Life Sciences 2017 Learner Doc. 26343

CURRICULUM GRADE 10 – 12 DIRECTORATE LIFE SCIENCES WINTER CLASSES LEARNER SUPPORT DOCUMENT GRADE 12 2017 1

CONTENTS TOPIC PAGE 1. DNA : Code of Life 3 2. MEIOSIS 8 3. REPRODUCTIVE STRATEGIES IN VERTEBRATES 12 4. HUMAN REPRODUCTION 13 5. GENETICS 18 6. NERVOUS CO-ORDINATION 29 7. ENDOCRINE SYSTEM AND HOMEOSTASIS 34 2

1. DNA: Code of Life 1.1. The diagram below shows part of a DNA molecule in a nucleus just before cell division 1.1.1 Identify the parts labelled: (a) 3 (1) (b) 4 (1) 1.1.2 Identify the nitrogenous bases labelled: (a) 1 (1) (b) 2 (1) 1.1.3 Identify the process represented by the diagram above, and Explain your answer. (3) (7) 3

1.2. The diagrams below shows a process that takes place in all living cells involving two types of nucleic acids. 13 11 12 10 3 7 8 6 9 1 15 2 4 5 3 16 14 amino acids 1.2.1 Name the process represented by the diagram. (1) 1.2.2 Name the nucleic acid labeled 12. (1) 1.2.3 Give a visible reason for your answer in 1.2.2 (1) 1.2.4 Provide the specific names for the nucleic acids labeled: (i) 6 (1) (ii) 9 (1) 1.2.5 Provide labels for the parts labeled 10, 11 and 13 and 14. (4) 4

1.2.6 Name the specific part of the process shown that is occurring at: (i) 3 (1) (ii) 15 (1) 1.2.7 What is the role of part 10 in the process that is represented in the diagram? (2) 1.2.8 What collective name is given to the triplet of bases represented by each of the following numbers? (i) 1 (1) (ii) 16 (1) 1.2.9 Name the bonds that are represented by the label 5. (1) 1.2.10 The table below indicates some amino acids that are carried by different tRNA’s. tRNA Amino tRNA Amino tRNA Amino bases acid bases acid bases acid GUU Glutamine CUA Aspartate GAU Leucine GCG Arginine GGU Proline UAU Isoleucine CCG Glycine ACG Cysteine GUG Histidine CUU Glutamate AGC Serine ACC Tryptophan Which amino acid is represented by: a) 2 b) 4 c) 7 d) 8 (4) (20) 5

2.1 Study the diagram below, which shows a stage in protein synthesis. 2.1.1 (a)Name the stage in protein synthesis represented by the diagram above. (1) (b) Describe the process named above. (6) 2.1.2 Write down the DNA base triplets that correspond to the codons numbered 6 and 10. (2) 2.1.3 The table below shows the amino acids coded for by various tRNA anticodons. Antico Amino acid dons coded for on tRNA CCU Proline GAA Glutamate GGA Glycine CUU Leucine GUG Histidine ACC Threonine CAC Valine UGG Tryptophan Use the information in the table above and: (a) Write down the names of the amino acids coded for by the codons numbered 7 and 9 (2) (b) Identify amino acid 5. (1) (12) 6

2.2 Read the extract below and answer the questions that follow. DNA TESTING OF MEAT Research by Stellenbosch University scientists found traces of donkey, water buffalo and goat meat in beef mince samples taken from across the country. Of the 139 samples tested, 95 (68%) contained species which were not indicated on the product labelling. Scientists at the University of the Western Cape did DNA tests on 146 kudu biltong samples. The results showed that 77% of the samples were mislabelled. In some cases the samples contained beef, giraffe, kangaroo, zebra or pork. DNA testing is expensive, at around R3 500 per sample. [Adapted from iol news, March 2013] 2.2.1 Explain how it was possible for scientists to identify the different species in the meat samples tested. (2) 2.2.2 Give TWO reasons why the biltong manufacturers would substitute kudu with beef or pork. (2) 2.2.3 Explain why the proper labelling of the meat products is important to some people. (2) 2.2.4 Give ONE reason mentioned in the text why testing for the composition of meat products is not done regularly. (1) 2.2.5 Give ONE reason that can be used to dispute the DNA results. (1) 2.2.6 State TWO uses of DNA profiling other than the one mentioned in the extract. (2) (10) 3. ESSAY: Describe the structure of DNA as well as the process of DNA replication. Also explain the significance of DNA replication for meiosis. Content (17) Synthesis (3) (20) NOTE: NO marks will be awarded for answers in the form of flow charts or diagrams 7

2 .MEIOSIS 1.1. Examine the cells undergoing cell division below and answer the questions that follow: 1.1.1 What specific process of cell division is shown here? (1) 1.1.2 Give two observable reasons for your answer to 1.1.1 (4) 1.1.3 Explain briefly how the chromatids in cells A and B became genetically different from each other. (4) 1.1.4 State the biological importance of this process. (1) 1.1.5 Name one specific organ in which these cells may be found. (1) [12] 8

1.2. Study the diagrams below showing the same phase in two types of cell division Diagram I Diagram II 1.2.1. What type of cell division is represented by Diagram I? (1) 1.2.2. What type of cell division is represented by Diagram II? (1) 1.2.3. Give a reason for your answer in Question 1.2.2 (1) 1.2.4. What phase is represented by Diagram 1 and Diagram II, respectively? (2) 1.2.5. Provide labels for A, B, C and D, respectively. (4) (9) 1.3. Study the diagrams below showing two stages of meiosis. Diagram I Diagram II 1.3.1. Name the phase of meiosis represented by Diagram 1 and Diagram II, respectively. (2) 1.3.2. State ONE visible reason in Diagram I which indicates that meiosis is taking place. (2) 9

1.3.3. How many chromosomes would be present in each daughter cell at the end of meiosis in this cell? (1) 1.3.4. Name the phase of meiosis that occurs after the phase represented by Diagram 1 and Diagram II, respectively (2) 1.3.5. State ONE difference between the events that occur in the two phases mentioned in 1.3.5 (2) (9) 1.4. The diagram below represents an animal cell in a phase of meiosis. chromatid A B 1.4.1. State which phase of meiosis is represented in the diagram above. (1) 1.4.2. Give a reason for your answer to QUESTION 1.4.1. (1) 1.4.3. Identify parts A and B. (2) 1.4.4. How many chromosomes … (i) were present in the parent cell before it underwent meiosis? (1) (ii) will be present in each cell at the end of the meiotic division? (1) 1.4.5. State ONE place in a human female where meiosis would take place. (1) 1.4.6. Could the cell represented in the diagram be that of a human? (1) 1.4.7. Explain your answer to QUESTION 1.4.6. (1) 1.4.8. Give TWO reasons why meiosis is biologically important. (2) 1.4.9. Sometimes the chromosomes may not all successfully separate during the phase represented. Explain how this could lead to Down’s syndrome. (5) (16) 10

2.1 Study the diagram of a phase in meiosis and answer the questions which follow. 2.1.1 Provide labels for parts B, C and D. (3) 2.1.2 Name the process in meiosis that is illustrated in the diagram above. (1) 2.1.3 State ONE importance of the process named in QUESTION 2.1.2 (1) 2.1.4 Draw a diagram of the structure labelled A to show its appearance immediately after the process named in QUESTION 2.1.2. (2) [7] 11

3. REPRODUCTIVE STRATEGIES IN VERTEBRATES 1 Read the passage below. REPRODUCTIVE STRATEGY IN KANGAROOS The red kangaroo reproduces by sexual reproduction. After mating, the fertilised egg undergoes gestation in the uterus. After 33 days of gestation, the red kangaroo gives birth to an offspring that is hairless, blind and only a few centimetres long. The offspring moves from the vagina by following a trail of saliva secreted by the mother to a protective pouch where it remains for a year. During this time the offspring drinks milk from the mother who has teats in her pouch. After 190 days it leaves the pouch. Pouch [Adapted from www.livescience.com] 1.1 State whether: (a) Fertilisation in the red kangaroo species is INTERNAL or EXTERNAL (1) (b) The red kangaroo species is OVIPAROUS, OVOVIVIPAROUS or VIVIPAROUS (1) 1.2 Give a reason for your answer to QUESTION 1.1(b). (1) 1.3 State TWO ways in which the survival of the offspring immediately after birth is ensured in the red kangaroo species. (2) (5) 12

4.HUMAN REPRODUCTION 1. Study the diagrams below and answer the questions that follow. bladder ) head G middle piece A B C tail D E Human male reproductive system Human sperm cell 1.1 Provide labels for A, B, E and G. (4) 1.2 State ONE function each of C and F, respectively. (2) 1.3 State the LETTER and NAME of the part where sperm are produced. (2) 1.4 Explain why it is necessary for part D to 'hang outside' the body of the male. (2) 1.5 Name the following: (a) The cells that secrete a male sex hormone (1) (b) The hormone that stimulates the development of secondary sexual characteristics in males (1) 13

1.6 During a vasectomy, part B is surgically cut. (a) Explain how this procedure will act as a method of contraception. (2) (b) Will it be possible for a man who is HIV positive to pass the HI virus to another person after he undergoes a vasectomy? (1) (c) Explain your answer to QUESTION 1.6 (b). (2) (17) 2. The table below shows the average human foetal length of males and females over a 40-week gestation period. Time (weeks) Foetal length (cm) Male Female 8 1 1 13 7 7 16 14 13 24 33 31 36 46 43 40 51 49 2.1 Draw TWO sets of bar graphs on the same system of axes to compare male and female foetal length over time. (11) 2.2 Draw TWO conclusions from the results shown in the graphs. (2) 14

3. The following two graphs show the changes in temperature in a woman's body and the level of the hormones oestrogen and progesterone during the menstrual cycle. The release of the ovum takes place when there is a very small increase in body temperature. Changes in body temperature of a woman 37,1 Temperature ºC 36,8 36,5 36,2 0 5 10 15 20 25 30 Day Changes in the level of oestrogen and progesterone Levels of hormones in blood Progesterone Oestrogen 0 5 10 15 20 25 30 Day (2) 3.1 What was the temperature of the woman on day 15? 3.2 Calculate by how many degrees Celsius her temperature varied in one menstrual cycle. Show ALL workings. (2) 3.3 From the graph, name THREE factors that indicate that ovulation occurred. (3) 15

3.4. Explain the importance of the higher level of progesterone (2) from day 15 onwards. 4. An investigation was conducted to determine the diameter of a healthy follicle in a human ovary during the menstrual cycle. A sample consisting of 50 women aged between 20 and 25, with regular menstrual cycles, was used for this investigation. The average changes in the follicle diameters of all 50 women during their menstrual cycles were measured and recorded. 4.1 Name TWO steps that were considered during the planning of this investigation (2) 4.2 The following results were obtained from the investigation. DAYS WHEN FOLLICLES AVERAGE FOLLICLE WERE MEASURED DIAMETERS OF THE 50 WOMEN (mm) 5 6,9 10 13,3 13 18,8 14 22,0 20 3,4 25 2,6 [Adapted from Journal of Reproduction and Fertilisation,1983] Use the results and explain: (a) The changes in the follicle diameters from day 14 to day 25 (3) (b) How the results would probably differ if all 50 women used contraceptive pills that contained a high level of progesterone (3) 16

5. ESSAYS: Explain the structural suitability of the sperm cell for its function and describe its involvement in the formation of a zygote and the development of this zygote until implantation. Content: (17) Synthesis: (3) (20) NOTE: NO marks will be awarded for answers in the form of flow charts, tables or diagrams. The unicellular zygote undergoes many developmental changes until it becomes a multicellular foetus, nourished and protected by the mother. Describe the changes that allow the zygote to eventually develop into a foetus and how this foetus is nourished and protected during the period of pregnancy. Content: (17) Synthesis: (3) (20) NOTE: NO marks will be awarded for answers in the form of flow charts, diagrams or tables. Describe how genetic variation is brought about in gametes through cell division and name and describe the specific process that takes place in the formation of an ovum. Content: (17) Synthesis: (3) (20) NOTE: NO marks will be awarded for answers in the form of flow charts, tables or diagrams. 17

5. GENETICS 1.1. The diagram below shows the offspring of crosses between a pure bred black coat bull and a pure bred white coat cow. The coat colours of the offspring of the first and second generations are also shown. Coat colour is controlled by two alleles, one for black and one for white coat colour. White cow Black bull 1 2 Parents 1st Generation 3 1 4 1 2nd Generation 5 6 7 8 1.1.1 Use the letters B and b and state which allele is responsible for …. (a) Black coat colour. (1) (b) White coat colour. (1) 1.1.2 Which animal/s (1 to 8) in the diagram must be homozygous for coat colour ? (3) (5) 1.2. In humans, the allele for wavy hair is dominant to that for straight hair. Use the letter H to represent the allele for wavy hair and the letter h to represent the allele for straight hair. 1.2.1 Explain why the statement below is true: “A person with wavy hair may be heterozygous or homozygous for this characteristic” (2) 1.2.2 Represent a genetic cross to show how a man with wavy hair who marries a woman with wavy hair may have a child with straight hair. (6) (8) 18

2.1 Study the genotypes and phenotypes below that show how the alleles for colour-blindness are inherited. X and Y represent sex chromosomes. A carrier does not suffer from colour-blindness but can pass the allele for colour-blindness to their children. NAME OF PERSON GENOTYPE PHENOTYPE Lindi XBXB Normal female Beauty XBXb Carrier female Sarah XbXb Colour-blind female Paul XBY Normal male Thabani XbY Colour-blind male 2.1.1 State why colour-blindness is referred to as a sex-linked disorder? (2) 2.1.2 Explain why Thabani is colour-blind while Beauty is not colour-blind 2.1.3 Sarah and Paul marry and have two children, a son and a daughter. (2) Represent this genetic cross by using the information in the table above to determine the genotypes and phenotypes of the son and the daughter. (6) (10) 19

2.2. In humans, the allele for brown eyes (B) is dominant over the allele for blue eyes (b). Also, straight hair (h) is recessive to wavy hair (H). A man who is heterozygous for brown eyes and wavy hair marries a woman with blue eyes and straight hair. 2.2.1. State why the example above represents a dihybrid cross. (1) 2.2.2. Write down: (a) the genotype of the woman (1) (b) all the possible gametes of the man (2) 2.2.3. The man and the woman have a child whose genotype is bbHh. What is the child’s phenotype? (2) 2.2.4. A man and a woman have a child with genotype BbHh. If the woman’s Genotype is bbhh, what are the possible genotypes of the man? (2) (8) [18] 20

3.1. Study the diagram below which shows three generations of snapdragon plants and answer the questions which follow. Use the following symbols for the contrasting alleles: W – for white flowers R – for red flowers A B C Diagram showing inheritance of colour of snapdragon flowers KEY: Snapdragon with pink flowers Snapdragon with red flowers 3.1.1 State the kind of dominance shown in the diagram above. (1) 3.1.2. Give a reason for your answer in 3.1.1. above (1) 21

3.1.3. Use the symbols R and W and write down the genotypes of each of the follwing snapdragon plants: (a) A (1) (b) B (1) (c ) C (1) (5) 3.2. An investigation was conducted by grade 12 learners on fruit flies to determine the genotypic and phenotypic ratios of the F2 generation. They placed 12 homozygous red-eyed females in a flask with 12 homozygous white-eyed males. The flask contained a ripe fruit and the opening of the flask was covered with cotton wool. After three weeks the F 1 offspring were crossed and the results (F2) are shown in the table below. Number of offspring (F2) Red-eyed 27 White-eyed 9 3.2.1 State TWO uses of the cotton wool in the investigation. (2) 3.2.2 State TWO ways in which the reliability of the results could be improved. (2) 3.2.3 Using the symbols R and r to represent the alleles for eye colour, state all the possible genotypes of the: (a) Red-eyed fruit fly of the F2 offspring (b) White-eyed fruit fly of the F2 offspring (3) 22

3.2.4. What is the ratio of red-eyed flies: white-eyed flies in the F2 generation? (1) (8) 3.3. A group of Grade 12 learners did a survey about the frequency of genetic disorders in a small human population. The results are shown in the table below. The number of people in the population is 1 200. RESULTS OF THE SURVEY ON THE FREQUENCY OF GENETIC DISORDERS IN A POPULATION GENETIC DISORDERS FREQUENCY IN POPULATION (%) Albinism 7 Down syndrome x Sickle cell anaemia 10 Without any disorder 78 3.3.1 According to the table, which disorder is most common in this community? (1) 3.3.2 Calculate the number of people with Down syndrome. Show ALL working. (3) 3.3.3 Which ONE of the disorders mentioned in the table above is caused by a chromosomal mutation? (1) (5) 23

3.4 Mr and Mrs Phonela are concerned that their baby girl does not appear to resemble either of them. They suspect that the baby they were given at the hospital was not theirs. Mr Phonela is blood type AB, Mrs Phonela is blood type B and the baby they were given is blood type O. 3.4.1 Give the possible genotypes of: (a) Mrs Phonela (2) (b) The baby girl (1) 3.4.2 Explain why the baby girl with blood type O cannot be Mr and Mrs Phonela's daughter. (3) 3.4.3 Explain why the use of blood type for paternity testing is not (2) conclusive. 3.4.4 Using your knowledge of sex chromosomes, explain why the sex of a child is determined by the male gamete. (5) (13) PEDIGREE DIAGRAMS Steps to follow when completing a pedigree diagram a. Study any key and opening statement / s provided to look for:- i. dominant and recessive characteristics ii. phenotypes b. Write in the phenotype of all the individuals as given in the problem c. Fill in the genotype of all the individuals with the recessive condition – it has to have two lower case letters d. For every individual in the diagram that has the recessive condition, it means that each allele was obtained from each of the two parents. So, work backwards and fill in one recessive allele for each of the parents e. If the parents showed the dominant characteristic, then fill in the second letter which has to be a capital letter f. Any other individual showing the dominant characteristic will most likely be homozygous dominant (two capital letters) 24

EXAMPLE: Freckles are small patches of coloured skin. The allele for freckles (a) is recessive to the allele for un-freckled skin (A). The diagram below shows a family where some of the people have freckles. Write down the genotypes of: (a) William (b) Ben (c) Dot (d) Claire If Paul and Cher had another child, what would be the chance of it having freckles? KEY A- no freckles a- freckles P1 phenotype No freckles x Freckles (Paul) (Cher) genotype Aa x aa meiosis G1 A, a x a fusion F1 genotype Aa ; aa phenotype 1 No freckles ; 1 freckles 25

EXERCISES ON PEDIGREE DIAGRAMS 1. Study the diagrams below that show some breeding experiments on mice. A single pair of alleles showing complete dominance controls coat colour (white or grey) in these mice. Female Male Female Male 1 2 3 4 Offspring Offspring Offspring Female Female Male Female Results of breeding experiments 1.1 State which sex chromosomes would be present in the gametes of parent mouse 2 and mouse 3, respectively. (2) 1.2 If mice 3 and 4 had a second set of offspring, what is the percentage chance that the first mouse born would be female? (1) 1.3 Which of the parent mice (1, 2, 3 or 4) is likely to be homozygous dominant for coat colour? (1) 1.4 State why mouse 3 can only be heterozygous for coat colour. (2) (6) 26

2. Study the family tree below which shows inheritance of type of little finger over four generations of a family. A B C D E F G Key: Male with straight little finger Male with bent little finger Female with straight little finger Female with bent little finger Pedigree diagram showing inheritance of type of little finger 2.1 How many members of the family have straight little fingers? (1) 2.2 Is person F homozygous or heterozygous for type of little finger? (1) 2.3 Which type of little finger is controlled by a dominant allele? (1) 2.4 Explain your answer in QUESTION 2.3 (3) 2.5 In the fourth generation of the family, what proportion will be female with straight little finger? (2) 2.6 Persons F and G are twins. Were they produced from a single fertilized egg cell? (1) 2.7 State TWO reasons based on the phenotype to support your answer in QUESTION 2.6 (2) (11) 27

3. Study the pedigree diagram of a family where some individuals have haemophilia. Haemophilia is a sex linked disorder. Use H for normal blood clotting and h for the haemophiliac trait. Peter Andrew Henry Enid David Anele Goliath Normal female Priscilla Key Male haemophiliac Clarence Normal male 3.1 From the pedigree diagram above, state the relationship between gender and the incidence of haemophilia. (2) 3.2 Write down all the possible genotypes of: (a) Peter (b) Enid (c) Clarence (6) (8) 28

6.NERVOUS CO-ORDINATION 1. Study the diagram below of a section through a human spinal cord and the neurons involved in a reflex arc. 1.1 Define a reflex action. (2) 1.2 Identify neurons A, B and C. (3) 1.3 Write down only the LETTER of the neuron (A or C) which is probably damaged if a person: (a) Can feel the stimulus but cannot respond (1) (b) Is able to walk but cannot detect any stimulus (1) 1.4 State the significance of the reflex action in humans. (1) (6) 29

2. The diagram below represents the central nervous system in a human. B C D A E 2.1 Identify part: (a) A (1) (b) C (1) (c) D (1) 2.2 State THREE functions of part B. (3) (6) 30

3. Study the diagram of a longitudinal section through a human eye below. A (a) B F (b) (3) E C D 3.1 Label parts A, B and E. (3) 3.2 Give the LETTER only of the part which: (a) Protects the delicate internal structures (1) (b) Transmits impulses to the cerebrum (1) (c) Becomes cloudy or opaque as a person gets older, leading to decreased vision (1) (d) Contracts or relaxes when the distance of an object from the eye changes (1) (7) 31

4. The diagram below represents a human ear. D C B E F G A 4.1 Identify parts A and D. (2) 4.2 Write down the LETTER only of the part which: (a) Conducts sound waves towards the middle ear (1) (b) Absorbs pressure from the inner ear (1) (c) Ensures equal pressure on either side of the tympanic membrane (1) (d) Transmits vibrations to the inner ear (1) (e) Contains the organ of Corti (1) (7) 32

5. The diagram below represents a neuron in a human. A B C 5.1 Identify the type of neuron represented in the diagram. (1) 5.2 State ONE function of part B. (1) (2) 33

7. THE ENDOCRINE SYSTEM AND HOMEOSTASIS 1. The diagram below represents parts of the endocrine system in humans. A C B D 1.1 Identify gland: (a) A (1) (b) B (1) 1.2 Give the LETTER and the NAME of the gland that secretes a hormone responsible for: (a) Starting puberty in males (2) (b) Stimulating absorption of glucose by cells (2) (c) Making the kidney tubules permeable to water (2) (8) 34

2. Study the flow diagram below of a homeostatic mechanism used to regulate the concentration of salts in the human body. 2.1 Define homeostasis. (2) 2.2 Give the name of the following: (a) Organ A (1) (b) Gland B (1) (c) Hormone C (1) 2.3 Describe the response by the effector at D. (2) (7) 3. Describe the negative feedback mechanism that occurs when the thyroxin level decreases below normal. (5) 35

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