Question
In ecosystems, energy is used to convert inorganic compounds into organic matter. Energy enters ecosystems through producers.
a. Explain the processes by which energy enters and flows through ecosystems. [8]
b. Producers extract phosphates and nitrates from soil. Outline how these ions are used in the synthesis of organic molecules. [3]
▶️Answer/Explanation
Markscheme
a. light energy is the initial energy source for (all) organisms
b. producers/autotrophs change light/radiant energy into chemical energy
OR
producers/autotrophs convert/trap light/radiant energy by photosynthesis
c. producing C6H12O6 /sugars/carbohydrates
d. carbon/organic compounds used for energy/growth/repair/storage
e. compounds/energy pass as food along food chains/trophic levels WTTE
f. cellular respiration releases energy as ATP from food
g. energy is lost as heat (during cellular respiration)
h. loss of energy at each trophic level
OR
only approximately 10% of energy is passed to the next trophic level / 90% is lost at each trophic level
i. energy lost in bones/hair when they die/not fully eaten by the next trophic level
j. energy lost in feces/urine
k. decomposers/saprotrophs remove energy from wastes/bodies
l. energy is not recycled
a. by photosynthesis / using energy from light
b. attached to carbon compounds
c. phosphates used to make phospholipids/nucleotides/nucleic acids/DNA/RNA/ATP
d. nitrates are used to make amino acids/proteins/nucleotides/nucleic acids/DNA/RNA/ATP
e. transported from roots to leaves (in xylem)
a. drawn in steps rather than triangle
b. drawn to scale (should be at least 1/5 of the box below it)
OR
annotated with appropriate numeric values
c. producer
d. primary consumer
e. secondary consumer
Question
a. Describe the structure and function of starch in plants. [3]
b. Outline the production of carbohydrates in photosynthesis.[4]
c. Discuss the processes in the carbon cycle that affect concentrations of carbon dioxide and methane in the atmosphere and the consequences for climate change.[8]
▶️Answer/Explanation
Markscheme
Structure:
a. «starch» is a polysaccharide/is composed of glucose molecules
b. contains amylose which is a linear/helical molecule
c. contains amylopectin which is a branched molecule
Function:
d. storage of glucose/energy in plants
e. storage form that does not draw water
a. light is absorbed by chlorophyll
OR
chlorophyll absorbs more red and blue light
b. «absorbed» light energy is converted to chemical energy
c. some of the energy is used for production of ATP
d. water molecules are split/photolysis
e. produces oxygen «as waste product»/hydrogen/NADPH
f. plants absorb/fix CO2 «from air or water»
g. ATP/energy is needed to produce carbohydrates/starch
a. CO2 is produced from respiration in organisms/combustion of biomass/fossil fuels
b. CH4 is produced by anaerobic respiration of biomass/«methanogenic» bacteria
c. CH4 is oxidized to CO2 and water
d. CO2 is converted into carbohydrates/organic compounds by autotrophs/producers/photosynthesis
e. CO2 can be converted to calcium carbonate/fossilized into limestone
f. «partially» decomposed organic matter/biomass can be converted into peat/coal/oil/gas/fossil fuels
g. CO2 and CH4 are both greenhouse gases/increase greenhouse effect
h. both absorb long-wave radiation from the earth and retain the heat in the atmosphere
i. increased CO2 concentrations in the atmosphere correlate with increased combustion of fossil fuels
j. rising average global temperatures correlate with more greenhouse gases in the atmosphere
k. cattle production/rice paddy/defrosting of tundra increase CH4 in the atmosphere
OR
increasing CO2 leads to acidification of marine/aquatic environments
l. the global temperature increase influences/disrupts climate patterns
Question
Plants have widespread influences, from food chains to climate change.
a. Draw a diagram of a palisade mesophyll cell labelling only the structures that would not be present in a pancreatic cell [3]
b. Explain the process of photosynthesis.[8]
c. Describe the process of peat formation.[4]
▶️Answer/Explanation
Markscheme
a. cell wall
Must be shown as a double line
b. large vacuole
c. chloroplast/plastid
d. starch grain
e. tonoplast
a. autotrophs perform photosynthesis
b. carbon dioxide and water are the reactants/raw materials required for «photosynthesis»
c. light splits water molecules/causes photolysis
d. «photolysis» releases oxygen as a «waste» product
e. light energy is converted into chemical energy
f. «photosynthesis» produces organic compounds/glucose/carbohydrates
g. photosynthesis occurs in chloroplasts
h. chlorophyll «photosynthetic pigment» absorbs light
i. different pigments absorb different wavelengths «of light»
j. chlorophyll absorbs red and blue light/ends of the spectrum
k. carbon dioxide concentration/temperature/light intensity are limiting factor
a. formed from dead plant material/leaves/mosses/Sphagnum
b. formed in waterlogged sites/bogs/mires/swamps
c. where bacteria/fungi/saprotrophs are not active/are inhibited
d. organic matter not fully decomposed
e. «occurs» in acidic conditions
f. «occurs» in anaerobic conditions
Reject anaerobic respiration
g. «very» slow process/takes a long time