Characteristics of Primates- Dentition and Vision (17)

Question 1

What are the two areas of evolutionary changes that takes place in dentation

Answer 1

1. number of teeth/ arrangement

2. Structure

Question 2

What are the two sets of teeth for primates

Answer 2

deciduous and permanent

Question 3

Whats a dental formula

Answer 3

• # of each type of tooth that a species has can be expressed as a dental formulagives number of each type of tooth in ¼ of jaw

Question 4

Explain the dental comb

Answer 4

Lemurs and lorises= unusual specialisation of incisor teeth= lower front incisors= slanted forward with crowns= narrow + closely spaced to form dental comb
• Used for grooming fur, only rarely for feeding/fighting

Question 5

Explain distema

Answer 5

o large lower have a gap (distema) b/w upper and 2nd incisor + upper canine to accommodate large lower canine
o To allow large upper canine= crown of 1st premolar slanted back + sharp edged

Question 6

How is canines sharpened

Answer 6

pper canine fits tightly against this premolar +sharpened by the grinding that occurs

Question 7

what is the general change in molar teeth

Answer 7

• little change from early mammals

o May be related to generalized diets

Question 8

Explain the evolution in cusps of molars

Answer 8

• 3 cusped molars of early mammals= evolved to 4 cusp pattern in Old World Monkeys
• Further trend= seen with apes + humans where lower molars- 5 cusps forming 4-5 pattern
  o

Pattern useful identifying teeth of fossil apes + humans= presumed to have evolved due to predominantly fruit diet of apes

Question 9

What does the hard enamel of teeth allow

Answer 9

resist decomposition

Question 10

Example of why care needs to be taken when using teeth to indicate diet

Answer 10

• Large canine teeth of old world monkeys + apes more important in predator defence and social displays that for meat-eating

Question 11

Is there an emphasis on vision in evolution and why

Answer 11

Arboreal life= emphasis on vision

Question 12

Due to arboreal life and increase in emphasis on vision, what decreased

Answer 12

• reliance on sense of smell, olfaction

- shift in sensory orientation

Question 13

what did the shift in sensory orientation (focus on vision and not smell) be accompanied by

Answer 13

overall change in shape of skull compared with other mammals

Question 14

what was the general skull evolution in result of chignon sensory orientation

Answer 14

• General tendency for facial portions of skull, particularly region around nose and snout, to become smaller and flatter
  o While region that houses the brain has become larger

Question 15

What evidence is used that supports shift of increase emphasis on vision > decrease on other sensory > nose flatter

Answer 15

Observable behaviour
o E.g. lemurs= use their snout and teeth for what apes use eyes and hands for (investigating an object, grooming, communicating)

Question 16

What is an important evolutionary trend of forward facing eyes

Answer 16

• Flattening face of primates + movement of eyes to face fully forward= important evolutionary trend
• Forward facing eyes= allow for stereoscopic (three-dimensional) vision

Question 17

explain difference in eye sockets of other mammals and primates

Answer 17

• Most mammals have eye socket that face sideways, but primates developed eye sockets that face forward

Question 18

what has change in eye sockets of primates allowed

Answer 18

o Enables fields of vision of each eye to overlap= distances judged accurately
o = important adaption for a tree living animals

Question 19

Why is depth perception important

Answer 19

• For primates: evolved for life in trees, the importance of depth perception cannot be overemphasized
  o A mistake in judging distances= fatal

Question 20

What is the ‘negative’ result of forward facing eyes

Answer 20

o However with both eyes facing forward, field of view much narrower than if the eyes face sideway

Question 21

How has primates compensated for narrower field of vision

Answer 21

♣ Primates compensate for this by evolving a highly mobile head and neck

Question 22

How has colour vision increased and allowed

Answer 22

♣ In addition= most primates have rods and cones in retina
• Rods= important for vision in dim light
• Cones= fine visual discrimination and colour vision (nocturnal= only has rods)
♣ Nerves connecting rods and cones to brain also improved // vision is more acute in each eye and coordination b/w two eyes far better than other mammals
♣ These modifications also enhanced stereoscopic vision

Question 23

Explain development of the eye socket and evidence in fossil skulls

Answer 23

• As eyes become more forward= bony eye socket developed to give protection

Gradual change in eye socket clearly visible in fossil primate skulls
o As position of eye socket changed for eyes to face forward, bone gradually closed in side and rear of socket

Question 24

How has brain developed in association with vision

Answer 24

• Increasing importance of vision= region of brain concerned with interpretation of visual information increased in size
  o While that concerned with olfaction decreased