Year 12 Human Biology Marking Key and feedback for students Trial WACE 2011

Section One: Multiple Choice (20 marks x 2)

Question Answer Question Answer 1 c 11 c 2 b 12 a 3 a 13 b 4 b 14 b 5 a 15 d 6 d 16 b 7 c 17 b 8 a 18 c9 c 19 b10 d 20 d

Section Two: Short Answers (100 marks) Question 21 (a) A – phosphate (1) B – sugar (1) [“deoxyribose sugar” or “ribose sugar” is better] (b) nitrogenous ( ½ ) Although the bases ARE complimentary, that is not their correct NAME. thymine ( ½ ) Not “thyamine”. (c) GCA (1) (d) Some stem cells can be differentiated into a greater variety of cells (1) (e) (i) 64 DNA molecules (1) (ii) (Any 2 of the following, 1 mark each) Copying/amplifying DNA collected from a crime scene

Copying/amplifying DNA for the purpose of electrophoresis

Copying/amplifying DNA collected from ancient specimens

When multiple copies of DNA are required for gene sequencing

Copying/amplifying DNA for identification of different antigens

Copying or amplifying is essential to mention, because that’s what PCR does.

Copying/amplifying DNA for identification of hereditary diseases

Copying/amplifying DNA for identification of mutations

(f) (i) Suspect 1 (1) (ii) Suspect 1 has more matching DNA bands than 2 or 3 (1) That is a better answer than simply saying “it is the same as the specimen”. You need to show that you know WHY it is the same. DESCRIBE the EVIDENCE. Don’t assume the reader knows what an “identical match” means.

Question 22 (a) (Any 1 of the following, 1 mark)

The higher / lower the amount of calcium consumed, the higher / lower the bone density. Calcium taken in tablet form will increase / decrease bone density more / less than calcium consumed through food eaten as part of a normal diet. Calcium consumption has no effect on bone density. Method of consumption of calcium has no effect on bone density.

(b) average bone density (1) (c) (Any 2 of the following, 1 mark each)

age / 50 years or older activity level female were already osteoporotic how they were assessed for bone density timings of bone density testing duration of experiment for all groups

(d) Title that includes time and bone density (1) e.g. “The Effect Of Calcium On Bone Density Over Time”

Titles for X axis title – Time (months) and Y axis - Average bone density (%) (1) Correct scale on both axes (1) Key for three groups / 3 labelled lines (1) All data points plotted correctly (1)

S

Why not “diet”? Because (a) it would be impractical (impossible) to ensure that all 90 people eat EXACTLY the same diet over a 6 month period and (b) We want to know the effect of the independent variable when people are eating NORMAL (i.e. varied) diets. Other variables that would NOT REALISTICALLY be expected to have an impact of bone density; The time of day the calcium was taken in (ingested) The “way it was taken” The number of people in each group

(e) The question says “explain the difference” not “describe the difference”. The majority of you described the difference, despite the simple wording in this Q. The difference between these two groups (1 & 2) is the way in which the calcium was ingested (via the normal diet or in a tablet), so the explanation for the difference in results is that; calcium in the diet is absorbed more effectively than calcium tablets (1) You could also say; absorption of calcium was greater in Group 2 than in Group 1 (1) This is a bit obvious, but it’s true. (f) The method in any investigation can be improved by thinking about three things; [a] how could you obtain more reliable data? - increase the number of participants (1) [b] how could you obtain more valid data? (i.e. make it a fairer test) - test a broader range of calcium “doses” (1) OR e.g. have a fourth group who are on a lower “dose” of calcium (same thing) [c] how could you reduce the limitations on the experiment, these being that they only tested females and they only experimented for 6 months - include males in the investigation (1) - extend the length of the study (i.e. give calcium for longer, measure bone density for longer) (1) (g) parathormone (1) (also known as Parathyroid hormone) (h) parathyroid glands (1) (Calcitonin, from the thyroid gland is also involved in calcium ion regulation) Question 23 (a) osmoregulation - hypothalamus (1) fine motor coordination – cerebellum (1) blood vessel diameter – medulla oblongata (1) (b) (i) axon (1) (ii) speeds up nerve transmission (1) Your book says “insulates” and “protects from damage” but they are trivial. Stick with the first function for the WACE. Dozens of people simply named it. Read the question!!! (iii) neurotransmitters (1) (iv) mitochondria (1) provide energy for neurotransmitter formation (1) Remember, the neurotransmitter gets broken down in the synapse – it has to be reabsorbed and then re-synthesized in the vesicles. That’s what the energy is needed for. Technically, a little energy will be required for the vesicles to undergo exocytosis in order to release the neurotransmitter in the first place ( ½ ). Vesicles do not move across the synapse: what was contained WITHIN THEM does. Lots of you need to revise what goes on at the synapse.

(c) (i) motor neuron (1) multipolar (1) is acceptable, but motor neuron is better, because this clearly IS a motor neuron. Not all multipolar neurons are motor neurons. (ii) X takes nerve impulses away from the cell body, Y takes nerve impulses to the cell body Both X and Y are processes (things that stick out of the neuron) so how are their functions different? Question 24 (a) (Any 1 of the following from each category, 1 mark each)

Structure – Skeletal is striated, smooth is non-striated Skeletal is multinucleated, smooth is mono-nucleate Skeletal cells are longer, smooth are shorter

Skeletal cells are cylindrical, smooth are spindle shaped Function – skeletal is voluntary, smooth is involuntary. Just writing one or two places where it is found does not describe the function of

something. (b) Neurotransmitter (1) We paid examples, like acetylcholine, but we shouldn’t have really. “Acetylcholine” doesn’t fit the definition, because it depends what neuromuscular junction we’re talking about ) Motor unit (1) Sarcomere (1) (c) (i) extension / relaxation (1) (ii) (Any 1 of the following, 1 mark)

(iii) (Any 2 of the following, 1 mark each)

the hip is a ball and socket joint, the knee is a hinge joint the hip allows movement in numerous planes, the knee in only one plane the hip is stabilised by muscles, tendons and ligaments, the knee is additionally stabilised by the patella the hip joint involves only two bones, the knee joint involves three bones

(iv) (Any 4 of the following, 1 mark each) meniscus patella bursae synovial fluid ligaments muscles / tendons crossing the joint “Tendon” on its own is no good, because it does nothing on its own. Articular cartilage is there to reduce friction. Indirectly, that could be argued to “protect” the joint but there were too many better answers for that answer to be paid. (v) Vertebral column The trend is a gradual move away from a C shaped vertebral column to an S – shaped one. (2) The lumbar vertebrae have changed from being a simple block shape towards being wedge-shaped. (2) Pelvis The trend seen is a gradual change from a narrow, long pelvis to one which is broader and shorter (bowl shaped) and tilted forwards. (2) Question 25 (a) (1 mark for each box in italics)

Production site Hormone produced Target organ/s Effect

Anterior pituitary

LH / luteinising hormone OR

FSH / follicle stimulating hormone

Ovary Stimulates ovulation ORcauses follicles to mature

Alpha cells of pancreas

Glucagon Liver Increases blood glucose

/ glycogenolysis

Hypothalamus Oxytocin Uterus/mammary

glands

Stimulate contractions during childbirth /

release of milk (not PRODUCTION of

milk, that’s prolactin)

The question mentions “function very differently” and “mode of action”. It wants you to talk about HOW they work on cells, not what they do. When you get asked to compare (or, in this case contrast) two things (A and B) then you have to do more than just ramble on about A and then ramble on about B. Write a paragraph in which each sentence highlights a difference between A and B e.g. “A does this thing, but B does that”. Don’t make it harder for the marker to find out that you actually DO know some differences by separating two things in different paragraphs. This happens time and time again in your writing and it is EASY to fix. Choose a topic & compare the two in one paragraph. Then choose another way to compare and write another paragraph.

(b) (Any 3 points compared, 2 marks each) Testosterone (steroid hormone) Adrenalin (water soluble hormone) Travel in blood attached to proteins Travel through blood in solution Effects are longer lasting Effects are short lasting Pass through plasma membrane Do not pass through plasma membrane Attach to receptor proteins in cytoplasm / mitochondria / organelles / nucleus

Attach to receptor protein on cell membrane

No secondary messenger involved Secondary messenger stimulated Move into the nucleus Do not move into the nucleus Bind to specific regions of DNA Do not bind to DNA Alters level of transcription at that DNA site Activates enzymes that generate cell changes

If you have not clearly given the point for both types of hormones, you cannot have the two marks. (c) More ADH (1)

ADH increases reabsorption of water from the filtrate / nephron / distal and collecting tubules into the bloodstream (1) You need to show you understand that the water is reabsorbed from a specific place back into the bloodstream.

Question 26 (a) (i) artificial, active (1) Herd immunity is not a category of immunity types. (ii) babies - immune systems not fully developed yet (1)

- incomplete vaccination means not enough memory cells have been formed (1) - if they haven’t started their vaccination program yet, they won’t have been exposed to this antigen before (1)

adults - number of memory cells against whooping cough has decreased (1) so they are no longer immune to the disease (1) Immunity through vaccination is not about making antibodies. It’s about making memory cells. Why suggest that adults aren’t immune because they haven’t been vaccinated, when the question clearly tells you that they have been vaccinated? (b) B cells recognises the antigen and become activated / sensitised (1)

the activated B cell increases in size and divides (1) to produce plasma cells (1) and memory cells (1) memory cells produce a faster response to this antigen in the future (1) plasma cells produce antibodies to that antigen (1) (and any 1 of the following, 1 mark) which can act by - inhibiting the antigen’s reactions with other cells

- coating bacteria to increase their edibility by phagocytes - causing agglutination to increase phagocytosis ability - dissolve organisms - make substances insoluble and therefore more phagocytic

(c) The development of antibiotic-resistant strains of bacteria is powerful evidence for evolution. Very few of you appear to understand that. Learn it off by heart. You should have used that knowledge to answer this question;

variation in antibiotic resistance exists in the bacterial population (1) That point is sooooooo important! If there’s no variation, then there’s no chance of antibiotic resistance developing.

stopping antibiotics too soon / not taking the whole course allows some bacteria to survive (1) These bacteria will then pass on their “resistant” genes to the next generation (1) and so over

many generations, the proportion of resistant bacteria in the population will increase (1) to the point where they’re all resistant (1)

The over-prescription of antibiotics increases bacterial exposure to antibiotics and can also

contribute to the above process (1) Many of you seem to think that “your body” becomes resistant to antibiotics.

Untrue. Also, many people wrote things like “the surviving bacteria stay in your body and become resistant”. This tells me nothing at all. Use your knowledge of natural selection to tackle a question like this in your WACE. Remember it’s artificial selection though. The antibiotic is acting as the selective agent. Question 27 (a) (i) 4 (1) (ii) stratigraphy / superposition (1) Come on guys, stratigraphy is not that hard to spell! (iii) This question is asking you to explain why fossil Y is ABSENT from another location. Many of you wanted to tell me that movements in the earth’s crust “flipped layers” or something like that. This type of geological event is incredibly unlikely! And also does not even go close to explaining why one species should be missing from a particular location. There were other far-fetched ideas, such as naughty hominins digging up the fossils and moving them….lol (sorry) Here are some PLAUSIBLE reasons why fossil Y was not found in this other sample; (Any 2 of the following, 1 mark each)

Organism Y was not present in that area (i.e. it didn’t live there!) Conditions were too acidic for fossilisation to take place Conditions were not sedimentary so fossilisation did not take place Organism Y was not buried rapidly enough

(b) A TREND is a gradual change or pattern . The question is asking you to describe the major trends. That does not mean please ramble on about Homo habilis did with his tools, or what Neanderthals did with their tools etc. The trends are (any 4 of the following, 1 mark each)

The tools began as very simple broken rocks and progressed to more complex tools. (You have to SAY that; we are not going to infer that you know that, via the other stuff you wrote)

tools made of rock becoming tools made of bone / antler (no bone until neandertals!)

there was a gradual increase in the number of pieces of chipped off the stone (to get a better edge)

one side / edge developed through to both edges / many sides worked no hafting (joining of a sharp rock to a long stick, using twine and natural resins) to

hafting / attaching handles one general purpose tool used for many tasks through to specific tools for specific

tasks (c) (i) time taken for 50% / half the sample to undergo radioactive decay (1) “Time taken for it to be halved” isn’t good enough – doesn’t show that you know what’s going on. 5730 years (1) (ii) (Any 2 of the following, 1 mark each)

can only date samples that are organic in origin / derived from something that was alive

NB – “carbon-containing” describes everything that is organic + everything that isn’t, like marble or diamond, and these substances cannot be carbon dated.

can only date samples up to 70,000 years can only date samples of 3 grams of more sample tested is destroyed in the process

Question 28 (a) any condition whose phenotype is due to the combination of a number of genes (1) skin colour / hair colour / eye colour / height / IQ / spina bifida / cleft lip (1) (b) (i) a genetic condition that has more than two alternatives / alleles / outcomes for the

gene (1) Not “two genes”. That’s polygenic inheritance. Your blood group, for

example, is determined by one gene, but there are 3 different alleles that exist (IA, IB and i) which is what makes it a multi-allelic form of inheritance. We have multiple alleles for the one gene here.

(ii) 3 (the ways you can be homozygous are IAIA, IBIB and ii) (iii) Jill is adopted (1) You need to show that you understand how the parents’ genotypes make it impossible for them to produce a type O child e.g.

For her blood type, she must inherit an i (IO) allele from both parents. Her mother must be IAIB if she is blood type AB, so she does not possess an i allele to pass on (1)

The “O” allele is written either I or IO, not Ii or Ii. Don’t say “blood type O is recessive”. It is the O allele which is recessive.

(c) Heterozygotes only suffer a mild version of the disease / do not die young (1) You all missed that key point. In order to suffer full-on sickle-cell anaemia, you must inherit the disease allele from both your parents (i.e. be homozygous).

Heterozygotes receive protection from malaria that could kill those homozygous for the sickle cell gene (1) This applies especially in malaria-ridden countries, but even in the USA, it would give these people a slight survival advantage.

Section Three: Extended Answers (60 marks) 29. (a) 10 marks from: stimulus – increased core body temperature (1) receptor – thermoreceptors (1) in the hypothalamus (1) modulator – hypothalamus (1) sends nerve impulses out to…(1) effectors – sweat glands (1)

smooth muscle of arterioles (1) responses – increased sweating (1) heat removed via evaporation (1)

vasodilation of arterioles in the skin (1) heat removed via radiation (1) feedback – reduced core body temperature (1) (b) (12 marks) (i) 4 marks any 2 of the 3 marks for each type of gene: Regulator genes (1) – pieces of DNA that switch other genes on or off (1) that act by regulating the rate of transcription of a specific gene (1) Promoter genes (1) – allow transcription of a gene to take place (1) acts as the binding site for RNA polymerase (1) (ii) 8 marks Transcription (Any 4 of the following, 1 mark each) DNA unwinds due to RNA polymerase (1) single strand of mRNA is formed (1) by matching to the template strand of DNA (1) following the base pairing rule A-U and C-G (1) mRNA moves out of the nucleus to a ribosome (1) Translation (Any 4 of the following, 1 mark each) mRNA moves through the ribosome one codon at a time (1) molecules of tRNA bring up the particular amino acid determined by the codon (1) anticodon on the tRNA matches the codon on the mRNA (1) ATP is broken down to join two amino acids together (1) a protein chain is formed by numerous amino acids joining together (1)

(c) (8 marks) (i) (5 marks) Causes (2 x 1 mark) – amyloid plaques / neurofibrillary tangles / genetic Symptoms (2 x 1 mark) – loss of short term memory / word substitution / inability to solve problems / inability to think logically / withdrawal from usual interests / get lost more frequently / rapid mood swings / poor coordination / confusion / sleep disturbances / incontinence / difficulty swallowing / loss of verbal skills / Treatment – (1 x 1 mark) no cure available / only able to treat the symptoms / cholinesterase inhibitors / glutamate antagonists / medication to reduce depression / medication to reduce anxiety / remain physically active / increase brain training activities (ii) (3 marks) Devalues human life Mechanism of health care cost containment Slippery slope effect that can expand to include other groups Goes against Hippocratic oath of medical fraternity Mental state of patient with Alzheimers to give permission can’t be assessed easily Cure might be found in the future 30. (a) (8 marks) (Any 3 comparisons, 2 marks each AND a specific example compared, 1 mark each) Nervous system Endocrine system Fast acting Slower action Acts for a short duration Acts for longer periods of time Highly specific Less specific Based on electrochemical activity Based on hormones Example: reflex arc acts quickly to prevent damage

Example: growth hormone acts over a long period of time and targets many cell types

(b) (13 marks) The thyroid gland (1) Feedback model (Either stimulus pathway is acceptable for 9 marks, 1 mark each) Stimulus – low metabolic rate / low core body temperature Receptor – hypothalamus/thermoreceptors in hypothalamus Modulator – hypothalamus Releases more TSHrf Which causes the anterior pituitary to release TSH So that the thyroid produces more thyroxine Effector – body cells Response – increase rate of cellular respiration Feedback – increased metabolic rate / increased core body temperature OR

Stimulus – high metabolic rate / high core body temperature Receptor – hypothalamus/thermoreceptors in hypothalamus Modulator – hypothalamus Releases less TSHrf Which causes the anterior pituitary to release less TSH So that the thyroid produces less thyroxine Effector – body cells Response – reduce rate of cellular respiration Feedback – reduced metabolic rate / decreased core body temperature Changes to the model (Any 3 of the following, 1 mark each) Lack of iodine results in less thyroxine being produced So rate of cellular respiration reduces And food consumed is stored rather than being used in cellular activities (c) (9 marks) Named example, must indicate removal from harm / damage (1) (Any 8 of the following, 1 mark each) Stimulus such as pain / temperature / pressure is detected by a receptor Which causes a nerve impulse to travel up the sensory neuron To the cell body in the dorsal root ganglion Then on to synapse with a connector / association neuron in the grey matter of the spinal cord Which synapses with a motor neuron also in the grey matter of the spinal cord The nerve impulse travels down the axon of the motor neuron To the effectors which are the skeletal muscles That contract and remove the body part from the stimulus At the same time the connector neuron sends a nerve impulse to the brain So that awareness / sensation is achieved after the action to remove the part has occurred

31. (a) (10 marks) (Any 10 of the following, 1 mark each) Variation in allele frequency would have existed in the original Scandinavian and Celt populations (1) Due to sexual reproduction / meiosis / fertilisation / mutation / sexual selection / random mating (any 2, 1 mark each) Individuals who migrated to Iceland won’t contain all the alleles of the original gene pool (1) Due to the small numbers who migrated there, the founder effect may have occurred (1) Whilst there, the population was isolated from other groups by geographical / ocean barriers (1) Random genetic drift of the Iceland population may occur (1) And result in random non-directional variation in allele frequency in that population (1) Mutations / inheritable random changes in DNA may also have occurred in that population (1) Over time, natural selection would have resulted in some characteristics becoming more common (1) due to the more favourable alleles being passed on / less favourable alleles dying out (1) (b) (10 marks) Comparative DNA All organisms have the same DNA code which suggests they are all related (1) The less the sequence of DNA varies, the more closely related / later the common ancestor (1) Comparative anatomy Compares the structural similarity between organisms to determine their degree of similarity (1) The closer the similarity, the more closely related / later the common ancestor (1) Homologous structures – high degree of structural similarity but perform different functions (1) Vestigial structures – believed to have been functional in our ancestors but now have no obvious function (1) Comparative embryology Compares the early stages of development of different organisms / vertebrate groups (1) The closer the similarity, the more recent the common ancestor (1) Comparative proteins The sequence of amino acids that determine a particular protein / eg: haemoglobin / eg: cytochrome C are determined for different species (1) The more similar the amino acid sequence the more closely related / more recent the common ancestor (1)

(c) (10 marks) (Any 5 descriptions with their matching trend identified, 1 mark each) Description (Any 5, 5 marks) Primate trend (Any 5, 5 mark) Size of the cerebral cortex Outer covering of the cerebrum

involved with memory and reasoning

Increased cerebral cortex due to more convolutions / greater surface area

Olfactory /optical shift Reduction in size of nose and eyes more forward facing Colour vision

Greater reliance on stereoscopic vision / ability to judge depth rather than smell More species with colour vision

Gestation time and parental care

Length of time of pregnancy and time spent looking after offspring after birth Number of offspring born at one time

Greater period of time of gestation and greater degree of parental care Less offspring born at a time

Mobility of digits Presence of an opposable thumb / ability to touch thumb to each finger Presence of nails

Greater degree of opposability More nails rather than claws / move away from presence of a toileting claw

Teeth shape and dental arrangements

Teeth shape vary due to diet / grooming behaviour Type and number of each type of tooth in each jaw

Teeth becoming more similar in size and shape to each other Less teeth in the jaw Addition of fourth cusp on upper molars / Y5 pattern on lower molars Less premolars

Marking guide key: Use the following to identify the information contained in the marking guide.   

Red  Blue Purple 

Original marks allocation  Additions to the marks allocation 

Teacher general comments 

  General comments:  * Your answers SHOULD fit in the booklet.  Spare paper should be used for planning and organising your thoughts to help you write a concise and clear response … that fits in the booklet  * Do NOT write out the question / reword the question – major waste of time  * Think about how to best present your answer – table, flowchart, diagram. The majority of you are writing ‘essays’ that: 

a) make little sense – they do not flow and are very disjointed      b) are writing way too much, and the majority of the ‘extra’ information is not necessary  c) are a mess and extremely difficult to read. WACE markers will not take the amount of time I did to mark your work. If they cannot read it, they will not mark it.  

 * Do not draw a table, flowchart, diagram AND write an essay answer – what is the point of writing your answer twice?  Use planning paper, think about what you are doing, then write your good copy. If you do not think you do not have time to plan, why do you have time to write your answer out twice? Follow this rule: Read (the question), Think (about the question), Think (about your answer), Plan (your answer), Write (your answer … once).   * Everyone needs to work on the correct use of appropriate scientific terminology.  You need to know your terms and use them in the right place at the right time.  Writing down every ‘big’ term you have encountered, but in the wrong context and/or using the wrong scientific term in a sentence tells the marker you have limited knowledge of what you are talking about. It is the terminology (in context) that is often the focus of many questions so you must know your terms.   * When checking your work using the marking guide on the following pages, make sure you clearly read any of the extra comments on the marking guide (and on your work) so that you understand what was expected and where you lost marks/can improve your responses.            

Question 29.  (30 marks)  

  (a)   In hot conditions, athletes must be able to control their body temperature to avoid major 

disruptions to cellular function.  Describe the physiological mechanisms that act to maintain the core body temperature of an athlete at such times.     (10 marks) 

 Stimulus    Increased core body temperature (1)  Receptor    Thermoreceptors (1) in the hypothalamus (1)     Not the skin as question specifically asks about ‘core body temperature’  Modulator    Hypothalamus (1) sends nerve impulses out to…(1)     via sympathetic nerves  Effectors    Sweat glands (1) 

Smooth muscle of arterioles (1) Blood vessels is not accurate  

Responses   Increased sweating (1) heat removed via evaporation (1) Vasodilation of arterioles in the skin (1) heat removed via radiation/convection (1)  

Feedback    Reduced core body temperature (1)   * Question asks for physiological NOT behavioural * Mechanisms refers to the feedback loops * Most people explained heat loss processes eg. how we sweat; vasodilation/constriction – but not in context of physiological mechanism   

Completed by 25/49 students 

Total average: 45% 

Part a: 47% Part b: 54% Part c: 34%

 (b)   Gene expression can be defined as the process of converting the information stored in DNA 

into a protein.                 (12 marks)  

(i) Name and describe two types of genes the cell uses to control gene expression, and  (4 marks) ‐ any 2 of the 3 marks for both types of gene:  Regulator genes (1):  Pieces of DNA that switch other genes on or off (1) Genes that switch other genes on/off Act by regulating the rate of transcription of a specific gene (1) Form an inhibitor gene = stops transcription  Promoter genes (1) Allow transcription of a gene to take place (1) Signals the beginning point of transcription Acts as the binding site for RNA polymerase (1)  * Structural genes do NOT control gene expression – they are the genes being “expressed”     

(ii) Outline the two stages of gene expression that result in the formation of a     particular protein.               

(8 marks)  Transcription (Any 4 of the following, 1 mark each): DNA unwinds/unzips due to RNA polymerase (1) ‐ ½ if no RNA polymerase single strand of mRNA is formed (1) by matching to the template strand of DNA (1) following the complimentary base pairing rule A‐U and C‐G (1) Some indication of this ‘rule’ shown mRNA moves out of the nucleus to a ribosome (1) Moves out of nucleus through nuclear pores into cytoplasm  Translation (Any 4 of the following, 1 mark each): mRNA moves through the ribosome one codon at a time (1) Start codon AUG initiates translation molecules of tRNA bring the particular amino acid determined by the codon (1) anticodon on the tRNA matches the codon on the mRNA (1) ATP (energy) is broken down to join two amino acids together (1) Bond between amino acids is called a peptide bond a protein chain is formed by numerous amino acids joining together (1)   * Reasonably well answered * Attention to detail and use of scientific terms needs refining        

(c)   Ageing is associated with a variety of degenerative conditions that reduce normal function. Alzheimer’s is one such condition.  

 (i) Describe the possible causes, symptoms and treatments for this condition. 

(5 marks) Causes (2 x 1 mark):  amyloid plaques / neurofibrillary tangles / genetic / degeneration of nerve fibres in the cerebrum  * NOT old age * NOT ‘what happens’ eg. messages cannot be sent between nerve fibres   Symptoms (2 x 1 mark):  loss of short term memory / word substitution / inability to solve problems / inability to think logically / withdrawal from usual interests / get lost more frequently / rapid mood swings / poor coordination / confusion / sleep disturbances / incontinence / difficulty swallowing / loss of verbal skills /    Treatment (1 x 1 mark):   no cure available / only able to treat the symptoms / cholinesterase inhibitors (Reminyl) / glutamate antagonists / medication to reduce depression / medication to reduce anxiety / remain physically active / increase brain training activities  * NOT “can be managed” – too broad * NOT “medication” – too broad 

    

(ii) Some people may consider the effects of Alzheimer’s as a reason to support voluntary euthanasia.  Give three statements that argue against this idea.    

                    (3 marks) Devalues human life / Religious reasons Mechanism of health care cost containment Slippery slope effect that can expand to include other groups Goes against Hippocratic oath of medical fraternity Mental state of patient with Alzheimers to give permission can’t be assessed easily Cure might be found in the future  * NOT any of the following:   More pain if it fails    Suicide is illegal   Not in physical pain so should be ok to live   Not in any pain so should be ok to live * “Murder” is not a good term to use 

Question 30.  (30 marks)  

  (a)   The two mechanisms of control the body has available to it are the nervous system and the 

endocrine system.  In several ways, these systems differ in the way they act. Contrast these two systems and, using specific examples, explain why it would be more advantageous to the body to use each system in certain circumstances.      (8 marks) 

(Any 3 comparisons, 2 marks each AND a specific example compared, 1 mark each)  

Nervous system  Endocrine system 

Fast acting / Fast response  Slower action / Slow response 

Acts for a short duration / Stops when stimulus stops 

Acts for longer periods of time / (Can) continues even after stimulus has stoped 

Highly specific / Local  Less specific / Widespread 

Based on electrochemical activity / Electrical impulse + neurotransmitters  Need to acknowledge both electrical and chemical aspect 

Based on hormones / Chemical 

Transported along neurons (nerve fibres)  Transported in the blood 

Example:  Reflex arc acts quickly to prevent damage / Movement of specific body parts at a specific time Initiation of the fight or flight response – dangerous situations (NOT endocrine as it is started by nervous)  Must address why the system is ‘better’ for the example, not just say the example ie. quick/ immediate 

Example:  Growth hormone acts over a long period of time and targets many cell types / FSH acts on the ovary to stimulate development of ovarian follicle over a few days / Thyroxine during winter   Must address why the system is ‘better’ for the example, not just say the example ie. slow/long lasting 

   * Must CONTRAST the two systems. This means if you say the nervous system is fast acting, then you MUST say the endocrine system is slow acting. If you do not contrast you get zero for that point. * Use a TABLE. If a question asks to contrast/compare always use a table. 

Completed by 35/49 students  Total average: 57%  Part a: 64% Part b: 52% Part c: 54%

 (b)   Some people who are overweight may blame their “glands” for the extra weight they carry, 

or claim they may have a “slow metabolism”. Name the specific gland they are referring to, describe its normal functioning using a feedback model and highlight how changes to this model may indeed lead to weight gain.           (13 marks) 

 Gland: Thyroid gland (1)  Feedback model (9 marks) ‐ Either stimulus pathway is acceptable:  Stimulus   Low metabolic rate / low core body temperature / Low thyroxine levels Receptor   Hypothalamus / thermoreceptors in hypothalamus Modulator   Hypothalamus OK to state  “hypothalamus detects the change AND secretes TSHRF” 

for both marks – just need to clearly indicate that the hypothalamus is the receptor and sends a message (an arrow does not show this clearly) Releases more TSHrf Which causes the anterior pituitary to release TSH Minus ½ if not anterior So that the thyroid produces more thyroxine 

Effector   Body cells Response  Increase rate of cellular respiration / increased metabolic rate / Breakdown of glucose 

in cells  Feedback  Increased metabolic rate / increased core body temperature / Indicate negative 

feedback  OR Zero students talked about High metabolic rate   Stimulus   High metabolic rate / high core body temperature Receptor   Hypothalamus/thermoreceptors in hypothalamus Modulator   Hypothalamus 

Releases less TSHrf  Which causes the anterior pituitary to release less TSH So that the thyroid produces less thyroxine 

Effector   Body cells Response  Reduce rate of cellular respiration Feedback   Reduced metabolic rate / decreased core body temperature   Changes to the model (Any 3 of the following, 1 mark each):  Lack of iodine results in less thyroxine being produced / Thyroid not secreting enough thyroxine MUST state name of gland and hormone here So rate of cellular respiration reduces / Glucose not being broken down to release energy And food consumed is stored rather than being used in cellular activities Food IS broken down by digestive system, but the nutrients are not being used by cells so they are stored instead    * Labelling the stimulus, receptor, modulator etc is not important. The steps are what are important. * Flowchart is the best way to present the main part of this question. 

 (c)   One particular mechanism of control does not actually involve the brain at all, just the spinal 

cord.  Describe a situation where use of such a mechanism would be advantageous to the body, and identify the structures and processes involved in such a procedure.  

                      (9 marks) Named example, must indicate removal from harm / damage (1)   (Any 8 of the following, 1 mark each)   Stimulus such as pain / temperature / pressure is detected by a receptor MUST have stimulus and receptor indicated – cannot skip straight from “touching nail” to sensory neuron carrying impulse Which causes a nerve impulse to travel up the sensory neuron To the cell body in the dorsal root ganglion Then on to synapse with a connector / association neuron / interneuron in the grey matter of the spinal cord Which synapses with a motor neuron also in the grey matter of the spinal cord The nerve impulse travels down the axon of the motor neuron This point must be clearly different to the one above to gain both marks To the effectors which are the skeletal muscles That contract and remove the body part from the stimulus  At the same time the connector neuron sends a sensory nerve impulse to the brain So that awareness / sensation is achieved after the action to remove the part has occurred   * Clearly labelled diagram is a great way to present your answer * No arrows on your diagram does not show the “process” as the question asks  

 Question 31.  (30 marks)  

  (a)   Genetic testing of natives of Iceland have indicated major differences in allele frequency to 

Scandinavians and the Celts of Ireland and Scotland from where they are believed to have originated.  Describe the ways in which changes in allele frequency can come about in populations such as those found in Iceland.          (10 marks) 

  (Any 10 of the following, 1 mark each)  Variation in allele frequency would have existed in the original Scandinavian and Celt populations (1) One student made this point Due to sexual reproduction / meiosis / fertilisation / mutation / sexual selection / random mating (any 2, 1 mark each) Zero students made this point Individuals who migrated to Iceland won’t contain all the alleles of the original gene pool  / allele frequency of the ‘new’ population is not necessarily representative of the ‘original’ population (1) * Not different between the “two populations” – must be clear Due to the small numbers who migrated there, the founder effect may have occurred (1) Whilst there, the population was isolated from other groups by geographical / ocean barriers (1)   * Must state HOW isolated  * Iceland is an island so the geographical barrier is the ocean – however, not penalised if you listed other geographical barriers * Not socio‐cultural barriers Random genetic drift of the Iceland population may occur (1) Need to say if it occurred or not – do not just define it Result in random non‐directional variation in allele frequency in that population (1) Random = ½  Mutations / inheritable random changes in DNA may also have occurred in that population (1) Over time, natural selection would have resulted in some characteristics becoming more common (1)  due to the more favourable alleles being passed on / less favourable alleles dying out (1) Need a statement about passing on traits Migration brings new alleles into a population [1] CANNOT have both migration and isolation  * Need to state the mechanism eg “Natural Selection” – marks given this time around  * Question was VERY poorly answered. * Many students wrote down everything they knew about the mechanisms of evolution but did not actually answer the question well. * Terminology needs work.  * Must clearly articulate your points with correct terms and link sentences together – build on points, do not just randomly write down everything that jumps into your head 

Completed by 36/49 students  Total average: 40%  Part a: 32% Part b: 33% Part c: 56%

 (b)   Recently, biotechnology companies have been focussing on differences in DNA to determine 

whether speciation has in fact taken place.  Describe how various comparative studies, including the study of DNA, can be used to support the theory of evolution. 

                      (10 marks) Comparative DNA (max 2 marks) All organisms have the same DNA code (A, T, C, G) which suggests they are all related (1) The less the sequence of DNA (nucleotides) varies, the more closely related / later the common ancestor (1)  * Junk DNA /ERV fits here also  Mitochondrial DNA (max 2 marks) mtDNA only comes from the mother / female ancestor [1] More mutations in common, the more closely related they are / later the common maternal ancestor [1]  Comparative anatomy Zero students mentioned either of the two points below Compares the structural similarity between organisms to determine their degree of similarity (1) The closer the similarity, the more closely related / later the common ancestor (1)  Homologous structures (max 1 mark) High degree of structural similarity but perform different functions (1) Minus ½ mark if do not mention different function  Vestigial structures (max 2 marks) Organs that no longer have a function [1] Believed to have been functional in our ancestors but now have no obvious function (1)  Comparative embryology (max 2 marks) Compares the early stages of development of different organisms (not foetuses) / vertebrate groups (1) The closer the similarity, the more recent the common ancestor (1) / More similarities = more closely related / Similarities are present = must be related, have common ancestor  Comparative proteins (max 2 marks) The sequence of amino acids that determine a particular protein / eg: haemoglobin / eg: cytochrome C are determined for different species (1) The more similar the amino acid sequence the more closely related / more recent the common ancestor (1)  * Must state what the ‘study’ tells us about relationship between species ie. More similarities = more closely related  * Do NOT gloss over this ie. allows us to see how closely related two species are 

 (c)   The primate order is a diverse group, including chimpanzees, lemurs, gibbons, baboons and 

humans.  All of these organisms have features in common, though to different degrees. Describe the key features that primates share, identifying the evolutionary trends that the group as a whole follow.              (10 marks) 

 You needed to identify THE feature and then describe the evolutionary trend of THAT feature – most people did one of the other OR listed various features and trends that did not match  (Any 5 descriptions with their matching trend identified, 1 mark each)  

  Description (Any 5, 5 marks)Describe the feature clearly (this is what the question asks for) do not just state it 

Primate trend (Any 5, 5 mark) – what happens to the features as you move ‘up’ the evolutionary ladder 

Size of the cerebral cortex 

Outer covering of the cerebrum involved with memory and reasoning / thinking / planning OR Increase in cranium size (due to brain) 

Increased cerebral cortex due to more convolutions / greater surface area / larger brain 

Olfactory / optical shift 

Reduction in size of nose / eyes more forward facing / reduced sense of smell – increased sense of sight   Colour vision  

Greater reliance on stereoscopic vision / ability to judge depth rather than smell / Smell brain area has decrease ‐ Sight brain area has increased  More species with colour vision / Lose night vision 

Gestation time and parental care 

Length of time of pregnancy and time spent looking after offspring after birth   Number of offspring born at one time 

Greater period of time of gestation and greater degree of parental care    Less offspring born at a time 

Mobility of digits 

Presence of an opposable thumb / ability to touch thumb to each finger  Presence of nails   Prehensile digits / Pentadactyl hand / Friction ridges 

Greater degree of opposability    More nails rather than claws / move away from presence of a toileting claw  No associated trend – so not a good example 

Teeth shape and dental arrangements 

Teeth shape vary due to diet / grooming behaviour   Type and number of each type of tooth in each jaw   

Teeth becoming more similar in size and shape to each other / smaller canines / no diastema  Less teeth in the jaw / Less premolars  Addition of fourth cusp on upper molars / Y5 pattern on lower molars 

* MUST be key features of the primate group – NOT just humans – NOT bipedal (or features for this); parabolic dental arcade; prognathic jaw * Tail is NOT a key feature of the primate group * For future reference ‐ BRACHIATION is NOT the only mode of locomotion – not all primates brachiate, in fact very few do!