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More
questions on homeostasis
Monacia
Williams, Contributor
Good
day students. How are you today? I
hope you had a brilliant week and
that working on your SBAs has not
been overwhelming you. Take heart
and try to accomplish something definite
every day.
Last
week, I ended the lesson by promising
to continue with the answers to the
questions from the previous lesson,
and begin the study of the nervous
system. However, I have decided to
change that. I will finish the answers,
then, instead of beginning to discuss
the nervous system, I will go through
another question on excretion/ homeostasis
with you. I am now beginning to realise
that many students have difficulty
in answering these questions correctly,
hence the reason for doing this.
Answer
to last week's question- cont'd
Let
me remind you of the question.
Account
for the effect of exercise on
- the
breathing rate
- the
pulse rate
How
to answer
Take
note that the question is not asking
you about what happens to the breathing
rate during exercise. The question
is asking you to give reasons to account
for what happens. Where do you begin?
You begin with what you know. What
do you know? You know that when you
exercise your breathing rate increases,
and you also know that as your breathing
rate increases, your pulse rate also
increases. Why does this happen? We
have already set the background; let
us now formulate the answer.
- Exercise
causes breathing rate to increase.
- This
is because more energy is required
for the increased activity in the
muscles.
- Therefore,
the rate of respiration has to increase.
- This
respiration is aerobic and requires
oxygen.
- To
supply the additional oxygen to
the cells, the rate of intake/breathing
has to increase.
- Increased
rate of respiration also produces
increased amounts of carbon dioxide.
- This
is toxic and has to be removed from
the tissues.
- This
also requires an increased breathing
rate to remove the carbon dioxide
from the lungs.
The
above list states the points that
should be included in your answer
to give you full marks. You can now
use these points to write your essay.
Let
us now look at the remainder of the
question
How
to answer
The
increase in the pulse rate has already
been mentioned above. Now we need
to take a closer look.
The
pulse rate is an indication of how
fast the heart is beating. The heart
beats in order to send blood with
oxygen to, and to remove carbon dioxide
from, respiring cells.
- Exercise
requires more energy.
- In
order to provide more energy, respiration
has to increase, hence more oxygen
is required and more carbon dioxide
is produced.
- Oxygen
can only get to, and carbon dioxide
can only be removed from, the tissues
by the blood.
- Hence,
the heart has to pump blood at a
faster rate.
- The
faster rate of pumping increases
the pulse rate.
You
can now use these points to write
an answer that will earn you full
marks.
New
question
- With
the aid of a diagram, describe the
structure of a kidney tubule and
explain why its structure makes
it well suited to its function.
8 marks
- Anti-diuretic
hormone, ADH, causes changes in
the functioning of the kidney tubule.
Explain
how these changes are brought about.
4 marks
- Suggest
TWO reasons why osmoregulation is
important in plants. 4 marks
- A
farmer selected crops which had
deeply penetrating roots, and leaves
with thick cuticles for a particular
area of land that he wished to cultivate.
Fully explain why the farmer would
select these features for his crops.
4 marks
Variations
of this question have appeared on
many CSEC examination papers, so I
am asking you to pay particular attention
to the advice and the answers that
are given. Note that in the new examination
format, the question would not be
as long since it would only be worth
15 marks
If
you have copies of past papers, and
it is recommended that you all should,
go through them as soon as you have
completed a topic and test yourself
by attempting to answer the questions
that relate to the topic you have
just completed. This will help you
to know if you have adequately covered
the topic. Remember that what you
have studied is all that you will
have available to you in the examination.
In going through the past papers you
will also notice that the questions
in Section B of Paper 02 invariably
begin by asking for a diagram. What
does this mean? It means that you
will need to practise drawing those
diagrams. You cannot learn how to
reproduce a diagram by just looking
at it. You need to draw and redraw
it in order to commit it to memory.
Let
us look at the question
You
are asked to use a diagram to help
you to describe the kidney tubule
and explain why its structure is well
suited to its function. This gives
you two options. You can use an annotated
diagram to do all of this, or you
can use a diagram and narrative. What
are the features that should be included
in the diagram? Those features that
are important to the functioning of
the tubule. This leads to the next
question: what are the functions of
the tubule? These are:
Join
me again next week as we integrate
these features into the answer. Have
a good week!
Monacia
Williams teaches at Glenmuir High
School. Send questions and comments
to kerry-ann.hepburn@gleanerjm.com
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