Populations [6]: Exam Questions (A Level Biology)


Uploaded by freeeschool on 07.10.2012

Transcript:
A Level Biology: Populations 6 – Exam Questions
Hi! Welcome to my sixth video on the series about Population. Today, we are going to be
answering some more exam questions.
So these questions, again, are taken from the AQA Biology course and it is taken from
the Unit 4 paper.
We look at the first question: Woods can be coppiced to provide a continuous supply useful
logs and poles. Coppicing involves cutting down some trees in a wood to leave stumps.
New shoots grow from the stumps and after about 15 years, these trees can be coppiced
again.
Because coppicing produces wood with patches of light and shade, the diversity of plants
and animals in a coppiced wood is high.
Ecologists investigate the effects of coppicing on the fly ring of wild daffodils growing
in a wood in Cambria. Some areas of the wood were coppiced and some were not. The graph
shows the results from this investigation.
What you’ve got, the hash line is not coppiced and so, no cut down of trees. The fore line
shows it being coppiced. You can clearly see here, there is a spike with the coppiced version.
You could collect data from coppiced plants by using quadrats. Describe how you place
the quadrats at random.
This is a standard question to do with quadrats. So what you would do is you grid the area
from a specified start point and then you randomly generate some coordinates off the
base of the computer, a random number generator, pulling numbers out of the hat or anything
of that nature.
The next question: Describe how you would decide the number of quadrats to use in order
to collect representative data.
There are several possibilities and this question is worth three marks, but there are several
things in which you could say. One of them is to ensure reliability and anything to do
with it should be mentioned in terms of reliability. That would be one mark.
Another simple one to tell is enough to do is a statistical test. You don’t even have
to name what the stat test is, but simply mentioning that.
Then, when using more quadrats fail to alter findings. Essentially, when you plotted the
data, by adding more data doesn’t have an overall effect or have a marked effect on
your results overall. That could possibly be another thing you could say. And so, any
two from three.
These previous two questions are pretty stock questions you would expect on a population
test. This one is more specific to the data you are given, so members of the public visit
this wood to see wild daffodils in flower. Explain how the information in the graph could
help the owners manage the wood so that there are many wild daffodils and flower every year.
If you actually look at the data that is given here, when it is being coppiced, there tends
to be a spike in the number of daffodils. When it is not coppiced, the numbers tend
to stay quite like. So you be able to identify where the peak is and the peak is out every
five years.
Now the question specifically asks so that there were many wild daffodils in flower every
year. So what you want is daffodils within the wood every year. To get high number of
daffodils, you are going to have to coppice. You are going to have to coppice every five
years. So that would be the first mark.
Now, it says in flower every year. So what you need is a system whereby regardless of
what year it is, people should be able to come and visit and see daffodils. Now, the
problem is, if you coppiced the whole lot, what you will end up doing is having no daffodils
for three to four years. So what you need to do is coppice in different part of the
wood every year. Therefore, that is the second mark.
On the final question: The ecologists analyzed the relationship between the number of daffodils
in flower and the whole wood and the date you collected from nearby weather stations
the previous year. They use Spearman rank correlation test. The data shows the results.
Ecologist concluded that a wet, cold summer produces good flower in the following spring.
Do you support this conclusion? Use the data on the table to explain your answer.
What it is saying is the ecologists said that when it was wet and it had a cold summer,
you normally got good flowering plants. If you look at the data here, if we look at this
first conclusion here, so wet, so with this, that would be related to the top two and the
total rainfall and what you notice here is there is a positive correlation. So it’s
.65 and .74. So you could say, by analyzing it that there is a positive correlation between
more rain and between the flowering plants. So wet corresponds to these top two results
here.
Now the cool summer conditions, you mean monthly temperature. That shows a negative correlation.
That basically means that the hotter it is, the more they grow. Again, you could reference
that. So with the cool, these two value here because it’s a negative correlation that
means that the cooler it is, the more they grow. That would obviously agree with the
conclusion.
The one final thing that you got here, you got this column here that talks about statistical
significance and therefore you could say that all of the results show significance and therefore,
this would back up the findings.
Another thing to note down there is because it significantly it would be unlikely that
it is not just down to chance and therefore, there are other factors involved, specifically,
the rainfall and the temperature.
[end of audio – 05:42] A Level Biology: Populations
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