Question
A broad bean is the seed of a species, Vicia faba, in the Fabaceae, a family of flowering plants. This family contains many species that are used as sources of food.
a. On the diagram, label the testa and the radicle. [2]
b. An experiment was done to test the hypothesis that temperature affects the rate of germination of the broad bean. Outline two factors apart from temperature that should be controlled in this experiment. [2]
c. State the genus of the broad bean. [1]
d. Broad beans are rich in starch and cellulose. Compare and contrast the structure of starch and cellulose. [2]
e. Once the germinated bean grows above the ground, state the process used by the bean in the production of starch. [1]
▶️Answer/Explanation
Markscheme
a. testa labelled ✔
b. radicle labelled ✔ (must point to the bottom half of the embryo or the tip).
a. same amount/type of soil/substrate / pH of soil ✔ e.g.: heater
b. same amount of water / humidity ✔
c. oxygen/aeration ✔
d. same measurement of germination / time ✔ e.g.: emergence of radicle
e. same number/source/age of seeds ✔
Accept discussion of light only in as much as it relates to temperature.
Vicia ✔
a. both polymers of glucose molecules / polysaccharides
OR
both form 1,4 glycosidic bond ✔
b. starch is formed by alpha glucose while cellulose is formed by beta glucose
OR
in starch C1 hydroxyl groups are found in same plane while in cellulose on different planes
OR
in cellulose, alternatively the beta glucose needs to be placed upside-down in order to have C1 hydroxyl groups on the same plane
OR
two types of starch (amylose and amylopectin) but one type of cellulose ✔
One similarity and one difference.
Comparison to cellulose needed.
photosynthesis
Question
Boreal forests stretch across Canada, Russia and Scandinavia. This northern ecosystem accounts for 29 % of the world’s forest areas. The long, cold winters favour tall evergreen trees with either needles or scale-like leaves. These trees are wind-pollinated and their seeds are not enclosed in a fruit. The photograph shows a typical boreal forest in winter.
a. Identify the dominant plant phylum in the boreal forest.[1]
b. In some areas there are gaps in the boreal forest where trees fail to grow and peat tends to accumulate. Suggest reasons for this. [2]
c. An increase in global temperatures poses a critical threat to boreal forests. Explain the consequences of climate change to this northern ecosystem. [2]
d.i. Suggest one advantage for the evergreen trees of the boreal forest being pollinated by wind. [1]
d.ii. Discuss the advantages of the production of seeds enclosed in fruit. [2]
e.i. The boreal forests are situated close to the north pole and even in summer the intensity of sunlight is lower than at the equator. Sketch a graph showing the effect of light on the rate of photosynthesis, labelling the axes.
[2]
e.ii. In some boreal species, Rubisco is down-regulated during the winter months. Describe the role of Rubisco in photosynthesis. [2]
▶️Answer/Explanation
Markscheme
coniferophyta/conifer/coniferous/gymnosperms/pinophyta ✔
a. waterlogged soils/poor drainage
OR
acidic soil
OR
anaerobic conditions/soil ✔
b. organic matter not «fully» decomposed «leading to peat formation»
OR
decomposers/saprotrophs less active/fewer in cold «temperatures» ✔
a. higher temperatures so more transpiration/droughts/dehydration/water shortage ✔
b. more forest fires ✔
c. more/new pests/diseases because of the changed conditions ✔
d. competition from trees/plants «that colonize/spread to boreal forests» ✔
e. trees/«named» organisms «of boreal forests» not adapted to warmer conditions
OR
trees/«named» organisms migrate/change their distribution due to warmer conditions ✔
f. trees die so loss of habitat for animals ✔
g. faster decomposition/nutrient cycling «so conditions in the ecosystem change» ✔
h. standing water/floods due to more snow/permafrost melting ✔
animals/insects/mutualistic «relationships» not needed «for pollination»
OR
pollen not eaten by animals/insects ✔
a. seeds are protected «inside the fruit» ✔
b. seed dispersal by fruits ✔
c. example of a strategy for seed dispersal by a fruit ✔
d. dispersal reduces competition/spreads seeds away from parent plant/to colonize new areas ✔
For mpc suitable strategies are dispersal by wind, by animals ingesting/carrying away succulent fruits, by animals being attracted to colourful/sweet/tasty fruits, by animals burying nuts, by burrs or other hooked fruits sticking to animals and by self-explosion.
a. x-axis labelled as light intensity/amount of light AND y-axis labelled as rate of photosynthesis/rate of oxygen release/rate of carbon dioxide uptake ✔
b. curve starting at/slightly to the right of the x-axis origin and rising rapidly and then more slowly and plateauing but never dropping ✔
a. carbon fixation/fixes carbon dioxide/carboxylation
OR
rubisco is used in the Calvin cycle/light independent stage ✔
b. carbon dioxide linked to RuBP/ribulose bisphosphate «by rubisco» ✔
c. glycerate 3-phosphate/glycerate phosphate produced «by rubisco» ✔