Module 3 Lecture Flashcards
(47 cards)
Extant
Still living
3 most important traits all primates share?
- Prehensile hands (capable of grasping, opposable 1st and 2nd digits)
- Flat nails (no claws, helps us grasp things)
- Forward-facing eyes (stereoscopic vision, 3-D, lock on targets)
Arboreal Hypothesis - under this hypothesis, what are the 3 main primate traits adaptations to?
- Enable safe and secure leaping from branch to branch
- Grasping fruit, leaves, or insects with great precision and more easily
- Accurately see and judge distances when leaping from branch to branch and seeing small insects for food
What was the refute to the Arboreal Hypothesis?
Squirrels can leap in trees, grasp branches, and see and grasp food in trees, but they do not have the 3 primate characteristic traits
Visual Predation Hypothesis - under this hypothesis, what are the 3 main primate traits adaptations to?
For catching prey - especially insects and smaller animals
Is the Arboreal Hypothesis still widely accepted?
Yes. The squirrel argument is not enough counter-evidence. Squirrels and primates can be an example of animals evolving differently but developing similar ways to live within their niches (analogous traits)
Besides main 3, other 5 primate characteristics?
- Generalized body plan (highly versatile and adaptable - can develop wide range of behaviours, access wide range of food types, live in wide range of habitats, have different locomotor behaviours)
- Generalized teeth (omnivorous dental abilities - can consume any food)
- Reduced olfactory system (vision primary sense)
- Enclosed bony eye orbit (protects the eyes from physical damage)
- Large encephalization quotient (large brain compared to body size)
7 ways of locomotion among primates?
- Vertical clinging and leaping
- Arboreal quadrupedalism
- Brachiation
- Terrestrial quadripedalism
- Knuckle-walking
- Bipedalism facilitative (sometimes)
- Bipedalism habitual/obligate (always)
Divergent evolution
Common ancestor, but then adapt different traits
2 examples of rapid speciation (divergent evolution) within a lineage to fill different ecological niches, usually following a major change in environmental circumstances?
- Explosion in diversity of flowering plants after appearance of insect pollinators
- Explosion of mammals after dinosaurs went extinct
Parallel evolution
The independent evolution of similar traits in different species - starting from a kind of similar, but very distant ancestor (evolved in similar ways for different reasons)
Example of parallel evolution?
The especially large brains in people and dolphins. Simply having a brain is a homologous trait because people and dolphins share a common ancestor who had a brain, but our BIG brains have evolved independently of each other and are the result of parallel evolution
Homologous traits
Traits that are similar to one another due to shared ancestry (share the same structure, genetics, or embryonic structure of their common ancestor - example: arms/wings in humans, horses, cats, bats, birds, and whales)
Convergent evolution
Different organisms independently evolve similar traits
Analogous traits
Similar function and superficial resemblance but have different origins (example: wings of a fly, moth, and bird evolved independently but are all adaptations for flying)
When did the first primates appear?
Sometime around 70 million years ago
Where do the oldest confirmed primate fossils come from?
East Asia (but there are some in Morocco and North America that are likely older)
Which country did primates never make it to?
Australia. Marsupials dominated the niche instead
What was the climate like back when primates were first evolving?
Much warmer and more humid than today. Most of world covered by tropical forest (grasses didn’t evolve until 65 mya)
First major stage in primate evolution?
First radiation in the Late Cretaceous. Appearance of first “primates” from common ancestor. Tooth shape indicates broadening of diet. Looks like a rodent
Second major stage in primate evolution?
Second radiation in the Paleocene (after dinosaurs went extinct). Emergence of true primates that had the fundamental primate traits (grasping hands, nails, vision dominance). 2 major lines: lemur-like and tarsier-like forms
Third major stage in primate evolution?
Third radiation in the Early or Mid-Eocene. Primitive monkeys appear, increased arboreal quadrupedalism (didn’t have to worry about dinosaurs seeing them in the trees), larger brain, increased reliance on vision
Fourth major stage in primate evolution?
Fourth radiation in Late Oligocene/Early Miocene. Split into two main groups - monkeys and primitive apes. Difference in diet - monkeys ate leaves, early apes ate fruit. All still arboreal
Fifth major stage in primate evolution?
Fifth radiation in the Late Miocene. Appearance of first true apes - large, barrel-like torso, limbs designed for hand-over-hand climbing, some terrestrial adaptations
