Populations [5]: Exam Questions (A Level Biology)


Uploaded by freeeschool on 07.10.2012

Transcript:
A Level Biology: Populations 5 – Exam Questions
Hi! Welcome to my fifth video on the series about Population. Today, we are going to be
looking at some more exam questions.
The questions we are going to do today are from the AQA Biology course and they’re
taken from the Unit 4 paper.
So if we look at the first question: Explain what is meant by the ecological term “population”.
This is only worth a single mark.
For this, you need to be quite specific. So you need to say that it is a number of a single
species living in a given area at a given time. So reference the important key terms
there: single species, then referencing the given area at a given time.
The next question is much trickier because it asks you to analyze a graph and then to
be able to interpret what it is basically saying. So if we look at it here, the diagram
shows the three survival curves A, B and C. Along the bottom, you have A, just a percentage
of the maximum and up beside, you have the number of survivors.
So the question says, assume that the maximum age of a person living in a developed country
is 95 years. The diagram can be used to find the average life expectancy of people living
in developed countries. Explain how.
It tells you that the maximum age that people can live to in a developed country is 95 years
and this is where this value here comes in ages, the percentage of maximum. So what it
is essentially saying where you have very little survivors, close to 0, then this value
here would correspond to 95 years. Now, it says, life expectancy of people living in
developed countries. So you need to use something on this graph to determine the average life
expectancy for people living in a developed country. So you need to tell which line it
is. If you look at the survival curves, if it is a developed country, then you would
expect people to live to an old age and therefore, you wouldn’t expect people to be dying young.
The only curve that represents that is C.
So it then asks for the average life expectancy. Now, on here, the average life expectancy
will be where you get a value for the number of survivors that’s half. The average would
be 5,000 in this case. So what you would do is draw a horizontal line across from 5,000,
go cross the line C and then down and to the age of the percentage of the maximum. What
should come out with this value would be roughly 90.
What this means is your average life expectancy would be 90% of the maximum and the maximum
in this case is 95 years. So therefore, you calculate what 90% of 95 years will be. Therefore,
you answer will come out at 85-86 years.
You can do this with the other curves, except their maximum values would be much less and
so there would be no one nearer than the 95 years. They would probably have a maximum
age of somewhere in the 50s, for instance.
The final question asked: Curve A is a survival curve of people living in the UK in the 1750.
Explain why the curve has this shape.
So what we can see here is this dramatic drop off of the number of survivors and what’s
happening here is people are dying. Therefore, the thing you could say is a high mortality
rate or high death rate.
The second mark is simply quoting a cause of this, so something like a disease, lack
of irrigation, nutrition and lots of them are valid at this point.
If you would like to join me on my next video, I’ll be looking at another exam question.
[end of audio – 03:44] A Level Biology: Populations 5- Exam Questions
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