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← Theoretical 1

Q43 — Giraffe FGFRL1 — Cardiovascular and Skeletal Adaptations

Theoretical 1 Real exam question — full text reproduced under IBO's CC BY-NC-SA 4.0 license
Cardiovascular Physiology Molecular Evolution & Neutral Theory

Giraffes (Giraffa sp.) have the longest necks of any mammal, up to 2 m long; the heart must maintain blood pressure 2.5× higher than humans for oxygen to reach the brain, yet giraffes don’t develop hypertension. Comparing Rothschild’s giraffe’s genome to other ruminants (e.g. okapi), scientists found giraffe-specific mutations related to the cardiovascular system, bone growth, sensory function, and circadian rhythms — including seven mutations in the FGFRL1 gene not found in any other ruminant. Mice engineered with the “giraffe” FGFRL1 gene become insensitive to hypertension and develop firmer bones. Giraffes have also lost at least 53 olfactory genes and sleep only ~3 hours a day.

Two images showing giraffe posture while eating (a) and drinking water (b). a. The position of a giraffe eating.

Giraffe drinking water, showing the characteristic splayed-leg posture. b. The position of a giraffe drinking water.

Using the information and images, determine whether the following statements are true or false:

A. The ancestors of giraffes lived on Earth during the Paleogene.
B. The giraffe FGFRL1 gene has a pleiotropic effect on the development of both the circulatory and musculoskeletal systems.
C. The unique mutations in contemporary giraffes probably involve genes that evolved to regulate both skeletal and cardiovascular development in parallel.
D. As a result of changes in the corresponding genes, the evolutionary advantages of the giraffe are: easy access to drinking water, avoiding predators and a better sense of smell.
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Question reproduced from IBO 2022, Theoretical Paper 1, licensed under CC BY-NC-SA 4.0 — attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)