W2 L1 primate diversity and evolution

Question 1

Meaning behind the word primate

Answer 1

Primates’ = ‘first rank’
Name represents view that Primates are the highest form of life
Controversially - Linnaeus included humans in his classification as primate

Question 2

Primate characteristic

Answer 2

• Grasping hands & feet *
• Opposable digits *
• Binocular vision *
• Reduced sense of smell
• Fingernails (instead of claws)
• Hind limb-dominated locomotion
• Extended maternal care
• Large brains
• Relatively small number of teeth

Question 3

Nearest living relative of primate

Answer 3

Flying lemur, diverged around 80 Mya

Question 4

The earliest primate

Answer 4

• Earliest primate fossils ≈ 65-55 Mya
• Most found in America, but also found in Asia and Africa (spread quickly)
• Small (20-30g), arboreal, insectivorous
• Similar in appearance and habits to modern tree shrews

Question 5

Primate Phylogeny

Answer 5

2 major group: Strepsirrhines & Haplorrhines
Splinted 78-63 Mya

Question 6

Moving from nocturnal to diurnal changer

Answer 6

-loss of tapetum
-the evolution of colour vision
-reduction in the sense of smell lead to change in the shape of the nose

Question 7

Loss of tapetum in dept

Answer 7

-the earliest primate (strepsirrhines) have a structure called tapetum that lies behind the retina. This structure reflect light back through the retina to increase the amount of light available in for the photoreceptor

Question 8

Tarsier, moving back to nocturnal case study

Answer 8

Arboreal primates (hands adapted)* Eat insects and small vertebrates
* Entirely carnivorous - insects
* Generally small (<100g; 12cm long)
* Characterised by enormous eyes (each eye is the size of the brain)
* They also have excellent hearing
* Colour vision (recent evidence suggests this predates diurnal living)

Question 9

The evolution of colour vision indepth

Answer 9

• Primates are the only mammal group to possess true trichromatic colour vision
• Colour vision arises via opsin genes which code for photoreceptors in the eye

Question 10

The evolution of colour in OWP and NWP

Answer 10

Old world (including humans)
* Trichromatic colour vision
* characterized by three retinal photopigments
* tuned to peak wavelengths of approximately 430 nm,approximately 535 nm and approximately 562 nm
New World (except howler monkeys)
* Dichromatic and trichromatic vision depending on genes
* Requires heterozygosity (i.e. expression of two different opsin genes at a locus).
* Results in only heterozygou

Question 11

Advantages of color vision

Answer 11

Detect fruits, detecting leaves, maybe predators, compensating for smell

Question 12

Trichromatic can have reduced vision?

Answer 12

Red-green colour blindness, cause by variation in functionality of remand and green option protein
* up to 1 in 12 males (8%)
* 1 in 200 females (0.5%)
* Colour vision also decreases in old age

Question 13

Reduction in the sense of smell in-depth

Answer 13

• Mammals can detect 1000’s of odours
• Smell relies on olfactory receptors in anolfactory organ (< receptors = better smell)
• Reduced smell related to the accumulation of pseudogenes – genes with accumulated deleterous mutations that impairs their expression

Question 14

Skull trait and olfactory reception corellation

Answer 14

Olfactory Receptors link to Olfactory Sensory Neurones which pass through a specialised structure call a cribiform plate
primate have small cribiform plate

Question 15

Different nose shape in primate

Answer 15

Strepsirrhines have larger snout and a better sense of smell
Haplorrhines have a flatter profile and less prominent snouts
Platyrrhines have wide flat noses nostrils well separated
Catarrhines have narrow downward noses, nostrils close together

Question 16

Four evolutionary traits in teeth

Answer 16

• Number
• Shape
• Size (canines in particular)
• Enamel thickness

Question 17

Implication of teeth evolution

Answer 17

-change in teeth structure can indicate changes in dietary

Question 18

Diurnality and the loss of vitamin C

Answer 18

• Single GLO gene mutation codes for Vitamin C
  Selection on the geNe is neutral, lead to high dietary need for vitamin C

Question 19

Changing habitats and habits
1. The prehensile tail

Answer 19

Platyrrhines (new world monkeys)
- long, muscular, prehensile tails
- used to hold onto branches
- increases places to feed in arboreal habitats
Catarrhines (old world monkeys)
- less muscular, shorter tail, some are absent

Question 20

Changing habitats and habits
2. Arms built to swing

Answer 20

• Smaller earlier primates - jumped from tree to tree
• As size increases - Brachiation evolved –swinging from tree to tree (reduced energetic costs)
• Selected for more flexible shoulders

Question 21

Changing habits and habitat: freeing the hand and loss of tail

Answer 21

• Selected for more flexible shoulders
• Humans have even more flexibility
• Move to ground associated with tail loss
• easier movement on ground
• Recent evidence suggests may be related to the cost associated with neural tube defect