What are the characteristics of primates Flashcards
What primates are included in the mammalian order Primates?
Prosimians, monkeys, apes and humans.
Where are new and old world primates found?
New world primates are found across central and south america.
Old world primates are found across Africa and Asia.
What are the general features of the primate pattern?
- No one trait identifies all primates.
- General tendencies expressed by all primates = overall primate pattern.
- Fall in 4 main complexes; 1) Grasping hands and feet. 2) Visual system 3) Large complex brains and associated behaviour 4)Skeletal and dental features.
- Primates possess combination of primitive and derived traits.
What are derived traits and give 2 examples.
These are specialised traits that are not shared with the last common ancestor.
E.g
In humans - bipedalism
In the aye-aye - long middle finger for extracting grubs from tree holes. Plus ever growing incisors due to biting holes in bark to access grubs.
Describe the features of the 1st complex - Grasping hands and feet and the advantages of this characteristic.
- Grasping hands and feet.
a) pendactyly (5 fingered)
b) opposable thumb
c) nails not claws and sensitive tactile pads. (More sensitivity in fingers gives a greater sense of touch and engagement with objects.)
- Power grip: Opposable thumb allows for power grip (clenched fist).
- Precision grip: holding something between index finger and thumb.
This makes behaviour more flexible and gives more options.
What group of animals is the pentadactyl trait shared with?
Primitive trait from common ancestor shared with reptiles.
Give an example of a human derived trait.
Opposable big toe - Derived trait - The loss of the opposable toe. Walking with a heel to strike action allowed humans to travel further for food with more endurance.
A prevailing theory suggests being bipedal gave advantages by reducing the amount of surface area in the sun.
What group of primate has re-developed claws and why?
Callitrichids - because they like to eat gum/sap from trees. Because callitrichids are small, they need to grasp onto the bark a bit like a squirrel does.
Describe the characteristics of the visual system in primates.
Olfaction (sense of smell) is reduced in primates so the vision is enhanced with forward facing eyes.
What are the benefits of forward facing eyes?
Stereoscopic vision = accurate depth perception.
Stereoscopic vision means there is an overlap in the visual field from each eye creating a 3-d image.
Better depth perception - better for hunting prey, aid in traveling across a canopy.
As we get closer to humans and apes, the eyes become closer together in comparison with lemurs where the eyes still face outward slightly.
What are the effects on physical characteristics due to the reduced reliance on olfaction?
- Reduction of snout.
- Reduction of olfactory centres in the brain.
- Increase in visual centres in the brain.
- Flattening of the face (less prognathic)
What are the characteristics of having large, complex brains in primates?
Primate brains are large relative to body size compared to other mammals.
There is an allometric relationship between brain and body size. (Allometric - things are growing at different rates)
Big neocortex
-Increases cognitive abilities like reasoning and consciousness.
-In primates the neocortex makes up 50-80% of the brains total volume.
What did the Dunbar: The social brain hypothesis?
There is a link between large brain size, sociality and learning.
Link between size of neocortex ratio and group size; prosimians to monkeys to apes.
When primates are grouped together into prosimians - monkeys - apes. There is a correlation between amount of neocortex and size of social group.
Give examples of the advantages of having a large neocortex.
If in a large group, a large amount of neocortex is advantageous because individuals showing aggressive behaviour can be recognised for example so the others no not to go near them to save conflict and risk injury.
Large neocortex allows for deception tactics. Especially when a good food source has been found.
If a low ranking female alerted her peers to a good food source she would be bullied off her discovery and go hungry. By suppressing these vocalisations she can keep the food for herself.
What are the characteristics of “Altricial newborns”?
- Typically single young (not litters)
- relatively helpless at birth
- little reliance on instinct - Social learning more important
- Infants depend on mothers
- grasping hands used to cling
- most are not left in nests (some exceptions)
