Life Sciences Grade 12 Final Revision Document of 2023
Question 2
Give the correct biological term for each of the following descriptions. Write only the term next
to the question numbers.
DESCRIPTION TERM
2.1 A gland whose secretions are transported through blood streams. endocrine
2.2 A system that is responsible for chemical coordination in the body. endocrine
2.3 A hormone that stimulates ovulation in humans LH
2.4 The process of maintaining a constant internal environment in the human
Homeostasis
body
2.5 A gland whose secretions are transported through ducts. exocrine
2.6 A hormone that stimulates mammary gland to produce milk. prolactin
2.7 A hormone that is responsible for osmoregulation in the body. ADH
2.8 Specialized cells in the pancreas that secretes insulin and glucagon. islet of langerhans
2.9 A hormone responsible for secondary sexual characteristics in males testosterone
2.10 A hormone that is responsible for maintaining salt balance in the blood. aldosterone
2.11 A gland that secretes FSH and LH in females. ovaries
2.12 Chemical messengers produced by endocrine glands. Hormones
2.13 A gland located in the neck that secretes thyroxin hormone. thyroid gland
2.14 A hormone that controls the metabolic rate in the body.
2.15 A hormone that increases the blood glucose level in the body. insulin
2.16 A hormone that lowers the blood glucose level in the body. glucagon
2.17 Promotes the secretions of hormones produced by thyroid glands.
2.18 A mechanism that detects imbalances and restores balance in the internal
NFM
environment
2.19 A hormone responsible for growth and development in the body. GH
2.20 The part of brain that controls body temperature hypothalamus
2.21 Groups of cells in the pancreas that secrete insulin and glucagon islet of langerhans
2.22 The homeostatic process whereby temperature is controlled in the body thermoregulation
(22 x 1) (22)
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Life Sciences Grade 12 Final Revision Document of 2023
Question 3
Indicate whether each of the descriptions in COLUMN I applies to A ONLY, B ONLY, BOTH A
AND B or NONE of the items in COLUMN II. Write A only, B only, both A and B or none next
to the question number.
Column I Column II
3.1 The hormone that is in excess in a person that grows A: ADH
abnormally tall B: Thyroxin none
3.2 A hormone that controls the salt content in a human body
A: Aldosterone A only
B: Adrenalin
3.3 The state of the blood vessels in the skin of a human A: Dilated
A only
when the environmental temperature is high B: Constricted
3.4 May cause a decrease in the pH of the blood A: excess carbon dioxide
B: excess glucose
3.5 Acts both as an endocrine and exocrine gland A: Adrenal B Only
B: Pancreas
(5x2) (10)
Question 4
The diagram below represent human endocrine system
pituitary gland
thyroid gland
pancreas
adrenal gland
4.1 Identify parts A and D (2)
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Life Sciences Grade 12 Final Revision Document of 2023
4.2 Write down the LETTER and the NAME of the part that
(a) Produces the hormone glucagon 3 - Pancreas (2)
(b) Produces a hormome that controls the growth of long bones 4 - adrenal gland (2)
(c) Produces an iodine-containing hormone 2 - thyroid gland (2)
(d) Produces a hormone that is involved in the re-absorption of some salts by the
kidneys (2)
4.3 State TWO similarites between hormones and nerves with regard to their
functions. The endocrine system through hormones, the nervous through electrical signals (2)
they both dictate how other parts of the body will function. (12)
Question 5
The diagram below shows the interaction between two endocrine glands.
the hypothalamus and the pituitary gland in the brain control normal secretion of thyroid
hormones, which in turn control metabolism
5.1 Name the type of interaction that occurs between hormone A and gland B. (1)
5.2 Identify:
(a) Glands B thyroid gland (1)
(b) Hormone A TSH (1)
(c) Hormone C Thyroxin (1)
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Life Sciences Grade 12 Final Revision Document of 2023
5.3 Name the disorder that results when gland B is overstimulated and becomes
enlarged. goitre (1)
5.4 Which hormone (A or C) will be expected to be high in the blood of the person
with the disorder named in QUESTION 5.3? C (1)
(6)
Question 6
The diagram below represents a part of the human skin
6.1 sweat glands (1)
6.2
capillaries constrict near skin surface to conserve heat. blood doesnt flow to the (3)
skin anymore
6.3
to ensure that all metabolic functions continue
(2)
(6)
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Life Sciences Grade 12 Final Revision Document of 2023
Question 7
The diagram below shows parts of the skin that are involved in thermoregulation.
sweat glands have ducts and secretions are released
onto a surface
7.1 Give TWO reasons why part A is classified as an exocrine gland. (2)
7.2 Describe the role of skin receptors in thermoregulation. skin receptors have the ability to
(2)constrict to
retain heat and to dilate to release heat
7.3 Explain why structure B dilates on a hot day. (2)
in order to lose heat to the environment and secrete sweat
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Life Sciences Grade 12 Final Revision Document of 2023
Question 8
The diagrams below show the human kidney and human brain.
8.1 Name the hormone secreted by gland C that has an effect on:
(a) Long bones GH (1)
(b) Mammary glands in the breasts PROLACTIN (1)
8.2 During an emergency situation, gland A releases a hormone that prepares the
body for a 'fight or flight' response by stimulating an increase in breathing rate
and heart rate. This increase leads to increased energy production in the
skeletal muscles and an increase in blood carbon dioxide levels.
ADRENALIN
(a) Name the hormone secreted by gland A in an emergency situation. (1)
(b) Explain how an increase in breathing rate and heart rate results in
increased energy production in skeletal muscles. (4)
8.3 Describe how part B is involved in carbon dioxide homeostasis (4)
(11)
High concentrations of CO2 lead to the formation of carbonic acid.
Increased breathing and heart rates
during exercise enhance skeletal muscle As a result, the pH of the blood will drop (the blood becomes more acidic).
energy production by ensuring a greater
supply of oxygen and glucose, which are Chemoreceptors in the carotid artery are stimulated by the drop in pH.
essential for aerobic energy production.
Faster breathing brings more oxygen into Impulses are sent to the medulla oblongata.
the lungs, and a faster heart rate pumps
more blood to deliver that oxygen and Breathing and heart muscles are targeted.
glucose to the working muscles.
Diaphragm and intercostal muscles contract increasing the rate and
depth of breathing.
Heart rate increases.
More CO2 moves to the lungs to be exhaled therefore blood CO2 levels
return to normal. Homeostasis is maintained
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Life Sciences Grade 12 Final Revision Document of 2023
Question 9
Read the extract below.
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Life Sciences Grade 12 Final Revision Document of 2023
9.1
5ug/dl (1)
9.2
(24 - 5 ) / 24 * 100 = 79.17%
(3)
9.3 (3)
the bodys metabolism is sped up rapidly
9.4
(4)
the concentration of TSH is expected to be low 8 hours after eating the ground beef because the elevated
thyroxin levels inhibit TSH secretion through the negative feedback mechanism (11)
Question 10
The table below shows the average rate of blood flow to the skin at different
environmental temperatures.
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Life Sciences Grade 12 Final Revision Document of 2023
10.1
50 deg C (1)
10.2
the higher the environmental temperature, the higher
(2)
the average rate of blood flow to the skin
10.3
(11-4) / 11 * 100 = 63.64% (3)
10.4
(4)
10.5
(2)
there is less bloodflow to the skin as the environmental temperature decreases hence chances
of the tissue dying are very high (12)
Question 11
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Life Sciences Grade 12 Final Revision Document of 2023
11.1
(2) increases the
caffeine increases the persons body temperature and
persons average pulse rate
11.2
30 minutes (1)
11.3
(4)
capillaries constricted, hence heat is conserved near the skin, which explains the high
average body temperatures captured
11.4
(2)
-duration (9)
- amount of caffeine consumed
Question 12
The graphs below show the effects of eating many small meals and eating fewer large
meals on blood glucose and insulin concentrations in a normal person.
The arrows on the graphs below indicate when meals were eaten. The normal blood
glucose concentration is 100 mg/dl.
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Life Sciences Grade 12 Final Revision Document of 2023
12.1
increases
(1)
12.2
When levels of
thyroxin
increase above
(5)normal, this is
detected by the
12.3 pituitary
(4)gland which is
then inhibited.
(10)
Less TSH is
Question 13 secreted from
the pituitary
gland.
13.1 Describe the negative feedback mechanism that occurs when thyroxin
levels in the blood are high (5)Lower
secretions of
TSH result in
13.2 A person has a medical condition that results in the under-secretion of the
thyroxin. thyroid gland
releasing less
thyroxin.
Explain why this person will gain weight if the thyroxin levels remain
continuously low in the blood (3)The level of
metabolissm rate is slow (8)thyroxin is
decreased back
to normal.
Question 14
14.1 Name the hormone that is secreted the
dangerous situation. adrenalin (1)
`
14.2 State THREE effects that the hormone in QUESTION 13.1 has on the body. (3)
14.3 Describe the homeostatic control of blood glucose levels in a person who
consumed a drink with large amount of sugar (5)
(9)
Question 15
Describe how the human body maintain the carbon dioxide concentration in the blood
when it rises above normal limits. (7)
Question 16
Describe the role of different glands of the endocrine system in providing the body with
extra energy during a dangerous situation. (9)
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Life Sciences Grade 12 Final Revision Document of 2023
Question 17
The diagram below shows the homeostatic control of blood glucose levels.
17.1 Identify:
(a) Gland A (1)
(b) Hormone C (1)
17.2 A certain disorder causes decreased production of hormone B.
(a) Explain how this will affect the blood glucose levels. (3)
(b) Name the disorder. (1)
17.3 Scientists have been investigating the use of adrenalin as a treatment for
people who cannot produce hormone C.
Explain why this treatment may work. (3)
Question 18
Wearing a face mask is recommended to reduce the spread of the coronavirus. There are
some concerns about the efficiency of breathing when wearing a face mask.
Scientists investigated the effect of wearing face masks on carbon dioxide levels in blood.
They:
Obtained permission from 150 healthy volunteers, aged 30, to participate in the
investigation
blood
Asked the participants to:
o Sit still for 10 minutes without wearing a face mask
o Sit still for 10 minutes while wearing a face mask
o Exercise for 10 minutes without wearing a face mask
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Life Sciences Grade 12 Final Revision Document of 2023
o Exercise for 10 minutes while wearing a face mask
Allowed a 15-minute interval between each 10-minute phase
Recorded the carbon dioxide levels at the end of each 10-minute phase
Ensured that the face mask covered the nose and mouth
18.1 Identify the:
(a) Independent variable (1)
(b) Dependent variable (1)
18.2 State TWO factors that were taken into consideration in the selection of the
participants. (2)
18.3 Give ONE reason why the results at the end of this investigation may be
considered reliable. (1)
18.4 Explain why scientists allowed a 15-minute interval between each phase. (2)
18.5 Give a reason why the carbon dioxide levels were measured while
participants were sitting still. (1)
18.6 Describe the homeostatic control of carbon dioxide when it is high in blood (7)
(15)
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