11 - Mammals

Question 1

Mammals and ancestral amniotes

Answer 1

most closely related group to ancestral amniotes1

Question 2

Premammalian synapsids

Answer 2

present during mid-triassic

Bad thermoregulation so probably not true homeotherms (dimetrodon and cynognathus)

Question 3

Evolutionary perspective mammals

Answer 3

• first amniote lineage

- started 200 mya with therapsid subgroup

Question 4

Therapsid subgroup

Answer 4

• mammal-like teeth
• hindlimbs directly beneath body
• separation of thoracic and abdominal regions
• near extinction 240 mya (dinos took over)

Question 5

During dinosaurs

Answer 5

• mammals survived nocturnally (bad colour vision)

Question 6

Mammalian radiaton

Answer 6

• 65 mya
• mass extinctioin of dinos and other taxa
• tertiary period “age of mammals”
• mammals were able to be outside during the day

Question 7

2 subclasses of mammals

Answer 7

• prototheria

- theria

Question 8

Subclass prototheria

Answer 8

• cloaca, oviparous

Question 9

Subclass prototheria infraclass

Answer 9

ornithodelphia (monotremes)

Question 10

Subclass theria 2 infraclasses

Answer 10

Metatheria (marsupials)

Eutheria (placental mammals)

Question 11

Monotremes

Answer 11

• 6 species
• found in australia/new zealand
• eggs
• ex: echidnas and platypus

Question 12

Marsupials

Answer 12

• around 250 species
• viviparous but short gestation periods
• born early but not developed so feed and develop in marsupium (pouch)
• ex: koalas, kangaroos

Question 13

Biogeography of mammals

Answer 13

Movement of continents explains the current distribution of mammals

Question 14

Hair

Answer 14

• guard hairs
• insulating underhair
• whiskers provide sense of touch

Question 15

Glands

Answer 15

• sebaceous (oil)
• sudoriferous (sweat)
• scent (pheromones)
• mammary (nutrition for offspring)

Question 16

Teeth

Answer 16

• heterodonts (unlike homodont in reptiles where they’re uniformly conical)
• specialized for different functions
• deciduous (milk) teeth and permanent
• single replacement of teeth is the diphyodont condition. reptiles are polyphydont

Question 17

diphyodont

Answer 17

single replacement of teeth

Question 18

4 types of teeth

Answer 18

• incisors
• canines
• premolars
• molars

Question 19

humans teeth

Answer 19

2,1,2,3 on each side

incisors, canines, premolars, molars

Question 20

Diastema

Answer 20

missing teeth section separates the biting teeth at the front of the jaw, from the chewing teeth at the rear

Question 21

Skeleton

Answer 21

• vertebral column

- appendicular skeleton

Question 22

Vertebral column 5 regions

Answer 22

Cervical
thoracic
lumbar
sacral
caudal

Question 23

Appendicular skeleton

Answer 23

• rotates under body

- appendages move in anteroposterior plane (makes them faster than reptiles)

Question 24

Digestive systems

Answer 24

Adapted for diverse feeding habits that reflect ecological specializations
Herbivores/ruminants: rumens, cecums and spiral loops (long digestive system)
Carnivores: much smaller, no storage/fermenting compartments

Question 25

Heart, circulation

Answer 25

- complete separation of pulmonary and systemic circuits - similarities with bird hearts result from convergence within synapsid and archosaur lineages (adaptations to active lifestyles)

Question 26

Fetal circulation

Answer 26

- nutrients/gases/wastes exchanged by diffusion across placenta - in fetus, blood shunted away from lungs until inflated at birth

Question 27

2 structures involved in shunting

Answer 27

- foramen ovale (shunt between left and right atria) - Ductus arteriosus (most blood in pulmonary artery bypasses lungs) These close off after birth

Question 28

Respiration

Answer 28

- respiratory passageways highly branched with large surface areas - thin membranes and high surface area - larynx, trachea, bonchi (1,2,3) bronchioles, alveoli

Question 29

Heat producing mechanisms

Answer 29

- shivering thermogenesis | - nonshivering thermogenesis (metabolism of brown fat: hibernation)

Question 30

Heat conservation

Answer 30

- insulating pelage and fat deposits (ex: hair, and blubber) - shunt blood from surface to core to keep it warm in water - heat conserving postures - countercurrent heat-exchange systems

Question 31

Cooling

Answer 31

``` Radiation into air Evaporative cooling (sweat glands/panting) ```

Question 32

Winter sleep

Answer 32

- less active and metabolic rates drop somewhat - easily aroused/periodically wake - body temperature doesn't change much - bears/raccoons

Question 33

Hibernation

Answer 33

- metabolic rates drop substantially - hypothalamic thermostat reset - not easily aroused - insectivores, rodents, bats

Question 34

Conserving water; kidneys

Answer 34

- very efficient kidneys - long loop of nephron (loop of henle) - concentrates urine and conserves water - countercurrent exchange system! - longer loop = better water usage

Question 35

More strategies for water conservation

Answer 35

- Dry feces - Nocturnal habits - Water condensation in respiratory passages - Low protein diets

Question 36

2 reproductive cycles

Answer 36

- estrus cycle | - menstrual cycle

Question 37

Estrus cycle

Answer 37

- Female behaviourally and physiologically receptive to male - hormonal changes stimulate maturation of ova and ovulation - uterine lining proliferates - vaginal swelling and discharge Males show heightened interest in females

Question 38

Menstrual cycle

Answer 38

- humans, apes, monkeys - periodic proliferation of uterine lining that correlates to maturation of ovum - Sloughing of lining occurs in absence of fertilization

Question 39

Delayed fertilization

Answer 39

Adaptation to winter dormancy in some bats. | suspended or slow growth of the embryo that can occur after implantation has occurred but prior to birth

Question 40

Embryonic diapause

Answer 40

- Development arrested after fertilization | - development occurs when resources are most plentiful

Question 41

Modes of development

Answer 41

- monotremes are oviparous | - all others are viviparous

Question 42

Viviparous

Answer 42

marsupials: nourished via uterine milk following short gestation period Eutherian mammals: form placenta and have long gestation periods