Lecture 21: Mammals 1

Question 1

3 unique features of mammals

Answer 1

1. hair (for insulation, camouflage, sensory/defence)
2. sweat glands (to generate cooling)
3. Mammary glands (milk production- only by females)

Question 2

When did reptiles and mammals diverge?

Answer 2

carboniferous era

Question 3

Skull types

Answer 3

1. Anapsid (turtles)- smooth outside, no holes
2. Synapsid (mammals)- have one hole on side
3. Euryapsids (extinct marine reptiles)- have one hole on side
4. Diapsid (dinosaurs and birds)- have two holes on side of head

Question 4

fenestrae

Answer 4

holes in skull that provide more surface area for attachment

Question 5

First mammals

Answer 5

small, shrew like, nocturnal

• they co existed with dinosaurs
• once dinosaurs went extent, the diversified to fill empty terrestrial & marine niches, then returned to the ocean

Question 6

Ambulocetus

Answer 6

• ancestor to whales
• feed on fish near shores
• similar ear to the whale (can hear well underwater)
• similar teeth to cetaceans

Question 7

Megatherium

Answer 7

• giant ground sloth
• herbivore
• elephant sized
• extinct most likely due to human hunting

Question 8

Smilidon

Answer 8

• saber-toothed cat
• contemporary with humans, mammoths, and giant ground sloths
• extinct most likely due to human hunting

Question 9

Mammal characteristics

Answer 9

• endothermic
• advanced nervous system
• internal fertilization
• specialization of teeth
• 4 chambered heart

Question 10

Sexual dimorphism

Answer 10

sexes appear different (in size, colour or morphology)

Question 11

Mammalian groups

Answer 11

1. Prototherians (egg laying)
2. Marsupials (pouched)(developed from early placentals)
3. Eutherians (placental)

Question 12

Prototherians

Answer 12

egg laying

• females lack placenta
• incubated by parents
• have mammary glands, but no nipples so milk is sucked from the fur
  ex. platypus
• lay 2-4 eggs that hatch in 8 days then nursed for 5 months
  ex. echidna
• temp pouch for egg, hatch in 8 days, in pouch for 3 weeks, live 50 years

Question 13

Marsupials

Answer 13

pouched

• early birth, fetus completes development in pouch
• new borns crawl into mothers pouch (attach to nipple)
  ex. kangaroos
• in pouch at 2 weeks old
  ex. Tasmanian devil
• largest marsupial carnivore
• scavengers
• extinct due to hunting and dingos (wild dogs)

Question 14

Eutharians

Answer 14

PLACENTAL

• embryo retained in female reproductive tract
• 94% of species
• viviparous
• embryo nourished by mother via placenta
• ** some marsupials have placentas***

Question 15

The placenta

Answer 15

• organ formed by embryo and mother after implantation
• formed by extraembryonic membranes and uterus lining of mother
• site of gas, nutrient and waste exchange between mom and embryo (DIFFUSION)
• produce hormones to maintain pregnancy

Question 16

Placental blood supply

Answer 16

There are 3 blood vessels in the umbilical cord

• 2 arteries carry deO2 blood to mom
• 1 artery carries O2 blood to fetus
• fetal hemoglobin has a higher O2 affinity than adults, therefore, the oxygen moves to the fetus