Question 19M.2.SL.TZ1.8
| Date | May 2019 | Marks available | [Maximum mark: 15] | Reference code | 19M.2.SL.TZ1.8 |
| Level | SL | Paper | 2 | Time zone | TZ1 |
| Command term | Describe, Explain, Outline | Question number | 8 | Adapted from | N/A |
Describe how detritivores obtain nutrition and the effects they have in ecosystems.
[4]
a. «detritivores» obtain nutrition from detritus/waste/dead bodies ✔
b. are heterotrophic ✔
c. removes large waste/cleans up the ecosystem
OR
helps control spread of disease ✔
d. facilitates further decomposition ✔
e. contribute to the supply of «inorganic» nutrients for autotrophs/nutrient cycling
OR
improve soil conditions/aeration ✔
Most candidates got max 2 for mp a (nutrition of detritivores) and mp e (recycling of nutrients). Candidates getting high marks were able to provide correct examples of detritivores and correctly link to their role in enriching the soil and remove dead material. The biggest problem was the notion that detritivores recycle energy.
Outline the role of amylase in digestion in humans.
[4]
a. amylase is an enzyme ✔
b. secreted by salivary glands/pancreas ✔
c. active/released into the mouth/small intestine ✔
d. acts on starch/polysaccharides ✔
e. breaks «glycosidic» bond by hydrolysis/adding water ✔
f. converts insoluble/large molecule to soluble/small molecules ✔
g. product is maltose/disaccharide/sugar molecule ✔
The name, location and correct function of the enzyme was very common making 3 max the most common marks. Students who got fewer marks gave generic explanations of the process of digestion. Some students made incorrect references to amylase digesting proteins. A few candidates ignored amylase and discussed digestion in general.
Explain how plants capture and use light in photosynthesis.
[7]
a. plants convert light energy into chemical energy by photosynthesis ✔
b. photosynthesis takes place in chloroplasts ✔
c. chloroplasts «are organelles that» contain the pigment chlorophyll ✔
d. chloroplasts/chlorophyll «in plants» absorb sunlight ✔
e. «chlorophyll» absorbs red AND blue light most effectively ✔
f. light causes photolysis/splits water molecule ✔
g. carbon dioxide AND water are reactants «in photosynthesis» ✔
h. glucose AND oxygen are products «of photosynthesis» ✔
i. light intensity is a limiting factor for the rate of photosynthesis ✔
j. organic/carbon compounds/glucose provide food/stored energy «for plant itself, animals,food chains» ✔
k. up to one additional mark for an accurate detail from AHL ✔
Generally well done with some very knowledgeable answers from the Higher Level programme sometimes to the detriment of the more basic answers required by the standard level examination. Many candidates who attempted this response got more than 4 marks for mp b, d, g and h which were the most common. Students getting higher marks were able to focus on correct conversion of energy, efficiency of red and blue light absorption, and photolysis. Some egregious misconceptions exist among candidates such as plants are green because they absorb green light. The idea that during photosynthesis light energy is converted to chemical energy was frequently neglected.
