LIFE SCIENCES
PAPER 1
GRADE 12 
NSC EXAMS
PAST PAPERS AND MEMOS NOVEMBER 2018

MEMORANDUM

SECTION A 
QUESTION 1 
1.1
1.1.1 B ✓✓
1.1.2 B✓✓
1.1.3 D✓✓
1.1.4 C ✓✓
1.1.5 C✓✓
1.1.6 A✓✓
1.1.7 B✓✓
1.1.8 C✓✓
1.1.9 A✓✓
1.1.10 C ✓✓ (10 x  2) (20) 
1.2
1.2.1 Amniotic✓ egg 
1.2.2 Precocial✓ development
1.2.3 Cerebellum✓
1.2.4 Choroid✓
1.2.5 Corpus callosum✓ 
1.2.6 Hypothalamus✓
1.2.7 Carbon dioxide✓/CO2  
1.2.8 Tropisms✓
1.2.9 Weed-killer✓/herbicide  
1.2.10 Poaching✓(10) 
1.3
1.3.1 None✓✓
1.3.2 A only✓✓
1.3.3 Both A and B✓✓ (3 x 2)  (6) 
1.4
1.4.1 Fertilisation✓(1)
1.4.2 Mitosis✓ (1) 
1.4.3

• Chorion✓
• Amnion✓
  (Mark first TWO only) (2) 

1.4.4

1. Zygote✓  (1) 
2. Morula✓  (1) 
3. Blastocyst✓/blastula   (1) 

1.4.5 Fallopian tube✓ (1) 
1.4.6 47✓ (1) (9)
1.5
1.5.1

1. Pituitary✓/hypophysis (1)
2. Thyroxin✓ (1) 

1.5.2 Negative feedback✓ mechanism 
1.5.3

• Less hormone B✓/thyroxin will be secreted (1)
• More hormone A✓/TSH will be secreted (Mark first TWO only) (2) (5) 

TOTAL SECTION A: 50

SECTION B 
QUESTION 2 
2.1
2.1.1

1. Prophase I✓(1)
2. Anaphase I✓ (1)  

2.1.2
(5) (7) 

Criteria for marking 

2.2
2.2.1

• Needed for spermatogenesis✓
• Stimulates the development of secondary male  characteristics✓/deeper voice/facial hair/body hair/increased  muscle mass/increase in size of the sex organs/sex drive
  (Mark first ONE only) Any  (1) 

2.2.2

• Administering testosterone✓/hormonal treatment
• Surgery✓ (2)
  (Mark first TWO only)  

2.2.3 33⅓✓ % (1) 
2.2.4

• It increases the risk of testicular cancer✓(1)
  (Mark first ONE only)  

2.2.5

• The temperature of the testes will be too high✓/poor blood  circulation/increased pressure on the testes
• therefore sperm will not mature✓/spermatogenesis will be  negatively affected (2) (7) 

2.3
2.3.1 To calculate BMI✓ (1) 
2.3.2 41/100✓ x 1510✓ = 619✓ (Accept 619,1)  (3) 
2.3.3 Only women with planned pregnancies will know how long it took  them to fall pregnant✓✓ (2) 
2.3.4 All the women: 

• were the same age✓/between the ages of 20 and 30 years
• were pregnant for the same amount of time✓/at least 20 weeks  pregnant
• had planned to fall pregnant✓
• had conceived naturally✓
  (Mark first ONE only) Any (1) 

2.3.5 Do not smoke if your BMI is <20 or ≥30✓✓ (2)
2.3.6

• Similar/same results were obtained✓
• in the second/repeated investigation✓ (2)(11) 

2.4
2.4.1

1. Transmits sound waves to the tympanic  membrane✓/Secretes ear wax (1)
   (Mark first ONE only) 
2. Equalises pressure on either side of the tympanic  membrane✓(1)
   (Mark first ONE only)
3. Releases pressure from the inner ear✓(1)
   (Mark first ONE only)  

2.4.2 

1. C✓ (1)
2. D✓ (1) 

2.4.3

• The receptors cannot convert the stimuli into impulses✓
• No impulses/fewer impulses are transmitted to the cerebrum✓
• and the person does not hear anything✓/hearing is impaired (3) 

2.4.4

• The sound vibrations are transmitted from the large tympanic  membrane✓
• to the smaller oval window✓
• through the ossicles✓
• which are arranged from largest to smallest✓
• This concentrates the vibrations✓, amplifying them
  Any  (3) 

2.4.5

• A change in speed/direction of movement✓
• stimulates the cristae✓
• The stimulus is converted to an impulse✓
• The impulse is transmitted to the cerebellum✓
• via the auditory nerve✓
• The cerebellum sends impulses to the muscles✓ to restore  balance
  Any (4) (15) [40]

QUESTION 3
3.1
3.1.1 Auxins✓ (1) 
3.1.2

1. Light✓ (1) 
2. Gravity✓ (1) 

3.1.3 Plant structure B has bent towards the light✓/towards A/positively  phototropic  (1) 
3.1.4

• Auxins accumulated on the lower side✓ of the root 
• The high concentration of auxins on the lower side of the root inhibits growth✓
• The lower concentration of auxins on the upper side stimulates  growth✓
• causing uneven growth✓/the root to bend downwards/positive  geotropism
  Any   (3) (7) 

3.2
3.2.1 A✓ (1) 
3.2.2 The impulse does not travel to the brain✓/goes directly from  receptor to effector via the spinal cord  (1) 
3.2.3

• Allows the person to respond rapidly✓ 
• and without thinking✓/involuntarily
• to a stimulus✓  
• to prevent damage to the body✓*  (3) 
  1* compulsory + any other 2  

3.2.4 Nerve✓/spinal cord  (1) 
3.2.5

• It acts as an insulator✓
• and therefore, speeds up the nerve impulse✓/prevents a short  circuit (2) 

3.2.6 

• The person would be able to feel the stimulus✓
• but would be unable to react✓
• because the impulse would not be transmitted to the effector✓ 
  Any (2) 

3.2.7

• The receptor receives the stimulus✓
• and converts it into an impulse✓
• which is transported by a sensory neuron✓ via the spinal cord
• to the brain✓*/cerebrum
• The brain/cerebrum interprets the impulse✓*
• The brain/cerebrum sends an impulse to a motor neuron✓
• which conducts the impulse to the effector✓
• to bring about a response✓
  2* compulsory + any other  4 (6) (16) 

3.3
3.3.1 The level increases✓
3.3.2  T✓

(Mark first TWO only) 1 for table + Any 2 x 2   
3.3.3

• A diabetic may not produce sufficient insulin✓
• When eating many smaller meals, less glucose✓ enters the  blood
• less insulin✓ is needed 
• to return blood glucose to normal✓
  OR
• A diabetic may not produce sufficient insulin✓
• When eating fewer larger meals, more glucose✓ enters the  blood
• more insulin✓ is needed 
• to return blood glucose to normal✓

3.4
3.4.1 B✓
3.4.2

• The person is sweating✓
• Vasodilation has occurred✓
  (Mark first TWO only)  

3.4.3 Adrenalin✓
3.4.4

• Blood vessels are constricted✓
• Less blood is sent to the skin✓/sweat glands
• Less sweat is formed✓/less evaporation occurs
• and less heat is lost✓
  Any (3) (7) [40] 

TOTAL SECTION B: 80

QUESTION 4 
The causes of rapid global warming (H) 

•  The concentration of greenhouse gases in the atmosphere has increased✓
• The burning of fossil fuels✓/use of vehicles/fires
• and industrial processes✓
• have released large amounts of CO2✓/N2O/CFC’s into the atmosphere
• Deforestation✓
• results in less CO2 being removed from the atmosphere✓
• Due to the decomposition of organic waste in landfills✓/rice paddies 
• and the increased number of livestock✓
• the concentration of methane/CH4 in the atmosphere has increased✓
• This has caused the enhanced greenhouse effect✓
• More heat is trapped in the atmosphere✓ (8)
  Any 

Impact of global warming on weather patterns (W) 

• Higher temperatures✓occur
• Heat waves occur✓
• The distribution of rainfall changes✓
• leading to increased rainfall in some areas✓
• while other areas will have decreased rainfall✓/experience droughts (3) 
• Storms are more severe✓/frequent 
  Any 

How changes in weather patterns affects food security (F) 

• Food security decreases✔* 

Changes in rainfall patterns cause: 

• Desertification✔ 
• increased flooding✔ 
• and wildfires✔ 
• which increases soil erosion✔ resulting in:
  • fewer crops to be planted✔ 
  • lower crop yields✔ 
  • less food for livestock✔ 
• Higher environmental temperatures negatively affects livestock✔/crops (6)
• These factors further decrease food availability✔
• Food becomes more expensive✔

1*compulsory + Any other 5  (17) 
(3) 
Content:  (20)
Synthesis: 

ASSESSING THE PRESENTATION OF THE ESSAY 

TOTAL SECTION C: 20 
GRAND TOTAL: 150