June examination memorandum G12 ~ Life Sciences LIFE SCIENCES GRADE 12 JUNE EXAMINATION 2014 MEMORANDUM

Transcription

1 LIFE SCIENCES GRADE 12 JUNE EXAMINATION 2014 MEMORANDUM

2 LIFE SCIENCES GRADE 12 JUNE EXAMINATION 2014 MEMORANDUM TOTAL: 150 SECTION A QUESTION A C C D D B A C D B (10 x 2) = (20) Law of segregation Heterozygous Centromere Cataract Endocrine Medulla Oblongata Aqueous humour Ribosome [8] A only B only A only B only (4 x 2) = (8) [8]

3 1.4.1 (a) E (b) D (c) C (d) B (e) A (1 x 5) = (5) Involuntary reaction (1) [6] (a) Menstruation. (b) Ovulation/fertilisation. (c) Implantation. (3) (a) Epididymis (b) Germinal epithelium (c) Sperm cells/spermatozoa (3) (d) Transports the spermatozoa from the epididymis to the ejaculation tube. (e) Provides the spermatids with nutrition. (2) [8] TOTAL SECTION A: 50

4 SECTION B QUESTION Crossing over. (1) Y Chiasma/ta. (1) It increases/promotes genetic variation produces recombinant gametes. (1) (Mark the first ONE only) Homologous chromosomes /bivalents pair up. Each chromosome has two chromatids. Chromatids overlap/cross over. Genetic material is exchanged between non-sister chromatids. After the process of crossing-over chromosomes have genes from the homologous partner. Max (3) [6] Co-dominance/multiple alleles. (1) Three. (1) Blood group B. (1) a I B i b I A i c ii d I A i e I B i (5) (a) Moe. (b) Tyra and the father. (3) % (1) [12] The double helix/dna-strands gradually unwinds on the one end. / The weak hydrogen bonds between the two DNA-strands break/the molecule zips open. Complementary free-floating nucleotides from the nucleoplasm pair with each string. Which leads to the formation of two identical DNA-molecules/replication occurs. Process is controlled/catalysed by enzymes/dna-polymerases. (Any 4) (4)

5 2.3.2 Process A/Replicating 1. A strand of DNA is produced. 2. Occurs during interphase of the cell cycle. 3. Complementary nucleotides contain thymine. Process B/Transcription 1. A strand of mrna is produces. 2. Occurs during protein synthesis. 3. Complementary nucleotides contain uracil. Any 2 x 2 (only mark first two) 1 (table format) (5) Molecule X is the mrna molecule and it copies the DNA template. It then leaves the nucleus and moves to the ribosome where its tripletbases/codons determine the sequence of the amino acids. to form a specific protein (Any 4) (4) Translation. (1) (a) 1 (b) 4 (2) (a) GGC (b) UAC (2) [18] M Placenta. N Umbilical cord. (2) Uterus /O has muscles to contract and the cervix/p is elastic in order to widen. (2) [4] TOTAL SECTION B: 40

6 QUESTION An increase in the mass of the applied GA leads to an increase in the height of the stems /growth of the dwarf-plant. (3) Experiment had to be done in a closed area so that evaporation of the sprayed GA could not have taken place. The method of application of the GA must ensure that all areas receive equal amounts of GA. (Only marks the first TWO) (2) The results will be more trustworthy. (1) When grapes are sprayed with gibberellins, each berry will grow bigger. The spray also causes that the phalanges of the grapes become bigger/longer and therefore there is more space for the individual bunches. The enlarged space leads to better air circulation and it reduces infection by pathogenic micro-organisms. (Any FOUR) (4) [10] Thyroxin. (1) Negative feedback If the original gland (pituitary gland) release a high amount of its hormone (TSH) It stimulate the receiving gland (thyroid) will increase its release of its hormone (Thyroxin) When the secretions (thyroxin) of the thyroid gland becomes too high Then the high Hormone (thyroxin) will inhibit the original gland (pituitary gland) The original gland will then secrete less of its hormone (TSH) Which will inhibit the thyroid gland to release less thyroxin (any FIVE) (5) [6] Warm /high temperatures. (1) Production of more sweat. Blood vessel is dilated. (2) Dermis. (1) Thyroid gland is more active. More thyroxin is secreted. The rate of cellular respiration in the cells increase and heat is released. (Any THREE) (3) Vasoconstriction is when the muscles blood vessels contract and the blood flow in the blood vessels become less (2) State 1 (1) [10] B Tympanic membrane/eardrum. C Hammer/ malleus. F Cochlea. (3)

7 3.4.2 The pinna is outside the body /big/has grooves to direct the sound waves to the tympanic membrane through the auditory canal. (2) (a) D (1) (b) G (1) (c) E (1) Middle ear infections accumulate fluid in the middle ear and can cause the eardrum to burst from the inside out. Even if it doesn t burst the pressure buildup will make vibration of the eardrum/tympanic membrane difficult. The person will not hear effectively, but very weakly in the ear affected. (any TWO) (2) Cerebellum (1) Cerebrum (1) The Government can make sign language a must in every school so normal hearing people can communicate with deaf people. They can available more funds for deaf people to equip them with hearing aids and possible operations to improve hearing They can create more job opportunities for deaf people (any Logical answers 2x1) (2) TOTAL SECTION B: 60 [14]

8 SECTION C QUESTION 4 Differences between meiosis 1 and meiosis 2. (1) Process differences - Two cells are produced during meiosis 1 while four are produced during meiosis 2. - Replication of genetic material/chromosomes takes place during interphase 1, but there is no replication in meiosis 2 - Homologous chromosomes are not in pairs/sequenced/single (during prophase 2) in meiosis 2, while homologous chromosomes appear in pairs (during prophase 1) of meiosis 1. - Crossing over /exchanging of genetic material take place between homologous chromosomes (during prophase 1) in meiosis 1 while it doesn t occur in meiosis 2. - (During metaphase 2) in meiosis, all single chromosomes are arranged on the equator, while the chromosomes line up in pairs (during metaphase1) in meiosis. - Chromosomes line up randomly in pairs in metaphase 1, but not in metaphase 2. - (During anaphase 2) in meiosis 2, chromatids are pulled apart from each other, while chromosomes are pulled away from each other during meiosis 1 in anaphase 1. (Any 6 x 2) (12) Importance - Meiosis divides the chromosome number into two or half the chromosome number and therefore allows the formation of haploid gametes and prevents the doublingeffect of chromosomes during fertilisation. - Cross over and independent /random arrangement of chromosomes brings about genetic variation in the gametes and the resulting offspring. - Allows for alternation of generations to take place in the lower order-plants, i.e. moss and ferns. - Variation in the offspring ensures better survival (Any 5) (5) ASSESSMENT OF THE PRESENTATION OF THE ESSAY Marks Description 3 Well-structured shows good insight and understanding of the question. 2 Small gaps or irrelevant information in the logic and the flow of answers. 1 Tried, but significant gaps and irrelevant information in the logic and flow. 0 No attempt/only question number is written/no correct information. Content: (17) Synthesis: (3) [20] TOTAL SECTION C: 20 GRAND TOTAL: 150