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.
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.
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. (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.