17. primate evolution

Question 1

what is a primate?

Answer 1

an animal of any order that is distinguished by having hands, feet similar to hands, forward facing eyes, and typically being tree dwellers

Question 2

what are characteristics of hands/feet in primates?

Answer 2

• pentadactyl
• nails instead of claws
• grasping fingers and toes, friction ridges for gripping
• opposable first digit

Question 3

what are characteristics of eyes in primates?

Answer 3

• forward facing for stereoscopic vision

- most able to distinguish colour

Question 4

characteristic of smell in primates

Answer 4

very poor sense of smell

Question 5

characteristics of teeth in primates

Answer 5

four incisors in both upper and lower jaw

Question 6

characteristics of the brain in primates?

Answer 6

large and complex

cerebral size increases as primates become more highly evolved

Question 7

characteristics of reproduction in primates?

Answer 7

not restricted to breeding season
rhythmical sexual cycle
usually only one offspring at a time
long period of parental care for offspring

Question 8

what are limbs like in primates?

Answer 8

tend to be unspecialised
they are pentadactyl (five digits on each limb)
digits are highly mobile

Question 9

What is the evolutionary trend towards digits?

Answer 9

they increase in ability to move the digits independently of each other- most highly developed digits are the thumb and big toe

Question 10

do all primate have opposable first digits?

Answer 10

yes
the degreee of opposability varies between species and depends on relative length of first digit
humans only primate that doesnt have opposable big toe but have great opposability with thumb due to lng length

Question 11

Do primates have nails or claws?

Answer 11

nails instead to improve grasping action, nails evolved from claws (some primates still have singular claws)

Question 12

why do the end of digits have sense receptors?

Answer 12

so they can grip and manipulate objects
tactile pads under the surface evolved with nails and developed small ridges to increase grip between the ends of the digits and an object - friction ridges vary between individuals and species

Question 13

how does dentition change between primates?

Answer 13

the number of teeth and their structure

changes to deciduous and permenant sets of teeth that each perform different functions

Question 14

has the number of teeth increased or decreased through evolution

Answer 14

decreased compared to early mammals, related to the gradual reduction in size of the face and jaw

Question 15

What teeth size has been reduced in evolution of primates?

Answer 15

the canines and the diastema

Question 16

how have the molars changed?

Answer 16

little change

movement from 4 to 5 cusps in humans, presumably to have evolved due to fruit diet of the apes

Question 17

How has vision changed through evolution?

Answer 17

• increasing emphasis on vision accompanied by a decreasing reliance on olfaction accompanied by change in the overall shape of the skull

Question 18

What do forward facing eyes allow for?

Answer 18

fully stereoscopic vision, with fields of vision that overlap so distance can be judged accurately, narrows field of view (compensated by development of highly mobile head and neck)

Question 19

What are the general tendency for facial portions through evolution?

Answer 19

region around nose and snout become smaller and flatter

Question 20

What do the rods and cones allow primates to see?

Answer 20

• see in dim light

- colour and visual discrimination for colour vision

Question 21

Have nerves connecting sight to brain improved or deteriorated in primates?

Answer 21

improved so vision is more acute in each eye, coordination improves, enhanced 3D vision

Question 22

How has the eye socket changed in primates?

Answer 22

developed to provide protection, bone closing in on the sides of the socket as the eyes face forward

Question 23

How has the cerebral cortex changed in primates?

Answer 23

cerebrum has progressively increased in size, as the outer cortex is associated with high thought functions necessary to cope with changes in the environment, general trend of an expansion and reorganisation of the brain with resultant consequences in behaviour

Question 24

Effects of the larger cerebral cortex size?

Answer 24

• large brains for body size the result of tree-dwelling environment and high natural selection pressures which favoured more accurate visual and tactile perception along with better coordination between sensory stimuli and muscle response
• reliance on vision creates a large amount of complex sensory information, resulting i expansion of cerebral cortex
• convultions enable greater SA of the brain
• Enables development of movement, social skills, tool making, greater variety of behavioural responses to meet environemtntal problems

Question 25

How is primates gestation and parental care different to other animals?

Answer 25

most not restricted to a reproductive season and show a rhytmical sexual cycle, most only have single offspring, associated with long period of growth and maturation

Question 26

How has the placenta evolved?

Answer 26

becomes more efficient as it takes nourishment from the mothers bloodstream

Question 27

what is difference in the gestation of primates and other animals?

Answer 27

it is remarkably long in primates compared with other mammals of a similar size and offspring are born immature- requires more care and protection

Question 28

how many nipples do most primates have?

Answer 28

usually a single pair

Question 29

what does the late arrival of sexual maturity allow?

Answer 29

due to the limiting number of offspring a female can have during her lifetime, it makes each offspring particularly important- significant time is invested in their care and survival

Question 30

Why does the extended period of parental care and learning help primates?

Answer 30

enables them to learn techniques and ideas to be passed from one generation to the next
- increases chance of survival

Question 31

How do humans differ from apes?

Answer 31

in appearance, structure, behavioural functions
relatively hairless
structure of limbs allows for bipedal locomotion