Explain how meiosis results in an effectively infinite genetic variety of gametes. [8]
� one (homologous) chromosome is from the mother and one from the father;
� homologous chromosomes pair (in prophase I);
� crossing over/chiasma formation in prophase I;
� recombination of linked genes / alleles/genes swapped;
� many possible points of cr
Explain the processes by which minerals are absorbed from the soil into the roots. [8]
� plants absorb minerals in ionic form/mineral ions;
� nitrate / phosphate / potassium / other example of mineral;
� minerals can be absorbed by (facilitated) diffusion;
� (diffusion is) movement of ions from high to low concentration/down concentration g
In anaerobic conditions, plants release energy by glycolysis. Outline the process of glycolysis. [6]
� occurs in cytoplasm (of cell);
� substrate is hexose/glucose/fructose;
� phosphorylation of glucose/fructose/hexose;
� to form hexose diphosphate/glucose 6-phosphate;
� requires ATP;
� glucose/fructose/hexose (diphosphate) converted into (two) pyruvates
Explain how the structure and function of the placenta helps to maintain pregnancy. [8]
� disc-shape organ that attaches to (inside of) uterus;
� connected to the fetus by the umbilical cord;
� produces hormones/HCG that maintain pregnancy;
� estrogen and progesterone maintain uterine lining;
� nutrients/oxygen from mother's blood transferre
Define habitat, population, community and ecosystem. [4]
� habitat: the environment in which a species normally lives / the location of a living organism / OWTTE;
� population: a group of organisms of the same species who live in the same/specific area at the same time/interact;(some reference to common place a
Outline how energy flows through an ecosystem. [6]
� producers/plants/autotrophs convert light energy into chemical energy/make food by photosynthesis;
� such as sugars/organic compounds;
� producers eaten by primary consumers, these by secondary consumers, (these by tertiary consumers)/energy moves up tr
Discuss the benefits and possible harmful effects of altering species by one example of genetic modification. [8]
� DNA is universal (genes can be transferred among species);
� gene modification is the transfer of genetic material between species;
� named example; (eg glyphosate resistant crops)
� source of gene; (eg bacteria)
� function of gene; (eg resistance to he
Draw a labelled diagram of the structure of a motor neuron. [4]
� cell body/nucleus; (these should appear toward end of neuron to award mark)
� axon; (at least four times the length the width of the cell)
� dendrites; (as branches of cell body)
� myelin sheath; (surrounding axon)
� nodes of Ranvier; (periodic gaps in
Outline the control of the heartbeat by the nervous and endocrine systems. [6]
� myogenic muscle contraction;
� contracts without stimulation;
� pacemaker/sino-atrial node/SAN in (wall of) right atrium;
� pacemaker/sino-atrial node/SAN initiates contraction;
� nerves (from brain) transmit messages to pacemaker;
� to alter/increase/d
Explain the principles of synaptic transmission. [8]
� Ca2+/calcium ions enter presynaptic neuron;
� release of neurotransmitter/acetylcholine;
� from pre-synaptic membrane/neuron;
� diffusion/movement across cleft/gap;
� to post-synaptic membrane/neuron;
� binding of the neurotransmitter to receptors/bindi
Membrane proteins vary in their positions within the membrane and in
their functions. Outline the positions and functions of proteins in membranes. [8]
� integral proteins are embedded in the membrane/phospholipid bilayer;
� peripheral proteins are on the surface of the membrane;
� some integral proteins (are transmembrane proteins that) extend from one side of the membrane to the other;
� hormone bindin
Explain how polar and non-polar amino acids help channel proteins and enzymes carry out their functions. [5]
� non-polar amino acids cause channel proteins to embed in a membrane;
� polar amino acids at either end cause channel proteins to be transmembrane / retain protein position in membrane;
� polar amino acids lining pore allow polar particles to pass throug
Compare competitive and non-competitive inhibition of enzymes. [5]
...
Explain how the collecting ducts can alter the volume of urine produced by the kidney. [5]
� ADH is secreted when the solute concentration of the blood is too
� high/OWTTE/converse;
� ADH makes the collecting duct more permeable to water / when not secreted the collecting duct is less permeable to water;
� (causes) more aquaporins in the (membr
Describe the structure of the ventilation system, including the alveoli. [8]
� ventilation occurs within the lungs;
� trachea divides to form two bronchi;
� bronchi divide to form bronchioles;
� several divisions of bronchioles;
� alveoli connected to bronchioles;
� trachea/bronchi/bronchioles/airways lined with cilia/ciliated epi
Outline the process of in vitro fertilization (IVF). [8]
� drugs used to (down-)regulate/stop the menstrual cycle;
� hormones/FSH injected to stimulate many follicles to develop;
� HCG injected to cause the follicles to mature;
� eggs are harvested/extracted from the follicles/ovaries;
� semen/sperm sample prod
All organisms in an ecosystem are involved in the carbon cycle. Outline the
roles of living organisms in the carbon cycle. [8]
� plants/producers fix carbon (dioxide)/use carbon (dioxide) in photosynthesis;
� sugars/carbon compounds (produced) in plants/producers from photosynthesis;
� (carbon compounds in) plants/producers eaten by animals/primary consumers/herbivores;
� (carbon
Explain how triose phosphate is produced and used in the chloroplasts of a plant. [5]
� ribulose bisphosphate/RuBP and carbon dioxide react together;
� (this is) carbon fixation/part of light-independent reactions;
� catalysed by RuBP carboxylase/Rubisco;
� glycerate 3-phosphate/GP produced;
� glycerate 3-phosphate/GP reduced/converted to
Explain the conditions that are needed to allow a seed to germinate. [5]
� water needed to rehydrate the seed;
� gibberellin released / active after water absorbed;
� gibberellin needed to produce amylase;
� water needed to allow substances inside the seedling to be transported;
� oxygen needed for (aerobic) cell respiration;
Outline the effect of temperature and substrate concentration on the
activity of enzymes. [4]
� enzymes most active at one temperature/optimum temperature;
� any deviation from that temperature lowers the enzyme activity;
� denaturing/change in active site/no activity at higher temperatures / inactivated at
� (very) low temperatures;
� increasing