Biodiversity

Question 1

What is meant by assessing ecosystems?

Answer 1

Quadrats are square frames of known size and can be used to sample various features of a habitat

Question 2

Biodiversity definition and example:

Answer 2

Biodiversity can be defined as the variety of different species and the numbers of individuals within those species in a habitat.
for example - a coral reef ecosystem has a high biodiversity.

Question 3

Quadrat meaning:

Answer 3

The population size of immobile (e.g., plants) or slow-moving organisms (e.g., limpets) can be estimated using random samples of quadrats. Quadrats can be used to estimate the biodiversity of a habitat.
The higher the number of different species in the quadrat samples, the higher the biodiversity.
The more even the number of individuals of the different species, the higher the biodiversity.

Question 4

population sizes definition:

Answer 4

The population size of a species in a habitat can be estimated by counting the number of individuals in various quadrat samples of the habitat.
This can also give an indication of the distribution of a particular species and whether a species is more abundant in one habitat compared to another.

Question 5

Quadrat information:

Answer 5

Quadrats are normally 1m2 square frame divided into 100 squares.
Each square represents 1% of the total area of the quadrat.
If an individual covers more than half of a square, it is counted as representing 1% of the quadrat.
Quadrats are used to count the population size within a large area.

Question 6

Sampling meaning:

Answer 6

If you wanted to investigate the size of a population, it would take hours to count every individual.
Taking samples (a small section of the total area) allows the population size to be estimated.
It is important that the samples accurately represent the total population size.

Question 7

Random sampling meaning:

Answer 7

Random sampling can be applied by dividing the area of interest into a grid and labelling the grid with coordinates.
A random number generator provides a set of random coordinates.
The quadrats can be placed using the coordinates.

Question 8

Transects meaning:

Answer 8

Quadrats could also be placed at regular intervals along a transect.
A transect is a line across a habitat, usually placed using a tape measure.
Transects are used when there is a change, or gradient, in abiotic conditions across the habitat.
Transects are used when looking for changes in the abundance or distribution of a species across the environment (e.g., how abundance changes from open field to forest).

Question 9

Line transect meaning:

Answer 9

A line transect records the species that makes contact with the tape measure at regular intervals along the transect.

Question 10

belt transect meaning:

Answer 10

A belt transect uses quadrats.
Quadrats are placed at regular intervals along the transect.
An abundance of different species in the quadrat can be measured by:
Percentage cover – estimate how much of the quadrat is covered by a particular species
Frequency – count how many individuals of a particular species are present in the quadrat.

Question 11

method for using quadrats to estimate a population size:

Answer 11

Divide the habitat up into a series of quadrat-sized cells.
Randomly select a given number of cells, then go out into the habitat and place the quadrat in these positions.
To evaluate the quadrat contents, either count the number of individual organisms of interest or record the percentage of the quadrat taken up by an organism (e.g. grass).
The samples from the quadrat are used to estimate the total population in a given area:

population = number counted x (total survey area / area sampled)

Question 12

example question

Answer 12

In a survey of a 100m2 area, you count a total of 30 dandelions in 10 quadrats. The quadrats have sides of 0.5m. Estimate the total population size in this area.
1)
Remember how to work out the area of a quadrat
Area of 10 quadrats = 10 x quadrat length (m) × quadrat height (m)
2.)
Calculate the total area covered by the quadrats
Area covered by 10 quadrats = 10 x 0.5 x 0.5 = 2.5m2
3.)
Calculate the ratio of survey area to area covered by quadrats
Survey area ÷ Area covered by quadrats = 100m2 ÷ 2.5m2 = 40
4.)
Write the formula for total population size
Total population size = (Survey area ÷ Area covered by quadrats) x population counted
5.)
Substitute the values in to get the answer
Total population size = 40 x 30 = 1200 dandelions