Lecture 34 & 35 Amniotes - Mammals

Question 1

where did animals evolve from?

Answer 1

• synapsids

Question 2

what does the synapsid clade include?

Answer 2

• reptile-like sailbacks

- numerous therapsida – mammals and close relatives

Question 3

all non-mammalian syapsids are?

Answer 3

extinct

all that is left is the mammals in therapsida

Question 4

what are mammals characterized by?

Answer 4

• enlargement of dentary bone in the jaw of therapsida ( in mammals jaw only consists of this bone)
• development of a secondary palate (bone partition between nasal and oral cavities – simultaneous chewing and breathing

Question 5

what are derived characteristics of mammals?

Answer 5

• mammary glands
• hair
• endothermic
• movement of leftover jawbones to middle ear
• dentary-squamosal jaw joints
• different detention
• occluding of teeth
• two sets of teeth over lifespan
• larger brains than vertebrates
• vertical placement of limbs beneath the body
• diaphragm
• all mammals transfer sperm via intromission

Question 6

what do mammary glands do?

Answer 6

• secrete milk for offspring

Question 7

what is hair made of?

Answer 7

fine cylindrical keratin fibres

- might have whiskers

Question 8

in regards to avian endothermy, how did mammal endothermy arise?

Answer 8

independently

• high metabolic rate
• hair and fat help for thermoregulation

Question 9

how many ear bones do mammals have?

Answer 9

3, reptiles have 1

• allow for higher pitched sound
• eardrum moves to deeper in mammals

Question 10

what does dentary squamosal mean?

Answer 10

dentary: lower jaw bone - carries teeth
squamosal: small cranial bone
both meet to form a joint
- in most gnathostomes joint consists of articular and quadrate

Question 11

how is mammalian detention different from reptile?

Answer 11

• greater diversity of tooth form

Question 12

what does a closer occlude lead to?

Answer 12

greater grinding of food

- bigger surface area

Question 13

what are the two sets of teeth of mammals?

Answer 13

• milk and adult (reptiles replace) teeth constantly

Question 14

what develops in the brain

Answer 14

neocortex – sensory percept, language, motor commants - HIGHER FXNS

Question 15

how does vertical placement of limbs help mammals?

Answer 15

greater support of the body, greater efficiency of movement

Question 16

what are the three extant lineages of mammals?

what are they based on?

Answer 16

monotremes - single order
marsupials -single order
eutherians - multiple order

based on modes of birth and development

Question 17

what are monotremes?

Answer 17

mammals - consist of echidnas and platypus

• lay eggs that are oviparous, but provide milk for young after they are born
• no nipples - specialized hairs
• cloacas
• lack teeth as adults
• feed on invertebrates

Question 18

what are characteristics of both marsupials and eutherans?

Answer 18

• viviparous - birth to live young
• placenta provides nourishment to young initially – extraembryonic membranes and lining of the uterus, transfers nuttients and oxygen from mother’s blood to embryo’s blood
• post birth: nurse on milk from nipples

Question 19

what are marsupials?

Answer 19

• opossums, kangaroos, koalas

- embryo develops within

Question 20

what are characteristics of both marsupials and eutherans?

Answer 20

• viviparous - birth to live young
• placenta provides nourishment to young initially – extraembryonic membranes and lining of the uterus, transfers nuttients and oxygen from mother’s blood to embryo’s blood
• post birth: nurse on milk from nipples

Question 21

what are marsupials?

Answer 21

• opossums, kangaroos, koalas
• yolk-sac placenta, live born
• embryo develops within a placenta in the mother’s uterus: young very briefly nourished via placenta
• born as partially developed embryos
• convergent evolution with mammals, analogous structures
• started in NA found their way to SA then Australia via Antartica

Question 22

what are eutharians?

Answer 22

non marsupial mammals
- more complex placenta – chorioallantoic placenta
- complete embryonic development in uterus, nourish young via placenta until very well developed
NO CLOACA

Question 23

whats up with cloacas?

Answer 23

Monotremes and marsupials have a single cloaca (though marsupials also have a separate genital tract), while most placental mammal females have separate openings for reproduction, urination, and defecation: the vagina, the urethra, and the anus

Question 24

what are bats?

Answer 24

eutherians

- only mammals capable of flight

Question 25

why did mammals return to water?

Answer 25

• abundant aquatic food sources
• escape from terrestrial predators
• few aquatic competitors
• availability of warm, shallow waters

Question 26

what are pinnepeds?

Answer 26

seals- semiaquatic

- descended from monophyletic carnivora lineage that includes otters, bears walruses

Question 27

what is the evolution of cetaceans?

Answer 27

• whales & dolphins (cetaceans), manatees, dugongs initially grouped together because of superficially anatomical structures – ANALOGOUS
• cetaceans descended from even toed ungulates (hoofed mammals)
• hippos are the closest living relatives of whales, but they are not the ancestors of whales

Question 28

what are adaptive changes of mammals who return to sea?

Answer 28

• shortening of legs
• hands and feet enlarge – paddles
• tail longer and more muscular
• nostrils – blowholes

Question 29

what are adaptive changes of mammals who return to sea?

Answer 29

• shortening of legs
• hands and feet enlarge – paddles
• tail longer and more muscular
• nostrils – blowholes
• hands, limbs and pelvis evolve to be reduced in size and separate from backbone – vestigal hind limb
• reduced neck fxn - fusion of cervical vertebrae
• other adaptations for feeding in water
• increased use of whole vertebral column including back and tail for locomotion
• swim: move tails up and down instead of back and forth like fishes, reflects ancient terrestrial heritage

Question 30

what is order dermoptera? colugos?

Answer 30

arboreal gliding mammals ex: sugar glider

• sister group to primates

Question 31

what is order primates?

Answer 31

lemurs, tarsiers, monkeys, apes

• generalist mammals
• arboreal
• hands and feet adapted for grasping
• thumb and toe widely separated from other digits
• fully opposable thumb, pentadactyl appendages
• flat nails
• large brain, short djaws
• forward facing eyes, stereoscopic vision, depth perception
• complex social behaviour
• shortened snouts