Life Sciences Grade 12 P2 NSC November 2018 Memo (English)

Downloaded from hlayiso.com NATIONAL SENIOR CERTIFICATE GRADE 12 LIFE SCIENCES P2 NOVEMBER 2018 MARKING GUIDELINES MARKS: 150 These marking guidelines consist of 9 pages. Copyright reserved Please turn over

Downloaded from hlayiso.com Life Sciences/P2 2 DBE/November 2018 NSC – Marking Guidelines SECTION A QUESTION 1 1.1 1.1.1 C  1.1.2 B 1.1.3 C 1.1.4 B 1.1.5 A 1.1.6 C 1.1.7 C 1.1.8 D 1.1.9 B (9 x 2) (18) 1.2 1.2.1 Hydrogenbonds 1.2.2 Genome 1.2.3 Culturalevidence 1.2.4 Speciation 1.2.5 Haemophilia 1.2.6 Foramen magnum 1.2.7 Alleles 1.2.8 Discontinuousvariation 1.2.9 Gonosomes (9 x 1) (9) 1.3 1.3.1 A only 1.3.2 Both A and B 1.3.3 A only (3 x 2) (6) 1.4 1.4.1 D- Chromatid E- Centromere (2) 1.4.2 23 pairs (1) 1.4.3 (a) E (1) (b) C/B (1) 1.4.4 (a) Nucleus Mitochondrion (2) (Mark first TWO only) (b) Double helix (1) (c) (DNA) Replication (1) (9) 1.5 1.5.1 Phylogenetic tree/ cladogram (1) 1.5.2 An exoskeleton (1) 1.5.3 (a) S (1) (b) T (1) 1.5.4 (a) Trilobites (1) (b) Helmetids (b)Tegopeltids (1) OR (1) (c) Tegopeltids (c) Helmetids (d) Naraoids (1) (8) TOTAL SECTION A: 50 Copyright reserved Please turn over

Downloaded from hlayiso.com Life Sciences/P2 3 DBE/November 2018 NSC – Marking Guidelines QUESTION 2 2.1 2.1.1 − Due to non-disjunction/ Non-separation of a chromosome pair − during Anaphase I − Two chromosomes moved to the one pole and − none moved to the other pole Any (3) 2.1.2 − Gamete A will have 24 chromosomes/an extra chromosome − and when it fertilises a normal ovum/gamete with 23 chromosomes − the zygote will have 3 chromosomes at position 21/ 47 chromosomes (3) 2.1.3 (a) Prophase I (1) (b) − Adjacent chromatids of homologous chromosomes cross − at a point called the chiasma − There is an exchange of DNA segments/genetic material (3) (c) − Crossing over introduces genetic variation in gametes − Genetic variation may result in favourable characteristics − that ensure a better chance of survival − when environmental conditions change OR − Crossing over introduces genetic variation in gametes − Genetic variation may result in unfavourable − characteristics − that reduce the chance of survival − when environmental conditions change Any (3) (13) 2.2 2.2.1 (a) Female without SCID (1) (b) Male with SCID (1) (c) XDXd (2) 2.2.2 − He inherited the recessive allele /Xd − from the mother/individual 4 (2) (6) Copyright reserved Please turn over

Downloaded from hlayiso.com Life Sciences/P2 4 DBE/November 2018 NSC – Marking Guidelines 2.3 2.3.1 (a) It allows for the production of organisms with desired characteristics/ high average milk yield (1) (Mark first ONE only) (b) − It reduces genetic variation in offspring − It results in no further genetic improvement − It is expensive − It may not be economical for commercial agriculture (Mark first ONE only) Any (1) 2.3.2 LMJC 865 had a high average milk-production yield/ produced 78 litres per day/ had the desired characteristic (1) 2.3.3 − A diploid cell/ a cell with all the genetic information is needed − An ovum is a haploid cell/ only contains half of the genetic information (2) 2.3.4 − The nucleus of an ovum is removed and replaced with − the nucleus of a somatic donor cell/ diploid donor cell − The zygote is stimulated − for mitosis to occur − The embryo is then placed into the uterus of an adult female OR − Plants may be cloned by vegetative reproduction/asexual reproduction /tissue culture/grafting − A plant with the desired characteristics is selected − A vegetative part of the “parent” plant structure is removed/(examples) and − placed inside a growth medium/(examples) − and allowed to grow Any 4 (4) (9) 2.4 2.4.1 Purple (1) 2.4.2 − When purple-flowering plants and white-flowering plants are crossed  − all the offspring have purple flowers /have no white flowers (2) 2.4.3 − The two alleles for a characteristic − separate during meiosis so that − each gamete contains only one allele for that characteristic (3) Copyright reserved Please turn over

Downloaded from hlayiso.com Life Sciences/P2 5 DBE/November 2018 NSC – Marking Guidelines 2.4.4 P1 Phenotype Purple x Purple Genotype Dd x Dd Meiosis G/gametes D, d x D, d Fertilisation F1 Genotype DD; Dd; Dd dd Phenotype Purple : White* P 1 and F1 Meiosis and fertilisation *Compulsory 1 + Any 5 OR P1 Phenotype Purple x Purple 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 Purple: White* P 1 and F1 (6) Meiosis and fertilisation (12) *Compulsory 1 + Any 5 [40] Copyright reserved Please turn over

Downloaded from hlayiso.com Life Sciences/P2 6 DBE/November 2018 NSC – Marking Guidelines QUESTION 3 3.1 3.1.1 − The jaw is large in the chimpanzeeand small in Homo sapiens − The jaw/ palate is rectangular in the chimpanzeeand rounded in Homo sapiens − Large spaces between the teeth in the chimpanzee and small/no spaces in Homo sapiens − Large canines/teeth in the chimpanzee and small canines/teeth in Homo sapiens Any 1 x 2 (2) (Mark first ONE only) 3.1.2 − The diet changed from eating raw food in Australopithecus − to a diet of cooked food in Homo sapiens (2) 3.1.3 (a) A transitional species shows intermediate characteristics between two genera/species OR It has characteristics common to both the ancestor species and the species that follows (1) (b) The jaw is smaller than that of the chimpanzee but larger than that of Homo sapiens OR The canines/ teeth are smaller than those of the chimpanzee but larger than those of Homo sapiens OR The jaw/ palate shape is more rounded than that of the chimpanzee but less rounded than that of Homo sapiens Any 1 x 2 (2) (Mark first ONE only) (7) Copyright reserved Please turn over

Downloaded from hlayiso.com Life Sciences/P2 7 DBE/November 2018 NSC – Marking Guidelines 3.2 3.2.1 − The bright colour pattern is associated with being poisonous − thus reducing predation and − improving the chances of survival (3) 3.2.2 − There is variation in the colour of kingsnakes − Some are bright in colour/resemble the coral snakes and − the others are dull in colour − Those with dull colours are killed by predators − Those with bright colours are not eaten − so they surviveand reproduce, − passing on the allele for bright colour to the next generation Any 6 (6) (9) 3.3 3.3.1 1900 (1) 3.3.2 80 �20� x 100 = 400% OR (100−20) � � x 100 = 400% 20 (3) 3.3.3 T Natural selection Artificial selection The environment or nature is Humans represent the selective the selective force force Selection is in response to Selection is in response to suitability to the environment satisfying human needs Occurs within a species May involve one or more species (as in cross breeding) 1 for Table + Any 2 x 2 (5) (Mark first TWO only) (9) 3.4 3.4.1 − They invade farm fields − They outcompete the crop plants for space Any (1) 3.4.2 (a) Type of herbicide  (1) (b) Time taken for development of resistance (1) 3.4.3 (a) Dicloflop (1) (b) Trifluralin (1) Copyright reserved Please turn over

Downloaded from hlayiso.com Life Sciences/P2 8 DBE/November 2018 NSC – Marking Guidelines 3.4.4 (a) − They would apply the herbicide to the weed and − observe if the weed survives over many generations (2) (b) − They used the same weed species as other weed species may have developed resistance to that herbicide − Each weed species may respond differently to a herbicide OR − It allows for a single variable − to which all results can be attributed (2) 3.4.5 Time taken for the evolution of resistance to T-  different herbicides S-  L- 30 Time taken for development of  26 25 25 20 15 resistance (years) 9 9 10 7 5 0 2,4-D Dalapon Picloran Dicloflop Trifluralin Herbicide Guideline for assessing the graph Type: Bar graph drawn (T) 1 Title of graph 1 Correct: − Scale for Y-axis and (S) − Width and interval of bars on X- 1 axis Correct: − Label for X-axis and − Label and unit for Y-axis (L) 1 Plotting of bars 1- 1 to 4 bars plotted correctly 2- All 5 bars plotted correctly (6) (15) [40] TOTAL SECTION B: 80 Copyright reserved Please turn over

Downloaded from hlayiso.com Life Sciences/P2 9 DBE/November 2018 NSC – Marking Guidelines SECTION C QUESTION 4 Structure (S) − RNA is single stranded − and is made up of nucleotideswhich comprise: − ribose sugar − phosphategroup − nitrogenous bases which are − adenine, uracil, guanine and cytosine/ (A, U, G and C) − The phosphate group is attached to the ribose sugar − and the nitrogenous base is attached to the ribose sugar − Bases on RNA are arranged in triplets − as codons on mRNA − and anticodons on tRNA − tRNA has a clover-leaf/hairpin structure − tRNA has a place of attachment for an amino acid Any (9) Involvement in protein synthesis (P) − mRNA forms − during transcription/by copying the coded message from DNA − and moves out of the nucleus − and attaches to the ribosome − During translation − the anticodon matches the codon − tRNA − brings the required amino acid to the ribosome − Amino acids become attached by peptide bonds − to form the required protein Any (8) Content: (17) Synthesis: (3) (20) ASSESSING THE PRESENTATION OF THE ESSAY Criterion Relevance (R) Logical sequence (L) Comprehensive (C) Generally All information provided is Ideas are arranged in a All aspects required by the relevant to the question logical/cause-effect sequence essay have been sufficiently addressed In this Only information relevant All the information regarding At least: essay in to the: the − 6/9 correct points for the Q4 - structure of RNA and - structure of RNA and structure of RNA (S) - involvement of the - the involvement of the − 5/8 for the involvement in different types of RNA different types of RNA in protein synthesis (P) in protein synthesis protein synthesis is given is given in a logical manner There is no irrelevant information Mark 1 1 1 TOTAL SECTION C: 20 GRAND TOTAL: 150 Copyright reserved