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Sample essays and suggested plans for content
1. The process of diffusion and its importance in living organisms
Definition
Ficks Law
Types of diffusion e.g. Facilitated diffusion, osmosis
Gas exchange in unicells, fish, mammals and plants
Digestion and absorption of products
Exchange of materials between blood in capillaries and tissues e.g. placenta
Transpiration, root pressure, water and ion uptake by roots
Translocation and mass flow hypothesis
Osmoregulation by blood and kidney, unicells e.g. Amoeba
Action potentials
Synaptic transmission
Muscle action
Intracellular diffusion e.g. mitochondria, chloroplasts, enzyme action, DNA replication andprotein synthesis
2. The different ways in which organisms use ATP OR ATP and its roles in living organisms
The nature/structure of ATP and its importance as energy currency.
Production and use of ATP in cytoplasm by glycolysis
Production of ATP by mitochondria in Krebs cycle and ETSaerobic respiration.
Anaerobic respiration.
Role of chloroplasts in ATP production via light independent reaction
Uses e.g. Active transport (carrier protein shape changes), Nerve action (maintaining restingpotentials via Na
+/K
+pump and resynthesis of ACh), selective reabsorption by nephron,
absorption by gut, Calvin cycle, muscle contraction (cross bridge formation), Biosynthesis of
organic compounds, Contractile vacuoles, Translocation (loading of phloem), cell division
(movement of chromosomes via spindle), CP formation in muscles, Nitrogen fixation (Blue-
green algae), Kidney function, movement of sperm, secretion of digestive enzymes in
saprophytic fungi, cilia and flagella action
3. The movement of substances within living organisms (Jan 2003) OR Transport mechanisms in
living organisms
Diffusion e.g. Ion movement in Roots, Synapse, within a cell, O2/CO2in lungs and gills, factors
affecting rate
Facilitated diffusion e.g. Glucose uptake, action potentials
Osmosis e.g. Turgidity, uptake of water in plant roots, Kidney function
Active Transport e.g. Na+/K
+pump, Cl
-in RBC, Glucose uptake in intestine, mineral ions in plant
roots, neurotransmitters into presynaptic membranes, carrier proteins, mechanism
Endocytosis / exocytosis / Pinocytosis / phagocytosis e.g. Feeding in Amoeba
Mass flow e.g. Phloem, Xylem, Peristalsis, Ventilation in lungs, gills and insect tracheoles,
Bloodstream, Excretion, Cilia
Unusual ideas e.g. Chromosome movement during cell division, organelle movement in cells,Sliding filament theory, reproductive cells
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4. Mutation and its consequences
Definition.
Types of mutationaddition, deletion, substitution.
Causes e.g. spontaneous, radiation, mutagenic chemicals.
Effect of mutation on protein synthesis.
A change in base sequence may result in a change in amino acid sequence of a polypeptide,which affects the protein structure and its function.
Metabolic blocks as a result e.g. PKU.
Mutation in CFTR gene in cystic fibrosis.
Haemophilia.
Somatic mutations e.g. cancer and germ line mutations e.g. colour blindness.
Introns and exonsmutation may be removed by post-transcriptional modifications.
Diploid carriers e.g. sickle cell anaemia.
The role of mutation in evolution e.g. sickle cell anaemia.
Mutation as a source of genotypic variation e.g. bacteria and antibiotics.
Natural selection leading to changes in populations, changes within a species e.g. pepperedmoth, formation of a new species.
5. The properties of enzymes and their importance in living organisms OR The role of enzymes in
living organisms
What is an enzyme?
How do enzymes worklock and key theory/induced fit and lowering activation
energy/enzyme substrate complexes.
Enzymes as proteins.
Effects of extremes of temperature and pHoptimumsgraphs.Inhibitioncompetitive and non-competitive.
Activators, substrate concs.
Extra-cellular digestion - Fungal feeding.
Digestion in animals e.g. proteases, lipases, carbohydrases.
Enzymes in chemical processes e.g. Photosynthesis, Respiration, Nerve conduction, synapses,
deamination, transamination, DNA replication, RNA production.
Synthesis reactions.
CO2carriage.
Acrosome in sperm.
Effect of insulin on enzyme production in liver cells.Gut symbionts and cellulase production.
Na+/K
+pump
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6. The ways in which a mammal maintains constant conditions inside its body
Blood pHdecreased pH counteracted by secretion of HCO3-from distal convoluted tubule and
NH4+from kidney cells and increased pH counteracted by secretion of H
+from distal convoluted
tubule
Exercise and blood flow to parts of the body
Temperature regulationhypothalamus, vasoconstriction/vasodilation, piloerection, shivering,
metabolic rate, sweating
Blood glucose regulationpancreas, islets of Langerhans, Insulin, glucagon, liver,
gluconeogenesis, glycogenesis
Water balance/OsmoregulationKidney, Nephron, ADH, permeability of the Loop of Henle,
hypothalamus, Pituitary, Cl-transport, Plasma sodium control by aldosterone
Regulation of hormones e.g. sex hormones
Negative feedback
7. Negative feedback in living organisms (June 2005)
principle of negative feedbackdeparture from a norm initiates changes which restore a
system to the norm.
importance in homeostasis; principles of detection of change, role of receptors, corrective
response, role of effectors.
Thermoregulation; roles of thermoreceptors and hypothalamus in detection; heat loss and heat
gain centres; sweating and vasodilatation in heat loss; vasoconstriction, hair erection, shivering
and increased metabolism in heat gain.
Regulation of blood glucose; role of receptors in pancreas, secretion of insulin or glucagons;effect of insulin on surface membrane receptors/carrier proteins in stimulating uptake of
glucose and glycogenesis; role of glucagons glycogenolysis.
Regulation of blood water potential; role of receptors in hypothalamus; secretion of ADH from
pituitary; effect of ADH on permeability of d.c.t and collecting duct; role of loop of Henle in
maintaining high ion concentration in the medulla; effect on urine concentration.
Control of ventilation; stimulation of chemoreceptors in medulla; effect on inspiration;
stimulation of stretch receptors in lungs; stimulation of expiratory cells in medulla.
Control of heartbeat; roles of chemoreceptors and pressure receptors; inhibitory and
acceleratory centres in medulla; effect on SAN and rate of heartbeat; effect of change in rate on
pH/pressure of blood.Metabolic pathways; examples of build-up of a product in a metabolic pathway resulting in
inhibition of its formation.
Population stability; effect of increasing competition/predation on increasing population size
and restoration of balance.
(selectionstabilising selection resulting in constancy of species)
(oestrous cycle; effect of feedback on hormone production, e.g. oestrogen on FSH and
progesterone on both FSH and LH. From Option 8)
Any other sensibly argued example showing negative feedback should be credited. In a good essay
the description of the changes in a system should be clearly related to the principles of negativefeedback, with sufficient detail for the relationship to be explained.
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8. Chemical coordination in organisms
Need for chemical coordination
General principles of chemical coordination
Endocrine control in animalsnature of hormones, glands, principles of hormone action
Animal physiologysexual reproduction, control of blood glucose, osmoregulationPGRs auxins, gibberellins, ethane, cytokinins, ABA
Plant physiologygrowth, seed dormancy, leaf fall, root growth, bud development
Ecdysis in insects
Chemotaxis
9. The production and elimination of metabolic waste products in living organisms
Requirement for removal of toxic metabolic waste products.
Mechanisms of removal via specialised pathways or organs.
CO2Aerobic respiration
Diffusion by unicells
Stomata/lenticels
Carriage by plasma in mammals as HCO3-
Bohr shift
Mass flow in lungs after diffusion from blood
Control mechanisms by medulla
Removal by insects
Nitrogenous waste
Produced by deamination of amino acidsUrea formation in liver (via ornithine cycle)
Transport of urea by plasma
Ultrafiltration and elimination by kidneys
Removal in other animals e.g. uric acid in birds and insects
Oxygen removal after photosynthesis
Leaf abscission e.g. tannins
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10.The biological importance of water (Jan 2003) OR The role of water in the lives of organisms
Structure - dipolar nature, hydrogen bonds
SolventHydrophobic/hydrophilic interactions leading to stability of membranes, proteins,
nucleic acids etc, diffusion of molecules, dilution of toxic compounds e.g. urea
Osmosis and turgidity and their effects on plant support
Transport mediumxylem, phloem, blood, lymph, secretion, excretionHigh heat capacitytemperature regulation, constant external environment for aquatic
organisms
High heat of vaporisationcooling effect e.g. sweating, panting, transpiration
Surface tension and cohesionTranslocation, mosquito larvae, pond skaters
Chemical reagent e.g. in P/S it is a source of Hydrogen, hydrolysis reactions
Incompressibilityhydrostatic skeletons, eyes, joints, seed germination, amniotic fluid, shock
absorption in brain
Densityfloats when frozen and insulates
Transparentlight penetration for aquatic organisms
Medium for movement e.g. gametes, seed dispersal, oceanic migration, mucus in alimentarycanal
Protection e.g. lachrymal fluid, mucus
Factor for evolution e.g. terrestrial organisms have to adapt to conserve water
Water vapour can act as a greenhouse gas
11.The importance of proteins in living organisms
Structure and chemical composition of amino acids, amphoteric nature
Essential and non-essential amino acids
Peptide bond, ionic bonds, disulphide bonds, hydrogen bondsDenaturation by heat, heavy metals, pH
Primary, secondary, tertiary and quaternary structures
Fibrous (Collagen in tendons and bone, myosin in muscle, silk in spiders webs, keratin in hair,
horn, nails and feathers) and globular (Enzymes, antibodies, hormones e.g. insulin, histones for
compacting DNA) proteins
Conjugated proteins e.g. phosphoproteins (Casein in milk), Glycoproteins (Mucin),
Nucleoproteins (viruses), chromoproteins (HB, Phytochrome, cytochrome), Lipoprotein
(Membranes and for lipid transport in the blood), Flavoprotein (FAD in ETS), metal proteins
(nitrate reductase in plants)
Structural collagen in connective tissue, keratin in skin etc, elastin in ligaments, sclerotin ininsect exoskeletons, mucoproteins in mucus, capsid proteins in viruses
Enzymes: RUBISCO, any named
Hormones: Insulin, glucagon
Transport: Hb, Mb, serum albumin for lipid transport
Protective: Antibodies, fibrinogen and thrombin for blood clotting
Contractile: myosin and actin
Storage: ovalbumin in egg white, casein in milk
Toxins: snake venom, diphtheria toxin
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12.How the structure of proteins is related to their functions (Jan 2004)
Structure
o Primary structurepeptide bond
o Secondary structure
o Tertiary structureGlobular (bonds between R groups give spherical shapeshape
determines functionactive sites and receptor sites)
o (Allow quaternary structure Hb incorporates ions for oxygen transport)
Structural proteins
o Fibrousregular pattern of H bondscoiling,
o (e.g. keratin coils twist together to form rope like structures flexible and strong, e.g.
collagen coils more tightly bound more rigid)
Transport
o Channelcomplementary shapecharges-gated
o Carriercomplementary shapecan change shape
o Active transportphosphate group attached by energy from ATPcan change shape
Enzymes
o Active site, enzyme-substrate complex
o
Activation energy reductionexplanation e.g. brings molecules closer
Receptors
o Synapse
o Insulin / glucagons
o ADH
o Rhodopsin
Muscle
o Actin thinbinding site
o Myosin thickcross bridges
o Tropomyosinblock binding sites
13.The importance of lipids in living organisms
Structure and chemical composition
Properties e.g. fats and oils, saturated and unsaturated, insolubility in water
Functions e.g. energy storage, insulation, protection of major organs, hydrophobic/hydrophilic
interactions, membranes, lipoproteins, myelin sheath in nerve action, buoyancy (aquatic
organisms), metabolic water on hydrolysis (kangaroo rats), waterproofing (leaf cuticle, insect
exoskeleton, synthesis of steroid sex hormones, glycolipids, structural (beeswax in
honeycombs), Scents, Pigments (carotenoids and chlorophyll), cholesterol, rubber
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14.The importance of carbohydrates in living organisms OR The structure and functions of
carbohydrates (June 2003)
Contain C, H, O.
Monosaccharides: glucose (blood transport) and fructose, monomers of which other
carbohydrates are composed. Glucose as a source of energy; a substrate in aerobic and
anaerobic respiration; brief outline of biochemistry of respiration. Structural formula.
Disaccharides: condensation reactions to form sucrose (glucose and fructose) used in phloem
transport and Maltose (glucose and glucose)- and poly- saccharides, formula, glycosidic bond,
hydrolysis.
Energy source e.g. glucose, fructose, galactose released via respiration
Respiration intermediates e.g. glyceraldehydes, dihydroxyacetone
Photosynthesis intermediates in light independent reaction e.g. Ribulose bisphosphate
formation of carbohydrates, CO2accepted by RuBP, reduction of gycerate-3-PO4to
carbohydrate and regeneration of RuBP.
Synthesis of e.g. Nucleic acids are pentoses (ribose and deoxyribose)sugar phosphate
backbone provides strength, coenzymes (NAD, NADP, CoA, FAD), AMP, ADP, ATP, Disacs(sucrose, lactose, maltose), Polysaccharides (Starch/amylose, glycogen, cellulose, callose, inulin)
- No osmotic effects, compact molecules, easily converted into sugars, relationship of structure
to function, starch, glycogen and cellulose are all polymers of glucose differing in the number
and arrangement of the glucose molecules. Starchhelical shape for compact storage,
insoluble for storage (osmotically inactive), large size cannot pass through membranes,
provides large numbers of glucose molecules for respiration.
Glycogensimilar to starch but more branches, insoluble storage compound in liver and
muscles. Conversion of glucose to glycogen for storage. Importance of control of blood glucose.
Structural e.g. cellulose (long straight chains, OH groups linked by H bonds forming microfibrils
and macrofibrils. Layers of fibrils orientated in different directions are interwoven and
embedded in a matrix providing a rigid cell wall; gaps in layers provide permeability), pectins,
hemicellulose, murein
Optical isomersonly D forms used in nature
Transport e.g. sucrose in phloem
Food store e.g. lactose in milk, starch in plants, glycogen in animals.
Glycoproteins, glycolipids, mucopolysacs (chitininsect exoskeletons, nails, mureinbacterial
cell walls, pectinsform gels, hemicellulose, heparin - anticoagulant, hyaluronic acid,
chondroitinvery viscous component of synovial fluid and cartilage and cornea, gums and
mucilagedrought resistance)
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15.How the structure of cells is related to their function (June 2002)
Leaf mesophyll cellschloroplasts, thylakoids for P/S
Xylemwaterproof, no end walls, lignified for support and water transport
Phloemminimal cytoplasm, end plates for sucrose transport
Guard cellsmechanisms of controlling gas exchange by stoma control
Epidermal cellsflattened for protectionSclerenchymapolygonal for support
Root endodermiscasparian strip for regulating entry of substances
Collenchymacells thickened at corner for support
Pollen grainshooks for attaching to insects
Ciliated tracheal epitheliummoving material away from lungs
Squamous epithelium of alveoli and bowmans capsulethin for diffusion
Gut epithelial cells - microvilli for absorption
Cornified cells of skinflattened and keratinised for protection
Nerve cellslong, myelin sheath, mitochondria, neurotransmitters
RBCshape for increased SA, Hb for carrying O2, no nucleusSperm cells - tail and mitochondria for swimming
Egg cells
Muscle cellactin and myosin for contraction
Secretory cells e.g. goblet cellssecretory vesicles, sER
Rods and Cones in retinalight sensitive pigments etc
Pyramidal neurones in brainmany dendrites = parallel processing
Bacterial cellsflagella for movement, capsule for defence/adhesion
16.Natural selection and the effects of environmental change
Natural selection
o Variety amongst individuals of same species
o Survival characteristics
o Selective advantages
o Survival, breeding genes/alleles passed on to next generation
o Advantageous characteristics become common
Change in gene pool Environment and selection pressure
o environmental factors exert pressure
o e.g.s of environmental factors e.g. climate change, pollution, predation, food
availability, diseaseo Environmental change favours certain characteristics
o Differential mortality/natality
o Stabilising selection
o Directional selection
o Disruptive selection
o Isolation and speciation
Specific examples
o Industrial melanism in the peppered moth
o Heavy metal tolerance in plants
o
Insecticide/antibiotic resistanceo Sickle cell anaemia in Afro-American population
o Banding patterns in Cepaea
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17.Gas exchange in animals and flowering plants
Surface area: volume
Specialised surfaces e.g. gills alveoli
Diffusion
Plants
o
Lenticelso Leaf structure, mesophyll and stomata
Animals
o Transport mechanisms
o Fishgills
o Insectstracheoles and spiracles
o Protozoans
Mammals
o thorax structure, alveoli, ventilation, breathing control
18.The importance of molecular shape in living organisms
Receptor interactions
o Drugs and Toxins
o Immunoglobulins or antibody/antigen
o Hormonessecond messenger or direct action
o Neurotransmitters and synapses
Carbohydrates
o Structural (cellulose), storage (starch, glycogen)
Proteins
o levels of structure, globular, fibrous, enzymes, specificity, properties, channel
proteins
Lipids
o Phospholipids, storage, structural (beeswax)
Water
o Dipolepolarity, cohesion, adhesion
Haemoglobin
o Quaternary structure and O2 binding/release
DNA Double helix
o accurate copying, stability, base pairing etc
Pigmentso Rhodopsins/opsins, chl, phytochrome
Isomers
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19.The factors affecting the growth and size of populations
Population defined
Description and explanation of typical population growth curve
Carrying capacity
Population change (Birth + immigration)(death + emigration)
Density dependent and density independent factorsExamples of abiotic factors e.g. light, inorganic ions, oxygen, temperature
Competition for abiotic factors
Examples of biotic factors e.g. food supply, spread of disease/parasitism, predator prey
relationships, interspecific competition, intraspecific competition, competitive exclusion
Demographic changes in human populations/ population pyramids
Birth control.
20.Cycles in Biology (June 2003)
Ecological cycleso N cyclerole of microorganisms in the processes of saprophytic nutrition, deamination,
nitrification, nitrogen fixation and denitrification.
o C cyclerole of microorganisms in the breakdown (respiration) of complex organic
compounds into CO2making it available for reuse
Metabolic cycles
o Krebs cycle: acetyl CoA combines with a 4C molecule to produce a 6C molecule which
enters Krebs cycle; the 4C compound is regenerated during the cycle involving a series
of oxidation reactions and the release of CO2; production of ATP and reduced NAD and
FAD.
o
ETS: cyclical reduction and oxidation of NAD, FAD and other carriers.o Synthesis and breakdown of ATP
o Light independent reactionsCO2 accepted by RuBP to form 2 molecules of Glycerate-
3-PO4, reduction of Glycerate-3-PO4 to carbohydrate, and regeneration of RuBP.
Physiological cycles
o Negative feedback mechanisms: regulation of body temp/blood glucose/blood water
potential.
o Cardiac cycle: relate pressure and volume changes in the heart and aorta to
maintenance of blood flow.
o Role of tropomyosin, calcium ions and ATP in the cycle of actomyosin bridge formation.
o Nerve functiondepolarisation/repolarisation of a neurone in terms of differential
membrane permeability and cation pumps, synthesis and resynthesis of Ach (synaptic
transmission)/rhodopsin (rods) and restoration of a resting potential.
o Menstrual cycle.
o Ventilation in fish, mammals, insects.
Life cycles
o Mitosis / cell cycleexplanation of stages of mitosis, importance in growth and sexual
reproductionvegetative reproduction.
o Meiosisimportance of maintaining a constant chromosome number from generation
to generation; outline of process (no detail).
o E.g.s of life cycles might be provided in terms of mitosis, meiosis, fertilisation, and
chromosome number.
o DNA replicationsemi-conservative replication.
o Predator / prey cycles.
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21.The causes of variation and its biological importance (Jan 2004)
Gene mutation
o Addition
o Deletion substitution
o Effect on alleles
o Effect on polypeptide / protein
Sexual reproduction
o Crossing over
o Independent assortment
o Random fusion of gametes
o (allow chromosome mutation)
Environmental
o Nutrients
o Disease
o Light
o Temperature
Biological importance
o Enables adaptation
o Natural selection
o Speciation
o Evolution
22.The process of osmosis and its importance to living organisms (June 2004)
definition
effects on cells
turgidity and support
plasmolysis (idea)
lysis
cystic fibrosis
importance in animals role in relationship between plasma and tissue fluid
role in medulla of kidney
reabsorption in gut
sweat production neutral
importance in plantsrole in movement of water from soil to leaves in plants
role in mass flow hypothesis for movement in plants
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23.Energy transfers which take place inside living organisms (June 2004)
ATP
Synthesis from ADP and P
Role as an energy source
Photosynthesis
o
excitation of electronso generation of ATP and reduced NADP
o photolysis
o reduction of glycerate phosphate to carbohydrate
o structure of chloroplast in relation to energy transfer
Respiration
o net gain of ATP in glycolysis
o production of ATP in Krebs cycle
o synthesis of ATP associated with electron transfer chain
o ATP production in anaerobic respiration
o Structure of mitochondrion in relation to energy transfer
Uses of energy in biological processes
o active transport
o muscle contraction
o nerve transmission
o synthesis
o translocation
o kidney function
o nitrogen fixation
o receptors
24.
How microscopes have contributed to our understanding of living organisms (Jan 2005)
reference to both light and electron microscopes
o e.g. resolution, magnification, techniques.
o good candidates e.g. clear distinction of advantages disadvantages of each, historical
developments, reference to wavelength employed and limitations.
cell structures (typically) visible with each
o good candidateshow observation of structures can inform about function; viewing
isolated organelles and their internal structure.
tissue structure
o
e.g. histology of digestive system related to function, muscle structure, kidney tubules,
leaf structure.
o good candidatesexplanation linking appearance of features to understanding function
observation of processes
o e.g. cell division, fertilization, capillary circulation
o good candidatesappreciation of using microscopes to observe dynamic processes, use
of tracers.
observation of organisms; classification
o e.g. bacteria and viruses, taxonomic differences in small organisms.
o good candidatesimportance in understanding of disease.
other uses
o e.g. understanding effects of disease/cancer, opportunities to improve/alter/etc living
organisms.
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25.Enzymes and their importance in plants and animals (Jan 2005)
principles of enzyme action
o e.g. catalysis, protein structure, active site, activation energy, enzyme-substrate
complex, specificity.
o good candidates relate protein structure to specificity/active site, catalysis to activation
energy
factors affecting enzyme action
o e.g. temperature, pH, enzyme/substrate concentration, inhibition
o good candidatesrelate changes in activity to denaturing/tertiary structure; effects of
concentration to active site availability, distinguish competitive/non competitive
inhibition.
enzyme synthesis
o reference to protein synthesis; link to genes, gene expression, effects of mutation.
o good candidatesappreciation of connection between genes and enzyme production,
e.g. one gene, one enzyme.
o
roles and functions of enzymes in different processes. In each case good candidates
should specify enzyme and its function.
digestion
o enzymes involved in mammalian digestive system, breakdown of polymers in other
circumstances, e.g. saprophytic digestion/mobilisation of storage compounds
o good candidatesrange of enzymes giving source and action in sequence in mammalian
digestion; reference to other breakdown.
metabolic pathwaysphotosynthesis and respiration
o e.g. light independent reaction, Krebs cycle, ATP formation.
o good candidatesreference to specific roles e.g. in light independent reseaction,
distribution in mitochondria/chloroplasts.
other specific examples
o e.g. in nervous system, such as role of acetylcholinesterase in synapses,
o in homeostasis, such as in glycogenesis,
o in muscle action, such as role of ATPase,
o in fertilisation, such as enzymes in acrosome,
o in transcription/translation, such as role of polymerase.
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26.Mean temperatures are rising in many parts of the world. The rising temperatures may result in
physiological and ecological effects on living organisms. Describe and explain these effects.
(June 2005)
Principle of destabilising effect of rising temperature on metabolic systems within organisms
and on balance in ecosystems.
effect on rate of diffusion/gaseous exchange; possible consequences, e.g..
increased evaporation, more rapid uptake of ions by plants.
effect on proteins; possible increased rate of denaturation of tertiary structure. Increased rate
of enzyme activity; possible increased dislocation of metabolic pathways.
Effect on photosynthesis (light independent reaction); increased rate with small increases,
disruption with larger; increased rate of growth of (some) plants; possible increased rate of
crop growth; effect of other limiting factors.
Effect on transpiration; increased rate of water loss and hence wilting /dehydration; reduced
stomatal opening may effect photosynthesis; possible consequences of drought on ecosystem
Effect on respiration and metabolism; increased effect on growth and activity, especially of
ectotherms.Ecological effects of disruption of food webs and the dynamics of ecosystems, with changes in
niches and hence communities.
Effect on species; extinction of species that are unable to adapt, especially ones with specialised
requirements, limited opportunity for plants and some animals to spread to more suitable
conditions as climate changes.
Effect on agriculture, increased growth of some crops and loss of others, and effect on
productivity; possible redistribution to different parts of the world, and overall loss of
agricultural land.
Ecological effect of increased rates of growth and reproduction, especially of bacteria, insects
and pests; possible increased incidence of disease.role of natural selection in adaptation to change.
There are many possible alternative approaches to this essay and any biologically sensible effect of
increasing change in temperature on living organism should be credited. In a good essay the
specific effects of rising temperature will be explained and explicitly linked to their possible effects
on physiology or ecology. A good candidate will also recognise the complex interactions involved
and avoid giving simplistic explanations and doomsday scenarios.
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27.The transfer of substances containing carbon between organisms and between organisms and
the environment
Transfer between organisms:
o food chains and feeding relationships
o carbon cycle
o nitrogen cycle
o
digestion
o cell transport
Transfer to/from the non-living environment
o photosynthesis
o respiration
o exchange surfaces
o (production and) removal of urea
o human activities
o agricultural ecosystems
Transfer of substances containing carbon between organisms and the environment
Transfer between organisms:
o Food chains and feeding relationships
o plants producers
o idea of food chains as feeding relationships
o with transfer energy
o in substances containing carbon
o Digestion and absorption (possible link to bacteria and fungi)
o digestion/hydrolysis of large carbon-containing compounds
o by enzymes
o producing small/soluble compounds
o
which can be absorbed
o Transport of organic molecules in and out of cells/across exchange surface
o (possible link to bacteria and fungi
o organic molecules (including sugars and amino acids) cross cell membranes
o by facilitated diffusion
o active transport
o which requires ATP from respiration
o involving carrier proteins and/or enzymes
Transfer to/from the non-living environment
o Carbon cycle (and relevant parts of nitrogen cycle)
o
carbon enters biotic by photosynthesiso leaves biotic by respiration/combustion
o role of bacteria/fungi as decomposers
o of dead organisms/ faeces/ excretory products/urea
Photosynthesis
o light-independent reaction
o carbon dioxide reacts with ribulose bisphosphate
o glycerate 3-P reduced to sugar
o reduced NADP and ATP from light-dependent reaction
o Calvin cycle
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Respiration
o link reaction/Krebs cycle
o oxidation of intermediates
o generation of reduced coenzymes
o loss of carbon dioxide
o Exchange surfaces - for carbon dioxide
o for animals
o
and plants
o large surface area - alveoli - mesophyll cells
o short diffusion pathways - epithelium and endothelium - thin leaves and many stomata
o maintaining diffusion gradient - capillary and respiration - photosynthesis and
o respiration in mesophyll cells (time of day)
o ventilation - breathing - via air spaces in leaf
28.Cells are easy to distinguish by their shape. How are the shapes of cells related to their
function? (June 2006)
Epithelial cells in animals
o epithelial cells from small intestine
o epithelial cells of alveoli, gill lamellae
Epidermal cells in plants
o palisade mesophyll cells
o stomatal guard cells
o root hair cells
Reproduction
o differences between egg and sperm cells
Transport of substances in organisms
o
red blood cells
o endothelial cells of capillaries
o xylem vessels
o phloem sieve cells
Nervous coordination
o neurones
o rod and cone cells
Muscle
o skeletal muscle
Animals:
o
Epithelial cells - intestinal, alveolar, kidney tubule, gill lamellae
o Two examples allowed
o As appropriate, relating to transport function(s)
(collectively) large SA
flattened - short diffusion pathway
folded membrane - larger SA for stated function
podocytes - pores for filtrate formation
o Bloodtransport
red blood cells
biconcave shape - increase SA for oxygen exchange
move through capillarieso Blood - exchange
endothelial cells of capillaries
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flattened - short diffusion pathway
fenestrated in glomerulus
o Blood white cells
phagocytes/macrophages
amoeboid properties.
related to movement into tissues/engulfing e.g. bacteria
Nervous system - neurones (and Schwann cells)
o
dendrites - make synaptic connection to other neurons
o axon/dendron - carry nerve impulses over long distances
o shapes of relay, motor and sensory
o related to function
o myelin sheath - faster transmission of impulses
o Nervous system - receptors - NB could be other than light
o cone/rod cells with distinctive heads - containing pigment
o detect light
o dendrites to synapse with bipolar/ganglion cell(s)
Muscle
o
elongated - contain rows of sarcomeres
o leads to contraction in length
o force generated in particular plane
o branched in cardiac - give contraction in more than one plane
Ciliated
o cells lining air passages/oviducts
o push mucus/eggs along
o remove trapped microorganisms/towards uterus
Sperm
o sperm have beating tail/flagellum
o
streamlined shape
o help sperm to move
o find egg cell
o acrosome with (digestive/hydrolytic) enzymes
o digest way into egg cell
Plants and any other organisms:
o Hair cells - of root
o root - extension of epidermal cell
o increases SA
o for absorption of water and mineral ions
o
Hair cells - of leafo leaf - extension of epidermal cell
o reduces air flow/traps air near leaf surface
o reduces water potential gradient for diffusion of water
o reduces water loss by transpiration
o Leaf cells (guard cell structure not in spec., but could be known and used)
o palisade mesophyll are elongated
o allows more to be packed side by side
o to absorb maximum amount of light for photosynthesis
o Transport in xylem and/or phloem
o
elongated cellso xylem vessels no end walls/ phloem sieve cells end plates
o rows end to end to form tubes
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o no/less resistance to flow
o Bacterial cells flagellum rotates pushes against external medium moves bacterium
o Fungal hyphae (though usually cyncitial)
o hyphae grow and branch through substrate increasing SA for absorption
29.Movements inside cells. (June 2007)
Plasma membranes and movement across
Protein synthesis
Movement through ER and Golgi
Cell division and chromosome movement
Water movement in plants/xylem
Translocation
Neurones and synaptic vesicles
Actin and myosin
DNA replication and mutation
Electron transport chainsMolecular/atomic/ionic movement
Any other sensible example of movement inside cells should be credited. In a good essay, the
emphasis should be on movement.
30.Transfers through ecosystems. (June 2007)
Photosynthesisenergy transfer
Respirationenergy transfer
Carbon cycle
Nitrogen cycleFood chains
Ecological pyramids
Pesticide toxicity/bioaccumulation
Eutrophication
Digestion and absorption
Transfer of genetic material
Water cycle
Any other sensible example of transfer through ecosystems should be credited. In a good essay,
the emphasis should be on transfers.
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31.The part played by the movement of substances across cell membranes in the functioning of
different organs and organs systems (June 2008).
Plasma membranes and movement across
Gaseous exchange system/ lungs
Digestive system/small intestine
Blood vascular systemTranspiration/root/stem
Mass flow/leaf/stem
Nervous system/eye
Excretory system/ kidney
Muscle systems
Liver, blood glucose
Root mineral ions
Lungs cystic fibrosis
Any other sensible example of the movement of substances across cell membranes in the
functioning of different organs and organ systems should be credited. In a good essay, theemphasis should be on movement across membranes involving organ function.
32.The part played by enzymes in the functioning of different cells, tissues and organs (June 2008)
Action of enzymes
Enzyme properties
Extracellular digestion
Nutrient cycles
Digestion in humans
Replication of DNAProtein and enzyme synthesis
Metabolic pathways
Mutations
Coenzymes and enzyme action
Homeostasis
Neurone/synapse
Muscle contraction
Pesticide toxicity
Any other sensible example of the part played by enzymes in the functioning of different cells,
tissues and organs should be credited. In a good essay, the emphasis should be on the partplayed by enzymes.
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33.Ions and Organisms (June 2009)
Osmosis and turgor
Haemoglobin dissociation, pH and carbon dioxid
Uptake/movement of water/mineral ions by/in plants
Ions in biological molecules
Hydrogen, photosynthesis and respirationAnaerobic respiration and lactate
Nerve impulses and synaptic transmission
Regulation of blood water potential/kidney function
Muscle contraction
Nitrogen cycle
Eutrophication
Movement across membranes
Cystic fibrosis
Any other sensible example of the role of ions, or exchange of ions by organisms should be
credited. In a good essay, the emphasis should be on the ions rather than describing a processand then linking an ion to the process.
34.DNA and the transfer of information (June 2009)
Genes/how information is carried on DNA
Replication of DNA
Cell division - Mitosis and meiosis
Transcription and translation
Mutation
Genetic engineeringGene therapy
Genetically modified organisms
Variation (in populations)
Evolution
Inheritance
Any other sensible example of the transfer of information involving DNA should be credited. In
a good essay, the emphasis should be on the transfer of information.
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35. Carbon dioxide may affect organisms directly or indirectly. Describe and explain these effects.
(June 2010)
Carbon dioxide affects the physiology of organisms
o Pulmonary ventilation and the mechanism of breathing
o Light-independent reaction of photosynthesis. Limiting factors
o Role of chemoreceptors in controlling heart rate
The direct effects of increasing carbon dioxide concentration
o Respiration, photosynthesis and human activity giving rise to short-term fluctuations
and long-term change.
o Yield of crop plants
Carbon cycle
o Indirect effects of increasing carbon dioxide concentration
o Role of carbon dioxide in producing global warming
o Life cycles and number of insect pests
o Distribution of animals and plants
o Effect of temperature on enzymes
36. The causes of disease in humans (June 2010).
Pathogens
o Pathogens include bacteria, viruses and fungi
o Pathogens cause disease by damaging cells and producing toxins
o Cholera bacteria produce toxins resulting in diarrhoea
o Symptoms and transmission of pulmonary tuberculosis
o Horizontal gene transmission and MRSA
Lifestyle
o
Risk factors associated with cancer and coronary heart disease
o The effects of fibrosis, asthma and emphysema on lung function
o The biological basis of heart disease
Genetics
o Differences in bases may lead to non-functional enzymes
o Relationship between the cell cycle and cancer
o Proto-oncogenes and tumour suppressor genes
o Gene mutations
37.
The role of carbon containing compounds in living organisms
38.The role of nitrogen containing compounds in living organisms
39.The roles of membranes in living organisms
40.The role of DNA in living organisms
41.Applications and implications of gene technology
42.Genetic variation and speciation
43.Control of the internal environment in living organisms
44.The movement of molecules and ions through membranes
45.Roles of pigments in living organisms
46.Light and life
47.
Support and movement in living organisms48.The chemical and biological control of insect pests
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