▶️ Answer/Explanation
Solution
a. On the diagram, label the testa and the radicle. [2]
– Testa: The seed coat that protects the seed.
– Radicle: The embryonic root, which grows downward during germination to anchor the plant and absorb water.
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]
– Water Availability: Germination requires consistent water across all experimental groups to ensure fair testing.
– Light Conditions: Standardizing light or darkness prevents bias in the germination rate, as light can influence the process.
c. State the genus of the broad bean. [1]
– The genus of the broad bean is \( Vicia \).
d. Broad beans are rich in starch and cellulose. Compare and contrast the structure of starch and cellulose. [2]
– Starch: A polysaccharide of glucose units linked by alpha-1,4 glycosidic bonds, existing in branched (amylopectin) or unbranched (amylose) forms, making it easily digestible for energy.
– Cellulose: A polysaccharide of glucose units linked by beta-1,4 glycosidic bonds, forming long, straight chains that provide structural support and are not easily broken down by most organisms.
e. Once the germinated bean grows above the ground, state the process used by the bean in the production of starch. [1]
– Once above the ground, the bean undergoes photosynthesis in its leaves, converting carbon dioxide and water into glucose, which is then stored as starch.
▶️ Answer/Explanation
Solution
a. Identify the dominant plant phylum in the boreal forest. [1]
– The dominant plant phylum in the boreal forest is Coniferophyta (Conifers). These evergreen trees, with needles or scale-like leaves, are well-adapted to the long, cold winters.
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]
– Cold Temperatures and Short Growing Seasons: The harsh winter climate and brief growing seasons may prevent tree growth, limiting the ability of young trees to establish themselves.
– Waterlogged Soils and Poor Drainage: In some areas, soil may become waterlogged due to low temperatures, which prevents tree roots from obtaining enough oxygen, leading to the accumulation of peat (partially decayed plant material).
c. An increase in global temperatures poses a critical threat to boreal forests. Explain the consequences of climate change to this northern ecosystem. [2]
– Melting of Permafrost: As temperatures rise, permafrost (permanently frozen ground) may melt, leading to changes in soil structure and release of stored carbon (as methane), which further accelerates climate change.
– Shifting Ecosystems: Warmer temperatures may allow for the encroachment of other plant species more suited to warmer climates, potentially displacing native boreal forest species and disrupting the ecosystem.
d.i. Suggest one advantage for the evergreen trees of the boreal forest being pollinated by wind. [1]
– Wind Pollination: Allows evergreen trees to reproduce even in cold climates where pollinators like insects may be scarce. It also reduces dependence on environmental conditions such as temperature or the presence of pollinators.
d.ii. Discuss the advantages of the production of seeds enclosed in fruit. [2]
– Protection of Seeds: The fruit provides a protective layer around the seed, reducing damage from environmental factors, herbivores, or pathogens.
– Seed Dispersal: The fruit can help in the dispersal of seeds over greater distances (e.g., through wind, water, or animals), allowing the plant to spread to new areas and increase its chances of survival.
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]
– Graph Description: In this case, I can describe the graph you would draw:
– X-axis: Light Intensity (Low to High)
– Y-axis: Rate of Photosynthesis (Low to High)
The graph would have a curve showing that as light intensity increases, the rate of photosynthesis also increases. However, after a certain point, the curve would level off, showing that the rate of photosynthesis reaches a saturation point. This is because beyond a certain light intensity, other factors (e.g., temperature or CO₂ levels) become limiting.
e.ii. In some boreal species, Rubisco is down-regulated during the winter months. Describe the role of Rubisco in photosynthesis. [2]
– Rubisco: (Ribulose bisphosphate carboxylase/oxygenase) is an enzyme that plays a central role in the Calvin cycle, which is part of the process of photosynthesis. It catalyzes the fixation of carbon dioxide (CO₂) into an organic molecule, starting the process of carbon assimilation.
– During the winter months, when photosynthesis is less active due to lower light levels and colder temperatures, down-regulating Rubisco helps conserve energy and resources as the plant does not need to fix carbon during the dormant period.