evo. lecture 4 Flashcards
1
Q
Time Frame and Climate
A
Major Epochs of the Cenozoic Era
- Paleocene: 65-56MYA
- Eocene: 56-34MYA
- Oligocene: 34-23MYA
- Miocene: 23-5MYA
- Pliocene: 5-2.59MYA
- Pleistocene: 2.59-0.01MYA
- Holocene: 0.01MYA-Now
- as we move from the Paleocene to present day, global temperatures have gotten colder and colder.
2
Q
Paleocene
A
- the Paleocene was the end of the age of dinosaurs, whom went entirely extinct, along with many other organisms.
- it was hotter and more humid, and there were no ice caps.
- gave rise to primate-like mammals called Plesiadapiformes.
3
Q
Plesiadapiformes | Paleocene and Primate-Like Mammals
A
- body size: tiny, shrew-sized to size of a small dog.
- niche: likely solitary, nocturnal quadrupeds, with well-developed sense of smell.
- diet: insects and seeds.
- used to be classified as primates because of primate-like teeth and limbs that are adapted for arboreal life.
- not actually primates because:
- no postorbital bar
- claws instead of nails
- eyes on side of head
- and enlarged incisors.
4
Q
Adapidae | Eocene
A
- North America and Europe
- from 100-6900g
- diurnal and nocturnal
- arboreal quadrupeds
- smaller ones ate fruit; larger ones ate fruit and leaves
- led to lemurs?
5
Q
Omomyidae | Eocene
A
- North America, Europe, and Asia
- from 45-2500g, most weighing less than 100g.
- nocturnal and diurnal
- specialized leapers
- dental morphology indicates interspecific variations in diet
- smaller ones eating insects
- larger ones eating fruits and a few ate leaves
- led to tarsiers?
6
Q
Oligocene
A
- as the average temperatures decreased, sea levels kept rising and dropping, which isolated lots of plants and animals.
- primates appear for the first time in fossil record of South American towards late Oligocene.
- three haplorhine features: fused frontal bone, full postorbital closure, and fused mandibular symphasis
- three taxonomic groups: Parapithecidae, Propliopithecidae, and Platyrrhini
7
Q
South American Primates
A
- origins of South American primates unclear.
- may have “rafted” over from Africa.
- computer generations show that Africa and South America were close together, and ocean currents would’ve been travelling from Africa to South America at the time.
- the monkeys found in South America today look at a lot like the moneys in Africa*.
- (*but looking alike doesn’t mean phylogenetic lineage.)
8
Q
Miocene
A
- it got colder in the Miocene; expansion of the ice fields and dry lands meant less tropical places and more dry places.
- early Miocene (23-16MYA) monkeys and apes (e.g. Proconsul) apparently confined to Africa.
- mid-Miocene (16-11.6MYA) ape-like catarrhines (e.g. Dryopithecus) were widespread and diverse in Europe and Asia.
- late Miocene (11.6-3MYA) apes (e.g. Sivapithecus) became rarer as woodlands and forests replaced by drier and more open habitats.
9
Q
Pliocene
A
- land masses still on the move; connection between North and South America opened via Panama canal.
- fluctuations in global temperatures.
- Mediterranean Sea dried up at the end of the Miocene and filled up again in the Pleistocene.
- two main taxa: Fossil Cercopithecinae (had cheek pouches) and Fossil Colobinae (gut tract adaptation for leaves).
- phylogenetic relations: unresolved.
- we can only look at the relationships in modern organisms since cheek pouches and digestive tracts don’t fossilize.
10
Q
Transitional Forms (Apes:Humans)?
A
- modifications of postcranial skeleton for bipedal locomotion.
- shape and size of canines, especially in males, changes so not pointy or blade-like. reduction in level of sexual dimorphism in canine size.
- expansion of brain size.
11
Q
Hominins
A
modern humans, chimpanzees, and fossil species more closely related to each other than to any other living species.
12
Q
Morphological Trends in Hominin Evolution
A
- mosaic evolution: major evolutionary changes tend to take place in stages, not all at once.
- bipedalism
- increased brain size: intelligence (but, it’s about connections, not pure size)
- relative vs. absolute intelligence, i.e. intelligence is socially and economically relative.
13
Q
Quadrupedalism vs. Bipedalism
A
- fingers: power, precision, movability (not locomotion)
14
Q
Hominin Brain Size
A
steady until 2 million years ago, when brain size started getting larger.
15
Q
Ardipithecus ramidus and Ardipithecus kadabba | Transitional Hominin Fossil
A
- Middle Awash, Ethiopia
- A. ramidus, 4.4MYA
- A. kadabba, 5.8-5.6MYA
- teeth and fragments of various upper and lower bones.
- both ape-like (thin enamel) traits and hominin-like traits (canines have reduced sexual dimorphism).
