Wednesday, 21 July 2021 11:36

LIFE SCIENCES GRADE 12 PAPER 1 MEMORANDUM - NSC PAST PAPERS AND MEMOS SEPTEMBER 2017

Share via Whatsapp Join our WhatsApp Group

LIFE SCIENCES
GRADE 12
PAPER 1 
NSC PAST PAPERS AND MEMOS
SEPTEMBER 2017

MEMORANDUM

SECTION A 
QUESTION 1 
1.1

1.1.1 D ✓✓ 
1.1.2 B ✓✓ 
1.1.3 D ✓✓ 
1.1.4 A ✓✓ 
1.1.5 B ✓✓ 
1.1.6 C ✓✓ 
1.1.7 D ✓✓ 
1.1.8 B ✓✓ 
1.1.9 A ✓✓ 
1.1.10 A ✓✓ (10 × 2) (20) 

1.2

1.2.1 Replication ✓ 
1.2.2 Acrosome ✓ 
1.2.3 Cytokinesis ✓ 
1.2.4 Stimulus ✓ 
1.2.5 Reforestation ✓ 
1.2.6 Testosterone ✓ 
1.2.7 Aquifer ✓ 
1.2.8 Centrioles ✓ 
1.2.9 Desertification ✓ 
1.2.10 Peripheral nervous system ✓ (10 × 1) (10) 

1.3

1.3.1 B only ✓✓ 
1.3.2 B only ✓✓ 
1.3.3 B only ✓✓ (3 × 2) (6) 

1.4

1.4.1

    1. Meiosis ✓ (1)
    2. Crossing over ✓ (1)
    3. Prophase I ✓ (1)
    4. Centromere ✓ (1) 
    5. Chiasma ✓ (1)
    6. Metaphase I ✓ (1) 

1.4.2 They are the same size and shape ✓ (1) 

1.5

1.5.1 Open dump site ✓/landfill site (1)
1.5.2 Methane ✓ (mark first 1 only) (1)
1.5.3 As a source of energy for cooking ✓/heating/lighting/fuel (1)
1.5.4 Recycling ✓ (1) 1.5.5 Glass ✓/plastic (mark first 1 only) (1)
1.5.6 Greenhouse gases (1)
1.5.7 Breeding spot for micro-organisms ✓/insects/rodents that causes  diseases (1)

TOTAL SECTION A: 50

SECTION B 

QUESTION 2 
2.1
2.1.1

  1. C ✓ (1) 
  2. B ✓ (1)

2.1.2

  1. Short sightedness ✓/Myopia (1) 
  2. Concave ✓ lens (1) 

2.1.3 *Accommodation ✓ 

  • Ciliary muscles contract ✓
  • Suspensory ligaments slacken ✓
  • Tension on lens decreases ✓
  • Lens becomes more convex ✓
  • Refractive power of lens increases ✓ 
  • A clear image now forms on the retina ✓
    (*Compulsory 1 + any 4) (5)

2.2
2.2.1 Insulin ✓ (1) 
2.2.2

  • Insufficient amounts or no insulin will be secreted by the pancreas ✓
  • and therefore less amounts of glucose will be absorbed by liver and  muscle cells ✓ 
  • hence less amount of glucose will be converted to glycogen ✓
  • causing an increase in glucose in the blood ✓ (any 3) (3) 

2.2.3 Water ✓ will move out/exosmosis of the cells to the blood ✓ results in  dehydration✓ of cells leading to underperformance/death of  cells. ✓ (any 2) (2) 
2.3
2.3.1 Growth of plant shoots ✓ growth response/bending of the tip (1)
2.3.2 Auxins ✓ (1)
2.3.3

  • Same environment in which the shoots are placed ✓/same intensity  of the light
  • Same type of shoot used ✓
  • Same age of the shoot ✓ (mark first 2) (any 2) (2)

2.3.4

  1. In investigation A:
    • Light from the right ✓/from one side/unilateral light
    • caused auxins to move to shaded side of the shoot ✓ 
    • leading to increased cell elongation and division ✓ on the  shaded side/There was therefore greater growth on the  shaded side ✓ 
    • thus bending the shoot in the direction of the source of light ✓ (3)
  2. In investigation C:
    • Since there is no light stimulus ✓ from the side (because of the  cap) there is no influence on the distribution of  auxins ✓/auxins evenly distributed below the cap
    • therefore the shoot grew upright ✓ (3) 

2.3.5

  • Repeat the investigation ✓
  • Use more than one plant for each treatment ✓/increase sample size (2)

2.4
2.4.1

  1. A Ganglion ✓ (1)
  2. E Effector ✓/muscle (1) 

2.4.2

  1. B Ensures one directional flow of impulses ✓(mark first 1 only) (1)
  2. C Transmits impulses from sensory neuron to motor  neuron ✓ (mark first 1 only) (1) 

2.4.3

  • Spinal cord shortens reaction time by sending impulses directly to  the effector ✓
  • If the brain is involved, it delays the reaction ✓
  • causing injury or even death ✓ (3) 

2.4.4

  • The myelin sheath is damaged by multiple sclerosis ✓
  • This will cause a slow transmission of impulses ✓ 
  • resulting in slower reaction time✓ which might leads to injury or  death ✓ (any 2) (2) 

2.4.5

  • The person will be able to feel the pain ✓ because the sensory  neuron is able to transmit the impulses to the brain ✓ since it is not  damaged
  • However no reaction will take place ✓
  • because of the fact that no impulse will reach the effector ✓ due to  the damage to the motor neuron (4) [40]

3.1
3.1.1

  1. A meiosis✓/oogenesis (1) 
  2. B ovulation✓ (1) 

3.1.2

  • High level of progesterone in the blood causes the pituitary  gland ✓/hypophysis ✓
  • to secrete less FSH ✓
  • therefore no new Graafian follicles will be formed ✓ 
  • and no ovulation and menstruation will take place ✓ (any 3) (3) 

3.1.3

  • Under the influence of LH, ✓
  • the Graafian follicle ruptures ✓
  • and causes ovulation ✓/release of the ovum
  • The LH converts the empty Graafian follicle ✓
  • into the corpus luteum ✓
  • The corpus luteum will secrete progesterone ✓ and
  • a little oestrogen. ✓ (any 6) (6) 

3.2
3.2.1

  1. 1981 – 1990 ✔ (1)
  2. 1981 – 1990 ✓ (1) 

3.2.2

  • % increase = 4 × 100   = 28,5% ✓ (2) 
                            14✓ 

3.2.3 
GRAPH ON SPERM COUNT 

Criteria 

Mark Allocation

Bar graph drawn (T) 

1

Title of graph (C) 

1

Correct scale for X-axis (equal  width and spacing of the bars)  and Y-axis (S) 

1

Correct label and unit for X-axis  and Y-axis (L) 

1

Plotting of the bars (P) 

0: No bars plotted correctly
1: 1 to 3 bars plotted correctly
2: All bars plotted correctly

NOTE: 

  • If a line graph is drawn – marks will be awarded for the ‘title and label  for X and Y axes' only
  • If a histogram is drawn – marks will be lost for the ‘type of graph and correct scale’ only (6)

3.3
3.3.1 C ✓ (1) 
3.3.2

  • If the patient swims after the grommet was put in, water will enter  the middle ear rather to drain out ✓
  • This will result in water building up in the middle ear ✓/middle ear  can’t dry out
  • which can result in middle ear infection✓/temporary loss of  hearing/middle ear infection can’t be cleared up. (any 2) (2) 

3.3.3

  • Three semi-circular canals are positioned in different planes ✓
  • so that the head movement in any direction ✓
  • can be detected ✓/cause liquid in at least one canal to move ✓ and  stimulates cristae ✓ (any 3) (3) 

3.3.4

  • Eustachian tube ✓
  • Equalises air pressure on either side of the tympanic membrane so  that air pressure does not cause bursting of the tympanic  membrane ✓ (2)

3.4
3.4.1 Pyrite ✓ (1) 
3.4.2

  • Pyrite mineral deposits are exposed to water and oxygen ✓
  • which breaks down (weathers), changes to sulphuric acid ✓ and  flows out (2) 

3.4.3 

  1. Impact on the infrastructure
    • The acid content causing the rusting of iron in structure ✓
    • causing the weakening of bridges and buildings in that  area ✓ (2) 
  2. Impact on the agricultural production
    • The pH of the water and soil drops ✓
    • which may lead to crop failure ✓
      OR
    • The acid water causing the leaching of essential nutrients out  of the soil ✓
    • reducing the fertility of the soil ✓ (any 1 × 2) (2) 

3.4.4

  • The acid water could kill the aquatic organisms ✓ 
  • causing the death of other species depending on them as food  source. ✓
  • Decomposition of dead organisms causes an increase in CO2 level  and decrease in O2. ✓
  • The lack of oxygen and food kill remaining organisms in the food  chain ✓ (4)

[40] 
TOTAL SECTION B: 80

SECTION C 
QUESTION 4 
*Thermoregulation ✓ 

  • When environmental temperature is high ✓
  • Receptors ✓ in the skin detects this 
  • Impulses are send to the Hypothalamus ✓ 
  • Which sent impulses to the blood vessels ✓ in the skin ✓ 
  • These blood vessels become wider✓/dilate/increase in diameter/vasodilation
  • More blood flows through the skin ✓ 
  • More heat is therefore lost ✓ from the body
  • Through radiation ✓ 
  • The sweat glands ✓ 
  • Produce more sweat ✓ 
  • That evaporates ✓ from the skin’s surface 
  • Leading to more heat is lost ✓ 
  • Cooling down the body ✓ (*Compulsory 1 + 9) (10)
  • Hypothalamus will respond to information received from osmoreceptors ✓
  • To release more ADH into the blood ✓ 
  • Higher concentration of ADH increases the permeability ✓
  • of the renal tubules✓/distal convoluted and collecting tubules
  • Allowing more water to be reabsorbed from the filtrate ✓ 
  • Passing into the surrounding blood capillaries ✓ 
  • Increasing the quantity of water in the blood ✓ 
  • Less urine will be excreted✓/more concentrated (any 7) (7) 

ASSESSING THE PRESENTATION OF THE ESSAY 

CRITERION 

RELEVANCE (R) 

LOGICAL SEQUENCE (L)

COMPREHENSIVE (C)

GENERALLY 

  • All information  provided is relevant to  the topic
  • Facts are  arranged in a  logical/ sequential order
  • All aspects required by  the essay have been  sufficiently addressed.

IN THIS ESSAY

  • Only information with  regard to  thermoregulation and  the role of the  hypothalamus  regulating water  content of the body is  given
  • The sequence  of events in  thermos regulation and  regulating water  content is  correct
  • The role of blood  vessels and sweat  glands in  thermoregulation is  given (7/10) and the role of ADH(4/7)

MARK 

1

Content: (17) 
Synthesis: (3) 

TOTAL SECTION C: 20 
GRAND TOTAL: 150

Last modified on Wednesday, 21 July 2021 12:12