Primates

Question 1

What is unique about primate joints?

Answer 1

• Retention of the clavicle (collarbone)
• Shoulder joint → allows limb movement in all directions
• Elbow joint→ allows forearm rotation (especially useful in arboreal lifestyles)

Question 1

Give some key morphological features of primates

Answer 1

• 5 digits (most have opposable thumbs)
• Reduced snout
• Reduction in no. of teeth
• Nails (not claws)
• Enlarged brain
• Forward facing eye

Question 2

Describe the main sense of primates

Answer 2

• Reduced olfactory system = vison is main sense
• Forward facing eye allows for binocular vison (good depth perception)

Question 3

What is thought to have facilitated primates switch to frugivorous diet?

Answer 3

Evolution of enlarged brain and forward facing eyes is associated with a switch in diet (frugivorous) due to improved vision

Question 4

Describe the prosimians

Answer 4

• Basal primates - branched off early
• E.g Lemurs, bush babies, pottos, tarsiers
• Small, nocturnal and small brained

Question 5

Describe the anthropoids

Answer 5

• Mostly larger than prosimians
• Larger brain and relatively small olfactory lobes
• Mainly frugivorous or folivorous
• Switch from nocturnal to diurnal may have also brought a switch from different types of locomotion

Question 6

Traditional phylogeny prefers to divide the primates into 2 suborders, what are these?

Answer 6

Prosimians (e.g lemurs) and Anthropoids (New world, Old world, Apes)

Question 7

What is the alternative classifcation of primates?

Answer 7

Strepsirrhini (wet noses) Haplorhini (dry noses)

Question 8

Describe the Strepsirrhini

Answer 8

• Usually small
• Long- snouted
• Nocturnal
• Frontal bones unfused & lower jaw halves unfused
• No orbital septum

Question 9

Compare the skulls of the Haplorrhini and the Strepsirrhini

Answer 9

Haplorrhini:
- Short rostrum
- plate separating orbits from temporal lobes

Stersirrhini:
- Long rostrum
- Postorbital bar
- No plate

Question 10

Describe the New world monkeys

Answer 10

• Platyrrhini = ‘broad-nosed’
• 3 premolars (more primitive state)
• Relatively good sense of smell
• Colonised SA from Africa 30 MYA
• No terrestrial radiation

Question 11

Describe the Old World monkeys

Answer 11

• Catarrhini = ‘narrow nosed’
• More specialised and species-rich
• 2 premolars
• Trichromatic colour vision
• Poor sense of smell

Question 12

Describe the key morphology of the Hominoidea (apes)

Answer 12

• Broad thorax and dorsal position of scapula
• Caudal vertebrae reduced
• Front skull - sinuses
• 5 cusps on molars

Question 13

What is the function of the broad thorax of Apes?

Answer 13

Assists balance in a bipedal pose centre of gravity near vertebral column

Question 14

Describe the female transfer system in primates

Give some examples

Answer 14

• Females leave natal group to join another upon reaching sexual maturity.
• Small group size
• One or many males
• Male behavior: territorial, sometimes kinship groups

e.g Chimp, Gorilla, Baboons, Colobus

Question 15

Describe the male transfer system in primates

Give examples

Answer 15

• Males leave natal group to join another after reaching sexual maturity
• Large group
• One or several males
• Male hierarchy

E.g Most Old World Monkeys

Question 16

Describe the monogamous system in primates

Give examples

Answer 16

• One family
• One male in group
• Both sexes participate in defence and parental care

e.g Gibbons, tamarins

Question 17

Describe solitary behaviour in primates

Give examples

Answer 17

• Individual or female + offspring
• Range overlaps with range of >1 female

E.g Organutan, Bushbabies

Question 18

Which primates have dichromatic vision?

Answer 18

Most New World monkeys and prosimians

Question 19

Which primates have trichromatic vision

Answer 19

Most Old World moneys and apes

Question 20

Describe the evolution of trichromatic vison in primates

Answer 20

• Ancestral primate had dichromatic (similar to other mammals)
• Duplication of opsin gene (green sensitivity) = new opsin gene sensitive to red wavelengths
• Duplication occurred 30-40 MYA in the ancestor of Old World Monkeys and apes

Question 21

What are the Advantages of Trichromatic Vision

Answer 21

• Enhanced ability to discern ripe fruits against a green foliage background = faciliated fugivory
• Better detection of social signals (e.g changes in skin colouration with emotional state)