Evidence of a Common Ancestor of Primates

Question 1

What does it mean to be arboreal?

Answer 1

• living in trees

Question 2

What classification do most present-day primates share?

Answer 2

• they are arboreal

Question 3

What characteristics do primates have that are adaptations to a previous arboreal way of life?

Answer 3

• the clavicle (collarbone)
• long, slender limbs that rotate freely at the shoulders and hips
• mobile opposable thumbs and separate fingers

Question 4

What is the purpose of the clavicle in primates?

Answer 4

• helps to stabilise the shoulder, allowing a primate to support its weight by hanging from its arms alone

Question 5

What is the purpose of having long, slender limbs that rotate freely in primates?

Answer 5

• helps their movement in trees

Question 6

What is the purpose of having opposable thumbs and separate fingers in primates?

Answer 6

• grants the ability to grasp and hold on to branches effectively

Question 7

What characteristics do all primates share?

Answer 7

• an enlarged and complex brain relative to body size
• a flattened face and reduced snout with a reduced sense of smell
• eyes that face forward
• digits with flat nails
• molar and premolar teeth with cusps that are low and rounded
• complex social behaviour
• usually only one offspring at a time
• extended care for the young

Question 8

What genetic evidence is there of a common ancestor for primates?

Answer 8

• primates share a large percentage of their DNA, suggesting that they must have had a common ancestor at some stage
• primates have a larger number of olfactory-receptor pseudo-genes than non-primates, which is consistent with the deterioration of the sense of smell in primates
• have full trichromatic colour vision, which is found only in the primate order

Question 9

What are pseudo-genes?

Answer 9

• remnants of genes that are no longer functional