;
- Collected from more sites/more years to increase accuracy of (mean) data;
An environmental scientist investigated a possible relationship between air pollution and the size of seeds produced by one species of tree.
He was provided with a very large number of seeds collected from a population of trees in the centre of a city and also a very large number of seeds collected from a population of trees in the countryside.
Describe how he should collect and process data from these seeds to investigate whether there is a difference in seed size between these two populations of trees.
- Use random sample of seeds (from each population);
- Use (large enough) sample to be representative of whole population;
- Indication of what size was measured e.g. mass;
- Calculate a mean and standard deviation (for each population);
- Use the (Student’s) t-test;
- Analyse whether there is a significant difference between (the means of) the two populations;
A student investigated the distribution of plants in a heathland.
The table below shows the number of plants he found in a sample area of 1 m2
What is the species richness of this sample?
4
Calculate the index of diversity of this sample. Show your working.
Use the following formula to calculate the index of diversity.
d =
where N is the total number of organisms of all species
and n is the total number of organisms of each species
2.68(6).
If answer incorrect:
Σn(n-1) = 242 = 1 mark
N(N-1) = 650 = 1 mark
Suggest how a student would obtain data to give a more precise value for the index of diversity of this habitat
- Take more samples and find mean;
- Method for randomised samples described.
Species richness and an index of diversity can be used to measure biodiversity within a community.
(a) What is the difference between these two measures of biodiversity?
Species richness measures only number of (different) species / does not measure number of individuals
Ecologists investigated the size of an insect population on a small island. They used a mark-release-recapture method. To mark the insects they used a fluorescent powder. This powder glows bright red when exposed to ultraviolet (UV) light.
(a) The ecologists captured insects from a number of sites on the island. Suggest how they decided where to take their samples
- Draw grid over (map of) area;
- Select squares / coordinates at random.
Give two assumptions made when using the mark-release-recapture method.
- No emigration / immigration;
- No losses to predation;
- Marking does not affect survival;
- Birth rate and death rate equal;
- (In this case) all belong to one population.
