StudyPacks
STUDY.
KS4
SCIENCE
Coordination & Control
Homeostasis
This Study Pack aims to cover:
1. Controlling internal conditions.
SB5
Study Packs are prepared by Qualified Teachers and Specialists and are a complete range of comprehensive
compiled resources based on the UK National Curriculum covering the Primary and Secondary Frameworks
including SATs and GCSE examinations.
Student Name
Contents
Homeostasis Notes
2-6
Practice questions
7-9
Exam questions
10-16
Mark scheme
17-19
1
2
Homeostasis
The conditions inside the body must be controlled within narrow limits. This is called
homeostasis. These conditions include water content, ion content, body temperature and
blood glucose concentration.
The thermoregulatory centre is the part of the brain that monitors and controls body
temperature. The pancreas meanwhile monitors and controls blood glucose concentration. It
produces a hormone called insulin that reduces blood glucose levels. Diabetes is a disease
which can be caused by insufficient insulin.
Removing waste products
Waste products must be removed from the body. If they are not, they will increase in concentration
and may interfere with chemical reactions or damage cells. Waste products that must be removed
include carbon dioxide and urea.
Production and removal of waste products
Waste
product
Why is it produced?
How is it removed?
carbon
dioxide
it is a product of aerobic respiration
through the lungs when we breathe out
urea
it is produced in the liver when excess amino acids
are broken down
the kidneys remove it from the blood and make urine, which is stored in
the bladder temporarily
Water enters the body through food and drink. It is also a product of aerobic respiration in cells. If the
amount of water in the body is wrong, cells can be damaged because too much water enters or leaves
them. The animation shows how the amount of water lost as urine is controlled. Note that you do not
need to know any details of this for the examination.
3
Controlling blood glucose
You found out in your GCSE Science Biology 1 studies that the blood glucose concentration is
controlled to provide cells with a constant supply of energy. You might want to check your
understanding of this by looking at the section in Bitesize AQA GCSE Science about Hormones.
The pancreas and insulin
The pancreas monitors and controls the concentration of glucose in the blood. It produces a hormone
called insulin. Insulin causes glucose to move from the blood into cells. It lowers the blood glucose
concentration if it has become too high. This can happen after eating a meal that is rich in
carbohydrates (for example, sweets, potatoes, bread, rice or pasta).
The animation shows how this works.
4
Controlling sugar
Sugar too High
Sugar too low
5
Temperature regulation
Human enzymes work best at 37ºC, so the body’s temperature is controlled. A part of the brain called
the thermoregulatory centre monitors and controls body temperature. It gathers information as
nerve impulses from temperature receptors in:

the brain - these are sensitive to the temperature of the blood flowing there

the skin - these are sensitive to skin temperature
Sweating
Sweating is one way to help cool the body. We sweat more in hot conditions, so more water is lost
from the body. This water must be replaced through food or drink to maintain the balance of water in
the body.
Ions such as sodium ions and chloride ions are also lost when we sweat. They must be replaced
through food and drink. If the body’s ion content is wrong, cells can be damaged.
Temperature regulation - higher
If you become too hot or too cold, there are several ways in which your temperature can be controlled.
They involve sweating, shivering, skin capillaries and hairs.
Too hot
When we get too hot:

Sweat glands in the skin release more sweat. This evaporates, removing heat energy from the
skin.

Blood vessels leading to the skin capillaries become wider - they dilate - allowing more blood to
flow through the skin, and more heat to be lost.
Too cold
When we get too cold:

Muscles contract rapidly - we shiver. These contractions need energy from respiration, and some
of this is released as heat.

Blood vessels leading to the skin capillaries become narrower - they constrict - letting less blood
flow through the skin and conserving heat in the body.
The hairs on the skin also help to control body temperature. They lie flat when we are warm, and rise
when we are cold. The hairs trap a layer of air above the skin, which helps to insulate the skin against
heat loss
6
Homeostasis worksheet
What does the word homeostasis mean? ______________________________________________
_____________________________________________________________________________________________
Our bodies have to keep three important matters balanced, they are:
1. ______________________________________
2. ______________________________________
3. ______________________________________
Too hot/ Too cold!
Explain what happens to your body when you get too hot:
__________________________________________________________________________________________________
________________________________________________
_________________________________________________________________________
Explain what
happens to your body when you get too cold:
_____________________________________________________________________________________________________________________
____________________________________________________________________________________________________________
Fill in the gaps using the words: increase, decrease, 37
Too Hot
_____________________
in temperature
Sweating, hairs lie flat, and
increased blood flow to the
skin leads to a ___________ in
temperature
Negative
Core temperature
_______ ⁰C
Shivering, hairs stand on end and
decreased blood flow to the skin
leads to an ___________ in
temperature
feedback
Core temperature
_______ ⁰C
_____________________
In temperature
7
Too Cold
How can the core body temperature be measured?
_____________________________________________________________________________________________________________________
_____________________________________________________________________
Very high and very low temperatures
If you get too cold you can develop
_______________________________________
If you get too hot you can develop
_______________________________________
Blood glucose levels
Inject
sugar
pancreas
hormone
food
diabetes
levels
insulin
blood
Some people suffer from a disease called d___________. They do not produce enough of a
h____________ called i_____________ from the organ in the body called the p______________. Insulin
controls the b____________ s___________ levels. Diabetics have to be careful that they do not eat
too much sweet f__________. They may also need to i______________ themselves with the hormone
insulin to help control there blood sugar l_________.
What is a hormone?
____________________________________________________________________________________________________
____________________________________________________________
8
Homeostasis
1.
Explain How temperature is regulated in the human body? 4 marks
2.
Explain how sugar levels are controlled within the human body? 4 marks
3.
Explain how water level is controlled within the human body? 4 marks
9
Exam Questions
Q1.
The table shows four ways in which water leaves the body, and the amounts lost on a cool
day.
3
WATER LOSS (cm )
(a)
COLD DAY
HOT DAY
Breath
400
the same
Skin
500
Urine
1500
Faeces
150
(i)
Fill in the table to show whether on a hot day the amount of water lost would be
less
more
the same
The first answer has been done for you.
(3)
(ii)
Name the process by which we lose water from the skin.
...........................................................................................................................
(1)
(b)
On a cool day the body gained 2550 cm3 of water.
1500 cm3 came directly from drinking.
Give two other ways in which the body may gain water.
1 ..................................................................................................................................
2 ..................................................................................................................................
(2)
(Total 6 marks)
Q2.
The diagram shows a water balance for a girl who spends most of the day working at a
desk. It is not complete.
(a) Complete the diagram by writing in the volume of sweat
produced.
1)
10
(b)
The next day she spent much of the day training, doing many different types of exercise.
State how each of the following would change and why it would be different from the
previous day.
(i)
The amount of water given off as sweat.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(ii)
The amount of water breathed out.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(iii)
The amount of urine passed, if she had the same water intake as on the previous
day.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(c)
Which organ controls the amount of water in the body?
....................................................................................................................................
(1)
(Total 8 marks)
11
Q3.
The diagram shows the amount of water lost by an adult in one day.
The width of the arrows shows how much water is lost in each way.
(a)
Work out from the diagram the water loss for urine, skin and lungs and write the correct
figures in the spaces on the diagram.
(4)
(b)
When it is hot, much more water is lost from the skin. Which other method of water loss
would also change significantly?
Explain your answer.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
(Total 7 marks)
12
The table shows how much water is lost from a boy’s body on a cold day and on a hot day.
(a)
WATER LOST (cm3)
COLD DAY
HOT DAY
in sweat
50
300
in breath
100
100
in urine
1000
750
How do the figures for the hot day compare with those for the cold day?
Answer in as much detail as you can.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(b)
The boy does the same things for the same amount of time on both days.
Explain why the amounts of water lost in sweat and urine change.
Sweat ..........................................................................................................................
.....................................................................................................................................
Urine ...........................................................................................................................
.....................................................................................................................................
(2)
(c)
The rate at which the kidney re-absorbs water depends on the percentage of water in the
blood.
13
Describe, as fully as you can, what the graphs tell you.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(4)
(d)
How does your body control the rate at which your kidney re-absorbs water?
.....................................................................................................................................
.....................................................................................................................................
(2)
(Total 10 marks)
Q5.
The photograph shows a sand gazelle.
The sand gazelle lives in the Arabian Desert where temperatures often
reach 45 °C.
(a)
The sand gazelle feeds only at dawn and at dusk. At other times
it stays in the shade.
Suggest how this helps the animal to conserve water.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(2)
(b)
During the dry season, the sand gazelle’s liver and heart shrink in size. This reduces the amount of
oxygen that the body needs.
Suggest how needing less oxygen helps the animal to conserve water.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(2)
(Total 4 marks)
Q6.
The gemsbok is a large herbivore that lives in herds in desert areas of South Africa.
14
Gemsboks feed on plants that are adapted to living in dry conditions. There are not many rivers,
lakes or ponds that can provide drinking water for the animals. The desert areas are hot during
the day but cool at night. As the air cools at night it becomes moist, and the plants absorb the
moisture.
(a)
A few lions live in the desert areas. They hunt and feed on the gemsboks.
Use information from the drawing of the gemsbok to suggest two ways in which it could
avoid being killed by lions.
1 ..................................................................................................................................
.....................................................................................................................................
2 ..................................................................................................................................
.....................................................................................................................................
(2)
(b)
The graphs show the water content of the desert grass and the times of day that the
gemsboks feed.
15
(i)
Describe how the water content of the grass changes during the day.
..........................................................................................................................
..........................................................................................................................
(1)
(ii)
Suggest why the water content of the grass changes.
..........................................................................................................................
..........................................................................................................................
(1)
(c)
(i)
Between which times of day are more than 25% of the herd feeding?
...................................... and ...........................................
(1)
(ii)
Suggest an advantage to the gemsbok of feeding mainly at these times.
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
(2)
(Total 7 marks)
16
Mark scheme
M1.
(a)
(i)
more
less
the same
(accept appropriate numbers)
for 1 mark each
3
(ii)
sweating / evaporation / perspiration
for 1 mark
1
(b)
in food / named solid food / eating
from respiration
for 1 mark each
2
[6]
M2.
(a)
850
1
(b)
(i)
more
because exercise makes us sweat or work harder
accept to cool the body
do not credit body hotter or giving off more heat
2
(ii)
more
because she respires more
accept she breathes (in and out) more or heavier or faster
2
(iii)
less
because (more) water has been lost by sweating or breathing out or other
methods
accept arguments about conservation of water
2
(c)
kidney
1
[8]
(a) A > B > C;
A + B + C = 2 800;
one number correct
two numbers correct
each for 1 mark
4
(b)
M4.
urine;
less produced;
kidneys absorb more water
or
to maintain (water) balance
each for 1 mark [7]
(a) breath same + sweat more* + urine less* (All three needed)
or
total same but split differently
for 1 mark
*either change correctly quantified eg
x cm3 more/less or n times more/less
for 1 further mark
17
sweat 250 more 6 x more
urine 250 less
¼/25%less
2
(b)
ideas that
•
you sweat (more) to keep cool on a hot day
•
urine adjusted (by kidneys) to keep balance / to keep same total loss
each for 1 mark
(NB credit these answers if in (a) candidates have answered more fully than expected)
2
(c)
ideas that
•
when blood water normal/100% / steady kidney re-absorbs water at
low/steady rate
•
when blood water percentage falls, the rate at which kidney re-absorbs water rises
•
when blood water percentage rises again, is high/normal the rate at which
kidney re-absorbs water falls
•
97 / 97.5% / 98% (of normal) blood water is the point at which the
kidney’s reabsorption rate starts to increase / decrease
each for 1 mark
[allow idea that there is delay between blood water percentage
changing and rate of re-absorption changing]
4
(d)
any reference to hormone(s) / pituitary (gland)
gains 1 mark
but
ADH or hormone(s) from pituitary (gland)
gains 2 marks
(do not allow ‘brain)
2
[10]
M5.
(a)
stays cool
ignore shade
1
less sweat
1
(b)
any two from:
•
breathing rate less
•
less water lost via breath
less can be implied
•
less water from respiration
2
[4]
M6.
(a) long / pointed horns and for defence
long legs and to run away reject strong / powerful legs
long legs and to kick predator
tall and can see predators a long distance away but accept
eyes on side of head and to see predator approaching
large ears and to hear predators approaching
pattern and for camouflage any
two for 1 mark each
2
18
(b)
(i)
fall in morning / day and rise at night or any reasonable
for 1 mark
description of whole pattern for one mark
1
(ii)
loss due to evaporation or transpiration in day / absorbed from air
at night / when cool
for 1 mark
1
(c)
19.30 – 20.30 and 07.30 – 08:30
(i)
for 1 mark
1
(ii)
highest moisture content in grass
needs water in desert conditions / response to shortage of drinking water
sensible reference to less chance of predation
any two for 1 mark each
2
[7]
19