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Date November 2019 Marks available 7 Reference code 19N.2.SL.TZ0.5
Level Standard level Paper Paper 2 Time zone TZ0 / no time zone
Command term Explain Question number 5 Adapted from N/A

Question

Draw a section of the Singer-Nicolson model of an animal cell membrane.

[4]
a.

Outline the principles used by scientists to classify organisms.

[4]
b.

Explain the movement of energy and inorganic nutrients in an ecosystem.

[7]
c.

Markscheme

a. bilayer of phospholipids with both “tails” towards the inside «of the bilayer» ✔ This can be taken unlabeled from diagram.

b. hydrophilic/polar and hydrophobic/non-polar annotation ✔

c. cholesterol between phospholipid tails ✔

d. glycoprotein ✔

e. integral proteins/channel proteins ✔

f. peripheral proteins ✔ Allow this if it does not extend across the membrane

Elements should be clearly drawn, correctly positioned and annotated.

a.

a. use of the binomial system ✔

b. agreed/developed by scientists / OWTTE ✔

c. hierarchy of taxa used ✔ Names of the seven taxa not required. 

d. three domains used/three domain names ✔ OWTTE

e. genome/DNA sequence similarities
OR
amino acid sequence of specific proteins ✔

f. species from a common ancestor are grouped together
OR
included in the same clade/branch in cladogram ✔

g. use evidence of evolutionary origin ✔ Allow example e.g. fossil record comparison

h. shared characteristics within a group
OR
similar embryonic development ✔

b.

a. autotrophs/producers/plants obtain inorganic nutrients from the «abiotic» environment ✔

b. energy provided «mainly» by sunlight ✔

c. light energy converted «to chemical energy» through photosynthesis ✔

d. photosynthesis/producers/autotrophs convert inorganic carbon/carbon dioxide and water into carbon/organic compounds ✔

e. «these» carbon compounds/foods contain/are a source of «useable» energy «for life» ✔

f. carbon compounds/energy are transferred along food chains when eaten by consumers/heterotrophs ✔ Allow OWTTE for mpf for passed up trophic levels.

g. respiration returns carbon «dioxide» to the environment ✔

h. respiration releases stored/chemical energy as ATP/heat ✔

i. energy/ATP is used to carry out life functions/synthesis/growth/movement ✔

j. energy is lost/not recycled ✔

k. nutrients are recycled / example of recycled nutrient e.g. carbon ✔

l. decomposers recycle minerals/inorganic nutrients ✔

c.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.

Syllabus sections

Core » Topic 4: Ecology » 4.2 Energy flow
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