Practice Lab Grading
Internal Assessment Grades for “Environmental Gradients” Lab
Background:
An environmental gradient is a progressive change in a physical variable over distance,
which generally gives rise to a parallel distribution pattern in the associated plant and
animal communities. For example, changing degrees of exposure at increasing heights in
the littoral zone of a marine system create an environmental gradient up and down the
shore. In this investigation, the candidate is asked to identify a distribution pattern for
organisms that suggests such an environmental gradient. He/she needs to design a
sampling method to quantify the pattern and to measure the changes in a physical
variable that he/she considers to be responsible for the gradient.
ASSESSMENT:
Planning A
The aim (focused problem) is vague, and it simply restates the general aim given by the
teacher. The level of achievement for aspect 1 is not at all. The hypothesis is stated, but
no meaningful explanation is given: there is no mention of the factor to which the
organisms are exposed. There should be an explanation of why the exposure time would
affect the number of species found. The level of achievement for aspect 2 is partial. In
a sampling of this sort, the independent variable might be height below the tide, or above
the water line, and the dependent variable would be the number/type of organisms found.
No mention is made of variables at all. The level of achievement for aspect 3 is not at
all.
[npn = 0]
Planning B
Although the materials selected are typical for field surveys, the size of the quadrat
should be mentioned. The level of achievement for aspect 1 is partial. Also, although
the aim states that a physical variable will be measured, there is no method for doing so.
The method for selecting the survey site is vague. The description of the method is
insufficient to ensure that sampling is unbiased and random. Even if there is no control
measured, there are definitely dependent and independent variables, and it is not clear as
to how far apart the quadrats are placed. The level of achievement for aspect 2 is not at
all. As the description of where the quadrats are placed is poor, and there is no relevant
information about the size of the quadrat, it is difficult to determine whether sufficient
relevant data is gathered. Therefore, the level of achievement for aspect 3 is partial.
[pnp = 1]
Data Collection
The collection of data does not indicate that the numbers are for the individual organisms
seen. It is not clear whether sampling starts in a low-tide zone or a high-tide zone; a
reference to figure 2 would help. Also, in the data table, numbers and percentages are
freely mixed without any explanation of how the percentages are calculated. It is not easy
to see which organisms are missing from each quadrat. No data for physical parameters is
presented. The level of achievement for aspects 1 and 2 is partial.
[pp = 1]
Practice Lab Grading
Data Processing and Presentation
Only one graph is produced on one organism, making it difficult to draw any conclusions.
No errors are mentioned. The level of achievement for aspect 1 and 2 is partial
[pp = 1]
Conclusion and Evaluation
The candidate states that there was a change in the distribution of organisms, but this is
not evident from the data presented. A number of statements are made regarding
tolerance, sun exposure and dividing the beach up into areas. However, these are not
supported by the data or the information provided. The level of achievement for aspect 1
is partial. The procedure is not evaluated. The candidate states that a random sample
was made, but the method states that the site was deliberately chosen. Although a reason
is given for the unsupported hypothesis, this is superficial. The level of achievement for
aspect 2 is not at all. The only suggestion provided is for further transects on different
environments. This is not explained clearly. The level of achievement for aspect 3 is not
at all.
[pnn = 0]
So in summary:
Criterion
Achievement of aspects
Achievement level awarded
Pl(a)
Pl(b)
DC
DPP
CE
npn
0
pnp
1
pp
1
pp
1
pnn
0