Lecture 15 Flashcards
1
Q
Mammals in modern world
A
- 3 lineages
- monotremes: egg laying (first kind)
- marsupials: develop in pouch
- placental: reproduction via placenta
2
Q
Defining characteristic of mammals
A
- not fur/reproduction
- ear
- incus and malleus form from old jaw articulation
- defining feature that distinguished mammals from reptiles
3
Q
What makes a mammal a mammal?
A
- hair
- three middle ear bones
- mammary gland in female
- neocortex
- did not all arise at same time
4
Q
Synapsid skull
A
-positioning of holes behind eye are what defined it as a synapsid
5
Q
Therapsid
A
- 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
6
Q
Dentition-later therapsids
A
- 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
7
Q
Teeth
A
- 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
8
Q
Jaw Evolution
A
-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
9
Q
Evolution of Female Reproductive systems in mammals
A
- 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
10
Q
Modern orders of mammal radiation?
A
- 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
11
Q
First model
A
- 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
12
Q
Second model
A
-classes and orders arise a couple million years after the extinction
13
Q
Gliders
A
-have gliders living today that are a couple million years after the extinction
14
Q
Evolution in size
A
- over evolutionary time mammals get bigger
- common trend for many species
15
Q
Horses
A
- 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
