21. Mammals I: Hair, milk, placenta

Question 0

Role of hair?

Answer 0

Like feather, except flight

Insulation, camouflage, sensory/defence

Question 1

3 unique features of mammalia?

Answer 1

1) Hair
2) sweat glands
3) mammary gland

Question 2

Which evolved first - mammals or birds?

Answer 2

Mammals

Question 3

Split reptilia/mammals before split reptilia/bird?

Answer 3

Yes - 350 mya

Question 4

What is diagnostic of different groups?

Answer 4

Holes in skulls

- Presence, size, numbers, temporal fenestrae

Question 5

Skull types of amniotes?

Answer 5

Anapsids (turtles) - no holes
Synapsids (therapsids, mammals) - single hole begins to fuse with eye orbit (through which muscle can go through - in turtles, outer bone covers it - mammals lost that outer bone)
Euryapsids (extinct marine reptiles) - single hole
Diapsids (dinosaurs + birds) - two holes

Question 6

When did mammals evolve?

Answer 6

225 mya (Triassic)
- Very small insectivores nocturnal (not many fossile possibilities)

Question 7

Characteristic of first mammals in Triassic?

Answer 7

Improvements to middle ear (bones we hear with) - modern mammilial way of earing. not in the same way that other animals hear

Question 8

Brain size of first mammals?

Answer 8

Bigger for body size than other groups

Question 9

When did mammals became dominant group?

Answer 9

When dinosaurs become extinct - opened up a bunch of opportunities (empty terrestrial and marine niches).

Question 10

What is the return to the ocean of the mammal?

Answer 10

Mammals return to ocean when dinosaurs disappeared. Ambulocetus, ancestor of whales (because of teeth structure and ear structure)

Question 11

Size of past mammal?

Answer 11

There existed giant ground sloth “dinosaur size” (megatherium) - bigger than dinosaur in redpath museum
Size of elephant

Question 12

Smilodon?

Answer 12

Saber-toothed cat (1.5 mya - 11 000 ya)

- Contemporary with humans, mammoths and giant ground sloths

Question 13

Why did Smilodon and Megatherium go extinct?

Answer 13

Hunting by humans! (not end of ice age)

• Why large in Africa? Evolved together. Animals learned to avoid humans. When humans arrived in NAmerica, these animals were not accustomed to humans.

Question 14

Teeth of mammalia?

Answer 14

Heterodonty: Different teeth specialized for different tasks (unlike reptiles and fish)

Different teeth depending on diet

Question 15

Humans and dolphins have largest….

Answer 15

Brain by body size

Question 16

Largest brain?

Answer 16

African elephants, blue whale, sperm whale

But human compared to body size

Question 17

Sexual dimorphism

Answer 17

In animal sexes appear different (not so much for humans, but a lot in lions, eg.): size, colour, morphology

Most impressive: elephant seal
Why: gender roles (female lion hunt; male lion chill and look impressive at each other)

Question 18

3 mammalian groups?

Answer 18

• Protoherians (monotremes)
• Marsupials
• Eutherians

Question 19

Specific of prototherians?

Answer 19

LAY EGGS!!!

Question 20

Typic of marsupials?

Answer 20

Pouches - early birth, fetus completes development in pouch

Question 21

Typic of eutherians?

Answer 21

Embryo in female reproductive tract - born much more advanced state

Question 22

Placenta in prototherians?

Answer 22

Lack placenta

Question 23

Why prototherians are still mammals?

Answer 23

Produce milk - but no nipples, young suck milk from fur

Question 24

Example of prototherians?

Answer 24

• Platypus

- Echnidna

Question 25

Platypus?

Answer 25

• Australia
• Bill to dig for crustaceans & worms
• Build nests in river banks
• Lay eggs, hatch in days, nurse for 5 mos

Question 26

Only poisonous mammals?

Answer 26

Platypus - male have poisonous at the back of leg (sexual dimorphism - could be in sexual selection, competition for mates - but usually not lethal? - we don’t know why - prof will let us know)

Question 27

Echidna?

Answer 27

“Spiny anteaters”

Insectivores, sticky tongue, temporary pouch for egg (hatch 8 days, spines form in pouch, live for 50 y!)

Question 28

Marsupials?

Answer 28

Short gestation, long nursing period
HAVE A PLACENTA (though non uterian)
Kangaroos, loalas, opossums

Question 29

Thyosine?

Answer 29

Extinct dog-like marsupials - but not at all related to dog (eg. of convergent evolution)

Question 30

Marsupial diverged from early placentals…

Answer 30

100 mya

Question 31

NA marsupials?

Answer 31

Most extinct, except opossum

Question 32

Eutherians make …. species

Answer 32

94%

Question 33

Eutherians - amniotic egg?

Answer 33

Retained in female reproductive tract

Question 34

Eutherians - nourrishment of embryo?

Answer 34

Mother placenta

Question 35

Most speciose group of mammals?

Answer 35

Rodents

Question 36

Placenta formed by?

Answer 36

• Embryo and mother after implantation - formed by extraembryonic membranes and uterus lining of mother

Question 37

Placenta is site of…

Answer 37

Gas, nutrient & waste exchange betwen mother and embryo

Question 38

Placenta produces…

Answer 38

Homrones necessary to maintain pregnancy

Question 39

Substances pass between mother and fetus by …

Answer 39

Diffusion (two separate blood systems, no mixing of blood cells or plasma)

Question 40

Placental blood supply?

Answer 40

3 blood vessels in umbilical cords
- 2 arteries carry de-oxygeneated blood to mother (AWAY from fetus)
- 1 vein carries O2 blood towards fetus
(opposite of adult)

Question 41

Catch up last slides.

Answer 41

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