NARRATOR:
You will hear two trainee teachers, Claire and Jake, discussing a science experiment for year 12 students.
NARRATOR:
First, you have some time to look at questions 21 to 25.
NARRATOR:
Now listen carefully and answer questions 21 to 25.
CLARE:
How is the practical teaching going?
JAKE:
It is more demanding than I expected.
JAKE:
Although some of my classes are excellent.
CLARE:
I'm having real difficulty with my year 12 science group.
JAKE:
Is their behavior hard to manage?
CLARE:
Discipline is not really the problem.
CLARE:
They simply cannot see how science connects with everyday life, and that is frustrating.
CLARE:
They listen, and their results in last week's test were reasonable, but they show almost no genuine interest.
CLARE:
For my teaching placement, I also have to plan an experiment for them.
CLARE:
I considered a project on children's diets, perhaps asking pupils to record their meals and comparing that information with their health.
JAKE:
The food records would be manageable, but you would also need medical information about the children.
JAKE:
Families might object because of confidentiality.
JAKE:
The findings could be valuable if you obtain the data.
JAKE:
Yet, getting it would probably be difficult.
JAKE:
Have you considered an experiment with animals instead?
CLARE:
Would the students find that distressing?
JAKE:
The animals would not need to suffer.
JAKE:
You could simply feed them a particular diet and observe the effects.
CLARE:
Would permission be difficult to obtain?
JAKE:
You would submit a short plan and complete a form, but the approval process is fairly simple.
CLARE:
Even if a diet changed in animals' health, though, we could not assume that people would respond in the same way.
JAKE:
Exactly, but every experiment has limits, so that issue cannot be removed entirely.
CLARE:
Which animals would be suitable for studying diet?
JAKE:
Yes, specially bred laboratory mice.
JAKE:
What precise question would the experiment investigate?
CLARE:
Something related to nutrition.
CLARE:
Perhaps the effect of supplements, such as additional iron or protein on health.
JAKE:
That covers too much.
JAKE:
You could narrow it to one supplement, perhaps examining how sugar affects the mice.
CLARE:
Actually, it may be better to ask whether mice regulate how much they eat.
JAKE:
You mean what they do when extra sugar is available, even though they do not need it?
CLARE:
Would they consume it or choose not to?
JAKE:
A later study could introduce another variable.
JAKE:
Some mice might have a wheel and be able to exercise, while the others remain inactive.
CLARE:
I could also repeat the trial with another food or a different genetic strain of mouse.
CLARE:
But varying the amount of exercise sounds more interesting, so I may develop that idea.
NARRATOR:
Before you hear the rest of the conversation, you have some time to look at questions 26 to 30.
NARRATOR:
Now listen and answer questions 26 to 30.
CLARE:
Can I describe a possible procedure for the experiment using a sugar supplement?
JAKE:
I carried out a similar study when I was at college.
CLARE:
How many mice should I use?
JAKE:
Around 12, all of them young, rather than a mixture of young and old animals.
CLARE:
I would divide them equally into two groups of six.
CLARE:
How could I distinguish one group from the other?
CLARE:
I thought of tags or some other kind of mark.
JAKE:
Food coloring would work and would not harm them.
CLARE:
Each group would then be kept in a separate cage.
CLARE:
Group A would be the control group and receive only ordinary commercial mouse food.
CLARE:
Is that easy to buy?
JAKE:
Yes, it is sold as dry pellets.
CLARE:
Group B would receive the identical food with additional sugar.
JAKE:
Would you give them sugar on its own?
CLARE:
No, it would probably be better to mix the sugar into something such as cereal.
JAKE:
You should weigh the mice once a week using an electronic scale.
CLARE:
We cannot hold them on the scale because that would alter the measurement.
JAKE:
Put each mouse in a weighing chamber so it cannot escape.
JAKE:
That sounds specialized, but a plastic box with holes in the lid will do.
CLARE:
Once we have recorded each mouse's weight gain, we can calculate the mean for both groups and the standard deviation.
CLARE:
Then decide how to continue.
CLARE:
The students should enjoy this.
JAKE:
There is one other point.
