DP Biology (first assessment 2025)

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Question 19M.2.HL.TZ2.6a

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Date May 2019 Marks available [Maximum mark: 3] Reference code 19M.2.HL.TZ2.6a
Level HL Paper 2 Time zone TZ2
Command term Describe Question number a Adapted from N/A
a.
[Maximum mark: 3]
19M.2.HL.TZ2.6a
(a)

Describe briefly the endosymbiotic theory.

[3]

Markscheme

a. eukaryotes evolved from prokaryotes ✔

b. prokaryotes engulfed other prokaryotes without digesting them ✔

c. engulfed aerobic cell/prokaryote became mitochondria ✔

d. engulfed photosynthetic cell/ prokaryotes became chloroplasts ✔

e. these organelles have a double membrane «due to the engulfing process» ✔

f. mitochondria/chloroplasts contain DNA/small ribosomes/70S ribosomes ✔

Examiners report

Endosymbiotic theory. Those who had been taught it gained at least one mark. Few mentioned that the cell that became the mitochondrion was aerobic, and that the one that became the chloroplast was photosynthetic.

Syllabus sections