<p>Higher Biology Cell Biology</p><p>Core Essay ‘Give an account of how the following cell structures are related to function: i) xylem ii) red blood cell </p><p>Mark Xylem Consists of xylem and tracheid vessels 1 Vessel consists of hollow tubes formed by end walls breaking down 1 Tube consists of very fine bore 1 So water adheres to vessel walls (capillarity) which helps upward transport 1 Walls strengthened by lignin 1 Lignin as rings or spirals which allow contraction/expansion 1 Walls contain pits for lateral transport of water 1 Tracheids consist of long narrow cells 1 Maximum 5 Red Blood Cells Small in size 1 So can fit through narrow capillaries 1 No nucleus as space saving measure 1 Bi-concave shape allows for a large surface area 1 Contains haemoglobin 1 Which combines with oxygen to form oxy-haemoglobin 1 Maximum 5 Maximum Total 10 Higher Biology Cell Biology</p><p>Core Essay ‘Give an account of respiration under the following headings: i) glycolysis ii) the Kreb’s (Citric Acid) cycle </p><p>Mark Glycolysis Occurs in the cytoplasm 1 Glucose broken down to/converted to/reduced to/oxidised to/ (two molecules) of pyruvic acid 1 C6 compound broken down to 2 X C3 1 Step by step breakdown by enzymes OR series of enzyme controlled reactions 1 Net gain/production of ATP/explanation of net gain of ATP 1 NAD accepts hydrogen/NADH produced and transferred to cytochrome system/cristae/electron transfer system (NOT stage 3) 1 Oxygen not required/anaerobic/occurs in aerobic and anaerobic conditions. 1 Maximum 5 Kreb’s Cycle Occurs in the matrix of the mitochondrion 1 Requires oxygen OR aerobic phase (DO NOT AWARD IF ALREADY AWARDED LAST MARK IN GLYCOLYSIS SECTION) 1 C2 acetyl group produced from pyruvic acid 1 Acetyl group joins with CoA 1 Acetyl CoA reacts/combines with a C4 compound to form C6 compound/citric acid 1 Cyclical series of reactions back to C4 compound 1 Carbon dioxide produced/given off/released 1 NAD accepts hydrogen/NADH produced and transferred to cytochrome system (DO NOT AWARD IF ALREADY AWARDED 1 IN GLYCOLYSIS SECTION) Kreb’s cycle needs/requires/is controlled by enzymes (DO NOT AWARD IF ALREADY AWARDED IN GLYCOLYSIS SECTION) 1 Maximum 5 Maximum Total 10 Higher Biology Cell Biology</p><p>Core Essay ‘Give an account of the absorption of light energy by photosynthetic pigments and the light dependent stage of photosynthesis.’ </p><p>Note: The marks may be awarded for information in a diagram. The relevant piece of information must be clearly shown in a carefully drawn and labelled diagram.</p><p>Mark Absorption of Light Energy Chlorophyll a and b, xanthophyll and carotene named 1 Chlorophyll absorbs red and blue light/colours/wavelengths 1 Xanthophyll AND carotene/accessory pigments absorb light from other regions of the spectrum/of other colours/of other wavelengths 1 Light absorption occurs over a wide range of spectrum/wider range of colours/more wavelengths 1 Energy absorbed by xanthophyll/carotene/accessory pigments is passed on to chlorophyll 1 Occurs in the grana (AWARD MARK ONCE ONLY) 1 Maximum 4 Light-Dependent Stage Occurs in the grana (AWARD MARK ONCE ONLY) 1 Light energy converted to chemical energy 1 Regenerate ATP from ADP and Pi 1 Split water OR energy used in photolysis of water 1 Hydrogen combines with NADP OR NADPH2/NADPH/reduced NADP formed 1 Oxygen is a by-product OR oxygen diffuses/passes/goes out of cells/leaf 1 NADPH2 and ATP diffuse/passes/goes to stroma/are used in Calvin cycle 1 Maximum 4 Coherence Coherence - The writing must be in sub-headings or divided into paragraphs There should be sub-heading/paragraph for each of the ‘bolded’ headings 1 above. - Related information should be grouped together. Information as listed under bold headings above should be grouped together - There must be a minimum of 5 points with at least 1 point given for each group. All must apply correctly to gain the coherence mark. Relevance - Must not give details of carbon fixation stage - Must give a minimum of 5 relevant points with at least 2 points from each of 1 the two headings. Both must apply correctly to gain the relevance mark. Maximum Total 10 Higher Biology Cell Biology</p><p>Core Essay ‘Give an account of the structure of RNA and its role in protein synthesis’ </p><p>Note: The marks may be awarded for information in a diagram. The relevant piece of information must be clearly shown in a carefully drawn and labelled diagram.</p><p>Mark Structure of RNA Single stranded 1 Made of nucleotides 1 Has a base, ribose (sugar) and a phosphate 1 Bases are guanine, cytosine, adenine, and uracil (NOT letters A, U, G, C) 1 Maximum 3 Role in Protein Synthesis mRNA carries information/code (for protein) from nucleus/from DNA 1 mRNA attaches to ribosome 1 Three bases on mRNA is a codon 1 tRNA transport amino acid to ribosome 1 tRNA transports specific amino acids 1 Three bases on tRNA is an anticodon 1 Codons match/pair with their anticodon 1 Joins/adds correct amino acid onto growing protein/polypeptide 1 Sequence of bases/codons on mRNA gives sequence of amino acids Maximum 5 Coherence Coherence - The writing must be in sub-headings or divided into paragraphs There should be sub-heading/paragraph for each of the ‘bolded’ 1 headings above. - Related information should be grouped together. Information as listed under bold headings above should be grouped together - There must be a minimum of 5 points with at least 2 points given for Structure section and at least 3 points for Role section </p><p>All must apply correctly to gain the coherence mark. Relevance - Must not give details of DNA structure or replication, protein transport or secretion 1 - Must be a minimum of 5 points with at least 2 points given for Structure section and at least 3 points for Role section </p><p>Both must apply correctly to gain the relevance mark. Maximum Total 10 Higher Biology Cell Biology</p><p>Core Essay ‘Give an account of cellular defence mechanisms in animals under the following headings: i) phagocytosis ii) antibody production and tissue rejection </p><p>Mark Phagocytosis Carried out by phagocytes/monocytes/macrophages. 1 (Penalise once for lymphocytes) Non-specific nature of process 1 Bacteria/foreign material/virus (NOT antigen) engulfed/enveloped OR description/diagram (NOT trapped) 1 Into a vacuole/vesicle (NOT pocket/pouch) 1 Lysosomes fuse/join to vacuole AND add enzymes to vacuole 1 Bacteria/foreign material/virus (NOT antigen) digested/destroyed/broken down by enzymes 1 IF ANTIGEN ALREADY PENALISED ABOVE DO NOT PENALISE AGAIN IF ENZYMES MENTIONED IN PREVIOUS MARK THEN NOT REQUIRED HERE. Maximum 4 Antibody Production Antibodies are proteins 1 They are produced by lymphocytes 1 Production stimulated by/in response to foreign/non-self antigens/proteins 1 Antibodies are specific/match the shape of the antigens/lock and key diagram 1 Antibody renders harmless/destroys/attacks/combats/neutralises/combines with 1 antigen (NOT kill antigen) Maximum 4 Tissue Rejection Transplanted tissues are antigenic/have foreign antigens/proteins are recognised as foreign/non-self 1 Will be rejected/attacked by patient’s antibodies OR antibodies made against transplant tissue (NOT kills transplant) 1 Risk of rejection is reduced by suppressors/immunosuppressors/drugs whish suppress/inhibit 1 immune system OR repressors which inhibit/suppress the immune system Maximum 2 Maximum Total 10 Higher Biology Genetics & Adaptation</p><p>Core Essay ‘Give an account of meiosis under the following headings: i) first meiotic division ii) second meiotic division iii) importance of meiosis</p><p>Note: Marks may be awarded for carefully drawn and labelled diagrams. Mark First Meiotic Division Start with a gamete mother cell/diploid cell 1 Each chromosome made up of two chromatids 1 Homologous chromosomes pair up (NOT homologous pairs join up) 1 Crossing over may occur 1 At chiasmata 1 Nuclear membrane disappears OR spindle forms 1 Independent assortment occurs OR (homologous) chromosomes line up on equator 1 Homologous chromosomes/pairs are pulled apart 1 New nuclear membrane formed OR division of cytoplasm 1 Maximum 6 Second Meiotic Division Chromosomes line up on the equator and chromatids pulled apart 1 New nuclear membrane formed OR division of cytoplasm 1 Mark awarded here OR in First Meiotic Division section Four cells produced 1 Maximum 2 Importance of Meiosis Produces haploid gametes 1 Crossing over gives recombination/variation/diversity 1 Meiosis/it gives variation/diversity 1 (Only award mark if neither of previous two marks awarded) Maximum 2 Maximum Total 10 Higher Biology Genetics & Adaptation</p><p>Core Essay ‘Give an account of gene mutation under the following headings: i) occurrence of mutant alleles and the effect of mutagenic agents ii)types of gene mutation and how they alter amino acid sequences</p><p>Mark Occurrence of mutant alleles and the effect of mutagenic agents Random/spontaneous/by chance 1 Low frequency/rare 1 One type of mutagenic agent, eg chemicals or named chemical such as mustard gas 1 Second type of mutagenic agent, eg radiation or named type – X-ray, gamma rays, UV light 1 Mutagenic agents cause or induce mutations/increase mutation rate/increase chance of mutation occurring/increase frequency of mutation 1 Maximum 3 Types of gene mutation and how they alter amino acid sequences Gene mutation is a change in bases/base types/base sequence/base order 1 (This must be stated and not shown in diagram. Also nucleotide equivalent to base) Substitution: base/bases replaced with another/others 1 Inversion: oreder of bases reversed/bases turned round 1 Previous two points may be shown as suitably labelled diagrams with only bases A, T, G and C used Substitution/inversion may change base order of codon 1 Substitution/inversion may change only one/two amino acid(s) 1 Deletion: base/bases deleted from chromosome/removed/taken out 1 Previous point may be shown as suitably labelled diagrams with only bases A, T, G and C used Insertion: base/bases inserted into chromosome/added/put in 1 Deletion/insertion changes codons/triplets after the mutation 1 Deletion/insertion changes all amino acids after the mutation 1 Protein made (following substitution or inversion) will work/be unaffected OR 1 protein made (after deletion or insertion) will not function/will not work/is the wrong protein/enzyme. Maximum 7 Maximum Total 10 Higher Biology Genetics & Adaptation</p><p>Core Essay ‘Give an account of evolution of new species under the following headings: i) isolating mechanisms ii)effects of mutations and natural selection</p><p>Note: Marks may be awarded for carefully drawn and correctly labelled diagrams. Mark Isolating Mechanisms A species is a group of interbreeding organisms capable of producing fertile young 1 Common gene pool 1 A species/a population separated into two by an isolating mechanism/barrier 1 Prevents gene exchange/gene flow/interbreeding between populations/groups 1 Two types of isolation given (eg geographical/ecological) 1 Third type of isolation given (eg reproductive) 1 Maximum 4 Effects of Mutation and Natural Selection Mutations occurring in each population/group will be different OR mutation 1 occurs in one group (Mutation) gives variation/different phenotypes/new genes/new alleles/alters gene pool 1 Different environments 1 Selection is different for each population/group 1 Best adapted/best suited survive OR survival of the fittest OR converse 1 (They/best adapted/best suited/fittest) pass on favourable characteristics/genes/alleles to offspring/next generation OR less well adapted/less suited/less fit do not pass their characteristics/genes/alleles to 1 offspring/next generation Many generations/long period of time 1 New species formed when populations/groups can no longer interbreed. 1 Maximum 6 Maximum Total 10 Higher Biology Genetics & Adaptation</p><p>Core Essay ‘Give an account of the problems of osmoregulation in freshwater bony fish and outline their adaptations to overcome these problems’</p><p>Mark Problems Fish (tissues)/body fluids hypertonic to surroundings/description OR converse 1 Water enters through gills and/or mouth by osmosis 1 Potentially leading to bursting of/damage to cells OR dilutes cytoplasm OR increases water content of cells 1 OR excess water must be removed OR water must be removed to keep water 1 balance Salts lost in urine through mouth lining/gills 1 Any 2 from 4 Maximum 2 Adaptations Kidneys have many glomeruli 1 Kidneys have large glomeruli 1 Kidneys have many large glomeruli (Award only if above two marks not given) 1 Filtration rate of kidneys/glomeruli/blood is high 1 Urine produced is dilute 1 Large volume/amount/quantity of urine produced 1 Chloride secretory cells present in gills absorb salts 1 Against the concentration gradient/by active transport/uptake/activity 1 Any 6 from 7 Maximum 6 Coherence - The writing must be in sub-headings or divided into paragraphs There should be sub-heading/paragraph for each of the ‘bolded’ headings above. - Related information should be grouped together. Information as listed 1 under bold headings above should be grouped together - There must be a minimum of 5 points with at least 1 point given for the Problems section and at least 4 points from the Adaptation section. All must apply correctly to gain the coherence mark. Relevance - Must not give details of salt water fish or desert mammals. - There must be a minimum of 5 points with at least 1 point given for the 1 Problems section and at least 4 points from the Adaptation section. Both must apply correctly to gain the relevance mark. Maximum Total 10 Higher Biology Genetics & Adaptation</p><p>Core Essay ‘Give an account of the problems of obtaining food in animals by reference to co-operative hunting, dominance hierarchy and territorial behaviour’</p><p>Mark Co-operative Hunting (Co-operative hunting means) animals/or example hunting in a social group/pack/team OR means working together in hunting/to get food 1 Advantage, eg larger prey/more successful, less energy used/pursuit time per individual, net gain of energy is greater than by foraging alone 1 Another different advantage from list 1 Maximum 2 Dominance Heirarchy 1 Is a rank/pecking order within a social group 1 Consists of dominant/alpha and subordinate individuals. NOT smaller/weaker, larger/stronger/leader 1 In feeding dominant/alpha individuals eat first (followed by subordinate) OR dominant gets bigger share of food OR converse 1 Ensured survival of dominant if food is scarce 1 Subordinate animal may gain more food than by foraging alone. 1 Penalise only once for lack of dominant Maximum 3 Territorial Behaviour Territory is (an area) marked/defended for feeding/hunting 1 Ensures food supply/must contain enough food OR the more food available 1 the smaller the territory OR converse Territorial behaviour reduces competition 1 Energy expended in marking, patrolling, defending 1 Maximum 3 Coherence - The writing must be in sub-headings or divided into paragraphs There should be sub-heading/paragraph for each of the ‘bolded’ headings above. - Related information should be grouped together. Information as listed 1 under bold headings above should be grouped together - There must be a minimum of 3 points from Co-operative Hunting and Dominance Heirarchy and 2 points from Territorial Behaviour All must apply correctly to gain the coherence mark. Relevance - Must not give details of individual foraging, mating behaviour or social defence. 1 - There must be a minimum of 3 points from Co-operative Hunting and Dominance Heirarchy and 2 points from Territorial Behaviour Both must apply correctly to gain the relevance mark. Maximum Total 10</p><p>Higher Biology Control & Regulation Core Essay ‘Give an account of the effect of light on shoot growth and development, and on the timing of flowering in plants and breeding in animals’</p><p>Mark Shoot Growth and Development Plants/shoot show phototropism OR shoots grow towards the light 1 Greater conc. of auxin/IAA on dark side OR less auxin/IAA on light side 1 Greater elongation of cells on dark side OR less elongation of cells on light side 1 Etiolation in absence of light/in the dark 1 Description of etiolation: small leaves; yellow/chlorotic leaves; long internodes/long and thin stems (any TWO for the mark) OR description of appearance of plant in light: large leaves; green leaves; short internodes/short 1 and thick stems (any TWO for the mark) Maximum 3 Timing of Flowering in Plants Plants show photoperiodism OR flowering is affected by the photoperiod 1 Photoperiod is the number of hours of light in a day/in 24 hours Long day plants flower when: The photoperiod reaches/is above a critical level/a certain number of hours 1 OR hours of darkness below a critical level/below a certain number of hours Short day plants flower when: The photoperiod is below a critical level/below a certain number of hours OR 1 hours of darkness above a critical level/above a certain number of hours Maximum 3 Timing of Breeding in Animals Long day breeders/birds/small mammals/named example – breed in spring as photoperiod increases 1 Short day breeders/large mammals/named example – breed in Autumn as photoperiod decreases 1 Young are born when conditions favourable/when food abundant OR young have long period of growth before winter/before unfavourable conditions 1 Maximum 2 Coherence - The writing must be in sub-headings or divided into paragraphs There should be sub-heading/paragraph for each of the ‘bolded’ headings above. - Related information should be grouped together. Information as listed 1 under bold headings above should be grouped together - There must be a minimum of 5 points with at least 1 point given for each group. All must apply correctly to gain the coherence mark. Relevance - Must not give details of any other effects of IAA or any effects of GA - Must give a minimum of 5 relevant points with at least 1 point from each of 1 the three headings. Both must apply correctly to gain the relevance mark. Maximum Total 10 Higher Biology Control & Regulation</p><p>Core Essay ‘Give an account of the effect of the Jacob-Monod hypothesis of lactose metabolism in Escherichia coli and the part played by genes in the condition of phenylketonuria.’</p><p>Mark The Jacob-Monod Hypothesis Operon composed of structural and operator genes 1 Structural gene codes for B-galactosidase 1 To switch structural gene off: Regulator gene produces repressor molecule/protein 1 Repressor molecule combines with operator and so switches structural/B- galactosidase gene off 1 To switch structural gene on: Repressor molecule combines with lactose 1 Repressor-lactose unable to fit into operator gene 1 Operator gene switches on structural/B galactosidase gene and B- galactosidase produced 1 When substrate/lactose used up repressor switches structural/B- galactosidase gene off again 1 Maximum 4 Phenylketonuria Phenylalanine normally broken down by a series of reactions/in a metabolic pathway 1 Phenylketonuria Is caused by a genetic mutation/abnormal gene 1 Normal allele for gene required to make enzyme for reactions is missing. 1 As a result normal/correct enzyme is not produced OR abnormal/incorrect enzyme is produced OR cannot code for normal/correct enzyme. 1 Phenylalanine cannot be metabolised as normal/converted to tyrosine/broken down OR phenylalanine conc. increases OR metabolic pathway is blocked 1 Phenylalanine converted to other compounds/phenylpyruvic acid/toxic 1 substances Maximum 4 Coherence - The writing must be in sub-headings or divided into paragraphs There should be sub-heading/paragraph for each of the ‘bolded’ headings above. - There must be a minimum of 5 points with at least 2 points given for each 1 group. All must apply correctly to gain the coherence mark.</p><p>Relevance - Must not give details of any other example in either section - Must give a minimum of 5 relevant points with at least 2 points from each of 1 the two headings. Both must apply correctly to gain the relevance mark. Maximum Total 10 Higher Biology Control & Regulation</p><p>Core Essay ‘Give an account of the principal of negative feedback with reference to the maintenance of blood sugar’ </p><p>Mark Principal of Negative Feedback Negative feedback maintains constant internal conditions in the 1 body/homeostasis A change from the normal level/set point is detected 1 A corrective mechanism is switched on/activated 1 When conditions return to normal level/set point, corrective mechanism switched off. 1 Maximum 2 Maintenance of Blood Sugar Level Blood sugar/glucose level (BSL) detected by pancreas/Islets of Langerhans 1 If BSL increases (more) insulin is made Insulin increases permeability of cells to glucose OR insulin increases uptake of glucose by cells 1 Liver/muscle cells convert glucose to glycogen OR glucose converted to glycogen and stored in liver/muscle 1 BSL returns to normal/set point* 1 If BSL decreases (more) glucagon is made Glucagon causes conversion of glycogen to glucose 1 Glucose released into the blood 1 BSL returns to normal/setpoint* 1</p><p>* Mark awarded once only Maximum 6 Coherence - The writing must be in sub-headings or divided into paragraphs There should be sub-heading/paragraph for each of the ‘bolded’ headings above. - There must be a minimum of 1 point for Principle of Negative Feedback and 1 at least 4 points for Maintenance of Blood Sugar Levels.</p><p>Both must apply correctly to gain the coherence mark. Relevance - Must not give details of control of water balance or temperature regulation. - Must give a a minimum of 1 point for Principle of Negative Feedback and at 1 least 4 points for Maintenance of Blood Sugar Levels.</p><p>Both must apply correctly to gain the relevance mark. Maximum Total 10 Higher Biology Control & Regulation</p><p>Core Essay ‘Give an account of populations under the following headings: i) the importance of monitoring wild populations ii) the influence of density dependent factors on population changes.</p><p>Note: Marks may be awarded for information in a diagram. The relevant piece of information must be clearly shown in a carefully drawn and labelled diagram</p><p>Mark The Importance of Monitoring Wild Populations Food species plus a strategy for management, eg prevent over-fishing/set quotas 1 Raw material species OR species used in medicine plus strategy for management, eg avoid over-harvesting 1 Pest species plus reason for monitoring, eg control of pest 1 Indicator species plus reason for monitoring, eg to assess levels of pollution 1 Endangered species plus reason for monitoring, eg to prevent extinction OR a consequential strategy, eg protection/conservation (or named example) 1 One named example from any of points above 1 One different named example from another of points above 1 Maximum 5 Influence of Density Dependent Factors on Population Changes Effect of density dependent factor increases as density increases (or converse) 1 Two density dependent factors named from list below 1 A third density dependent factor named from list: 1 - Disease/parasites/infection - Food supply/availability - Predation - Competition for food/space/territory - Toxic waste made by organisms Relate population change to effect (listed below) of two factors 1 Relate population change to effect of third factors: 1 - if population increases then increase in disease/in spread of disease/parasites/infection. - if population increases then decrease in food available to individuals - if population increases then increase in predation - if population increases then increase in competition for food - if population increases then increase in competition for space/territory - if population increases then increase in production of toxic waste (converses of the above also acceptable) (linked to last two points) Relate any of the above effects to a subsequent decrease in population OR (if converses given in last two points) relate any of the above effects to 1 subsequent increase in population. Population returns to a size that the environment can sustain/to a stable level. 1 Maximum 5 Maximum Total 10</p>