Biodiversity (Cambridge (CIE) A Level Biology): Flashcards
Exam code: 9700
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Define an ecosystem.
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Define an ecosystem.
All the living organisms (the community) and non-living (abiotic) components in a particular area, together with the interactions between them.
Define an organism's niche.
The role of an organism within its ecosystem — including how it obtains its food and its interactions with biotic and abiotic factors.
Define a habitat.
The place where an organism lives.
Define a population.
All the organisms of the same species living in a habitat at a given time.
Define a community.
All the populations of different species living and interacting in the same area.
The role of an organism within its ecosystem is called its .
The role of an organism within its ecosystem is called its niche.
True or False?
An organism's niche is simply the place where it lives.
False.
The place where an organism lives is its habitat. Its niche is its role, including how it feeds and interacts with biotic and abiotic factors.
Define biodiversity.
The variety of living organisms in an area — including the range of ecosystems, the number and abundance of species, and the genetic variation within species.
State the three levels at which biodiversity can be assessed.
The number and range of different ecosystems and habitats
The number of species and their relative abundance
The genetic variation within each species
Define species diversity.
The number of different species and their relative abundance within a community.
Define genetic diversity.
The variety of genes (alleles) within a species.
Define habitat diversity.
The number of different habitats and ecosystems within an area.
Genetic diversity refers to the variation in within a species.
Genetic diversity refers to the variation in alleles within a species.
True or False?
Species diversity depends only on the number of species present.
False.
Species diversity depends on both the number of species and their relative abundance (how evenly individuals are spread between species).
Define random sampling.
Selecting sample sites so that every location has an equal chance of being chosen (e.g. using randomly generated coordinates).
Why is random sampling important when determining the biodiversity of an area?
It avoids bias, so the sample is representative of the whole area.
This makes the results valid and allows reliable statistical conclusions to be drawn.
How can sampling of an area be made random?
Generate random coordinates (e.g. using a random number generator) and place quadrats at those positions.
Why should a large number of samples be taken?
To make the results more reliable and representative, and to reduce the effect of anomalies.
Random sampling reduces , making the results more representative of the whole area.
Random sampling reduces sampling bias, making the results more representative of the whole area.
True or False?
Placing quadrats where you can see the most plants is a form of random sampling.
False.
Deliberately choosing where to place quadrats introduces bias, so the sample is no longer random or representative.
Define a frame quadrat.
A square frame of known area placed on the ground and used to sample the abundance of organisms.
Define percentage cover.
The proportion of the ground within a quadrat that is covered by a particular species, estimated as a percentage.
When is a transect used instead of randomly placed quadrats?
To measure how the distribution of organisms changes across an environmental gradient (a gradual change in an abiotic factor across an area).
What is the difference between a line transect and a belt transect?
Line transect: record only the organisms touching the line.
Belt transect: record organisms in quadrats placed at intervals along the line, giving abundance over an area.
Which method is used to estimate the abundance of mobile animals?
Mark-release-recapture, using the Lincoln index.
Describe the mark-release-recapture method.
Capture a sample, mark the animals and release them.
After time to mix, capture a second sample.
Use the proportion that are marked to estimate the total population size (Lincoln index).
State three assumptions made when using the Lincoln index.
No births, deaths, immigration or emigration during the study.
Marking does not harm the animals or affect their survival.
Marked individuals mix randomly back into the population.
Abundance of plants is often measured by counting organisms inside a square frame of known area called a .
Abundance of plants is often measured by counting organisms inside a square frame of known area called a quadrat.
When is Pearson's linear correlation used?
When two variables show a linear relationship and the data are quantitative and normally distributed.
What does the Pearson correlation coefficient (r) tell you?
The strength and direction of a linear correlation between two variables, on a scale from −1 to +1.
What do values of r = +1 and r = −1 indicate?
r = +1: a perfect positive linear correlation.
r = −1: a perfect negative linear correlation.
What does a Pearson coefficient of r = 0 indicate?
There is no linear correlation between the two variables.
State two conditions that must be met to use Pearson's rather than Spearman's correlation.
The data are quantitative and normally distributed.
The relationship between the variables appears linear.
Pearson's linear correlation can only be used when the data are distributed.
Pearson's linear correlation can only be used when the data are normally distributed.
True or False?
A Pearson coefficient close to +1 indicates a strong positive linear correlation.
True.
The closer r is to +1, the stronger the positive linear correlation between the variables.
When is Spearman's rank correlation used?
To test for a correlation between two variables when the data are not normally distributed or are ordinal (can be ranked), or when the relationship is not linear.
What does Spearman's rank correlation coefficient (r_s) measure?
The strength and direction of the correlation between two sets of data that have been placed in rank order.
What do values of r_s = +1, −1 and 0 indicate?
+1: perfect positive correlation.
−1: perfect negative correlation.
0: no correlation.
What is the first step in calculating Spearman's rank correlation?
Rank each set of data separately, from highest to lowest (or lowest to highest).
Why might Spearman's rank be chosen instead of Pearson's?
Because the data are not normally distributed (or are ordinal), so the conditions for Pearson's linear correlation are not met.
Before calculating Spearman's coefficient, each set of data must first be placed in order.
Before calculating Spearman's coefficient, each set of data must first be placed in rank order.
True or False?
A Spearman's rank coefficient of −0.9 indicates a strong negative correlation.
True.
A value close to −1 shows a strong negative correlation — as one variable increases, the other decreases.
What does Simpson's index of diversity (D) measure?
The biodiversity of a habitat, taking into account both the number of species and the relative abundance of each species.
What is the range of Simpson's index of diversity (D)?
D has a value between 0 and 1.
What do high and low values of D indicate?
A value close to 1 indicates high biodiversity.
A value close to 0 indicates low biodiversity.
Which two components of a community does Simpson's index take into account?
The number of different species (species richness).
The abundance of each species (species evenness).
Why is a habitat with a high value of D generally considered more favourable?
High biodiversity means the ecosystem is more stable and better able to withstand change (more resilient).
A Simpson's index of diversity value close to indicates high biodiversity.
A Simpson's index of diversity value close to one indicates high biodiversity.
True or False?
A habitat with a Simpson's index of diversity of 0.9 is more biodiverse than one with 0.3.
True.
The closer D is to 1, the greater the biodiversity, so 0.9 represents higher biodiversity than 0.3.
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