Exam 4 Ch 20

Question 1

True or False. Mammals have synapsid ancestry from pelycosaurs through diverse therapsids.

Answer 1

True.

Question 2

Therapsids have the five following characteristics:

Answer 2

1. they had mammalian skeletons with a reduction in ribs and a developing diaphragm.
2. they were homodonts (all teeth same shape and size.)
3. they had enlarged temporal fenestrae
4. intermediate inner ear bones
5. disappeared largely in Triassic period (200 mya)

Question 3

True or False. The Cynodont group survived the extinction of Therapsids (small, chunky, rat-sized).

Answer 3

True

Question 4

What four traits allowed Cynodonts to survive?

Answer 4

1. high metabolic rate
2. specialized jaw musculature
3. heterodont teeth
4. greater agility (not as bulky)

Question 5

True or False. The earliest mammals (late Triassic) were shrew-like nocturnal animals.

Answer 5

True.

Question 6

True or False. After the Great Extinction of Cretaceous, diversification was possible by adaptive radiation after extinction of many amniote groups.

Answer 6

True.

Question 7

In what ways did modern mammals change from cynodonts?

Answer 7

1. turbinate bones
2. bony palate
3. loss of lumbar ribs (as diaphragm developed)
4. diphyodonts (loose baby teeth)

Question 8

In what way do modern mammals ears differ from Cynodonts?

Answer 8

the inner ear bones transformed from the articular and quadrate bones to the malleus, incus, and stapes.

Question 9

In what two ways do mammals skeleton differ from reptiles as discussed in lecture?

Answer 9

reptiles have a multi-bone jaw that moves into the ear, whereas mammals have one bone for the jaw.
Reptiles only have one little ear bone.

Question 10

True or False. Mammals are endothermic, with hair, sebaceous (oil glands) and sweat glands (pheromones, marking territory).

Answer 10

True.

Question 11

True or False. Like the platypus, early mammals hatched from eggs and relied on maternal milk.

Answer 11

True.

Question 12

True or False. Mammary glands evolved before the end of the Jurassic period.

Answer 12

False. This occurred during the Triassic period.

Question 13

Explain mammal diversity.

Answer 13

5700 species living, 643 species “critically endangered” or “endangered” (should be more)

Question 14

Mammals are divided into these three groups based on reproductive traits.

Answer 14

Prototheria (egg laying mammals)
Metatheria (marsupials)
Eutheria (placental mammals)

Question 15

What are the seven General traits of modern mammals?

Answer 15

1. hairy
2. milk producing
3. homeothermic endotherms
4. high metabolic rate
5. good hearing (better than birds/reptiles)
6. most placental (90%+)
7. specialized teeth and jaw for processing food

Question 16

What seven characteristics were discussed in lecture in regard to the benefits of hair on mammals?

Answer 16

1. mating
2. protection (predation, elements)
3. health of the animal
4. camouflage
5. guard hairs
6. vibrissae (whiskers) for sensory purposes
7. quills (modified hairs for protection)

Question 17

Name the three characteristics of mammalian skin discussed in lecture.

Answer 17

1. epidermis, dermis, hypodermis (outside to inside)
2. callus formation (outer layers become thicker w keratin layers)
3. thicker than other vertebrates

Question 18

Compare horns and antlers as variations of skin.

Answer 18

1. Horns are made of keratin (hair that grows together), antlers are made of bone.
2. Horns have less branching whereas antlers branch more. Antlers can shed whereas horns are permanent. 3. Horns have a continuous supply of blood and grow longer each year, but antlers get blood from the velvet on antlers.

Question 19

What four characteristics listed in lecture explain the variety of integumentary glands in modern mammals?

Answer 19

1. sweat glands
2. sebaceous glands (oil glands)
3. sweat glands (marking territory)
4. mammary glands (down two lines of the body)

Question 20

What characteristics of modern mammalian teeth were discussed in lecture?

Answer 20

1. differentiation for cutting, seizing, gnawing, etc. resulted in heterodont dentition.
2. I, C, P, M
3. Diphyodont (deciduous/milk teeth and adult teeth)
4. Thecodonts (teeth in sockets)
5. precise occlusion

Question 21

True or False. Feeding specializations include these four: Insectivores, Herbivores, Carnivores, and Omnivores.

Answer 21

True.

Question 22

What modern mammals are insectivores?

Answer 22

bats and anteaters.

Question 23

What four characteristics were discussed concerning modern Herbivores?

Answer 23

1. Browsers, grazers, gnawers (rabbits)
2. absent canines, molars broad with higher crown
3. anaerobic fermentation chambers for metabolizing cellulose in ceca
4. coprophagy for additional fermentation (still has nutrients in it second time around)

Question 24

What two characteristics of Carnivores were discussed in lecture?

Answer 24

1. most feed on herbivores

2. high protein diet is easily digestible with a shorter digestive tract

Question 25

What two characteristics of Omnivores were discussed in lecture?

Answer 25

1. true omnivores (pigs, raccoons, rats, bears, primates) | 2. carnivores eating a veggies snack when prey is scarce

Question 26

What two prototherians were mentioned in lecture?

Answer 26

Spiny anteater and platypus

Question 27

What else are egg laying mammals called?

Answer 27

monotremes

Question 28

What characteristics of Prototherian reproduction were discussed in lecture?

Answer 28

1. eggs laid once per year 2. Embryos develop for 10-12 days in the uterus 3. Thin, leathery shell is secreted around embryo before eggs laid 4. eggs incubate for 12 days 5. after hatching, young nourished by milk lapped off mother's fur near mammary glands.

Question 29

True or False. Marsupials are Metatherians, pouched, viviparous mammals.

Answer 29

True

Question 30

What five characteristics of Metatherian reproduction were discussed in lecture?

Answer 30

1. primitive choriovitelline (less vascularized) or yolk sac placenta 2. Embryo is encapsulated by shell membranes and floats in uterine fluid for several days 3. hatch from cell membranes (inside the uterus) 4. embryo erodes shallow depression in uterine wall and absorbs nutrient secretions by a vascularized yolk sac. 5. brief gestation, give birth to tiny young that are still embryos.

Question 31

True or false. Most Eutherian mammals are primates.

Answer 31

False. Most are rodents.

Question 32

What are the five characteristics of Eutherian reproduction discussed in lecture?

Answer 32

1. embryo nourished in uterus through placenta 2. chorioallantoic (clean) placenta 3. Gestation and body size loosely correlated to maturity at birth. 4. Humans have slower developmental period that any other mammal (to sexual maturity) 5. longer gestation than marsupials.

Question 33

Which has more lactation: Metatherians, or Eutherians?

Answer 33

Metatherians have more lactation, but Eutherians have greater gestation.