LIFE SCIENCES GR12 MEMO JUNE2023_English.pdf

Downloaded from hlayiso.com NATIONAL SENIOR CERTIFICATE GRADE 12 JUNE 2023 LIFE SCIENCES MARKING GUIDELINE MARKS: 150 This marking guideline consists of 11 pages.

Downloaded from hlayiso.com 2 LIFE SCIENCES (EC/JUNE2023) PRINCIPLES RELATED TO MARKING LIFE SCIENCES 1. If more information than marks allocated is given Stop marking when maximum marks are reached and put a wavy line and 'max' in the right-hand margin. 2. If, for example, three reasons are required and five are given Mark the first three irrespective of whether all or some are correct/incorrect. 3. If whole process is given when only a part of it is required Read all and credit the relevant part. 4. If comparisons are asked for, but descriptions are given Accept if the differences/similarities are clear. 5. If tabulation is required, but paragraphs are given Candidates will lose marks for not tabulating. 6. If diagrams are given with annotations when descriptions are required Candidates will lose marks. 7. If flow charts are given instead of descriptions Candidates will lose marks. 8. If sequence is muddled and links do not make sense Where sequence and links are correct, credit. Where sequence and links are incorrect, do not credit. If sequence and links become correct again, resume credit. 9. Non-recognised abbreviations Accept if first defined in answer. If not defined, do not credit the unrecognised abbreviation, but credit the rest of the answer if correct. 10. Wrong numbering If answer fits into the correct sequence of questions, but the wrong number is given, it is acceptable. 11. If language used changes the intended meaning Do not accept. 12. Spelling errors If recognisable, accept the answer, provided it does not mean something else in Life Sciences or if it is out of context. 13. If common names are given in terminology Accept, provided it was accepted at the national memo discussion meeting. 14. If only the letter is asked for, but only the name is given (and vice versa) Do not credit. Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/JUNE 2023) LIFE SCIENCES 3 15. If units are not given in measurements Candidates will lose marks. Marking guidelines will allocate marks for units separately. 16. Be sensitive to the sense of an answer, which may be stated in a different way. 17. Caption All illustrations (diagrams, graphs, tables, etc.) must have a caption. 18. Code-switching of official languages (terms and concepts) A single word or two that appear(s) in any official language other than the learner's assessment language used to the greatest extent in his/her answers should be credited, if it is correct. A marker that is proficient in the relevant official language should be consulted. This is applicable to all official languages. Copyright reserved Please turn over

Downloaded from hlayiso.com 4 LIFE SCIENCES (EC/JUNE2023) SECTION A QUESTION 1 1.1 1.1.1 B ✓✓ 1.1.2 A ✓✓ 1.1.3 A ✓✓ 1.1.4 B ✓✓ 1.1.5 A ✓✓ 1.1.6 D ✓✓ 1.1.7 C ✓✓ 1.1.8 C ✓✓ 1.1.9 C ✓✓ 1.1.10 C ✓✓ (10 x 2) (20) 1.2 1.2.1 Incomplete ✓ dominance 1.2.2 Non-disjunction ✓ 1.2.3 Karyotype ✓ 1.2.4 Haemophilia ✓ 1.2.5 Meninges ✓ 1.2.6 Ovovivipary ✓ 1.2.7 Parental care ✓ (7 x 1) (7) 1.3 1.3.1 Both A and B ✓✓ 1.3.2 A only ✓✓ 1.3.3 None ✓✓ (3 x 2) (6) 1.4 1.4.1 Dihybrid cross ✓ (1) 1.4.2 (a) bbnn ✓✓ (2) (b) Bitter ✓ (1) (c) BN Bn bN bn ✓✓ (2) 1.4.3 bbNn is sweet with yellow spots ✓ Bbnn is bitter with no yellow spots ✓ (2) 1.4.4 The various ‘factors’ controlling the different characteristics are separate entities, not influencing each other in any way, and sorting themselves out independently during gamete formation. ✓✓ (2) Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/JUNE 2023) LIFE SCIENCES 5 1.5 1.5.1 Cloning ✓ (1) 1.5.2 - Better quality fruits/vegetables/meat/increased shelf-life/better nutritional value ✓ - Better yield/higher quantity of products - More money for the farmer/community ✓ (MARK FIRST TWO ONLY) (2) 1.5.3 (a) Mitosis ✓ (1) (b) Meiosis ✓ (1) 1.5.4 (a) 38 ✓ (1) (b) 38 ✓ (1) TOTAL SECTION A: 50 Copyright reserved Please turn over

Downloaded from hlayiso.com 6 LIFE SCIENCES (EC/JUNE2023) SECTION B QUESTION 2 2.1 2.1.1 Chromosomes ✓/chromatids/genes/allele (1) 2.1.2 - Mitochondria ✓ - Chloroplasts ✓ (Mark first ONE only) (1) 2.1.3 (Nitrogenous) bases ✓ (1) 2.1.4 - Transcription✓* - The double helix DNA unwinds ✓ - The double-stranded DNA unzips ✓/weak hydrogen bonds break - to form two separate strands ✓ - One strand is used as a template ✓ - to form mRNA ✓ - using free RNA nucleotides from the nucleoplasm ✓ - The mRNA is complementary to the DNA ✓/A complements U, G complements C - mRNA now has the coded message for protein synthesis ✓ 1 compulsory mark + Any 5 (6) 2.2 2.2.1 (a) 4 ✓/ Four (1) (b) 3 ✓/Three (1) 2.2.2 CTC ✓ (1) 2.2.3 - The DNA triplet CAG changed to TAG ✓/ C changed - The codon GUC changed to AUC ✓ - The anticodon sequence changed ✓/ CAG to UAG - The amino acid valine was replaced by isoleucine ✓ - This results in a different protein ✓/ enzyme - The active site of the enzyme changes ✓*/shape of enzyme changes - Therefore, the enzyme no longer fits the substrate/ carbohydrate ✓* * 2 compulsory marks + Any 3 (5) 2.3 2.3.1 Crossing over ✓ (1) 2.3.2 Homologous chromosomes ✓ (1) 2.3.3 - Attaches the chromosome to the spindle fiber ✓ - Joins the two halves of a double-stranded chromosome (Any 1) (1) Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/JUNE 2023) LIFE SCIENCES 7 2.3.4 - Chromosomes pair ✓ up/homologous pairs form - exchange of genetic material occurs ✓ - between chromatids ✓ /adjacent chromosome pairs - at points called chiasmata ✓/chiasma (Any 3 x 1) (3) 2.3.5 - It brings about variation ✓ which may - improve chances of survival ✓ of organisms (2) 2.4 2.4.1 Progesterone ✓ (1) 2.4.2 - The blood concentration of hormone Y increased after day 14 ✓ / ovulation - maintaining the thickness of the uterus lining ✓/endometrium (2) 2.4.3 Endometrium ✓ (1) 2.4.4 - The level of hormone Y/progesterone decreased ✓ - resulting in a decrease in the thickness of the uterus lining ✓ - followed by menstruation ✓ - This indicates that fertilisation did not occur ✓ (Any 3 x 1) (3) 2.4.5 - FSH ✓ / Follicle Stimulating Hormone - stimulates the development of the follicles into an ovum ✓ - LH ✓/ Luiteinising Hormone - stimulates ovulation ✓ (4) 2.5 2.5.1 (a) An allele that is expressed (shown) in the phenotype when found in the heterozygous and homozygous condition ✓ (1) (b) Two parents (Tom and Lee) both with Cadasil have a child (Abby/ Bob) without Cadasil ✓ OR If recessive all of Tom and Lee’s children would have Cadasil ✓ (1) 2.5.2 (a) Heterozygous ✓ (1) (b) He has children without Cadasil ✓ OR If he was homozygous all children would have Cadasil (1) Copyright reserved Please turn over

Downloaded from hlayiso.com 8 LIFE SCIENCES (EC/JUNE2023) 2.5.3 P1 Phenotype Male with Female without Cadasil x Cadasil ✓ Genotype Dd x dd ✓ Meiosis G/gametes D, d x d, d✓ Fertilisation F1 Genotype Dd, Dd, dd dd ✓ Phenotype 50% child with Cadasil, 50% child without Cadasil ✓* P1 and F1  Meiosis and fertilisation  *1 compulsory mark + Any 5 OR P1 Phenotype Male with Female without Cadasil x Cadasil ✓ Genotype Dd x dd ✓ Meiosis Gametes D d Fertilisation d Dd dd d Dd dd 1 mark for correct gametes 1 mark for correct genotypes F1 Phenotype 50% child with cadasil, 50% child without cadasil ✓* P1 and F1  Meiosis and fertilisation  *1 compulsory mark + Any 5 (6) 2.6 2.6.1 - Stemcells are undifferentiated cells ✓ - That have the ability to grow and differentiate ✓ - into any tissue ✓ in the body (3) 2.6.2 It is less controversial ✓using skin cells than embryonic cells. (1) [50] Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/JUNE 2023) LIFE SCIENCES 9 QUESTION 3 3.1 3.1.1 Man A has: - Many  /enough/more sperms - normally shaped  /healthy sperms OR Man B has - Fewer /not enough/lesser sperms - abnormally shaped  /unhealthy sperms (2) 3.1.2 - Sperm has a neck area with large amount of mitochondria  which will produce energy  for the sperm to move to the Fallopian tube. - Sperm has a tail  which propel the sperm/make movements  so the sperm could move to the Fallopian tube (2 x 2) (4) 3.1.3 - Females have XX (identical) type and males have XY (non-identical) chromosome and one Y chromosome  - When the sperm with X chromosome fuses with the ovum, the child will have XX type of sex chromosomes (girl child)  - If the sperm with a Y chromosome fuses with the ovum, the child will have an XY type of sex chromosome (boy child)  (3) 3.1.4 Spermatogenesis Oogenesis Occurs in the testes/ seminiferous Occurs in the ovary ✓ tubules ✓ Influenced by testosterone ✓ Influenced by FSH Occurs continuously ✓ Occurs once during every menstrual cycle ✓ Four sperm cells are produced✓ One ovum is produced ✓ (Mark first TWO only) Table 1 + (Any 2 x 2) (5) 3.2 3.2.1 Middle ear  (1) 3.2.2 Ossicles  (1) 3.2.3 - The bones will not move and vibrate  in reaction to sound - resulting in hearing loss  (2) 3.2.4 - Eustachian tube * - When a person goes skydiving, the atmospheric pressure changes all the time  - When descending, the Eustachian tube cannot equalise the pressure  on both sides of the tympanic membrane/the pressure on both sides will not be the same. - which may cause the tympanum to rupture /damage 1* compulsory mark + 3 (4) 3.2.5 The surface area of the eardrum is larger than that of the oval window, ✓ thus a greater force is concentrated into a smaller area. ✓ (2) Copyright reserved Please turn over

Downloaded from hlayiso.com 10 LIFE SCIENCES (EC/JUNE2023) 3.3 3.3.1 Reflex action ✓ (1) 3.3.2 As the bee approaches the man’s eye, - light from the bee reaches the light sensitive cells (receptors) in the eye ✓ /the receptors in the eyes are stimulated and converted stimulus into an impulse ✓ - the impulse travels via the sensory neuron ✓to the spinal cord - In the spinal cord, the sensory neuron makes a synaptic contact ✓ - with the interneuron. ✓ - Which makes synaptic contact with motor neuron ✓ and - transmits the impulse ✓ - to the muscles in the eyelid ✓/ effectors - The muscles in the eyelid respond by contracting ✓ - shutting the man’s eye before the bee hit his eye ✓ - This is known as reflex action. (Any 5 x 1) (5) 3.3.3 (a) - cataract scatters and blocks the light ✓ as it passes through the lens, - preventing a sharply defined image from reaching your retina ✓ - as a result, your vision becomes blurred ✓ (Any 2 x 1) (2) (b) 17,2 ✓ x 151,34 ✓ million = 26,03 million ✓ (3) 100 3.4 3.4.1 (a) effect of caffeine ✓ (1) (b) (an individual’s) reaction time ✓ (1) 3.4.2 99 (8 + 13 + 11 + 17 + 10 + 14 + 13 + 13) =  = 12,4 ✓ (2) 8 3.4.3 - The experiment was repeated seven more times ✓ - The average was used ✓ (1) 3.4.4 - Use a larger sample of individuals  / perform investigation on several other people - Use other (measures) amounts of coffee  - Use different / more time intervals  (Mark first TWO only) (2) Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/JUNE 2023) LIFE SCIENCES 11 3.4.5 Distance the ruler fell before it was caught before and after drinking coffee 20 18 16 Distance the ruler fell (cm) 14 12 10 8 6 4 2 0 Average distance before drinking coffee Average distance after drinking coffee. Criteria for marking the graph Title of the graph (both variables) (T) 1 Bar graph is drawn (Type) (B) 1 Correct labels for X- and Y-axes + correct unit (L) 1 Appropriate scale for both axes (S) 1 Only the correct 3 areas have been represented (A) 1 Plotting of the graph (P) 1 bar drawn correctly: 1 2 bars drawn correctly: 2 NOTE: If the wrong type of graph is drawn, marks will be lost for: • Correct type of graph  • Plotting of the graph  The axes can be transposed. A bar graph can have horizontal bars. (6) 3.4.6 Caffeine slows down /reduce an individual’s reaction time.  (2) [50] TOTAL SECTION B: 100 GRAND TOTAL: 150 Copyright reserved Please turn over