Lecture 15

Question 1

Mammals in modern world

Answer 1

• 3 lineages
• monotremes: egg laying (first kind)
• marsupials: develop in pouch
• placental: reproduction via placenta

Question 2

Defining characteristic of mammals

Answer 2

• not fur/reproduction
• ear
• incus and malleus form from old jaw articulation
• defining feature that distinguished mammals from reptiles

Question 3

What makes a mammal a mammal?

Answer 3

• hair
• three middle ear bones
• mammary gland in female
• neocortex
• did not all arise at same time

Question 4

Synapsid skull

Answer 4

-positioning of holes behind eye are what defined it as a synapsid

Question 5

Therapsid

Answer 5

• evidence of vibrissae-means it has the ability to have hair
• less upright, not sprawling
• these early creatures were acquiring warm-bloodedness and other such mammalian characteristics that we have today

Question 6

Dentition-later therapsids

Answer 6

• changes so that reptilian teeth out front but has molar like teeth in back
• for chewing and grinding, not ripping
• something on its way to being a mammal

Question 7

Teeth

Answer 7

• reptiles eat prey item whole and are capable of absorbing that much of animal into gut
• mammals can’t do this so they need teeth for grinding
• can’t hold breath very long
• can breathe while chewing because of palate that separates mouth from air duct
• warm blooded

Question 8

Jaw Evolution

Answer 8

-as you get toward mammals the dentary bone that has the teeth get’s increasingly larger and the contact between the jaw and skull that’s present in the reptilian ancestor is co-opted to do something else

Question 9

Evolution of Female Reproductive systems in mammals

Answer 9

• monotreme: see what’s present in reptiles: uterus and anal canal same tube and feed down to cloaca
• marsupial anal canal not separate from cloaca but eggs and urine come out of cloaca
• placental all three functions now separate tubes

Question 10

Modern orders of mammal radiation?

Answer 10

• present already in mesozoic or do they arise only after non-avian dinosaurs are extinct
• two views
• in the cretaceous
• post cretaceous
• molecular extrapolations suggested one thing, and fossil data demonstrated something else

Question 11

First model

Answer 11

• can use rate of gene evolution to determine when animals diverged from each other
• says primates arose in Mesozoic but you don’t find fossils of them in that period

Question 12

Second model

Answer 12

-classes and orders arise a couple million years after the extinction

Question 13

Gliders

Answer 13

-have gliders living today that are a couple million years after the extinction

Question 14

Evolution in size

Answer 14

• over evolutionary time mammals get bigger

- common trend for many species

Question 15

Horses

Answer 15

• occasionally horses are still born with three toes because they used to have three toes and they still have the genes for this so it shows how recent it really is
• mammals don’t generate new teeth but have tactics used to prolong lifetime of teeth
• low crown vs. high crown in new horses

Question 16

High crown vs. low crown

Answer 16

• dinos didn’t have tall crowns so they couldn’t chew their food
• if they had short crowns and chewed their food they wouldn’t have any teeth left
• horses chew so much grass which is hard on their teeth so their teeth are long so as the grass wears them down they just push though a little more.

Question 17

Brian Evolution

Answer 17

• cerebral cortex much larger than most other animals because we have higher functioning
• brains from lemurs are similar to those seen in Eocene
• midbrain and hindbrain features also vary in size between animals through time

Question 18

Primates, Major features

Answer 18

• binocular vision
• grasping hands and feet and opposable thumbs
• closed eye sockets
• fingernails
• some adapted brachiation (body made for reaching upward like they do when they’re swinging)
• enhanced brains and intelligence
• strong social organization in many: dominance, territorial, long parental care

Question 19

Human characteristics

Answer 19

-lots are really exaggerations of functions and such that evolved from our primate ancestors

Question 20

Old Phylogeny

Answer 20

• showed humans as separate from apes but that’s not the case, we are apes so says new phylogeny tree
• Homo sapiens are right in middle of chimps, gorillas, and orangutans so we are a branch of giant apes

Question 21

Mammal evolution

Answer 21

• evolve from synapsids (major clades of reptiles) appear in late Carboniferous
• by permian evolve into therapsids (likely warm blooded and covered by hair) and begin developing mammal like detention
• mammals evolve from therapsids in the Triassic

Question 22

Skeletal and dental features

Answer 22

• allow us to determine relationships of fossil animals
• tell marsupial skeleton from placental?
• marsupials have pouch, which gets some skeletal support–epipubic bone

Question 23

Primate adaptive history

Answer 23

Terrestrial ancestor–>arboreal–>humans terrestrial (secondary)

Question 24

Terrestrail ancestor

Answer 24

• small forest floor animals
• no stereovision smell primary
• plantigrade
• claws

Question 25

Arboreal

Answer 25

- small/moderate size - intelligence - stereovision - reduced - sense of smell - vertical body - balance - nails - grasping hand

Question 26

Humans Terrestrial (secondarily)

Answer 26

- bipedal - vertical spine - foramen magnum - under skull - reduced hair - carnivory - enlarged brain - precision grip - tool making

Question 27

Higher Primates-classic tree

Answer 27

- anthropoids-first appear in oligocene - platyrrhines=new world monkeys - south america: prehensile tails, relative primitive monkeys - catarrhines=old world monkeys Africa, Asia

Question 28

Pongids

Answer 28

-classical term for all apes

Question 29

Newer Tree of primate relationships

Answer 29

- based on cladistic analysis | - no more pongids instead have homminoids (humans and apes)