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1 SECONDARY SCHOOL IMPROVEMENT PROGRAMME (SSIP) 2015 GRADE 12 SUBJECT: LIFE SCIENCES TEACHER NOTES (Page 1 of 86) © Gauteng Department of Education 2 TABLE OF CONTENTS SESSION NO TOPIC PAGE 5 Genetics and Inheritance Part 1 3 - 23 6 Genetics and Inheritance Part 2 and Responding to the environment - Humans: Nervous system Part 1 24 - 41 7 Responding to the environment - Humans: Nervous system Part 2 and Eye and Ear 42 - 58 8 Consolidation 58 - 68 9 Consolidation 69 - 78 10 Consolidation 79 - 86 © Gauteng Department of Education 3 SESSION NO: 5 TOPIC: GENETICS AND INHERITANCE PART 1 Teacher note: Learners MUST understand the link between meiosis and genetics. During the crossing over in prophase I of meiosis, chromosomes share information and then during metaphase I, separate randomly. This determines the combination of chromosomes and genes that you have as an individual. Genetics determines individual variation (to be different) and survival of the fittest. They MUST have a clear understanding of the genetic terminology in order to study genetics and answer genetic problems. Mendel’s Laws are very important - understand the concepts of dominance and how this plays a role in monohybrid crosses (mono = one = one characteristic or trait). Be aware of confusing the word ‘cross/ crossing’ with ‘crossing over’ in Meiosis. You cross individuals and calculate the chances of a characteristic or trait being in the offspring. Learners must be clear of the difference between these two terms. Questions on blood group inheritance and sex determination are often asked. The more examples of genetic crosses that they do, the better they will do. Pedigree diagrams are a popular way to express family history and are often asked in exams. Make sure they know how to answer them. There are basically FOUR crosses. If they know these crosses, they will be okay. 1. 2. 3. 4. Introduce session – 5 minutes (and go over basic idea as per the above introduction) Typical exam questions and solutions – 50 minutes (Questions that are not completed must please be included with Homework) Notes on Content – 15 minutes Answer/memo discussion – 20 minutes SECTION A: TYPICAL EXAM QUESTIONS QUESTION 1: Multichoice 7 minutes (Taken from various sources) (Note: When answering multi-choice questions: 1. Read the question while covering the answers. 2. Think of the correct answer. 3. Look for your answer. 4. Write the letter down on your answer sheet. BUT: If you do not know the answer after point 1 and 2, then: 3. Look at the options. 4. Try to think of why an option is wrong for the question and cross it out. If there is an option that you don’t know, write a ? next to this option. 5. If you still do not know the answer, then select the ? option) (Reminder: there are only 4 basic types of crosses. Make sure you are able to use them properly. Do a quick cross in pencil, next to the relevant question to find the correct answer) 1. The term for the physical appearance of an organism due to the genetic composition: © Gauteng Department of Education 4 A B C D heterozygous genotype homozygous phenotype 2. When the allele genes on homologous chromosomes differ, the organism is A homozygous B dominant C heterozygous D recessive 3. The genotype of a plant that results from a cross between a plant with red flowers (RR) and white flowers (rr) will be: A RR B Rr C rr D rR 4. Choose the correct cross if the result is 50% homozygous dominant and 50% heterozygous in the F1 generation: A Bb xbb B BB x Bb C BB x bb D Bb x Bb 5. Two white heterozygous cats were crossed where white fur is dominant over black fur. Choose the correct phenotype of the F1 generation: A 25% white and 75% black B 50% black and 50% white C 25% black and 75% white D 100% white 6. A heterozygous red flower plant was crossed with a homozygous white flower plant and yielded 300 new plants. What number of the new plants will carry white flowers? A 150 B 225 C 300 D 196 7. The babies of a purebred while rabbit were crossed with a purebred black rabbit. Black hair dominates over white hair. The offspring of the F2will be: A all black B all white C 75% black and 25% white D 75% white and 25% black (7 x 2 ) [14] © Gauteng Department of Education 5 QUESTION 2: 11 minutes (Taken from DoE November 2008 Paper 1) (The following question is based on a pedigree diagram. Please see the content summary for hints to answer questions on pedigree diagram. In this diagram, the family history is shown as a schematic diagram. Always identify the recessive individuals first. Write their trait symbols next to the number e.g.: S = straight hair and s = wavy hair. So ss = homozygous for the recessive trait) The eight items below are based on the pedigree diagram which shows the phenotypes of offspring from wavy-haired parents. Write down the letters A, B, C or D according to the following key: A - if the statement is TRUE B - if the statement is FALSE C - if there is a 25% chance that the statement is TRUE D - if there is a 50% chance that the statement is TRUE P 1 2 5 6 F1 3 4 9 10 7 8 11 12 F2 = straight = wavy = curly 2.1. 2.2. 2.3. 2.4. 2.5. 2.6. 2.7. 2.8. Wavy hair is dominant. (1) Individual 1 is homozygous (1) If individual 6 married a woman with straight hair, all of the offspring would have straight hair. (1) Individual 4 is homozygous. (1) One of the parents of 2 had the same genotype as 2. (1) If 10 married someone with wavy hair, the first child would have wavy hair (1) If 1 and 2 had another child, the child would have curly hair. (1) If 3 and 4 had more children than those shown, they might have straight hair. (1) [8] © Gauteng Department of Education 6 QUESTION 3: 8 minutes (Taken from DoE November 2009 Paper 1) Fur colour in mice is controlled by a gene with two alleles. A homozygous mouse with black fur was crossed with a homozygous mouse with brown fur. All the offspring had black fur. Using the symbols B and b to represent the two alleles for fur colour, show as a Punnit square, a genetic cross between a mouse that is heterozygous for fur colour with a mouse with brown fur. Show the possible genotypes and phenotypes of the offspring. (6) (Check the content summaries for an example of the 4 possible crosses. Remember to include P1 and F1, as well as genotype and phenotype, rations and % in your work.) QUESTION 4: 5 Minutes (Taken from DoE November 2008 Paper 1) People with albinism are unable to produce the dark pigment, melanin, in their skin. This condition is caused when an individual is homozygous recessive for this characteristic. The family tree below shows the occurrence of albinism over three generations. (This is a pedigree diagram. Always first mark the homozygous recessive individuals on the diagram before trying to work out the genetic traits for the other individuals. Albinism is homozygous recessive, so an individual with albinism will be ‘aa’ and a person who is not an albino will be either ‘AA’ or ‘Aa’.) 4.1. Indicate whether each of the individuals below could be homozygous dominant, homozygous recessive or heterozygous: (a) 1 (2) © Gauteng Department of Education 7 (b) 2 4.2. (1) Explain your answer to QUESTION 4.1 (a). (2) [5] QUESTION 5: 6 minutes (Taken from Free State Prelim 2009) Sello crosses two pure breeding garden pea plants in the laboratory. Plant A produces yellow peas and plant B green peas. He knows that the gene, for yellow peas (Y), is dominant over the gene for green peas (y). The diagram below shows the results he obtained for two generations of pea plants. Study the diagram and answer the questions that follow: (A reminder: yellow is dominant and green is recessive. For a pea plant to yield green peas, this plant must be ‘yy’ – so homozygous recessive. Also refer to Mendel’s law of dominance and segregation in the content summary.) 5.1. 5.2. 5.3. Give the genotype for plant A and plant B. Provide the phenotypic ratios for the F2 generation. If Sello allows plant G to self-pollinate, give the phenotype and genotype of the offspring. (2) (2) (2) [6] QUESTION 6: 6 minutes (Taken and adapted from Study & Master Biology Grade 11) Blood typing can be used to identify a parent in that the blood type can prove that a person is not the parent of a child rather than determine without question who the parent is. A, B, AB and O blood groups are the result of three alleles. Allele A and B are incompletely dominant and O is recessive to both A and B. Should the discrepancy continue, tissue typing and DNA fingerprinting will be used. Read © Gauteng Department of Education 8 through the following information and answer the questions below: In a maternity ward of a hospital, two newly born babies were mixed up. One baby is blood type O and the other is type A. Both mothers believe the baby with blood type O is their baby. Can you sort it out? On testing the parents’ blood it was found that: 1. Mr. Xhosa is blood group AB and his wife is blood group B 2. Mr. Mbundwini is type A. Who owns baby ‘O’ and who owns baby ‘A’? Explain / show your reasoning. [6] (Remember that in blood groups there are three alleles A, B and O. A and B are co-dominant over O which is recessive. There must be two of the same alleles if a recessive trait is present in the individual) QUESTION 7: 12 Minutes (Taken from DoE Nov 2011 Paper 1) Haemophilia is a sex-linked disease caused by the presence of a recessive allele (Xh). A normal father and heterozygous mother have children. (Remember: XH is dominant and normal. Xh will carry the recessive haemophilia gene) 7.1. 7.2. 7.3. Represent a genetic cross to determine the possible genotypes and phenotypes of the children of these parents. What are the chances of the parents having a child that will be a haemophiliac male? Explain why the father is not a carrier for haemophilia. (6) (2) (2) [10] SECTION B: NOTES ON CONTENT GENETICS AND HEREDITY Genetics is the science of inheritance and studies the principles of heredity and variation. The hereditary instruction carried within the DNA ensures that offspring resemble their parents and ensures that genetic variation can take place, resulting in survival of the fittest. Genetics and sexual reproduction: During sexual reproduction, offspring are produced that resemble the parents. Remember that two haploid gametes are the result of the process of meiosis. The gametes fuse during reproduction and the result is a diploid zygote, containing a double set of chromosomes. One set of the chromosomes came from the male gamete, which contains the DNA from the father. One set of chromosomes came from the female gamete and contains the DNA from the mother. The child therefore contains DNA from both parents. © Gauteng Department of Education 9 DEFINITIONS AND IMPORTANT TERMS AND CONCEPTS: Chromatin network: visible as thread-like structures in the nucleus of an inactive cell Chromosome: consists of DNA (which makes up the genes) and protein. Gene: the heriditary unit of DNA that occupies a specific location on a chromosome and controls the development of the characteristics Allele: one of two contrasting genes that determine alternative characteristics in inheritance because they are situated in the same position or locus on homologous chromosomes Locus: The exact position or location of a gene on a chromosome. Genotype: This is the total genetic composition of an organism. It is the information present in the gene alleles, for example BB, Bb or bb. Phenotype: This is the external, physical appearance of an organism. The phenotype is determined by the genotype. (Dominant traits will be displayed in the offspring (BB or Bb). The recessive gene allele is not displayed when the offspring is heterozygous for a trait. The recessive allele is always present and can be transferred to offspring. A recessive trait is only displayed in the phenotype, when both recessive gene alleles are present e.g.: bb) Dominant allele: an allele that masks or suppressed the expression of the allele partner on the chromosome pair and the dominant characteristic is seen in the homozygous (e.g: TT) and heterozygous state (e.g: Tt) Recessive allele: an allele that is suppressed (dominated) when the allele partner is dominant. The recessive trait will only be expressed/seen if both alleles for the trait are recessive e.g: tt Homozygous: when two alleles that control a single trait are alike for a characteristic resulting in true-breeding for a particular characteristic Heterozygous: when two alleles on the same locus are different for a particular characteristic. This will result in a hybrid. Gene mutation: a change of one or more bases in the nuclear DNA of an organism. If the mutation is favourable, the organism survives but should the mutation be unfavourable, the organism will die. Multiple alleles: when there are more than two possible alleles for one gene locus. Complete dominance: one allele is dominant over the other allele, which is recessive. The recessive trait will be masked in the homozygous dominant and heterozygous offspring. Incomplete/partial dominance: No one allele is dominant over the other allele/s and are thus not recessive or dominant. When combined, they produce a new third phenotype e.g: black fur and white fur = grey fur Examples: Incomplete dominance in flowers: Colour key: R (red) W (white) P1 Phenotype : red x white Genotype: RR x WW Meiosis Gametes RR x W W © Gauteng Department of Education 10 Fertilisation F1 Genotype: 4:4 RW Phenotype: 100% pink Incomplete dominance in humans: Curly CC plus Straight SS = Wavy CS Co-dominance: Both gene alleles are equally dominant so the heterozygous individual expresses both traits, example: blood groups. Protein A and protein B are coded by alleles A and B. If no protein A or B is present, then these cells will be coded by the allele O. This means that there are three possible alleles for this one gene locus in humans. When there are more than two possible alleles, it is termed multiple alleles. Any two of these alleles will occur in combination in an individual. The alleles A and B are co-dominant and A and B completely dominate allele O. When two individuals with AB blood type have children, the children can be type A, type B or type AB. Phenotype/Bloo d type Genotype Can receive blood from: A IA I A A or O A A I I B IB IB B B I I AB I A IB A, B, AB or O (also known as the universal acceptor because blood group AB can accept blood from any other group) O i i O (also known as the universal donor because any blood group can receive O blood) B or O Co-dominance in humans: Homozygous dominant = IA IA (blood group A) Homozygous recessive = IB IB (blood group B) Heterozygous = IA IB (blood group AB) Co-dominance in flowers: Homozygous dominant = RR (red) Homozygous dominant = WW (white) Heterozygous = RW (white with red markings/red with white markings) © Gauteng Department of Education 11 Monohybrid cross: when one pair of traits is crossed to determine the possible inheritance in the offspring. There will always be 4 possible combinations. Dihybrid cross: the crossing of two pairs of contrasting traits to determine the possible inheritance of the offspring. The filial generation will result in 16 possible combinations (4 x 4 possibilities = 16). Dihybrid crosses relate to Mendel’s law of independent assortment. Filial generation: The first generation of parents (P1) will produce offspring that result from a cross called the first filial generation (F1) and shows the possible inheritance of the offspring. When the offspring mature they will become the P2 (second parent generation) and produce offspring in the second filial generation (F2). EXAMPLES OF MONOHYBRID CROSSES: There are basically FOUR types of crosses. If you know these crosses, you should not have a problem. Learn them well. We will use one general trait like hair colour: B = brown hair colour (dominant trait) b = blonde hair colour (recessive trait) CROSS EXAMPLE 1: (Homozygous dominant x Homozygous recessive) [OFTEN ASKED] P1 (first parent generation) Phenotype: Brown x blonde Genotype: BB x bb Meiosis Gametes: B B x b b fertilization B B b Bb Bb b Bb Bb F1 (first filial generation = first offspring) Genotype: Bb 4:4 heterozygous offspring Phenotype: 100% brown CROSS EXAMPLE 2: (Heterozygous x Heterozygous) [OFTEN ASKED] P1 Phenotype: Brown x Brown Genotype: Bb x Bb Meiosis Gametes: B b x B b © Gauteng Department of Education 12 fertilization B b B BB Bb b Bb bb F1 Genotype: 1:4 BB homozygous offspring 2:4 Bb heterozygous offspring 1:4 bb homozygous Phenotype: 75% brown and 25% blonde CROSS EXAMPLE 3: (Homozygous dominant x Heterozygous) P1 Phenotype: Genotype: Gametes: Brown x Brown BB x Bb Meiosis B B x B b fertilization B B B BB BB b Bb Bb F1 Genotype: 2:4 BB homozygous offspring 2:4 Bb heterozygous offspring Phenotype: 100% brown CROSS EXAMPLE 4: (Homozygous recessive x Heterozygous) P1 Phenotype: Genotype: Blonde x Brown bb x Bb Meiosis Gametes: b b x B b fertilisation b b B Bb Bb b bb bb F1 Genotype: Phenotype: 2:4 Bb heterozygous offspring 2:4 bb homozygous offspring 50% brown and 50% blonde © Gauteng Department of Education 13 HOW TO TACKLE ANSWERING PEDIGREE DIAGRAM QUESTIONS Generation 1 2 3 A E G F J K M L N D H I 4 5 C B O P Female with blonde hair Male with blonde hair Female with brown hair Male with brown hair Analysing the genetic lineage in a pedigree diagram: Step 1: Mark all the homozygous recessive individuals with blonde hair. This will be all the white shapes: E, F, G, I, K, N and P as bb on the pedigree chart. Step 2: Work from the generation line 5 up towards the generation line 1 so that you start with the last offspring on the pedigree diagram. To produce an offspring with bb, BOTH parents must have at least one homozygous recessive gene (b). If the parent is a white shape – then the parent is bb and already marked. If the parent is a shaded shape and produced a bb offspring, then the parent must be heterozygous Bb. Mark the Bb parents on the pedigree diagram. Step 3: Parents that are shaded shapes and produce only shaded shape offspring, can be homozygous BB or heterozygous Bb. Look to the next generation and then work backwards. Mark the parents on the pedigree diagram. © Gauteng Department of Education 14 Step 4: Answer the questions that relate to the pedigree diagram. Try to work out the genotype of A, B, C, D, H, J, L, M and O on your own first. Let us see if you were right: o A and B are Bb because they produce G (bb) o If C is BB then D must be Bb or C is Bb then D is BB because H must be Bb to produce K (bb) o J is Bb because G is bb and H is Bb (produced sister K - bb) o L and M are both Bb because parent J is Bb and I is bb so they cannot be homozygous BB AND L and M produce a son (N) and daughter (P) that are both homozygous bb o Offspring O can be either BB or Bb because both parents are heterozygous Bb Karyotype: this is the number and appearance of the chromosomes arranged in homologous pairs, in the nucleus of an individual belonging to a specific species. In humans, we have 46 chromosomes = 23 pairs (22 pairs are autosomes and 1 pairs are sex chromosomes). The karyotype is used to study chromosomal aberrations, cellular functions, taxonomic relationships and to determine evolutionary links and events. Sex determination in humans: the somatic cells in humans are all diploid and contain 23 pairs of chromosomes in each nucleus. There are 22 pairs of autosomes and one pair of sex chromosomes (gonosomes) in the human genome (genetic make-up). Females have identical XX sex chromosomes while males have dissimilar XY sex chromosomes. The Y chromosome is smaller and hook-shaped. During gametogenesis (the formation of sex cells), meiosis takes place in the ovaries and testes. Each egg cell will contain an X chromosome. In the male, half the sperm cells will have X and half will have Y chromosomes. Each time fertilisation occurs, there is a 50% chance of the zygote being male and a 50% chance of the zygote being female, X + X = XX and X + Y = XY. P1 Phenotype: Genotype: Gametes: male x female XY x XX Meiosis X Y x X X fertilization X X X XX XX Y XY XY F1 Genotype: Phenotype: XX 2:4 XY 2:4 50% males 50% females Sex-linked alleles are alleles related to the sex chromosomes of the individual. Autosomal chromosomes have the same number of alleles in both homologous chromosomes. With sex chromosomes there will be more genes on the X © Gauteng Department of Education 15 chromosome than on the Y chromosome because the Y chromosome is shorter. Let’s look at haemophilia: Haemophilia: Haemophilia is a hereditary bleeding disorder caused by a sex-linked recessive gene. The clotting factor deficiency, prevents the blood from forming a stable fibrin clot. Blood seeps into the tissue and joints. Haemophilia can be the result of two possible genes. Both haemophilia A and B are inherited as X-linked recessive genes. One gene controls the production of the protein called factor VIII and causes haemophilia A, which affects 85 per cent of haemophilia sufferers. The other gene controls the production of the protein factor IX and causes haemophilia B, which affects 15 per cent of the cases. Males carry one X chromosome only. The Y chromosome carries no gene for blood clotting. This means that the condition of haemophilia is seen in males with only one defective gene present. A female with one defective gene will be a carrier because the other X chromosome will carry the normal dominant gene. For a normal male and female carrier (heterozygous) cross: P1 Phenotype: normal male x female carrier Genotype: XHY x XHXh Meiosis Gametes: XH Y x XH Xh fertilization XH Xh XH XH XH XH Xh Y XH Y X hY 1:4 XH XH 1:4 XH Xh 1:4 XH Y 1:4 Xh Y Phenotype: 25% XH XH: female is clear and does not carry the trait. 25% XH Xh: female is a carrier. 25% XH Y: male is clear. 25% Xh Y: male is affected – has haemophilia. F1 Genotype: For an affected male and normal female cross: P1 Phenotype: affected male x normal female Genotype: Xh Y x XH XH Meiosis Gametes: X h Y x X H XH fertilization XH XH Xh XHXh XHXh Y XHY XHY © Gauteng Department of Education 16 2:4 XHXh (trait is carried on this X chromosome) 2:4 XHY Phenotype: 50% female is a carrier 50% male is clear and normal F1 Genotype: The Principles of Heredity: (Make sure that you know Mendel’s laws) Mendel’s law of dominance and segregation When two individuals with contrasting pure breed characteristics are crossed, the individuals of the first generation (F1) will ALL resemble the parent possessing the dominant characteristic. P1 Phenotype: Genotype: Gametes: Tall plants x short plants TT x tt Meiosis T T x t t fertilization T T t Tt Tt t Tt Tt F1 Genotype: 4:4 Tt heterozygous offspring Phenotype: 100% Tall Note that the F1 offspring show characteristics from both parents but in the phenotype, all are tall. The plants of the F1 grow and mature (Tt). When they reproduce, half of the gametes will contain the characteristic for tallness (T) and the other half, for shortness (t). The characteristic for shortness is the recessive characteristic and it will appear in the second cross offspring called the F2 generation. P2 Phenotype: Genotype: Gametes: Tall plants x tall plants T t x T t Meiosis T t x T t fertilization T t T TT Tt t Tt tt © Gauteng Department of Education 17 F2 Genotype: 1:4 homozygous Tall, 2:4 heterozygous Tall, 1:4 homozygous short (1 TT : 2 Tt : 1 tt) Phenotype: 75% tall (1 homozygous tall + 2 heterozygous tall) 25% short (1 homozygous short) Mendel’s law of independent assortment Each characteristic is controlled by allele genes on a separate pair of chromosomes. Mendel stated that the different pairs of chromosomes segregate independently in a hybrid so each characteristic or trait is sorted out independently of any other trait in the hybrid. Mendle used peas with a genetic trait for a round seed versus a wrinkled seed AND a yellow versus green colour of the seeds. Independent combinations for the traits round and yellow, round and green, wrinkled and yellow or wrinkled and green will result. (4 x 4 = 16 combinations) DNA sequencing: Scientists agree that individual organisms change to adapt to the environment. A species is a group of organisms that are similar in appearance, share the same DNA sequences, perform the same mating rituals and interbreed. It is the sequence of bases in the DNA that is the code for that organism. The sequence (order) of bases tells the cell what proteins to make. The sequence of bases dictates the sequence of amino acids, which determines the shape of a protein. The sequence of the DNA and the number of chromosomes, provides evidence of relationships between groups of organisms. Similarly, the DNA sequencing of all mammals further suggest phylogenic relationships. Mutations (also refer to the note sets on DNA Sessions 1-4)) A gene mutation is a change in the genetic material/DNA sequencing in the cell. A mutations that assist the organism to adapt to its environment, is favourable and will become a fixed mutation, passed to the next generation. It will ensure variation, natural selection and survival of the species by increasing the gene pool. Lethal mutations are unfavourable and will result in death. A neutral mutation has no immediate effect on the individual. It is passed on to the next generation and when the environment changes, the mutation may assist the organism to adapt and cope with the change. Mutations occur when: a codon is substituted – a frameshift mutation results altering the gene expression of the codons so a different amino acid is translated from the original resulting in different proteins one or more nitrogenous bases are deleted from the codon or replaced – a point mutation results (e.g.: sickle cell anaemia) additional nitrogenous bases are included into the DNA – a point mutation results Chromosomal aberrations/anomaly: when there is an incorrect number of chromosomes or a structural abnormality in one or more chromosomes. This occurs when there is an error in cell division (meiosis or mitosis). A chromosomal aberration is an accident and not inherited, e.g.: when an individual is missing a chromosome from a pair or has more than two © Gauteng Department of Education 18 chromosomes to a pair. A Down’s syndrome baby has three copies of chromosome 21, rather than two so the chromosome's structure is altered like when: a portion of the chromosome is missing or deleted a portion of the chromosome is duplicated so it will carry extra genetic material a portion of one chromosome is transferred to another chromosome a portion of the chromosome has broken off and reattached so that the genetic material is inverted. Albinism as an example of a mutation: Albinism is a rare inherited defect that results in a lack of the pigment melanin in the skin, hair and eyes making them sensitive to sunlight and susceptible to skin cancer. Albinism is caused by a single pair of recessive alleles and will only show in the homozygous state. Heterozygous parents are carriers and stand a 25 per cent chance of producing a baby with albinism. When one parent is affected and one is normal: P1 Phenotype: affected parent x normal parent Genotype: bb x BB Meiosis Gametes: b b x B B fertilization F1 b b B Bb Bb B Bb Bb Genotype: 4:4 heterozygous Bb Phenotype: 100% appear normal - offspring will be carriers as both recessive genes are required for the trait to come through in the genotype and phenotype. When both parents are heterozygous carriers: P1 Phenotype: normal heterozygous parent x normal heterozygous parent Genotype: Bb x Bb Meiosis Gametes: B b x B b fertilization B b B BB Bb b Bb bb © Gauteng Department of Education 19 F1 Genotype: 2:4 heterozygous Bb 1:4 homozygous BB 1:4 homozygous bb Phenotype: 50% will be carriers 25% will be clear + 50% carriers = 75% will appear normal 25% will be affected Genetic Engineering: the process where scientists alter, swap or manipulate the genes on the DNA, to produce a different organism. Genetic engineering involves the transfer of genes from one organism to an unrelated species. Diabetics are people who cannot produce their own insulin. Insulin is a hormone needed to regulate blood sugar. Biochemists have devised a way in which to produce artificial insulin. A similar process is used to genetically modify many different organisms. Make sure you know the basic process: Bacteria produce restriction enzymes that ‘cut’ DNA molecules. These restriction enzymes are extracted from the bacteria. DNA is removed from a healthy person’s pancreas cells. Restriction enzymes are used to ‘cut’ out a piece of DNA, which contains the genes that produce insulin. When the genes are transferred from one organism’s cells to another, the DNA in the recipient cell is called recombinant DNA. Insulin is produced by using recombinant DNA in the bacterium called Escherischia coli (E. coli), which lives in the human gut. Plasmids are taken out of a bacterium and cut open with the restriction enzyme. The human genes are inserted into the plasmid. The healthy bacterium absorbs the plasmids. The piece of human DNA continues to produce proteins, which make insulin, inside the bacterium. The insulin is then extracted from the bacterium cell. Diabetics inject themselves with this insulin everyday, so that they can regulate their blood sugar. Advantages of GM crops Better nutritional value Greater crop yield resulting in higher food production and long term reduction in costs Crops are better adapted to less favourable environments and climates Disease and pest resistant means less insecticides and pesticides are released into the environment Increased biodiversity as new varieties are developed Efficient use of scarce agricultural land as well as land that may Disadvantages of GM crops Possible increase in allergen and carcinogen levels Nutritional changes and possible toxicity Traits can be transferred to other species like weeds Cause un-natural selection pressure Expensive start-up costs DNA alteration of the new varieties are owned and controlled by biotechnology company which may lead to issues with ethics and ownership © Gauteng Department of Education 20 previously not have been fit Lack of transparency regarding what is in our food Cloning With cloning, the nucleus of a somatic cell (2n) of one organism is removed. An egg cell (n) is taken from an ovary. The nucleus of the egg cell is destroyed. The somatic cell’s nucleus (2n) is then placed inside the egg cell. The egg cell is put back into a uterus where it is allowed to grow and differentiate into an embryo. When the baby is born, it is identical to the original organism. A sheep called Dolly was cloned successfully in 1997. Advantages of Cloning Disadvantages of Cloning Produce individuals with desired traits Objections to interfering with God’s creation Better yields Reducing the gene pool by reducing variation Resistant to diseases Cloned organisms may have developmental problems Organisms produced in a shorted time Costly process Saving endangered species Generate experimental waste Produce body parts/organs for transplant May lead to killing clones for organs/body parts Produce offspring when organisms are infertile Cruelty to animals and inhumane behaviour Stem Cell research: A stem cell is a cell that has the potential to regenerate multiple cell type tissue and self-renew so a stem cell is able to produce new cells over a long term by the process of mitosis. Once mitosis occurs, the cells are able to differentiate into many different types of specialized cells and tissue. Stem cells can be harvested from umbilical cord blood (once a baby has been born), a foetal blastocyst and bone marrow. Stem cell therapy can be used to treat a variety of different human diseases: cancers like Leukemia degenerative diseases like Multiple Sclerosis diabetes mellitus where the pancreas no longer produces insulin muscle damage organ damage and certain genetic diseases in conjunction with gene therapy © Gauteng Department of Education 21 SECTION C: HOMEWORK QUESTIONS (Questions for homework taken from DoE Additional Exemplar 2008 Paper 1 and Gauteng Prelim 2009 Paper 1) QUESTION 1: 10 minutes In mice, brown (B) coat colour is dominant over grey (b) coat colour. Show a cross between a heterozygous parent with a brown coat colour and one with a grey coat colour up to the F1 generation. Also give the phenotypes of the F1 generation. (8) QUESTION 2: 8 minutes Learners want to investigate eye colour in fruit flies (Drosophila melanogaster). Fruit flies can have red (R) eyes or white (r) eyes. Red eye colour is dominant and white eye colour is recessive. Male fruit flies, homozygous for red eye colour, were bred with female fruit flies, homozygous for white eye colour. Show how the possible phenotypes and the genotypes of the F1 generation for eye colour may be obtained. (6) QUESTION 3: 10 minutes Haemophilia is a sex-linked hereditary disease that occurs as a result of a recessive allele on the X-chromosome. Study the family tree below and answer the questions that follow: (Use the symbols H for normal and h for haemophilia above the sex chromosomes, for example.: XHXh) 3.1. 3.2. Write down the genotype of Stefan. (2) Peter and Susan would like to have a fourth child. Calculate the percentage probability of this child having haemophilia. (6) © Gauteng Department of Education 22 SECTION D: SOLUTIONS FOR SECTION A 1.1 1.2 1.3 1.4 1.5 1.6 1.7 D C B B C A C (7x2) (14) 2.1 2.2. 2.3. 2.4. 2.5. 2.6. 2.7. 2.8. A C A B D D C D (8) 3. P1 Phenotype: Genotype: Black x Brown Bb x bb Meiosis Gametes: B, b x b fertilisation b b B Bb Bb b bb bb F1 Genotype: Bb and bb Phenotype: Black and brown 1 mark for stating P1 AND F1 (must have both) 1 mark for stating meiosis AND fertilisation (must have both) any 6 = (6) 4.1 4.2 5.1 5.2 5.3 (a) homozygous dominantand heterozygous (2) (b) homozygous recessive (1) Normal is dominant and the dominant condition can show up in either homozygous or heterozygous state OR To have a normal child the person must have at least one dominant gene/phenotype is normal (2) Plant A - YY Plant B - yy (2) Yellow: green = 3 : 1 (2) Phenotype – green peas Genotype – yy(2) © Gauteng Department of Education 23 6. 1. Mr. Xhosa - IAIB Wife - IBIB or IBi F1 is IAIB or IBIB or IBi or IAi. Baby ‘A’ is the only possible blood group . Baby ‘O’ is not a possibility (Remember that in blood groups there are three alleles A, B and O. A and B are co-dominant over O which is recessive. There must be two of the same alleles if a recessive trait is present in the individual) 6.2. Mr. Mbundwini - IAIA or IAi Wife – Not given, but assume she is recessive . Therefore baby ‘O’ is the possible blood group as ‘O’ cannot be the result of Mr. Xhosa and his wife . (Each tick = ½ mark) (6) 7. 1. P1 ( for P1 and F1 – if both are present then half mark each) Phenotype: normal father x carrier mother {***mother is heterozygous} Genotype: XHY x XHXh Meiosis ( for meiosis and fertilization – half mark each) Gametes: XH Y x XH Xh fertilization XH Xh XH XH XH XH Xh Y XH Y X hY F1 XH XH XH Xh XH Y Xh Y (all 4 genotypes: ) Genotype: 1:4 1:4 1:4 1:4 Phenotype: 50% normal daughters (XH XH and XH Xh) 25% normal son (XH Y) 25% son with haemophilia (Xh Y) (all phenotypes correct = ) Max (6) 7.2. 25% chance /1 out of 4/ ¼ 7.3. The male has only one X chromosome Y chromosome does not have the allele for this trait OR If he had ‘h’ he would be a sufferer, therefore he must have had ‘H’. Max (2) (2) © Gauteng Department of Education 24 SESSION NO: 6 TOPIC 1: GENETICS AND INHERITANCE Part 2 TOPIC 2: RESPONDING TO THE ENVIRONMENT - HUMANS: NERVOUS SYSTEM Part 1 Teacher note: Topic 1: Mutation, natural selection and genetic engineering: tell learners to read about genetic engineering so that they form an opinion of whether this is good or bad, but also so that they understand the basic process and the benefits to human being. See notes on content in session 5. Topic 2: Make sure that learners know and understand the nervous system and all its components, the different types of nerves and also the reflex arc 1. 2. 3. 4. Introduce session – 5 minutes (and go over basic idea as per the above introduction) Typical exam questions and solutions – 50 minutes (Questions that are not completed must please be included with Homework) Notes on Content – 15 minutes Answer/memo discussion – 20 minutes SECTION A: TYPICAL EXAM QUESTIONS TOPIC 1: QUESTION 1: 12 minutes (Taken from DoE Feb/March 2009) Read the following passage and answer the questions that follow. GENETICALLY MODIFIED PIG BRED WITH 'GOOD FAT' Scientists in the United States of America have produced genetically modified pigs with fat containing omega-3 fatty acids. These fatty acids, which are usually found in salmon, mackerel and fresh tuna, are thought to be responsible for a number of benefits, from combating heart disease to improving intelligence. Researchers from the University of Pittsburgh – School of Medicine created piglets capable of converting less useful omega-6 fatty acids into omega-3 fatty acids. They implanted 1 800 embryos into 14 female pigs. Ten live offspring, which were able to make high levels of omega-3 fatty acids, were born. [Adapted from: Cape Argus, 27 March 2006] (Read the passage through and underline what you think will be the important facts. Read the passage again, now answer the questions.) 1.1. 1.2. 1.3. Name TWO health benefits of omega-3 fatty acids. (2) What percentage success did the scientists have with the implanted embryos in forming a clone of pigs capable of producing omega-3 fatty acids? Show ALL working. (3) (Show each step of the calculation.) To produce genetically modified pigs, the gene that produces omega-3 fatty acids is inserted into the pig embryos. Describe the steps in forming and © Gauteng Department of Education 25 1.4. introducing many copies of the desirable gene (using bacteria) into the pig embryos. (4) Give TWO reasons why: a) Some people may support the use of genetically modified pigs to produce omega-3 fatty acids. (2) b) Some people may be against the use of genetically modified pigs to produce omega-3 fatty acids. (2) [13] QUESTION 2: 12 minutes (Taken from DoE November 2008 Paper 1) The diagram below shows the steps of an experiment in which a large number of genetically identical frogs were developed from unfertilised frog eggs. The nucleus of each unfertilised egg was destroyed and replaced by a nucleus obtained from a body cell from frog X. (Reminder: refer to the notes on cloning) 2.1. 2.2. The diploid number of chromosomes in the above frogs is 26. How many chromosomes are present in the nucleus of the following cells? (a) Cell A (1) (b) Cell B (1) Why can an egg containing a nucleus from the body cell of a frog develop © Gauteng Department of Education 26 2.3. 2.4. 2.5. into a tadpole? Explain why all the frogs produced from the treated eggs are genetically identical. Name the method of producing genetically identical offspring as shown in the diagram. State ONE reason why some people might: (a) Favour the process shown in the diagram (b) Be against the process shown in the diagram (2) (2) (1) (2) (2) [11] QUESTION 3: 10 Minutes (Own source) A homozygous black rabbit with brown eyes is mated with a homozygous white rabbit with blue eyes. Black fur colour is dominant over white fur and brown eyes is dominant over blue eyes. Show the genetic cross and indicate the genotypes of the F1 generation. (8) (Hint: Let B = Black fur, b = white fur, G = brown eyes and g = blue eyes. Homozygous black with homozygous brown eyes = BBGG and homozygous white with homozygous blue eyes = bbgg) TOPIC 2: QUESTION 4: 3 Minutes (Taken from various DoE HG Paper 2 exams) (Hint: Please do not to waste time when you answer Multi Choice questions. Read the question, underlining the operative words, while covering the answers. Then think of the correct answer. Uncover the answer options and check if your answer is there. If it is, then tick next to the letter. If it is not, reread the question and try to see exactly what is being asked. Then review the answer options again to find the correct answer. Always answer Section A last with the Multi-choice questions answered right at the end of the exam paper as you can waste a lot of time on them.] Various possible options are provided as answers to the following questions. Choose the correct answer and write only the letter (A – D) next to the question number. 4.1 Which of the following structures will enable a dancer to carry out dance movements? 1. Cerebellum 2. Proprioceptors 3. Hypothalamus 4. Cerebral cortex A 1 only B 1 and 2 C 1, 2 and 3 D 1, 2, and 4 4.2 Which of the following parts of the brain regulates appetite? A Medulla oblongata B Cerebellum C Hypothalamus D Cerebrum © Gauteng Department of Education 27 4.3 The autonomic nervous system controls … A the skeletal muscles. B the senses. C the contraction of involuntary muscles. D reflexes. (Questions 4.4 to 4.8 Taken from DoE Exemplar 2011 Paper 2 ) The diagram below shows the human brain (longitudinal section), spinal cord (transverse section) and the right leg. Four options are provided as possible answers to the following questions. Choose the answer and write only the letter (A–D) next to the question number. 4.4 Which part of the brain is indicated by 1? A Cerebrum B Medulla C Cerebellum D Hypothalamus 4.5 Which ONE of the following is a function of the part of the brain numbered 2? A Perception of sensations B Centre for control of breathing C Maintenance of equilibrium and balance D Centre for regulation of body temperature 4.6 Under normal circumstances, which numbered part coordinates the movements of the legs? A 2 B 3 C 4 D 5 4.7 Which ONE of the following comparisons between 3 and 4 is FALSE? A 3 is a sensory neuron, while 4 is a motor neuron. © Gauteng Department of Education 28 B C D 4.8 3 leads from the receptor, while 4 leads to the effector. 3 enters the dorsal root, while 4 leaves through the ventral root. The cell body of 3 is located in the spinal cord, while that of 4 is found outside the spinal cord. Which ONE of the following is FALSE about the role of the brain and spinal cord involved in the action in the diagram? A The brain is aware of the tap on the knee with the hammer. B An effector is stimulated to bring about a response. C The spinal cord receives sensory impulses from the knee. D The brain receives sensory impulses from the spinal cord and sends motor impulses to the leg muscles. (8 x 2) [16] QUESTION 5: 3 Minutes Letters X and Y represent neurons that conduct impulses to and from the brain via the spinal cord. Study the diagram and answer the questions that follow. Using the given key, write down the correct letter (A, B or C in key) of the condition that explains each of the following: [Remember: damage to X will mean that sensory neurons will not be able to send impulses to the CNS. Damage to Y will mean that the motor neurons will not be able to stimulate muscles to move.] © Gauteng Department of Education 29 5.1 5.2 5.3 When the skin of the toe is stimulated, the toe moves and the person knows that it is moving. (1) The person can move the toe, but cannot feel the movement. (1) The person can feel a pin pricking the toe, but cannot move the toe. (1) [3] QUESTION 6: 6 Minutes (Taken from DoE Feb/March 2012 Paper 2) Study the following diagram showing a reflex arc. 6.1. 6.2. 6.3. 6.4. Identify the neuron labelled A. Name the type of neuron that is connected to structure B. Explain the effect on the body if the neuron mentioned in QUESTION 6.2 is damaged. Explain the significance of reflex actions in humans. (1) (1) (3) (2) QUESTION 7: 10 Minutes (Modified from DoE Nov 2012 P2) Study the diagram representing the structure of the human brain below. © Gauteng Department of Education 30 7.1. 7.2. 7.3. Identify the parts labelled: a) C b) E Write down the letter (A to F) of the part which: a) controls body temperature b) controls heart beat and breathing rate c) perception of senses, higher intelligence, memory d) controls balance, equilibrium and muscle tone e) point of the reflect arc Explain how the brain is protected. (1) (1) (1) (1) (1) (1) (1) (5) [12] SECTION B: NOTES ON CONTENT TOPIC 1: Refer to session 5 notes on content. TOPIC 2: RESPONDING TO THE ENVIRONMENT - HUMANS: NERVOUS SYSTEM Terminology & definitions: Homeostasis: processes to maintain a stable, balanced internal environment within the body involving co-ordination between the nervous system and the endocrine system. Central Nervous System: is made up of the brain and the spinal cord Peripheral Nervous System: receives internal and external stimuli, converts the stimuli into impulses and sends impulses to the central nervous system. Autonomic Nervous system: is made up of the sympathetic and parasympathetic nervous systems that regulate homeostasis. Both systems function antagonistically. © Gauteng Department of Education 31 The sympathetic nervous system stimulates organs and the parasympathetic nervous system inhibits the same organs. Double innervation: Each organ in the body is supplied with nerves from both the sympathetic and parasympathetic nervous systems. Neuron: a single nerve cell. Nerve: is made up of millions of neurons Neurotransmitters: this is a chemical substance secreted by synaptic vesicles in the presynaptic neuron, to assists in transmitting an impulse across the synaptic gap. Meninges: membranes that surround the brain. There are three meninges namely: the duramater, the arachnoid and the piamater. Reflex arc: This is the path travelled by the nerve impulse from the receptor to the effector, through the spinal cord. Reflex action: a rapid automatic response as a result of a stimulus received by a receptor, converted to an impulse that passes through the spinal cord reflex arc to a receptor. The Nervous System: controls the functioning of all the systems in the body. It allows humans to react to internal and external stimuli. The nervous system controls and co-ordinates every movement and all organs, glands and blood vessels in response to information received. The nervous system can be divided into three systems, which together coordinate the functioning of the body: Central nervous system – brain and spinal cord Peripheral nervous system – sensory, motor and mixed nerves Autonomic nervous system – sympathetic and parasympathetic Nervous tissue: Animals have a complex system of nervous tissue called neurons or nerve cells to send information to the central nervous system. Nervous tissue is adapted to carry and react to all stimuli. A nerve is composed of nerve fibres that are held together by connective tissue. One nerve consists of millions of neurons. Receptors receive the stimulus and convert it to an impulse. The impulse travels along the neurons in milliseconds. The types of neurons are: Sensory neurons: They are unipolar (one pole) and bipolar (two poles). Sensory neurons always conduct impulses from the receptor to the CNS (spinal cord and brain). Motor neurons: They are multipolar neurons with many dendrites. Multipolar neurons always carry impulses away from the CNS (spinal cord and brain). Connector / inter-neurons: They are multipolar and connect sensory neurons to motor neurons in the spinal cord and the brain. Make sure you can identify and state the function of each of the following sensory and motor neuron structures: nucleus – controls all the cell’s functions cell body – consists of cytoplasm with a nucleus © Gauteng Department of Education 32 cytoplasm – contains very fine neurofibrils that extend into the axon and dendrites. Also contains Nissl bodies that contain rRNA responsible for the synthesis of proteins myelin sheath – covers and protects the axon (provides electrical insulation). May also be responsible for repairing damage to the axon. axon – conducts impulses away from the cell body dendrites – receive impulses and conduct them to the cell body Transmission of nerve impulses: the synapse is the point where an impulse passes from the terminal branch of one neuron to the dendrite of the next neuron. The neurons do not touch each other. The gap between the two neurons is called the synaptic gap. Neurotransmitters carry the impulse across the synaptic gap. Once they reach the opposite side, enzymes destroy the neurotransmitters to prevent the impulse from being carried backwards. The impulse can only ever travel in one direction. © Gauteng Department of Education 33 [Only learn the position of the following structures: nucleus, cell body, cytoplasm, myelin sheath, axon, dendrites) The Central Nervous System: Brain: protected by the bones of the cranium and the spinal cord is protected by the bones of the vertebrae and surrounded by three layers of membranes called meninges for protection. The cortex consists of cell bodies and is called the grey matter. The medulla consists of the nerve fibre axons and is called the white matter. The brain is divided into two hemispheres (left and right). The corpus callosum connects the left and right side of brain allowing the two hemispheres to communicate and coordinate activities. © Gauteng Department of Education 34 Make sure that you know the location and function of the following (see diagram – functions are included): cerebrum cerebellum corpus callosum medulla oblongata spinal cord The Spinal Cord: protected by the vertebrae, the 3 meninges with the cerebrospinal fluid. The spinal cord is the pathway for all the impulses that are conducted to and from the brain and also processes reflex actions. Sympathetic and parasympathetic nerve impulses are conducted along the spinal cord to all organs. The reflex arc: a reflex arc is the path travelled by the nerve impulses. It is a rapid automatic response to a stimulus that is received by a sensory organ to ensure a quick response. The reflex arc will cause a reflex action, allowing the body to respond very quickly to protect itself against severe injury. © Gauteng Department of Education 35 The mechanism of a simple reflex arc is as follows: The finger is pricked by a pin. Sensory receptors in the skin of the finger receive the stimulus. The physical stimulus is transformed into a nerve impulse. The sensory neuron conducts the impulse to the spinal cord. The impulse enters the dorsal root of the spinal cord. It passes into the cell body of the sensory neuron situated in the dorsal root ganglion. The impulse moves along the axon into the dorsal horn of the grey matter. The impulse is transmitted over the synaptic connection to the dendrite of the connector neuron. The impulse travels along the axon of the connector neuron. The impulse is transmitted over the synaptic connection to the dendrites of the motor neuron cell body. The impulse is carried away from the cord by the axon of the motor neuron. The impulse exits the cord through the ventral root. The terminal end branch of the motor neuron ends in the muscles of the forearm. The impulse causes these muscles to contract and pull the hand away from the painful stimulus of the pin prick. Effects of drugs on the central nervous system: drugs that are legally prescribed by a doctor and are used according to instructions are acceptable to treat illness and alleviate pain in patients. When drugs are used to enhance performance or as a © Gauteng Department of Education 36 psychoactive for non-therapeutic and non-medical effects, it becomes a problem. Substances that are addictive and harmful are alcohol, amphetamines, barbiturates, cocaine and opium alkaloids. It is a criminal offence to abuse any of these substances. Common drugs and how they affect the nervous system: Dagga: Drug that leads to hallucinations. Prevents long term memory and decreases short term memory and problem solving abilities. Affects the parts of the brain responsible for memory, emotions and decision making. Heroin: Causes lethargy (tiredness and listlessness), loss of self-control, and leads to mental and physical deteriation. There is a serious danger of overdose, leading to coma and death. Ecstasy: A synthetic drug with hallucinogenic properties and classified as a stimulant. Ecstasy tablets produce an intensely enhanced sense of selfconfidence and energy and users experience a desire to touch others. Tik /Crystal Meth: Extremely addictive man-made stimulant and use can lead to severe physiological and psychological dependence. The Autonomic Nervous System: functions involuntarily and automatically and is NOT controlled by the will. It maintains homeostasis by controlling vital activities. It consists of nerves that are connected to the hypothalamus of the central nervous system. The autonomic nervous system is subdivided into the sympathetic and parasympathetic nervous systems that function antagonistically. The sympathetic nerves stimulate organs to prepare the body for action. The parasympathetic nerves slow the systems down and bring the body back to a state of rest. Each organ in the body is supplied with nerves from both systems and is termed double innervation. The organs are stimulated (sympathetic) or inhibited (parasympathetic) by the autonomic nervous system. Functions regulated automatically by the autonomic nervous system include: the heartbeat and breathing rate (through the medulla oblongata) digestion and peristalsis pupil size bladder size sweat glands liver function amount of blood in the arteries. Peripheral nervous system: is made up of sensory cells called receptors that respond to stimuli. When the receptors are stimulated, they convert the stimulus into a nerve impulse. This nerve impulse is transmitted along sensory neurons to the central nervous system. There are 12 pairs of cranial nerves and 31 pairs of spinal nerves that enter from the body and form art of the peripheral nervous system. Examples of receptors: Photoreceptors are sensitive to light stimuli, for example the eye. Chemoreceptors are sensitive to chemicals as a solution or gas, for example the tongue and nose. © Gauteng Department of Education 37 Mechanoreceptors are sensitive to changes in pressure such as touch, sound and gravitational stimuli, for example the ear, skin, muscles and tendons. Proprioceptors: They respond to gravitational pull to maintain balance and equilibrium of muscles and tendons. Diseases and disorders of the nervous system: Alzheimer’s disease: the frontal and temporal lobes of the cerebral cortex are affected so the conscious part of the brain that produces memory is slowly destroyed. The cells that produce acetylcholine begin to deteriorate. Acetylcholine is a neurotransmitter that is involved with memory formation. The neuron function decreases and the neurons die, the brain shrinks because there is a loss of the nerve cells. It has been found that Alzheimer’s is passed on genetically and therefore runs in families. During the primary stages of this disease, patients become very forgetful, as the short-term memory is affected. In advanced stages, the patient may not even recognise close family members. Patients lose the ability to speak, read, walk and control their bladder and bowel movement. This is a very stressful disease as patients feel their minds slipping away and become very confused. Multiple sclerosis Multiple (many) sclerosis (scarring) is a degenerative disease resulting when the myelin sheath surrounding the neuron axons in the white matter of the brain and spinal cord are attacked and damaged by the body’s own immune system. The neurons loose the ability to conduct impulses and communicate effectively once demyelination occurs. Multiple sclerosis may be caused by a combination of a number of factors like genetics, environment and infectious diseases. Genetic variations of specific genes have been linked to an increased risk of developing the disease. Environmental factors like high stress levels, lack of vitamin D (reduced sunlight), various toxins and solvents, smoking and poor diet may contribute to the risk of developing multiple sclerosis. Infectious diseases that affect the brain and cerebrospinal fluid may cause demyelination of the neurons like encephalomyelitis. Other viral diseases that have shown to impact the onset of multiple sclerosis are human herpes viruses, measles, mumps and rubella. Symptoms would include sensations like tingling, numbness in limbs, loss of coordination, weakness and chronic pain in muscles and various cognitive problems like depression. There is no known cure for multiple sclerosis. Various treatments and medication is used to treat the symptoms to improve quality of life. © Gauteng Department of Education 38 SECTION C: HOMEWORK QUESTIONS TOPIC 1: QUESTION 1: 10 minutes (Taken from DoE Additional Exemplar 2008 Paper 1) Study the diagram below that shows the cloning of a sheep named Dolly. 1.1. 1.2. 1.3. 1.4. 1.5. Why was it necessary to remove the nucleus from the egg cell of the second donor before the sheep could be cloned? (2) Would Dolly have any characteristics of the second donor sheep? (1) Explain your answer to QUESTION 1.2. (2) Number 5 on the diagram states that 'the embryo is cultured'. Through which process of cell division does the embryo develop? (1) Describe TWO reasons why people could be against genetic engineering. (4) © Gauteng Department of Education 39 TOPIC 2: QUESTION 2: 12 Minutes (Modified from DoE Nov 2011 Paper 2) Study the diagram below and answer the questions that follow. 2.1. 2.2. 2.3. Write down only the letter (A–D) of the part which: a) Controls heartbeat b) Contains the centres that control balance, muscle tone and equilibrium c) Has centres that interpret what you see d) Coordinates voluntary muscle movements e) Has grey matter on the inside and white matter on the outside Name one function of the corpus callosum. Explain the difference between a sensory neuron and a motor neuron. SECTION D: 1.1 1.2 1.3 SOLUTIONS FOR SECTION A - Combating heart diseases - Improving intelligence (2) (Mark first TWO only) 10 x 100 1 800 = 0,55 % (3) The gene responsible for producing omega-3 fatty acids is located in the DNA of salmon/fresh mackerel/tuna © Gauteng Department of Education (1) (1) (1) (1) (1) (2) (5) 40 1.4 2.1 2.2 2.3 2.4 2.5 This gene is cut from the donor organism, inserted into a plasmid of a bacterium Bacteria replicates to form many copies of the gene These genes are then inserted into the cells of the zygote /embryo any (4) (a) Support - Healthier for humans to eat /combating heart disease - Mass production of healthy fat - Improves intelligenceany (2) (Mark first TWO only) (b) Against - Cultural objection to eat meat from pigs - The success rate is very low - Expensive procedure - No value for vegetarians - Objection to eating any genetically modified food any (2) (Mark first TWO only) (a) 13 (1) (b) 26 (1) Has a full set of chromosomes /Diploid number of chromosomes/ complete set of chromosomes (2) They have same/identical chromosomes /genetic material / DNA from the nucleus of the somatic/body cell collected from the same frog/X (2) Cloning (1) (a) In favour: - Producing individuals with desired traits - Better yield - Resistant to diseases - Organisms produced in a shorter time - Saving endangered species - Producing body parts - Produce offspring for organisms that cannot have offspring (1 x 2) (2) (Mark FIRST answer only in learner’s script) (b)Against: - Objection to interfering with God’s /Supreme Being’s creation/nature - Reducing the gene pool by reducing variation/ Reduces genetic diversity - Cloned organisms may have developmental/morphological problems - Costly process - May generate more experimental waste - May lead to killing of clones to obtain spare body parts - Cruelty to animals (1 x 2) (2) (Mark FIRST answer only in learner’s script) 3. P1 ( for P1 and F1 – if both are present then half mark each) Phenotype: Genotype: black + brown eyes x white +blue eyes BB GG crossed with bb gg Gametes: Meiosis( for meiosis and fertilization – half mark each) B G x b g © Gauteng Department of Education 41 bg bg bg bg F1 BG BbGg BbGg BbGg BbGg fertilization BG BbGg BbGg BbGg BbGg BG BbGg BbGg BbGg BbGg BG BbGg BbGg BbGg BbGg Genotype: 16:16 BbGg heterozygous offspring Phenotype: 100% black with brown eyes Max (8) 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 D C C A B D D D (8 x 2) (18) 5.1. 5.2. 5.3. C A B (1) (1) (1) 6.1. 6.2. 6.3. Interneuron/connector neuron/association neuron (1) Motor neuron (1) The person will become aware of the stimulus but the motor neuron will not be able to transmit the impulse from the interneuron to the effector organ / muscles and movement will not take place/ reaction will not occur (Max 3) Helps to protect the body by reacting quickly The interneuron makes a short cut /not going to the brain/ uses a reflex pathway that is immediately available (Max 2) 6.4. 7.1. 7.2. 7.3. C = cerebellum (1) E = medulla oblongata (1) a) hypothalamus b) medulla oblongata c) cerebrum d) cerebellum e) spinal cord (5) protected by the bones of the cranium three layers of membranes called meninges namely: duramater, arachnoid and piamater (5) © Gauteng Department of Education 42 SESSION NO: 7 TOPIC: RESPONDING TO THE ENVIRONMENT - HUMANS: NERVOUS SYSTEM PART 2 Teacher Note: ensure that learners know structure versus function of the human eye, formation of the image, binocular vision, accommodation of the eye, pupillary reflex mechanisms , short and long sightedness, astigmatism and cataracts. Ensure that they know structure versus function of the human ear, hearing and balance, middle ear infections, deafness and the treatment thereof. 1. 2. 3. 4. Introduce session – 5 minutes (and go over basic idea as per the above introduction) Typical exam questions and solutions – 50 minutes (Questions that are not completed must please be included with Homework) Notes on Content – 15 minutes Answer/memo discussion – 20 minutes SECTION A: TYPICAL EXAM QUESTIONS QUESTION 1: 15 minutes (Taken from Study and Master Grade 12 Biology) (Note: When answering multi-choice questions: 1. Read the question while covering the answers. 2. Think of the correct answer. 3. Look for your answer. 4. Write the letter down on your answer sheet. BUT: If you do not know the answer after point 1 and 2, then: 3. Look at the options. 4. Try to think of why an option is wrong for the question and cross it out. If there is an option that you don’t know, write a ? next to this option. 5. If you still do not know the answer, then select the ? option) Various possible options are provided as answers to the following questions. Choose the correct answer and write only the letter (A – D) next to the question number. 1.1. The tough, non-elastic tissue covering the outer portion of the eyeball is the: A choroid B sclera C conjunctiva D iris 1.2. The shape of the lens in the human eye may be altered by the contraction or relaxing of the: A optic nerve B muscles of the iris C muscles of the ciliary body D pupil © Gauteng Department of Education 43 1.3. The sensation of sight in human beings originates in the : A yellow spot B optic nerve C cerebrum D retina 1.4. The yellow spot of the human eye: A cone cells only B more cone than rod cells C cone and rod cells in equal number D rod cells only 1.5. The following are part of the human eye: 1 cornea 2 lens 3 retina 4 iris Which parts are respectively concerned with/in: Adjusting the focus? Preventing internal reflection? Recording changes in light intensity? A B C D 1.6. 5 choroid 2, 4 and 3 3, 4 and 1 2, 5 and 4 4, 1 and 5 When the tension of the suspensory ligaments in the human eye is slackened, the…. A lens becomes less convex B eye is focused for distant vision C pupil enlarges D lens bulges QUESTIONS 1.7 to 1.9 refer to the diagram of the human eye. © Gauteng Department of Education 44 1.7. The parts that control the amount of light rays that enter the eye are….. A 1 and 2 B 1 and 3 C 2 and 3 D 3 and 4 1.8. The greatest convergence takes place when light rays pass through the part numbered….. A 4 B 5 C 6 D 11 1.9. The function of part numbered 9 is to: 1. reflect light 2. change the shape of the eyeball 3. refract light rays 4. prevent reflection 5. supply the retina with nutrients and oxygen 6. absorb excess light Choose from the options numbered 1 to 6 to provide the functions of part numbered 9: A 1, 2, 3 B 4, 5, 6 C 2, 4, 6 D 1, 3, 5 1.10. When the tension of the suspensory ligaments in the human eye increases, the… A lens becomes more convex B eye is focused for distant vision © Gauteng Department of Education 45 C D pupil opens wide lens bulges 1.11. When the pupil of the human eye constricts, the receptors and effectors are respectively the…. A fovea centralis and ciliary muscle B pupil and ciliary muscle C pupil and radial muscles of the iris D fovea centralis and the circular muscles of the iris 1.12. In accommodation of the human eye, the…. A pupil enlarges B ciliary muscles are involved C suspensory ligaments are always in a state of tension D circular muscles of the iris contract 1.13. Images of objects less than 6m from the eye are clearly focussed onto the retina, when the…. A ciliary muscles contract B pupil widens C muscles of the iris contract D curvature of the lens decreases 1.14. The optical disc where the fibres of the optic nerve leaves the eyeball, is the…. A yellow spot B iris C blind spot D retina 1.15. Which of the following occurs when you look up from reading a book to look at a distant mountain on a clear, sunny day? The…. A radial muscles of the iris contract B the pupil becomes more dilated C the ciliary muscles contract D the lens becomes thicker and rounder (15 x 1 ) (15) QUESTION 2: 4 minutes (Taken from DoE May/June 2008 Paper 2) Explain why, when a person enters a dimly lit room after being in bright sunlight, objects become visible only after a while. (4) QUESTION 3: 18 minutes (Taken from Bios best 2008 Grade 12 Biology) The diagram below that represents a section through part of the human eye. © Gauteng Department of Education 46 3.1. 3.2. 3.3. 3.4. 3.5. 3.6. Supply labels for the parts numbered 1, 3 and 5. (3) Supply the number and name the part that controls the amount of light that enters the eye. (2) Mention the changes that the part names in Question 3.2 will undergo when exposed to bright light. (4) List one function for each of parts 4 and 7. (2) Supply the number and the name of the part that is responsible for the accommodation of the eye. (2) Explain the changes that will take place when the part named in Question 3.5 views an object closer that 6m. (5) QUESTION 4: 18 minutes (Taken from DoE May/June 2008 Paper 2) Study the following diagram of the human ear and answer the questions that follow. © Gauteng Department of Education 47 4.1 4.2 4.3 4.4 4.5 4.6 Identify parts B and G. (2) State the function of each of parts C and E. (2) Explain: a) Why you can often clear a buzzing/humming in the ear by swallowing (3) b) Why the membrane labelled F is much larger than membrane C (2) A dog has lost part A in an accident. Part A is replaced with a stiff, non-elastic, solid plastic structure. a) Is the plastic structure as effective as the original ear of the dog? (1) b) Explain your answer to QUESTION 4.4 (a). (2) Explain how part D and the retina of the eye function in similar ways. (4) Give ONE reason for part D being spirally shaped. (2) SECTION B: NOTES ON CONTENT Terminology & definitions: Photoreceptors: Specialized receptors to receive the stimulus of light and convert it to an impulse. Photoreceptors in the retina of the eye are called rod and cone cells. Refraction: To bend light – refraction takes place when light passes through a lens that is bent by a convex [ ( ) ] shape or a concave [) ( ] shape Stereoscopic vision: Also known as binocular vision - to see with two eyes, where each eye will produce a slightly different image of the same object and allows us to judge distance, depth and size of an object. © Gauteng Department of Education 48 Accommodation: The ability to change the focal length of the object by changing the convex shape of the lens to assist with focussing on a near or distant object. Myopia: Short-sightedness caused by a cornea that is too rounded so the image falls short of the retina. Hypermetropia: Long-sightedness caused by a lens that cannot become rounded enough to refract light so the image falls behind the retina. Mechanoreceptors: The Organs of Corti are receptors located in the cochlea of the ear, which are stimulated by sound waves and convert the sound waves into impulses. Ossicles: Three little bones called the hammer, anvil and stirrup located in the middle ear and that function to amplify sound. Otis media: inflammation and infection of the middle ear which causes pressure on the eardrum. The Human Eye The eyes are organs that make it possible for us to see. Path of Light: Light rays pass from an object to the eye, through the transparent convex cornea, aqueous humour, the biconvex lens and vitreous humour. As the light rays pass through the curved surfaces of the cornea and the lens, light is refracted (bent). The lens refracts the light rays and forms an inverted (upside-down) image on the retina, bringing the image into focus by making fine adjustments. © Gauteng Department of Education 49 The rod and cone cells (photoreceptors) are stimulated by the light rays and convert the stimulus into impulses. These impulses are transmitted along the optic nerve across the optic chiasma (cross-over) so that impulses enter the lower visual centres on opposite sides of the mid-brain at the occipital lobes. The upright images are interpreted for size, shape and colour of the object that was seen. Accommodation: Binocular vision means to see with TWO eyes (bi = two). We are able to focus on one object with both eyes increasing the field of vision. A sharp image falls on each retina. The image from the left eye is always slightly different to the image from the right eye. The two images join in the brain (occipital lobes) and results in stereoscopic vision, which allows us to judge distance, depth and size of objects. The eyes can change the convex curve of the lens and therefore the focal length. This process is termed accommodation. Near vision (round lens) - When viewing an object at a distance of less than 6 metres: The ciliary muscles contract, causing the ciliary body to move closer to the lens. This causes the tension on the suspensory ligaments to slacken. This results in tension on the lens being released. The lens becomes more convex and rounded, increasing the refractive power of the lens. The focal length decreases, bringing the object into focus onto the yellow spot of the retina. Distant vision (long lens) - When viewing an object at a distance of more than 6 metres: At rest, the eyes are set for distant vision. (When people daydream, they have a faraway look because their eyes are set for distant vision.) The ciliary muscles relax, causing the ciliary body to pull back from the lens. © Gauteng Department of Education 50 This causes the tension on the suspensory ligaments to increase, so they become taut (pull tight). This results in the lens pulling to a longer, thinner shape (less convex), decreasing the refractive power of the lens. The focal length increases, bringing the object into focus onto the yellow spot of the retina. Pupillary mechanism (reflex): The pupillary mechanism is a reflex action regulated by the Autonomic Nervous System, to prevent excess light from passing into the eye at one time. Excess light will cause damage to the retina and the photoreceptors (rod and cone cells). The iris functions to control the amount of light that enters the eye by controlling the size of the pupil. The circular and radial muscle fibres in the iris regulate the size of the pupil. © Gauteng Department of Education 51 Visual defects: Short-sightedness This is also called myopia or near-sightedness. It is a refractive defect where the image focuses in front of the retina because the cornea is too rounded. Distant objects are seen as blurred. Myopia may be genetic or it may result when people place regular strain on their eyes by working on computers or in a job where they are required to focus closely on objects, like microscope work. Glasses and contact lenses that are concave [)(] are prescribed to reduce refraction. Refractive surgery may be an option, where the cornea is reshaped to flatten it and so decrease refraction. This causes the image to be focused onto the retina. Long-sightedness This is also called hypermetropia or farsightedness. This is a refractive defect where the image focuses behind the retina. The person will not be able to see objects when they are close by, as the images are blurred. This condition is caused by the following: An eyeball that is too short (genetic): This is corrected with prescription eyeglasses or contact lenses which assist to increase refraction of light by using convex lenses [()]. When the lens cannot become round enough during accommodation: This may be genetic or it may be as a result of aging. As one ages, the ciliary muscles are unable to contract enough to cause the lens to become rounder. Eyeglasses or contact lenses are prescribed to assist to increase refraction of light by using convex lenses [()]. A cornea that is too flat: Refractive surgery is performed in extreme cases. © Gauteng Department of Education 52 Astigmatism This is an optical defect that results in blurred vision. It is caused by an irregular curvature of the cornea or the lens so the eye has different focal points that occur in different planes. Glasses and hard contact lenses correct the irregular focal points. Cataracts This is the clouding of the lens when the lens cortex liquefies to form a milky white fluid. Cataracts progress over time and may result from long-term exposure to ultraviolet light, radiation, diabetes, hypertension, old age and physical trauma. Genetically, people may have a predisposition to cataracts. Cataracts must be removed surgically. Extra-capsular surgery (ECCE) can be used to remove the lens, leaving the lens capsule intact. Intra-capsular surgery (ICCE) is used when both the lens and capsule are removed. The lens is replaced with a plastic lens in both cases. © Gauteng Department of Education 53 The Human Ear: The ears are the sense organs for hearing. Mechanoreceptors in the ear are stimulated by sound waves, which are converted to impulses. The impulses are transmitted via sensory neurons to the auditory centre in the cerebral cortex of the brain where they are interpreted. The ears are also the organs for balance and equilibrium. These impulses are transmitted via sensory neurons to the cerebellum where they are interpreted to ensure balance and equilibrium. [Please note typo on the diagram: ossicles and not ossides] The Human Ear Path of Sound Sound waves move from the vibrating source (for example, a person talking or a car driving past) in horizontal waves. Humans hear sounds with a vibration frequency of between 16 and 20 000 Hz. Sound waves are collected by the pinna and passed down the external auditory canal. The vibrations reach the eardrums (tympanic membranes). The eardrum vibrates according to the frequency of the sound waves. The vibrations are transmitted to the three ossicles (the hammer, anvil and stirrup) in the middle ear, to amplify the vibrations. The stirrup passes the vibration through the oval window, into the inner ear. The oval window vibrates and causes wave movements in the liquid of the perilymph. © Gauteng Department of Education 54 The wave movements are transferred to the endolymph inside the cochlea. The hair cells of the organs of Corti (the mechanoreceptors) brush or bend against the membranes, which converts the mechanical stimulus of the sound wave into an impulse. The impulse is passed through the auditory nerve to the auditory centre in the cerebral cortex of the brain. The sensation of sound is perceived and interpreted by the cerebral cortex. Excess vibrations are passed out through the round window, to prevent sound pressure and echoes. Balance and equilibrium: Maintaining balance and equilibrium with regard to the perception of head movements: function of the semi-circular canal is a swelling called the ampulla, which contains fine sensory hair cells called crista. The crista are embedded in a dome-shaped gelatinous capsule. When the head moves, the endolymph in the ampulla moves as well stimulating the crista and a nerve impulse is discharged and transmitted to the cerebellum. Maintaining balance and equilibrium with regard to perception of the position of the head in relation to gravity: function of the sacculus and utriculus contain sensory hair cells called macula. Hairs are embedded in the otolithic membrane covered with calcium carbonate granules, which lie on the hair cells. When the head position changes, the otoliths move according to the pull of gravity. This stimulates the maculae, which convert the stimulus into an impulse transmitted to the cerebellum. Hearing defects Middle ear infection: called otitis media and refers to an inflammation of the middle ear. When the middle ear becomes infected by bacteria, there is extreme pain as pressure builds up behind the eardrum caused by pus that collects in the middle ear cavity. The Eustachian tube becomes blocked so there is a lack of the ability to equalise the pressure on both sides of the eardrum. In some cases, the eardrum can burst and pus drains out of the ear. Antibiotics are generally prescribed. Severe scarring of the eardrum can affect the person’s hearing. Ear-nose-and-throat specialists (ENTs) will insert little rubber structures called grommets into the eardrum. Grommets look like mini dumbbells with a hole through the centre. This allows fluids and pus to drain out from the middle ear, preventing the pressure that causes earache. Deafness: The terms ‘hearing impairment’, ‘hard of hearing’ or ‘deafness’ mean that the person has a loss of the ability to detect sounds either partially or completely. Hearing aids and cochlear implants: A hearing aid is an apparatus that is worn in or behind a person’s ear. The apparatus amplifies sound, so that the person is able to hear better. Hearing aids are generally used when hearing deteriorates gradually. A cochlear implant is a surgically implanted electronic device that stimulates the auditory nerves with an electronic field, inside the cochlea. Cochlear implants are used when a person has © Gauteng Department of Education 55 severe hearing loss or impairment. It is a very expensive procedure and requires much therapy to assist the deaf person to become accustomed to the devise. SECTION C: HOMEWORK QUESTIONS QUESTION 1: 35 minutes (Modified from various DoE exam papers) Study the diagram of the eye and answer the questions that follow: 1.1. 1.2. 1.3. Name the parts numbered 1 to 15. (15) Name the functions of the iris, choroid and lens. (12) Label in the correct order, all those parts that would indicate the path of light stimulus from the point where it enters the eye until it reaches the brain. Provide the number and the name of each structure in order. (8) [35] © Gauteng Department of Education 56 QUESTION 2: (Modified from various DoE exam papers) Study the diagram below and answer the questions that follow: 2.1. State the letter and name of the part 2.2. 2.3. 2.4. associated with each of the following statements: a) the part that secretes cerumen (ear wax) b) the part that intensifies sound waves c) the part that carries impulses to the brain d) the part that is responsible for balance e) the part that ensure that the air pressure is equal on both sides of the eardrum Explain what would happen if part F was blocked. Describe the sequence of events that occur between the entry of a sound wave into the ear canal, until it reaches the auditory nerve. Briefly discuss what a middle ear infection is and how this is solved. SECTION D: SOLUTIONS FOR SECTION A QUESTION 1: 1.1. B 1.2. C 1.3. C 1.4. A 1.5. C 1.6. D 1.7. C 1.8. C 1.9. B 1.10. B 1.11. D © Gauteng Department of Education (2) (2) (2) (2) (2) (4) (14) (10) [38] 57 1.12. 1.13. 1.14. 1.15. B A C C (15 x 1) = (15) QUESTION 2: - In bright light the pupil size was small - to reduce the amount of light entering the eye - Now in dimly lit room the pupil size has to increase - to increase the amount of light entering the eye (4) QUESTION 3: 3.1. 1 = cornea 2 = pupil 3 = suspensory ligaments 3.2. Number 2 , the iris 3.3. The radial muscles of the iris relax the circular muscles contract this will cause the pupil to constrict allowing less light to enter into the eye 3.4. 3.5. 3.6. Part 4 = the lens focusses the light rays onto the retina at the back of the eye . Part 7 = the viterous body / viterous humor is part of the refracting medium of the eye and helps to maintain the shape of the eyeball Number 6 = the ciliary muscles in the ciliary body The ciliary muscles contract Releasing the tension on the suspensory ligaments so they become relaxed The tention on the elastic lens becomes less The lens becomes rounder/more convex This increases the refraction of light through the lens sothat the image focusses on the retina (18) QUESTION 4: 4.1 B : Semi-circular canals G : Auditory meatus/canal (4) 4.2 C : Transmits pressure waves to the perilymph of the inner ear (2) E: Prevents pressure build-up of sound waves / distortion /eases vibrations out of the inner ear/ absorbs vibrations (any two) (2) 4.3 (a) A buzzing sound is caused by a difference in the pressure between the outer and the middle ear Swallowing opens / closes the Eustachian tube to equalize the pressure (3) (b) © Gauteng Department of Education 58 4.4 To amplify Sound (2) (a) No (1) (b) It is not moveable or flexible for more accurate collection of sound / for finding the direction that the sound is coming from (2) 4.5 Both receive stimuli and convert to impulses which they send through the sensory neuron (Any 2 x 2) = (4) 4.6 Larger surface area to accommodate more receptors fits into smaller area / takes up less space (Any 2) = (2) SESSION NO: 8 CONSOLIDATION: NUCLEIC ACIDS, MEIOSIS, GENETICS AND INHERITANCE Note to teacher: Sessions 8, 9 and 10 are consolidation sessions where learners will get an idea of what to expect in the exam as questions have been extracted from past examination papers to assist with exam technique and time allocation. Please make sure that they adhere strictly to the time allocations for each question. Show learners that they will find that there are questions that combine sections/topics of work covered. Please make sure that they do not learn topics as individual units, but that you understand how they interrelate. Meiosis, DNA and Genetics combine well, as does the Nervous system, Hormone regulation and Homeostasis although at this point they have not as yet complete Hormones and Homeostasis. Remind the learners to keep this in mind when preparing for their exams. Please note that there are no content summaries included in Consolidation sessions so there is no Section B. Refer to the previous sessions should learners need to check up on content information. When answering questions in an exercise, test or exam: Read the question first and underline the operative words so that you are clear about what is being asked of you. Take careful note of the mark allocation, as this will guide you to the number of facts that you need to write. Do not waste time writing 5 facts when the examiner only asked for 2. They will only mark the 1st two answers. Answer the question as if you are answering someone whom you like, is intelligent but knows nothing about Life Science – then you will not leave anything out. Please note: an examiner will never ask 2 questions with the same answer. If you have written the same answer then one of them is definitely wrong. Please re-read each of the questions and you will see that each one requires a different answer. © Gauteng Department of Education 59 If you are asked to ‘tabulate’ – then you MUST answer in the form of a table. You will be penalized if your points are not listed in a table format. You will also receive a mark for drawing the table and the appropriate headings. When you are asked to compare two things/aspects/component/terms, then rather use the table format. This way you will remember to write equally about both of the factors and compare fact /characteristic properly. When answering questions with diagrams: Study the diagram and write missing labels in on the diagram itself FIRST. Now read through the questions and answer each one. If you do not know the answer, then write the number on your answer page, look at the mark allocation and leave enough lines to write the answer in later, i.e.: if the mark allocation is 2, then leave two lines open. Graphs and Pie-charts: Make sure that you know the difference between a Line graph, Bar graph, Histogram and a Piechart. Make sure that you practice the skill of graphing and representing data from a table as a graph. Make sure that you are able to read information from a graph accurately. Use a ruler and draw lines on the graph – through the X and Y axis so that your readings are accurate. Calculations: You will be expected to do calculations in a test and exam. Make sure that you take a calculator in with you. Make sure that you understand how to calculate the average, the difference between and percentage. Generally, the examiner will ask you to show your calculations. You must write out your calculation step by step otherwise you will only be awarded a mark for the answer – if it is correct. Always add the unit to your answer (if there is one). 1. 2. 3. Introduce session – 5 minutes (and go over basic exam techniques as per the above hints) Typical exam questions and solutions – 55 minutes (Questions that are not completed must please be included with Homework) Answer/memo discussion – 30 minutes SECTION A: TYPICAL EXAM QUESTIONS QUESTION 1: 10 Minutes (Taken from DoE November 2008 Paper 1) Some people have the ability to roll their tongue (rollers) while other people cannot roll their tongues (non-rollers). A Grade 12 learner wanted to determine the frequency of learners in the school that could roll their tongues. She went to each grade in the school and counted the © Gauteng Department of Education 60 number of rollers and non-rollers. She presented her results in the graph below. 1.1. 1.2. 1.3. State a hypothesis for this investigation. Which grade had the most learners that could roll their tongues? Use the data in the graph to draw a table that shows the results she obtained. Calculate the ratio of rollers to non-rollers. Show ALL working. (2) (1) (7) 1.4. (4) [14] [Remember: to give the table suitable headings/captions. Always compare the same characteristics for each point in the columns] QUESTION 2: 8 Minutes Two newborn babies were accidentally mixed up at the hospital. In an effort to determine the correct parents of each baby, the blood types of the babies and the parents were determined as follows: Baby 1 – type O Mr Smith – type AB Mr Jones – type B 2.1 2.2 Baby 2 – type A Mrs Smith – type B Mrs Jones – type B Who are the parents of Baby 2? Provide evidence for your answer in 4.1 by showing your working in a Punnett square. [ Remember: Blood group is a result of multiple alleles and is an example of co-dominance. A and B are equally dominant and will dominate over O. Blood type O can only occur if both alleles are recessive = ‘OO’] © Gauteng Department of Education (2) (6) [8] 61 QUESTION 3: 12 minutes (Taken from various sources) 3.1. Where is DNA found? (2) 3.2. What are the constituent groups of molecules that form the nucleotides?(3) 3.3. Name the pyrimidines and purines of DNA and RNA. (6) 3.4. Name the mRNA produced by each of the following strands of DNA: a) AACGGCTAT (1) b) CCGTAACGAATT (1) c) GCGAATTCA (1) [14] QUESTION 4: 3 minutes (Taken from various sources) A child is born out of wedlock and the mother wants to find out who is the father of the child. Using the DNA fingerprints below determine who the father of the child is. Explain your answer. (3) [Hint: Remember to ALWAYS use a ruler horizontally across the strands so that you do not make a mistake when comparing the VNTR markers. Place a mark next to each VNTR marker that corresponds] QUESTION 5: 20 minutes (Taken from various sources) Study the diagrams below on the principle of meiosis. Answer the questions that follow: [Hint: Remember to ALWAYS first label the diagram before going on to the questions] © Gauteng Department of Education 62 a) b) c) d) e) How many chromosomes does cell B have? Would this be n or 2n? Give a reason for your answer. How many chromosomes does each cell in F have? What would the ploidy of each cell in F be? Does each cell in F have exactly the same number of chromosomes? (1) (2) (1) (1) (1) 5.2. Tabulate the differences between meiosis 1 and meiosis 2. [Hint: Remember to give the table suitable headings/captions. Always compare the same characteristics in each of the columns) (8) 5.3. 5.4. Why is meiosis important in the formation of sex cells? What is the significance of crossing over during prophase I? (4) (2) [20] QUESTION 6: 7 Minutes (Taken from DoE Nov 2011 Paper 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 [HINT: you have been told to use W for white flowers. So a homozygous white flower will be WW. A homozygous red flower will be RR. This means that a © Gauteng Department of Education 63 heterozygous flower will be WR. Do NOT use any lower case letter for the recessive gene because you have been provided with the symbols for the alleles. ONLY use the W and the R] 6.1 6.2 State the kind of dominance shown in the diagram above. (1) Use the symbols R and W and write down the genotypes of each of the following snapdragon plants: a) A (2) b) B (2) c) C (2) [7] SECTION C: HOMEWORK QUESTIONS QUESTION 1: 26 minutes The following diagram illustrates the formation of mRNA using a single strand of a DNA molecule as a template. Study the diagram and answer the questions that follow. © Gauteng Department of Education 64 [Hint: Remember to ALWAYS first label the diagram before going on to the questions] 1.1. 1.2. 1.3. 1.4. 1.5. Identify the parts numbered 1 to 12. (12) Name the chemical bond at X. (1) Where in a cell does the process illustrated in the diagram occur and when? (2) Tabulate three differences between RNA and DNA. (7) [Hint: Remember to give the table suitable headings/captions. Always compare the same characteristics in each of the columns) How do mRNA and tRNA differ with respect to structure and function? (4) [26] QUESTION 2: 12 Minutes The pedigree for albinism is inherited as an autosomal recessive trait. The trait is not sex linked and is shown by both males and females. The affected female in the third generation has phenotypically normal parents. Refer to the diagrams on the following page and answer the questions that follow from the diagram and from your knowledge. © Gauteng Department of Education 65 Use the following symbols to understand the pedigree Normal female Affected female Carrier Affected male Normal male Carrier (heterozygote 2.1 2.2 2.3 2.4 3.5 What change would occur in the genetic structure for albinism to arise? List 2 characteristics shown in the phenotype of a person with albinism. Explain what is meant by autosomal recessive trait. Distinguish between genotype and phenotype. Explain how: (i) All generation II offspring are carriers for the albino allele. (ii) III-2 is an albino girl whose paternal grandmother and maternal grandfather are also albinos. (iii) All her other relatives in Generation III show normal phenotypes. [Hint: remember that albinism is a mutation] (1) (2) (2) (3) (6) [14) QUESTION 3: 10 Minutes (Taken from DoE Feb/March 2009 Paper 1) An investigation to determine the effect of increasing radiation on lethal (deadly) mutations on X chromosomes in fruit flies was undertaken by scientists. The results are shown in the graph that follows: © Gauteng Department of Education 66 3.1. 3.2. 3.3. 3.4. 3.5. 3.6. Formulate a possible hypothesis for this investigation. (2) Name ONE factor that was varied by the scientists in this investigation. (1) How many different values of the factor named in QUESTION 1.2 above were used? (1) Name TWO factors that would have to be kept constant during this investigation. (2) What conclusion can be drawn from the results presented in the graph? (2) If you were carrying out this investigation, describe ONE way in which you would ensure that the results obtained are reliable. (2) [10] SECTION D: SOLUTIONS FOR SECTION A QUESTION 1: 1.1 Most learners in the school can roll their tongue OR Most learners cannot roll their tongue OR Equal number of rollers and non-rollers OR Difference in the number of rollers and non-rollers OR Tongue rolling occurs /does not occur among the learners 1.2 Grade 10 1.3 The number of rollers and non-rollers in the different grades © Gauteng Department of Education (2) (1) 67 OR The number of rollers and non-rollers in the different grades Caption Correct column headings Correct row headings Data in table: 5 rows correct 3 to 4 rows correct 1 to 2 rows correct Drawing of table as blocks with columns and rows (7) 1.4 160 + 150 + 180 + 140 + 120 = 750 40 + 50 + 20 + 60 + 80 = 250 750 ÷ 250 OR 750/250 3 : 1 OR 75% : 25% OR 1 non-roller: 3 rollers (4) [14] QUESTION 2: Baby 2 – type A 2.1. Parents are Mr and Mrs Smith√√ 2.2. P1 Mr Smith AB x Mrs Smith B P1 IAIB √ X IBIB OR IBi√ (2) Punnett square: IA IB IB IA IB IB IB i IA i IB i gametes √√ Punnett square correctly done√√√ F1: blood type A √ or AB √ or B √ Only Mr and Mrs Smith could have a baby with type A √ blood or I Ai √ (12 x half = 6) QUESTION 3: 3.1. DNA is found in the threadlike chromosomes in the nucleus of a living cell 3.2. A phosphate ion ,a pentose sugar and a nitrogenous base (3) 3.3. Pyrimidines of DNA – cytosine and thymine Pyrimidines of RNA - cytosine and uracil Purines of DNA and RNA – adenine and guanine (6) 3.4. a) UUGCCGAUA (1) b) GGCAUUGCUUAA (1) c) CGCUUAAGU (1) © Gauteng Department of Education (2) 68 QUESTION 4: Male 2 is the father . The child has more matching bands in common with the mother and male 2 than with the mother and male 1 (3) QUESTION 5: 5.1. a) 4 (1) b) 2n . There are two sets of chromosomes / the homologous pairs of chromosomes are present (2) c) 2 (1) d) n / haploid (1) e) Yes (1) 5.2. This answer must be in table form. Meiosis 1 Meiosis 2 Prophase: Chromosomes are in homologous pairs. Chromosomes are not in homologous pairs. Prophase: Crossing over occurs. No crossing over occurs. Metaphase: Chromosomes are arranged at the equator in pairs. Chromosomes are arranged randomly at the equator. Anaphase: One of each pair of chromosomes moves to opposite poles. The centromere does not split. Daughter chromosomes move to opposite poles. The centromere splits. Telophase: One complete set of chromosomes reaches each pole. A nuclear membrane does not reform. Daughter chromosomes reach opposite poles. A nuclear membrane reforms around each nucleus. Two daughter cells form with the haploid number of chromosomes. Four daughter cells form the haploid number of chromosomes (Mark any 3 correct answers for each of Meiosis 1 and 2. Allocate 1 mark for the table and 1 mark for the correct headings per column) (8) 5.3. 5.4. The sex cells / gametes must contain one set of chromosomes only so that when the zygote is formed after fertilisation , it will contain two sets of chromosomes (4) Crossing over ensures genetic variation within a species (2) QUESTION 6: 6.1. Incomplete dominance (1) 6.2. (a) RR/CRCR (b) RW /CRCW (c) WW/CWCW (6) © Gauteng Department of Education 69 SESSION NO: 9 CONSOLIDATION: RESPONDING TO THE ENVIRONMENT: HUMANS (NERVOUS SYSTEM, EYE AND EAR) Teacher note: Refer to Session 8 for tips on answering exam questions. Please ensure that the learners adhere to the time limits so that they learn to work under pressure. Let the class work through each question within the time limit. 1. 2. 3. Introduce session – 5 minutes (and go over basic exam techniques as per the above hints) Typical exam questions and solutions – 55 minutes (Questions that are not completed must please be included with Homework) Answer/memo discussion – 30 minutes SECTION A: TYPICAL EXAM QUESTIONS QUESTION 1: 16 minutes (Taken from various DoE Paper 2) Study the diagram below and answer the questions that follow: 1.1. 1.2. 1.3. What is meant by the term ‘reflex action’? (4) Provide a reason why reflex actions are of importance to the human body. (2) Name the structures, that are missing on the diagram and in their correct order, that will ensure that an individual does not burn his/her finger. (3) [Hint: think about the neurons involved – in the correct order to ensure that the hand is pulled away] © Gauteng Department of Education 70 1.4. Name the microscopic gap that will transmit impulses between the structures named in QUESTION 1.3. (1) 1.5. In this reflex action above, name the: (i) stimulus (1) (ii) effector (1) 1.6. Tabulate THREE differences between a motor neuron and a sensory neuron. (7) [17] QUESTION 2: 10 minutes (Taken from DoE Nov 2005 Paper 2) Study Diagrams I and II that illustrate the lens and parts of one layer of the human eye, as well as the graph below and answer the questions that follow. [HINT: label the diagram first, study the graph and then answer the questions] © Gauteng Department of Education 71 2.1 2.2 2.3 2.4 2.5 Identify parts A and B. (2) Which Diagram (I or II) shows parts of the eye: (i) where the ciliary muscles are contracted (1) (ii) are under dim light conditions (1) Explain your answer in QUESTION 2.2 (i). (2) Which letter on the graph indicates each of the following: (i) The eye looking at a nearby stationary object (1) (ii) The eye looking at an object moving towards the viewer (1) [Hint: the eye is normally set for distant vision when it is relaxed. The lens must be accommodated to adjust to view an object as it moves closer to the viewer.] Explain the significance of the elastic nature of the lens. (2) [10] © Gauteng Department of Education 72 QUESTION 3: 17 minutes (Taken from DoE Nov 2005 Paper 2) Study the following diagrams and table and answer the questions that follow. Table indicating how much of the human brain’s sensory area is allocated to certain body parts, depending on the number of sensory receptors on the part: [HINT: label the diagrams first and then start with the questions] 3.1 3.2 3.3 3.4 3.5 Identify parts A and D. (2) After only the sensitive coverings of the brain were injected to make them insensitive, part C of a normal person was pierced with a sharp object, but the person did NOT experience any pain. (i) Give a possible explanation for the person not experiencing a pain sensation. (3) (ii) Explain a possible disadvantage if a body part is pierced with a sharp object, but the person does not experience any pain. (2) (i) Give the letter of the part that will interpret impulses conducted along part B. (1) (ii) Explain your answer in QUESTION 3.3 (i). (2) Explain why damage to part F may lead to immediate death. (2) Give a possible explanation for the high representation of the tongue in the sensory area of the brain as compared to the leg. (2) © Gauteng Department of Education 73 3.6 (i) With which body part shown in the table, will the abdomen most probably have the same size area representation in the sensory part of the brain?(1) (ii) Explain your answer in QUESTION 3.6 (i). (2) [17] QUESTION 4: 30 minutes (Modified from Study & Master Grade 12 –old syllabus) Study the diagram of the human eye and answer the questions that follow: [HINT: label the diagrams first and then start with the questions] 4.1. 4.2. 4.3. 4.4. 4.5. 4.6. 4.7. Write down the number and the name of the layer: a) giving colour to the eye (2) b) that prevents the reflection of light rays in the eye (2) c) which contains rod and cones (2) Write down the number and name of the structure: a) mainly responsible for the refraction of light rays (2) b) where the clearest image of the object is formed. (2) Write down the numbers and names of FOUR parts which refract light rays in order, as they pass through the eye. (4) Write down the number and name of the layer which changes light energy into nerve impulses. (2) Write down the number and name of the layer of the structure which controls the amount of light entering the eye. (2) Explain the process and functioning of the structure named in QUESTION 4.5, when there is bright light. (4) Explain the process that takes place in the eye when we focus on an object that is closer that 6m. (8) [30] © Gauteng Department of Education 74 QUESTION 5: 15 minutes (Taken from DoE Nov 2005 Paper 2) A person hears a car moving out of control and crashing into another vehicle. Describe the events that will lead to the person hearing the crash. [Hint: think about the path of sound as the sound waves travel through the ear] Content: (15) Synthesis: (3) [18] SECTION C: HOMEWORK QUESTIONS QUESTION 1: 10 Minutes Study the diagram below and answer the questions that follow: 1.1. 1.2. 1.3. 1.4. 1.5. 1.6. Supply a suitable heading for the diagram. (1) Label the parts numbered 1, 2, 5 and 6. (4) What number represents a synapse? (1) What type of neuron has been left off the diagram? (1) Name the end point of the structure named in QUESTION 1.4. (1) If part number 6 is damaged, what will the consequences be for the body? (3) [11] © Gauteng Department of Education 75 QUESTION 2: 14 Minutes (Taken from various DoE exam papers) Study the passage and diagram below and answer the questions that follow: Under certain abnormal conditions, the middle ear can become filled with a thick, sticky mucus. This condition is known as ‘glue ear’ It affects mainly children. To treat this condition, surgeons are required to drain the mucus and reduce the pressure in the middle ear. They do that by placing a very small tube called a ‘grommet’ in the membrane labelled A in the diagram below. 2.1. 2.2. 2.3. 2.4. 2.5. Identify parts numbered A, B, C and E. State two consequences of a build-up of pressure in the middle ear. Explain the effect on the functioning of part B should mucus be left to accumulate in the child’s middle ear. Explain the function of part E. Once a ‘grommet’ is in place, the child should not go swimming. Give two reasons for this precaution. (4) (2) (2) (2) (4) [18] QUESTION 3: 7 Minutes A person took part in an experiment on the eye’s response to light. A lamp was placed at seven different positions from the person’s face. The diameter of the person’s pupil was measured at each position. The table below shows the diameter of the person’s pupil when the light was placed at various distances from the person’s face. © Gauteng Department of Education 76 3.1. 3.2. Position of the lamp Diameter of the pupil (mm) 1 2 3 4 5 6 7 1,2 1,8 2,4 3,0 3,6 4,2 4,8 (i) At which position was the lamp furthest from the eye? (1) (ii) Explain your answer to QUESTION 3.1 (i). (2) The lamp was moved from position 1 to position 2. What happened to the muscles in the iris of the eye, that caused the change in the diameter of the pupil? (4) [7] SECTION D: SOLUTIONS FOR SECTION A QUESTION 1: 1.1. A fast automatic response by an effector (muscle / gland) to a stimulus received by a receptor (any 4 = 4 marks) 1.2. protects the human body against damage OR regulates secretions from glands (2) 1.3. - sensory neuron / afferent neuron / unipolar neuron / monopolar neuron (must be mentioned first) - connector neuron / inter neuron (if mentioned second) - motor neuron / efferent neuron / multipolar neuron (if mentioned third) (3) 1.4. Synapse (1) 1.5. (i) heat / flame / candle fire (1) (ii) muscle in the arm to pull the hand away (1) 1.6. Motor neuron Sensory neuron Conducts nerve impulses Conducts nerve impulses away from the central nervous towards the central nervous system system Axon only myelinated Both axon and dendrite myelinated Only multipolar structures Unipolar / Monopolar or Bipolar structures Many dendrites One dendrite (Any three difference per neuron PLUS 1 mark for the table and correct captions) (7) © Gauteng Department of Education 77 QUESTION 2: 2.1 A: Ciliary body/Ciliary muscle (1) B: Suspensory ligament (1) 2.2 (i) Diagram II (1) (ii) Diagram I (1) 2.3 Suspensory ligament slackens OR Lens looks smaller/ more convex (2) 2.4 (i) D (1) (ii) F (1) 2.5 - Can change its shape - to focus image onto the yellow spot - irrespective of the distance from the eye OR for near or distant vision OR for accommodation (3) QUESTION 3: 3.1. A: Eustacian tube (1) B: Corpus callosum (1) 3.2. (i) - absence of pain receptors - thus no impulse is generated - to be interpreted by the brain OR - Cerebrum is damaged - any impulse received - cannot be interpreted (3) (ii) - pain is a protective function - part could be lost or damaged - and loose its function for the body - because the person is unawre of the harm - therefore does not respond appropriately / correctly - leading to further damage (Any TWO = 2) 3.3. (i) E (1) (ii) - originates from part of the ear containing the balance receptrs - and E / cerebellum controls balance (2) 3.4. Vital processes will stop / breathing and hearbeat will stop (1) 3.5. - tongue is more sensitive / is a sense organ - has more receptors - is needed for the reception of a large variet of stimuli ANY TWO = (2) 3.6. (i) Hand / upper arm / leg (1) (ii) Has more or less the same amount of receptors as the abdomen (2) QUESTION 4: 4.1. a) 2 – iris (2) b) 9 – choroid (2) c) 10 – retina (2) 4.2. a) 6 – cornea (2) b) 12 - yellow spot / fovea centralis (2) 4.3. 6 – cornea 5 – aqueous humour © Gauteng Department of Education 78 4.4. 4.5. 4.6. 4.7. 3 – lens 7 – vitreous humour (Answer must be in the correct order with correct number AND structure) (4) 10 – retina (2) 2 - iris (2) Bright light: circular muscles contract causing pupil to constrict (get smaller) radial muscles relax less light is allowed into the eye (4) Near vision: ciliary muscles contract causing the ciliary body to move closer to the lens suspensory ligaments slacken tension on the lens is released lens becomes more convex and rounded increasing the refractive power of the lens focal length decreasesbringing the object into focus onto the yellow spot of the retina (8) QUESTION 5: Collision / crash causes vibrations That generate sound waves Which are transmitted by the air The pinna directs the sound waves Along the auditory canal The sound waves cause the tympanic membrane To vibrate And the vibrations are transferred to the ossicles Which will amplify the waves And transmit the vibrations to the oval window Which will also vibrate to transfer the sound waves to the perilymph The vibrations are then transferred to the endolymph Where the organs of Corti / hair cells / mechanoreceptors Situated in the cochlea Convert the sound waves into nerve impulses Which are conducted via the auditory nerve To the hearing centre In the brain / cerebrum Where the sensations of hearing are experienced (ANY 15 = 15 marks) Assessing the presentation: (3) © Gauteng Department of Education 79 Criterion Generally Relevance (R) All information provided is relevant to the topic Logical sequence (L) Ideas are arranged in a logical/cause-effect sequence Comprehensive (C) All aspects required by the essay have been sufficiently addressed In this essay [18] SESSION NO: 10 CONSOLIDATION: HUMAN REPRODUCTION Teacher Note: Refer to Session 8 for tips on answering exam questions. Please make sure that the learners all adhere to the time limits so that they learn to work under pressure. Get the group to answer each question together within the time limit and then go over the answer with them. 1. 2. 3. Introduce session – 5 minutes (and go over basic exam techniques as per the above hints) Typical exam questions and solutions – 55 minutes (Questions that are not completed must please be included with Homework) Answer/memo discussion – 30 minutes SECTION A: TYPICAL EXAM QUESTIONS QUESTION 1: 12 Minutes (Taken from various sources) [Reminder: there are only 4 basic types of crosses. Make sure you are able to use them properly. Do a quick cross in pencil, next to the relevant question to find the correct answer] Various possible options are provided as answers to the following questions. Choose the correct answer and write only the letter (A – D) next to the question number. 1. In mammals, fertilization takes place in the A Fallopian tubes B vagina C uterus D ovary 2. During the development of the embryo, the function of the amnion is to A give rise to the placenta B protect the embryo against harmful chemical substances C enclose the fluid which protects the embryo against injury D prevent the developing embryo from moving about 3. The following is NOT a function of the placenta of mammals: A transports nutrients to the embryo © Gauteng Department of Education 80 B removes waste products from the embryo C protects the embryo against mechanical injury D protects the embryo against harmful chemical substances 4. The fusion of an egg cell and a sperm cell is known as A copulation B cleavage C fertilization D ovulation 5. The human embryo obtains: A nutrients and oxygen from the mother’s blood B nutrients and CO2 by diffusion across the placenta C yolk and albumen from the allantois D nutrients and oxygen by diffusion across the placenta 6. The human foetus is immediately surrounded by the… A allantois B amnion C chorion D placenta 7. The human foetus is surrounded by A amniotic fluid B air C wastes D mother’s blood 8. Fertilization occurs when the…. A sperm penetrates the ovum B sperm makes contact with the ovum C nucleus of the sperm fuses with the nucleus of the ovum D fertilization membrane has formed around the ovum 9. Which of the following pairs indicates a reproductive structure and its function accurately? A Fallopian tube – production of sperm B Vagina – fertilization C Uterus – development of the embryo D Testes – production of the ovum 10. The main function of the amnion and amniotic fluid is: A shock absorber B medium that removes excretory waste C medium from which oxygen is obtained for the growing embryo D medium in which secretions take place 11. Which of the following is the hormone responsible for the birth process? © Gauteng Department of Education 81 A B C D 12. prolactin oestrogen progesterone oxytocin Dizygotic twins…. A result when one egg cell is fertilized and separates into two structures B will be identical in genetic inheritance and appearance C result when two or more eggs are fertilized D will always be the same sex (12 x 2) [24] QUESTION 2: 6 Minutes (Taken from NSC LS Exam November 2009 paper 1) Choose an item from COLUMN II that matches a description in COLUMN I. Write only the letter next to the number. COLUMN I 2.1. The type of reproduction involving a male gamete that fuses with a female gamete COLUMN II A gestation B identical 2.2. The type of fertilization that occurs outside the body in a glass petri dish in a laboratory 2.3. The type of twins formed as a result of the fertilization of two ova C placenta D cancer E sexual 2.4. The muscular, hollow organ in mammals in which the embryo develops F fraternal/ dizygotic/ non-identical 2.5. The period of development of an embryo between fertilization and birth G in-vitro 2.6. Forms as a result of uncontrolled division of cells H asexual I uterus (6) QUESTION 3: 11 Minutes (Taken from the NSC Exemplar 2008 Paper 1) © Gauteng Department of Education 82 The diagram below represents a part of the human female reproductive system after copulation. Study the diagram and answer the questions that follow. 3.1. 3.2. 3.3. 3.4. 3.5. Give labels for parts A, E and G respectively. (3) Name the process that takes place at B. (1) When, during the menstrual cycle, does the process mentioned in QUESTION 3.2. take place? (1) Describe the process represented by D. (3) Write down the number of chromosomes that would be present in the nucleus of the following: a) Cell C (1) b) One cell of F (1) c) Cell H (1) [11] QUESTION 4: 8 Minutes (Modified from Study and Master Grade 11 – old syllabus) Study the following diagram and answer the questions that follow: © Gauteng Department of Education 83 4.1. 4.2. 4.3. Provide labels for the parts numbered 1 to 5. The structure numbered 1 contains enzymes. What is the function of these enzymes during fertilization? The structure numbered 3 is packed with mitochondria. Explain the relevance of the mitochondria to the sperm cell. (5) (2) (2) [8] QUESTION 5: 12 Minutes (Modified from Study and Master Grade 11 – old syllabus) The following questions are on the reproduction process in humans. 5.1. Name the function/s of the following structures in the male testes: a) epididymis (1) b) seminal vesicle (2) c) prostate gland (1) d) Cowper’s gland (1) 5.2. Name the process by which the ovum is released by the ovary. (1) 5.3. Where does fertilization of the ovum take place? (1) 5.4. Name the function during the development of the embryo, of each of the following structures? a) chorion and chorionic villi (3) b) amnion and amniotic fluid (3) c) umbilical cord (2) [14] QUESTION 6: 20 Minutes (Taken from DoE Exemplar 2014) Name the hormones produced by the testes and ovaries and describe the role of each hormone in human reproduction. Content: (17) Synthesis: (3) [20] NOTE: NO marks will be awarded for answers in the form of flow charts or diagrams. SECTION C: HOMEWORK QUESTIONS QUESTION 1: 20 minutes (Taken from various NSC exams) Describe the menstrual cycle and how it is influenced by different hormones. Content: (17) © Gauteng Department of Education 84 Synthesis: (3) SECTION D: [20] SOLUTIONS FOR SECTION A QUESTION 1: 1.1. A 1.2. C 1.3. C 1.4. C 1.5. D 1.6. B 1.7. A 1.8. C 1.9. C 1.10. A 1.11. D 1.12. C (12 X 2) (24) QUESTION 2: 2.1. E 2.2. G 2.3. F 2.4. I 2.5. A 2.6. D (6 X 1) (6) QUESTION 3: 3.1 A- Ovary , E- Fallopian tube , G- endometrium (3) 3.2 Ovulation (1) 3.3 day 14/middle of the menstruation cycle (1) 3.4 Fertilization takes place. The sperm (haploid/n) fuses with the (haploid/n) egg cell/ovum to form a diploid zygote (2n) - (any 3 points = 3 marks ) 3.5 a) 23 chromosomes (1) b) 46 chromosomes (1) c) 23 chromosomes (1) QUESTION 4: 4.1. 1 : acrosome 2 : nucleus 3 : neck 4 : tail 5 : head (5) 4.2. digest the plasmalemma of the ovum (to allow penetration of the sperm cell nucleus) (1) 4.3. mitochondria produce the energy (ATP) required for the sperm cell to travel (swim) (from the vagina through the uterus to the Fallopian tube) (2) QUESTION 5: 5.1. a) storage of maturing sperm cells (1) b) secrete extra fluid to assist with sperm cell motility and fluid contains nutrients (fructose) as a source of food for the sperm cells (2) c) secretes an alkaline fluid to neutralize acidity of the vagina (1) © Gauteng Department of Education 85 5.2. 5.3. 5.4. d) secretes an alkaline fluid directly into the male urethra to neutralize any acidity caused by remaining urine (1) ovulation (1) in the Fallopian tubes (1) a) chorion develops villi which grow into the placenta and allows: diffusion of respiratory gases, nutrients and waste materials between the embryonic and maternal blood; chorionic villi act as a micro-filter preventing pathogenic substances to pass to the embryo (Any 3) (3) b) allows free movement of the embryo; protects against desiccation; protects against temperature changes (3) c) contains the umbilical artery and the umbilical vein to transport oxygen and nutrients to the embryo ; transport carbon dioxide and wastes from the embryo; it attaches the embryo to the placenta (any 2) (2) QUESTION 6: Testosterone Produced by seminiferous tubules in the testes During puberty testosterone stimulates: The deepening of the voice as vocal cords elongate in the larynx The development of muscles The growth of facial, pubic and body hair Development of the penis and testes The production of sperm in the testes max (5) Oestrogen Produced by the Graafian follicles in the ovaries Causes the lining of the uterus /endometrium to become thicker/more vascular in preparation for a possible implantation of the embryo and development of the foetus During puberty oestrogen stimulates: The widening of the pelvis/hips The growth and development of the breasts The growth of the female sex organs The start of the menstrual cycle, ovulation and menstruation max (7) Progesterone Produced by the corpus luteum and placenta Progesterone causes further thickening of the endometrium so that it is ready for implantation of the embryo should fertilisation occur High levels of progesterone inhibits the secretion of FSH by the pituitary gland which in turn prevents the further development of any new ovum in the ovary max (5) Content (17) Synthesis (3) [20] Assessing the presentation of the essay (synthesis) © Gauteng Department of Education 86 Criterion Relevance Elaboration Mark All information provided is relevant to the topic 1 Logical Ideas arranged in a logical/cause-effect sequence sequence Comprehensive Answered all aspects required by the essay © Gauteng Department of Education 1 1