Short notes on Edexcel A2 Biology - Part 3

5.3 Global warming

Role of (herbivorous/omnivores) animal in recyling carbon

• reference to {carbon / organic / eq} compounds in plant material ;
• idea that digestion provides respiratory substrates ;
• carbon dioxide released (from respiration) ;
• (this carbon dioxide is) available for photosynthesis ;
• reference to woodlice {eaten / decompose} ;

Role of microorganisms in recycling carbon

• reference to {decomposition / decay / putrefaction } (by microorganisms) ;
• reference to respiration ;
• releases carbon dioxide for photosynthesis / eq ;
• methane released in anaerobic (conditions);
• (methane) available as fuel / eq ;

Biofuels may help to reduce global warming

• reference to biofuels being (possibly)carbon neutral ;
• idea that {plants / crops} are used for biofuels;
• idea that carbon dioxide used for photosynthesis (by plants / in production of biofuels) ;
• idea of using biofuels to replace fossil fuels ;

Disadvantage of using biofuels to reduce global warming

• land has to be cleared to grow plants for biofuels / eq ;
• burning produces carbon dioxide / the plants growing there would have been {photosynthesising / using carbon dioxide} / machinery uses fossil fuels / loss of habitat ;
• decomposition of dead plant material (after clearing) / eq ;
• produces carbon dioxide / eq ;
• idea that the land could have been used for food production ;
• less food produced / eq ;
• ref to use of fertilisers ;
• idea of eutrophication OR use oil-based products

Production of biofuels may not be carbon neutral

• idea that biofuel production may (overall) results in more carbon dioxide in the atmosphere ; OR idea that carbon neutral means that the carbon dioxide produced equals the carbon dioxide used ;
• idea of forests as carbon {sinks / eq} ;
• idea that {clearing land / deforestation} results in (net) increase in carbon dioxide (in atmosphere) ;
• (less plants means) less carbon dioxide {removed / used / eq} by photosynthesis ;
• {burning / eq} trees produces carbon dioxide ;
• idea that (increased) decomposition produces carbon dioxide;
• idea of using {(fossil) fuels / petrol / diesel} by {lorries / machinery / eq}produces carbon dioxide ;
• {burning /eq} of biofuels produces carbon dioxide ;

Combustion of biofuels may lead to global warming

• reference to production of {greenhouse gases / named greenhouse gas} ;
• idea that these gases {build up/ remain / form a layer} in (upper) atmosphere;
• which {absorb / trap / eq} {heat energy / infra-red / IR / eq} ;
• reflected from earth’s surface ;
• idea that increased levels of these gases increase the greenhouse effect ;
• idea that (mean) temperature of earth’s {surface / atmosphere} is increasing ;

Forest fires may lead to global warming

• reference to {fires / burning / eq} produces carbon dioxide ;
• which is a greenhouse gas ;
• idea that these gases {build up / remain / form a layer / increase} in (upper) atmosphere;
• which {absorb / trap / eq} {heat energy / infra red / IR / eq} ;
• reflected from earth’s surface ;
• idea that increased levels of these gases increase the greenhouse effect ;
• idea that (mean) temperature of earth’s {surface / atmosphere} is increasing ;
• idea that less carbon dioxide {removed / used / eq} by photosynthesis ;

Greenhouse effect by methane and carbon dioxide

• (carbon dioxide and / or methane) are greenhouse gases / eq ;
• which {absorb / trap / eq} {heat / infra red / IR / long wave} (radiation) / eq ;
• {reflected / (re)radiated} from the Earth’s surface / eq ;
• prevent {heat / infra red / IR / long wave / eq} (radiation) escaping ;
• idea of temperatures maintained higher (than they would be) ;

Reduction in use of fossil fuels may not prevent further global warming

• carbon dioxide produced {by using / in production of / eq} fossil fuels / eq ;
• no (direct) evidence that increased carbon dioxide leads to global warming / eq ;
• reference to carbon dioxide released from {other processes / named process} ;
• idea of removal of {carbon sinks / named example / eq} (also) leads to increase in carbon dioxide ;
• stated example of any other greenhouse gas released from another source e.g. CFC, water vapour, methane ;
• description of source e.g. ruminant animals, paddy fields, melting ice, clearance of peat land ;
• idea of natural {cycles / events / phenomena / eq} may be involved (in global warming) e.g. solar, volcanoes ;
• idea of evidence from past is being used ;
• idea of {(past evidence) is not in indicator of future events / limitations of (climatic) models} ;
• idea that scientists may be biased ;
• description of bias e.g. employed by {company / country} with vested interest, self promotion ;
• specific example of problem with / disadvantage of} alternative source of energy ;

Why body temperature effects rate of development of animals

• reference to increase in {metabolic rate / enzyme activity / eq} as temperature rises ;
• reference to increase in {kinetic / eq} energy of molecules (as temperature rises) / eq ;
• reference to increase in {enzyme- substrate complexes / energy of collisions / eq} (as temperature rises) ;
• idea of {inactivation at lower temperatures/ denaturation at higher temperatures} of enzymes ;
• idea that temperature affects {differentiation / growth /division / eq} ;

Affect of global warming on distribution

• idea that global warming will increase the temperature (at the latitudes) ;
• idea that temperatures (at these latitudes) may become too high for any of the species ;
• idea that new temperature may be above the maximum to complete development or above the upper lethal limit ;
• idea that species move { to cooler regions / eq} ;
• ref to change in {food source / predators / competition / eq}

Short notes on Edexcel A2 Biology - Part 2

5.2 How ecosystem works

NPP

• (rate of) {production of / energy incorporated into / eq} {biomass / organic material / eq} ;
• reference to {losses in respiration / GPP – respiration / eq} ;
• in {producers / plants};

Why NPP may increase due to increase in temperature

• idea that the rate of {(bio)chemical / metabolic / photosynthetic / named} reactions increases ;
• idea of increase in {movement / kinetic energy} of {enzyme / substrate / molecules / particles} / eq ;
• idea of (increase in reaction rate) because of more enzyme substrate interaction ;

Importance of NPP to farmer to use a land for cattles

• cattle {are primary consumers / herbivores / eat grass / eat plants / eq} ;
• (therefore) gain energy (available as NPP) ;
• idea of grazing capacity of the grassland ;
• idea of affect on yield of {meat / milk / eq} ;
• idea of changing to a more {efficient / NPP yielding} crop ;

Factors which may influence NPP

• grazing / {consumers / herbivores / named herbivore} / eq ;
• trampling / eq ;
• shading by {plants / named plant} / eq ;
• competition from other plants / eq ;
• disease / eq ;

Succession

• idea of (a sequence of) changes in {a community / organisms / species / plants} ;
• over a period of time / eq ;

Climax community

• idea of final {stage / sere / community} ;
• feature of community described e.g. self-sustaining , stable, one dominant species, a few codominant species ;

Importance of conserving endangered plants

• idea of conservation of {genetic diversity / genetic variation / biodiversity} ;
• idea of extinction ;
• idea of aesthetic reasons ;
• idea that these plants may be useful e.g. as medicines ;
• idea that other animals depend on these plants as a {source of food / habitat} ;

Nich

• idea of the {role / purpose / interaction / eq} of {organism / sea anemone / species / eq} ;
• reference to trophic level(s) ;

Succession

• reference to lichens and mosses as pioneer community ;
• able to grow in {little / no} soil / eq ;
• (that) breaks up (rock) fragments / forms {thin / shallow / eq} soil;
• reference to {plants / eq} with {small / short / eq} roots ;
• (able to) grow in {thin / shallow / eq} soil / eq ;
• idea that changes in soil structure enable {trees / shrubs} to grow / eq ;
• general points to be included:
  • reference to soil able to {hold / retain / contain / eq} {water / minerals} ;
  • as plants {lose leaves / die / decay / eq} ;
  • reference to {organic matter / humus / eq} {increases / released / eq} ;
  • reference to competition effects ;

Climax community

• includes (both) animals and plants / has many species / has high biodiversity / eq ;
• reference to {interaction / eq} between species / eq ;
• idea of balanced equilibrium of species ;
• reference to {dominant / codominant} (plant or animal) species ;
• reference to stable if no {change to environment / human influence} ;

Short notes on Edexcel A2 Biology - Part 1

5.1 Photosynthesis

Thylakoids

• (made of) membranes ;
• (arranged as) {stacks / grana / eq} ;
• contain {pigment / chlorophyll} / eq ;
• (arranged as) quantasomes / photosystems ;

Advantage of growing crop in glasshouse rather than open field

• crops can be grown {out of season / all year round} / eq ;
• plants photosynthesise 24 hours a day / eq ;
• idea of less physical damage from {weather /animals / eq} ;
• pest control easier / eq ;
• ref to control of other named factor, eg CO2, temperature, humidity, water supply ;

Difference between abiotic and biotic factors

ref to biotic factors involve {organisms / living} abiotic are {physical / chemical / non-living} (factors) / eq ;

Using quadrat to obtain mean density of two species in an ecosystem

• ref to {several / many / more than 2} readings ;
• ref to use of random quadrat positions ;
• description of suitable process to give random positions / eq ;
• ref to {known / stated} area of quadrat ;
• number of individuals in each quadrat {counted/ recorded} / eq ;
• description of how mean density calculated using total count e.g. total number (of each species) divided by total area sampled ;

Reasons for not using all the light hitting the surface of a leaf is not used

• idea of reflection ;
• reference. to {incorrect / eq } {wavelength / colour / frequency} ;
• idea of {not hitting the {chloroplast / chlorophyll}} / it is transmitted ;
• idea of light being in excess e.g. at max. photosynthesis so more light can be used ;

Light dependant stage of photosynthesis (also see A2 revision guide page 9)

• reference to {thylakoids / thylakoid (membranes)} ; in {granum / grana} ;
• (light energy) raises energy level of electrons / {chlorophyll / electrons}excited / eq ;
• electrons released from {chlorophyll /photosystem / eq} / eq ;
• reference to electron {carrier / eq} ;

reference to series of {redox / oxidation & reduction / eq} reactions ;

• reference to energy level of electrons {falls / eq} ;
• reference to {synthesise ATP from ADP +P /phosphorylate ADP} ;
• reference to photophosphorylation ; reference to ATP {synthetase / synthase /ase} ;
• reference to {chemiosmosis / eq} ;
• idea of electrons from {photolysis / eq} used to replace those lost ;
• reference to involvement of {accessory pigments / named example} ;

Production of oxygen in light-dependent reaction of photosynthesis

• reference to energy from light ;
• reference to photolysis ;
• of water ;

Structure of chloroplast involved in ATP formation

• reference to {granum / grana} ;
• reference to (a granum is) a stack of {thylakoids / membranes} OR grana are connected by lamellae ;
• reference to (thylakoids contain) {electron carriers / eq} / chlorophyll / photosystems ;
• reference to (membranes contain) {ATPase / ATPase channel} ;
• idea that {electron carriers / ATPase /eq} are associated with {thylakoid / thylakoid membranes} ;

Why can't light independent stage of photosynthesis occur without light dependant stage

• idea that products of light- dependent stage are {needed for / used in / eq} {light-independent stage / Calvin cycle} ;
• reference to (products of light- dependent stage) are {reduced NADP / eq} and ATP ;
• reference to use of {reduced NADP / eq} for {reduction / eq} of {carbon dioxide / GP / eq} ;
• reference to use of ATP as source of energy ;

Importance of thin lamina in leaves

• idea of {fast / maximum} {gas exchange / uptake of carbon dioxide / eq};
• idea of penetration of light ;
• idea that carbon dioxide is used in the {light-independent stage / Calvin cycle / formation of GP}; OR
• idea that light is used in {light-dependent stage / photolysis / photophosphorylation /eq } ;

Importance of midrib in leaves

• transport (in xylem) of water (to the leaves) / eq ;
• transport (in phloem) of {sucrose / sugar / carbohydrates } (away from the leaves) / eq;
• (water) for {light-dependent reaction / photolysis / source of hydrogen (ions)}; OR
• idea of (transporting sugar) to make more room for more carbohydrate synthesis ;

How GALP is used to synthesise cellulose

• GALP is a 3C molecule / eq ;
• reference to conversion (of GALP) to glucose / eq;
• idea of enzymes involved in the synthesis of {glucose / cellulose} ;
• (which is) β glucose ;
• reference to formation of glycosidic bonds ;
• between C1 and C4 / these bonds are 1-4 (glycosidic bonds) ;
• by condensation ;
• reference to {straight / unbranched} (chains of glucose) ;
• reference to cellulose as a {polysaccharide / polymer of glucose / eq} ;

How GP is used to synthesise starch

• idea of conversion of GP to GALP / eq ;
• using ATP and reduced NADP / eq ;
• idea of conversion (of GALP) to {glucose /hexose} eq ;
• (which is) α glucose ;
• reference to formation of glycosidic bonds ;
• these bonds are 1-4 and 1-6 (glycosidic bonds)/ eq ;
• by condensation ;
• ref to amylose and amylopectin ;
• credit details of amylose e.g. straight chain, 1-4 bonds ;
• credit details of amylopectin eg branched, 1-4 and 1-6 bonds ;