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Date May 2018 Marks available 2 Reference code 18M.2.HL.TZ1.2
Level Higher level Paper Paper 2 Time zone Time zone 1
Command term State Question number 2 Adapted from N/A

Question

State two features that are found only in mammals.

[2]
a.

Birds, bats and humans are all vertebrates with pentadactyl limbs. Birds and bats use their forelimbs to fly whereas humans can use them to lift and manipulate objects. Outline how the bird, bat and human forelimb can be used to illustrate the concept of homologous structures.

[2]
b.

Markscheme

a. hair/fur 

b. mammary glands/breasts/(secretion of) milk/lactation 

c. sweat glands 

d. lungs with alveoli

e. placenta (in most mammals) 

f. fetus develops in uterus/gives birth to live young

Do not award marks for any answers after the first two given.

a.

a. (homologous structures have evolved) from a common ancestor 

b. divergent evolution/adaptive radiation 

c. similarities in forelimb bones (in birds, bats and humans) / description of the similarities in bones 

d. different uses/functions

Do not accept (positive) correlation.

b.

Examiners report

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

Syllabus sections

Core » Topic 5: Evolution and biodiversity » 5.3 Classification of biodiversity
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Core » Topic 5: Evolution and biodiversity
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