Lecture 21 Flashcards
1
Q
What makes mammals unique? (3, with that one where other animals have it as well)
A
Hair (all mammals), milk (only mammals nurse young with milk), placenta
Other animals have a placenta or similar structures but major innovation; important for long gestation periods
2
Q
Class Mammalia
A
- 5000 species
3
Q
3 unique features:
A
- Hair: insulation, camouflage by modifying color patterns, sensory & defense
- Sweat glands: mammals only ones to sweat; major thermal regulator = evaporation generate sweat that evaporates heat from body to cool
- Mammary glands (milk production): only females
- Divergence between reptilian & mammalian-like amniotes during Carboniferous (350 MYA)
4
Q
Skull Morphology (4 sids, key difference (3))
A
- Key to compared relatedness amniotes
a. Anapsids (turtles, no hole)
b. Synapsids (therapsids & mammals, one hole)
c. euryapsids (extinct marine reptiles, one hole)
d. Diapsids (dinosaurs & birds, two holes)
Key Different btwn skulls is presence, size, number of temporal fenestrae = holes on side of skulls, provide more surface area of muscle attachment)
5
Q
Mammalian Evolution (When? Characteristics? First mammal?)
A
- True mammals evolved - 225 MYA (Triassic) before dinosaur extinction
At first, small arboreal, shrew-like insectivores, nocturnal, improvements to middle ear (increase hearing)
First mammal: Hadrocodium Wui (large brain for their body size) (middle ear bones derived from jaw)
6
Q
Didn’t radiate until after dinosaur extinction (65 MYA)
A
- Coexisted with Saurs
- became dominant group upon “saurs” extinction
- diversified
- filled empty terrestrial & marine niches (large herbivores & carnivores)
- return to ocean
7
Q
Ambulocetus (5, ancestor, characteristics (3), evolution)
A
ancestor to whales (50MYA) - ear similar to whales - can hear well underwater - similar teeth to cetaceans Whales evolved: terrestrial, amphibious, fully aquatic
8
Q
Megatherium (3)
A
- herbivorous
- elephant-sized giant ground sloth
- 2 MYA to 8,000 years
9
Q
Smilodon (3)
A
- saber-tooth cat
- 1.5 MYA to 1,000 year Pleistocene
- Argued most large fruits & trees in North America specialised for dispersal by extinct large mega herbivores
10
Q
Why did Smilodon & megatherium go extinct?
A
by humans
11
Q
Mammalia (other features) (5)
A
- Endothermic
- Advanced nervous system
- Internal fertilization: egg implants in mother’s reproductive tract when develops & nourished by placenta
Unlike reptile & fish: show heterodonty (different teeth in mouth specialized for different tasks) (specialization among species reflects varied diets; incisors, canines, molars) - 4 chambered heart
12
Q
Mammal Brain Body Size
A
- increase complexity of nervous system: evidenced by larger brain
Man: largest brain for body size, others = dolphins & chimps
Largest brain = sperm whale
Bats = small brain since heavy & energetically expensive - Energetic, oxygenic, or weight limits brain size
13
Q
Sexual Dimorphism (Not only in mammals)
A
- different sexes: size, color, morphology
- competition among males coz of monopolized mating opportunities, females make choices for evolution of these traits in male
- influence mating opportunities independent of ability to produce offspring
14
Q
Mammalian Groups
A
- monotremes (Prototherians)
- Eutherian (therians)
- Marsupials (therians)
15
Q
Prototherians
A
- eggs laying (oviparous)
- egg incubation until hatching
- females lack placenta
- have mammary glands, no nipples, young suck milk from fur
