FINAL EXAM DECK - MAMMALS Flashcards
04/29 - 05/06 (61 cards)
Synapsid
One temporal fenestrae
Thecodont
Teeth rooted into sockets
Did non-mammalian reptiles (synapsids) arise before or after what we consider the “reptile” reptiles (diapsids)? What does this mean about their evolutionary history?
Before –> Synapsid reptiles before diapsid reptiles.
This means they have a slightly longer evolutionary history.
What does complete endothermy mean?
Maintaining body temperature throughout the entire body.
Was the first or second instance of complete endothermy found in mammals?
Second.
First was avians.
What is regional endothermy?
Where certain areas of the body are able to be kept warmer than other, cooler areas.
What is required for endothermy?
Subcutaneous fat
What new challenges do subcutaneous fat pose to endothermic organisms?
- Need the ability to lose heat to the environment so an organism does not overheat, especially for larger-bodied mammals.
(ex. exercise raises body temp, need to be able to lower it). - Higher metabolic rate – subcutaneous fat must be maintained, so energy is constantly being contributed to that in addition to reproduction, growth, etc. (contributing energy to something you don’t want to use).
Where can marine mammals lose heat from?
Fluke and tongue, sometimes dorsal fin.
Everything else is well-insulated
How do synapsid sailbacks seen in the video regulate body temperature?
Using their sails (thins and vascular).
Turned toward the sun to heat up, can be used to radiate off lots of heat to cool down as well.
Can animals readily switch what they eat?
No. Many animals need specific nutrients and will not be successful switching to a new diet. It may cost more energy to digest (ex. feathers)
As organisms transition from non-mammalian reptiles to being mammals, what changes about their skulls/jaws?
- Changes from multiple bones to a single bone (dentary)
- Attachment changes from quadrate-articular to dentary-squamosal
- Quadrate and articular become bones of the middle ear (was only the stapes in reptiles)
What change occurs between reptiles and mammals that would require mammals to be better able to pick up vibrations in the air?
Their bodies lifted up higher from the ground –> greater need to sense vibrations in the air (2 more middle ear bones) as opposed to through the ground.
More ancestral mammals, like monotremes, may have what sort of gait?
Sprawling
What muscle might be missing in ancestral mammals? What will they have instead?
Diaphragm.
Ribs extending the full length of the trunk.
Are dimetrodons dinosaurs? Why/why not?
No.
Different number of fenestrae (different skull). Lack the changes to pelvic and pectoral girdle (pull limbs under) and ankle joint that dinosaurs had.
What is a key group of organisms leading into mammals?
What changes do we start to see in them?
Therapsids.
Loss of some trunk ribs, possible appearance of diaphragm.
Changes to wrist/ankle joints,
allowing for different stances, more propulsion/speed, greater mobility.
Why is ankle mobility relevant to speed?
Speed is affected by how much of the foot is placed on the ground.
More foot -> more friction -> slower
Which organism is considered the tipping point for moving into modern-day mammals? Why?
The cynodont.
Loss of lumbar ribs, appearance of diaphragm. Skull and other body changes that reflect mammalian characteristics.
What is a characteristic of cynodonts that could imply multiple ancestors to modern-day mammals?
Cynodonts have a mammalian stance… monotremes still have a reptilian stance and therefore it is unlikely the cynodont was its direct ancestor. There is a possibility there was a secondary transition back.
Volant
Flying
Glissant
Gliding
Saltatorial
Hopping
Fossorial
Burrowing
