DP Biology (first assessment 2025)

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Question 21N.2.HL.TZ0.6a

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Date November 2021 Marks available [Maximum mark: 4] Reference code 21N.2.HL.TZ0.6a
Level HL Paper 2 Time zone TZ0
Command term Describe Question number a Adapted from N/A
a.
[Maximum mark: 4]
21N.2.HL.TZ0.6a
(a)

Describe the endosymbiotic theory.

[4]

Markscheme

a. theory that eukaryotic cells evolved from prokaryotes
OR
origin of eukaryotic organisms based on some organisms living inside/engulfed by other organisms
OR
prokaryotic cell engulfed another prokaryote including it in cytoplasm without digesting it;
b. mitochondria/chloroplasts have double membranes;
c. mitochondria/chloroplasts have their own DNA/loop of DNA/naked DNA;
d. mitochondria/chloroplasts have similar size to prokaryotes;
e. mitochondria/chloroplasts can reproduce by binary fission;
f. mitochondria/chloroplasts have 70S ribosomes (same as prokaryotes);

Examiners report

The theory of endosymbiosis was quite well known. Common errors included the original engulfing process being carried out by a eukaryote, rather than a prokaryote.

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