Describe how the mark-release-recapture method could be used to estimate the population of mice in the area being studied.
Method of trapping, trap a large sample to be representative, Method of marking; (in an unobtrusive way, does not make them more vulnerable to predation or less likely to reintegrate, shave a little piece of fur form underneath), Release and wait a period of time to allow reintegration into population, Number marked are counted then released, Number recaptured are counted, Number of marked animals/in second sample are recorded
Ground beetles are large black insects. The mark-release-recapture method can be used to estimate the ground beetle population on a roundabout. Describe how.
Sample of ground beetles captured and counted; Released and second sample captured; Count total number of beetles and number marked; Detail of method e.g. pitfall trap/marking with tippex; Refinement to ensure greater accuracy e.g. large number/marking in position such that does not affect survival
Give two conditions necessary for results from mark-release-recapture investigations to be valid.
No immigration/migration (Ignore references to emigration); No reproduction (Ignore references to death); Idea of mixing; Marking does not influence behaviour / increase vulnerability to predation; Sample/population large enough
Describe the techniques you would use to obtain reliable data in order to compare the sizes of the populations of the snail in a muddy area and in a area covered by vegetation.
Use of large numbers of quadrats in each area (if number stated then 10+); random sampling method (e.g. grid + random numbers)/systematic sampling method (allow regular sampling along a transect); counting.
Describe how you would use quadrats in an investigation to determine whether or not there is a difference in the number of clover plants in two large areas of equal size
Large (and equal) number of quadrats in each area; (reject several), random sampling method, described; (accept described ?systematic? method) percentage cover/point hits per quadrat/count plants; mean/average value for each area; statistics test to see if differences significant
Describe how you would use a half meter by half meter quadrat frame and a 30-metre tape measure to produce a transect along a stream to investigate the distribution of species growing there
Use of tape measure to produce transect, placing of quadrats, transect placed across stream, score presence of each plant species, use quadrat at regular, intervals along tape, Repeat transect several times along stream, at random or regular intervals
Explain what limits the size of populations in a climax community.
1. Named nutrient availability; 2. Numbers of producers providing energy (for a food chain); 3. Light intensity affecting the rate of photosynthesis; 4. Disease killing (weaker) members of species; 5. Space for nest building / niches;6. Reproductive rate balancing death rate; 7. Competition for a named limited resource; 8. (Intra and interspecific) competition explained; 9. Predation described
Using one example of each to illustrate your answer, explain the difference between density dependent and density independent factors
Example of density dependent factor (factors whose effect change as population size changes), e.g. food, space, disease; Example of density independent factor, e.g. light, temperature (reject: weather, climate); Density dependent factors depend on / affected by size of population; Density independent factors affect organisms whatever the population size, or, examples used to explain, e.g. increasing competition for food
Suggest how predation by weasels acts as a density-dependent factor controlling great tit population size.
At low densities / high distance between nests few are killed by weasels; so more great tits survive; Great tit population increases; so greater percentage taken by weasels; or At high densities / low distance between nests more are killed by weasels; so fewer great tits survive; Great tit population decreases; so smaller percentage taken by weasels
Give three uses of energy from ATP in a liver cell.
Active transport; Phagocytosis; Synthesis of glycogen; Protein / enzyme; DNA / RNA; Lipid / cholesterol; Urea in glycolysis; Bile production; Cell division
ATP is sometimes described as an immediate source of energy. Explain why
Energy release) only involves a single reaction/one-step/(energy released) in ATP ? ADP (+Pi)/ energy transfer direct to reaction requiring energy
Explain why humans make more than their body mass of ATP each day
1. ATP is unstable; 2. ATP cannot be stored / is an immediate source of energy; 3. Named process uses ATP ; 4. ATP only releases a small amount of energy at a time;
Describe how the leaf is adapted to allow photosynthesis to occur effectively
Large surface area to collect solar energy; transparent nature of cuticle to allow light penetration; position of chlorophyll to trap light; stomata to allow exchange of gases; thin / max. Surface area to volume ratio for diffusion of gases; spongy mesophyll / air spaces for carbon dioxide store; xylem for input of water; phloem for removal of end products
Describe how the structure of a chloroplast is adapted to its function in photosynthesis.
Membranes / (disc) shape provides large surface for light absorption; layering of membrane allows a lot of pigment; (permeable) membrane allows diffusion of gases / carbon dioxide; membranes provide surface for attachment of electron / hydrogenacceptors; stroma / matrix containing enzymes for Calvin cycle /light?independent reactions; Contains chlorophyll / pigments for light absorption; Different pigments to absorb different wavelengths; Stacking / arrangement of grana/thylakoids maximises light catchment; Stroma contains enzymes for photosynthesis; Outer membrane keeps enzymes in chloroplast; Starch grains / lipid droplets store products of photosynthesis; Ribosomes / DNA for enzyme/protein synthesis; Shape of chloroplast gives large surface area for CO2, absorption
Describe how plants absorb light energy from the sun and use this energy to produce useful substances in the light-dependent stage of photosynthesis
Light absorbed by/strikes,chlorophyll/photosystem/PSI/PSII; electrons excited; pass down chain of carriers; energy released/transferred; producing ATP from ADP and phosphate; reduced NADP/formed with electrons; photolysis of water /allow light splits water; (water) supplies protons/H+ ions to reduce NADP
Describe the light-independent reactions of photosynthesis and explain how they allow the continued synthesis of hexose sugars
1. 5C/RuBP combines with CO2; 2. to form 3C compound / TP / GP; 3. using ATP; 4. and reduced NADP / eq; 5. 2 molecules of 3C compound/ TP / GP form hexose; 6. all RuBP is regenerated; 7. 10 molecules of 3C/TP/GP form 6 molecules of 5C/RuBP
Explain the roles of water, light and ribulose bisphosphate in the process of photosynthesis
provides hydrogen; to reduce NADP; provides electron; to stabilise / reduce chlorophyll; LIGHT : excites / oxidises / removes an electron from chlorophyll / photosystem; photophosphorylation / ATP produced; electron used in reduction of NADP; RIBULOSE BISPHOSPHATE: carbon dioxide acceptor; forms GP;
Explain why an increase in temperature will increase the rate of photosynthesis
Enzymes are involved; extra kinetic energy / molecules move faster; molecules collide more often / more enzyme substrate complexes formed; increased rate of diffusion of raw materials
The carbon dioxide concentration was monitored at ground level in the centre of a small roundabout. The measurements were made on a summer day. Describe and explain how you would expect the concentration of carbon dioxide to fluctuate over the period of 24 hours
1 Higher carbon dioxide concentration at night/during darkness; 2 Photosynthesis only takes place during light; 3 Photosynthesis removes carbon dioxide and respiration adds carbon dioxide; 4 Respiration taking place throughout 24 hours; 5 Quantitative considerations such as that in plants overall photosynthetic rate greater than respiration rate; 6 Human effects such as additional carbon dioxide from heavy daytime traffic/street lighting could prolong photosynthesis
Describe how ATP is made in mitochondria
1. Substrate level phosphorylation / ATP produced in Krebs cycle; 2. Krebs cycle/link reaction produces reduced coenzyme/reduced NAD/reduced FAD; 3. Electrons released from reduced /coenzymes/ NAD/FAD; 4. (Electrons) pass along carriers/through electron transport chain/through series of redox reactions; 5. Energy released; 6. ADP/ADP + Pi 7. Protons move into intermembrane space; 8. ATP synthase
Explain why oxygen is needed for the production of ATP on the cristae of the mitochondrion
ATP formed as electrons pass along transport chain; oxygen is terminal electron acceptor / accepts electrons from electron transport chain; electrons cannot be passed along electron transport chain if no O2 to accept them; forms H2O / accepts H+ from reduced NAD/FAD / oxidises reduced NAD/FAD
Mitochondria in muscle cells have more cristae than mitochondria in skin cells. Explain the advantage of mitochondria in muscle cells having more cristae
(more cristae / larger surface area) for electron transport chain / more enzymes for ATP production/oxidative phosphorylation; muscle cells use more ATP (than skin cells)(not just more respiration)
Describe the effect of lactate production on muscles.
Decrease pH/Increase in acidity; Muscle fatigue; Denaturation / alteration of proteins / enzymes
Suggest two reasons why not all of the solar energy can be used in photosynthesis
Light missed plant / leaf/ chloroplast / reflected; wrong wavelength of light / inefficiency of photosynthesis /other limiting factors; Some light reflected/ not absorbed/refracted (if qualified) back into?atmosphere; some light misses chloroplasts/chlorophyll; only certain wavelengths of light used (in photosynthesis). 2 Energy lost as heat/by respiration/metabolic processes; qualified comment on the inefficiency of photosynthesis e.g. 25% efficient/energy lost as electrons passed on; carbon dioxide/temperature limiting
Explain why a food chain rarely contains more than four trophic levels
Energy losses (at each trophic level) / energy use; In named process ? e.g. excretion / egestion / movement / respiration / ? / as heat; (NOT ?growth? ? CANCEL, ignore ?waste?) Not available / (too) little left to sustain higher trophic levels /to be passed on
Explain how the intensive rearing of domestic livestock increases net productivity
1 Slaughtered when still growing/before maturity/while young so more energy transferred to biomass/tissue/production; 2 Fed on concentrate /controlled diet /controlled conditions/so higher proportion of (digested) food absorbed/lower proportion lost in faeces / valid reason for addition; 3 Movement restricted so less respiratory loss / less energy used; 4 Kept inside/heating/shelter / confined so less heat loss / no predators; 5 Genetically selected for high productivity
Explain how farming practices increase the productivity of agricultural crops
1. Fertilisers/minerals/named ion (added to soil); 2. Role of named nutrient or element e.g. nitrate/nitrogen for proteins / phosphate/phosphorus for ATP/DNA; 3. Pesticides/biological control prevents damage/consumption of crop; 4. Pesticides/weed killers /herbicides/weeding remove competition; 5. Selective breeding / genetic modification (of crops); 6. Glass/greenhouses enhance temp/CO2/ light; 7. Ploughing aerates soil/improves drainage; 8. Ploughing/aeration allows nitrification/decreases denitrification; 9. Benefit of crop rotation in terms of soil nutrients/fertility/pest reduction; 10. Irrigation/watering to remove limiting factor; 11. Protection of crops from birds/pests/frost by covers/netting etc
Explain why plants may fail to grow if high concentrations of nitrate are applied to the soil
Water potential of soil reduced/more negative/ reduced water potential gradient; less water moves into roots/water moves out of roots by osmosis
Fertilisers are added to soils to replace the nutrients lost when crops are harvested. Give two advantages of using an organic fertiliser such as farmyard manure
More micronutrients / greater range of nutrients; Nutrients released slowly; Improves soil quality / adds humus / adds microbes / improves soil structure; Improves water-holding capacity of soil / reduces leaching/eutrophication; Improves soil aeration; Already available
Describe why phosphates are needed by a growing plant
Production of phospholipids; in cell membranes; synthesis of ATP; production of DNA; production of RNA; production of NADP