1
Q
who gave rise to Lissamphibia (modern amphibians)?
A
temnospondyls
2
Q
describe the temnospondyls
A
semiaquatic, robust bodies, flat skulls, occupied wide range of niches, from 350 MYA
3
Q
what are lepospondyls?
A
group previously thought to give rise to amphibians, occupied specialized niches related to body (eel-like = aquatic, lizard-like = more terrestrial)
4
Q
what were the 7 major changes from fish to tetrapods?
A
- fins become chiridium (muscular limb, able to have digits, new humerous + radius/ulna angle)
- fused shoulder becomes true neck (loss of operculum, evolution of atlas vertebrae)
- reinforced vertebral column and girdles (centra becomes ossified, zygosphores appear to aid V.C. in holding the body up, both girdles become attached to V.C. point of attachments for locomotion muscles)
- skull shortening, loss of hyomandibular arch (hyomandibular arch becomes stapes, braincase is now supported by roof of mouth connection)
- snout elongation and change in eye and nostril location (nostrils connect to oral cavity, eyes moved to top of skull)
- reduction of skull bone pattern (fusion of small nasal region bones, loss of opercular bones)
- integument modifications (dermal scales become gastralia to cover tetrapod belly)
5
Q
describe movement in early tetrapods
A
lateral undulation (limbs are used as pivot points)
6
Q
what is a muscle?
A
a collection of modified cells that can gen. contractile force along the axis of their fibers (can produce or restrict movement)
7
Q
how are muscles “excited”?
A
electrically, respond to nervous simulation
8
Q
what are other functions of muscles?
A
gen heat, gen electric shocks/fields (eels + electric fish)
9
Q
how are muscles classified?
A
- location (somatic and visceral)
- nervous control method (voluntarily or involuntarily)
- microscopic appearance (skeletal, cardiac, or smooth)
10
Q
where are smooth muscles found?
A
blood vessels and visceral organs
11
Q
T or F: all muscles are derived from the dermis
A
False! all muscles are derived from the mesoderm
12
Q
what parts of the mesoderm form muscles?
A
- somites (dermatome (skin), myotome (skeletal muscle), scleretome (parts of skeleton))
- hypomere (heart and gut muscles)
- mesenchyme (forms muscles in limb buds)
13
Q
what are the muscle action groups?
A
- flexors and extensors (bend + straighten)
- abductors and adductors (draw limbs away + toward body)
- pronators and supinators (turn palm/sole up + down)
- constrictors and dilators (close + open orifices)
- protractors and retractors (moves body region parallel to ground)
14
Q
explain the skeletal and muscular relationship
A
- skeletal muscles are attached to bones by tendons
- bones attach to bones by ligaments
- muscles work oppositely to achieve function
15
Q
what are the 3 extant groups of amphibians?
A
- anura (frogs and toads)
- caudata (salamanders and newts)
- gymnophiona (caecilians)
16
Q
what glands do amphibians have in their integument?
A
- mucous glands (secretes mucous to help with cutaneous respiration)
- granular glands (secretes poisonous alkaloid compounds for defense)
17
Q
which amphibian groups sometimes have osteoderms?
A
toads and caecilians (the bony elements aids in defense)
18
Q
describe the difference between metamorphosis and paedomorphosis
A
metamorphosis is the indirect development from egg/larval form to adult
paedomorphosis is the retention of larval characteristics into “adulthood”
19
Q
describe pedicellate teeth
A
- unique to modern amphibians (and some extinct temnospondyls)
- each tooth crown sits on a pedicel base separated from crown tip by fibrous suture connection
20
Q
main characteristics of the anuran class
A
- paired limbs
- absence of tails in adults
- “jumpers”
- tympanum (helps transmit sound to inner ear)
- external fertilization in almost all
21
Q
describe the anuran skull
A
- flattened, open, with big jaws
- palate is highly reduced, eyes can drop down when swallowing prey
- hyomandibula becomes the stapes
- splanchnocranium, chondrocranium and dermatocranium all present
22
Q
describe the anuran axial skeleton
A
- specialized to support jumping hindlimbs
- 9 or fewer vertebrae in vertebral column
- atlas forms moveable joint with 2 condyles to improve head mobility
- post-sacral vertebrae use to form urostyle, lies in between 2 ilium bones
23
Q
describe the anuran appendicular skeleton
A
- pectoral girdle and radius/ulna used to absorb the landing shock
- tibia/fibula and ankle bones are fused for sturdiness
- increase in length of hindlimbs (for jumping)
24
Q
what are the main characteristics of salamanders?
A
- paired limbs + long tail
- suction feeding in water + projectible tongue on land
- no tympanum
- external + internal (transfer of spermatophore) fertilization
25
describe the salamander skull
- flattened, open skull with large orbits
- poor ossification (loss of bones is common)
- splanchnocranium, dermatocranium + chondrocranium all present
26
how does suction feeding work in salamanders?
floor of throat rapidly expands and jaws part open, creating a current to pull in small prey
27
describe the axial + appendicular skeleton in salamanders
- long back with 10 to 60 pre-sacral vertebrae
- use short walking limbs + swimming tail
28
describe the main characteristics of caecilians
- no limbs or girdles
- skull is solid + compact for burrowing
- only in tropical climates
- internal fertilization (aquatic or terrestrial hatchlings)
- 60 to 285 trunk vertebrae
- eyes are reduced but paired tentacles on head help with chemoreception
29
what are the hypothesis for amphibian origins?
- temnospondyl hypothesis
- lepospondyl hypothesis
- polyphyletic hypothesis
30
explain the temnospondyl hypothesis of amphibian origin
- modern (extant) amphibians form a monophyletic clade (lissamphibia)
- derived from temnospondyl amphibian ancestors
31
explain the lepospondyl hypothesis of amphibian origin
- modern amphibians form a monophyletic clade (lissamphibia)
- derived from lepospondyl amphibian ancestors
32
explain the polyphyletic hypothesis of amphibian origin
- lissamphibia form a polyphyletic clade
- frogs + salamanders are derived from temnospondyl amphibian ancestors
- caecilians are derived from lepospondyl amphibian ancestors
33
what are the main groups of tetrapods?
1. temnospondyls
2. lepospondyls
3. amniotes
34
describe the early amniotes
- evolved roughly 350 MYA
- often small (20 cm) with a highly ossified skeleton
- jaws, teeth and neck all modified for predation
35
what are the major groups of amniotes?
1. sauropsids (reptiles and birds)
2. synapsids (mammals)
36
what are the major lineages of sauropsids?
1. turtles
2. crocodiles
3. birds
4. 'lizards' + snakes
37
what makes up the diapsids?
1. lepidosaurs ('lizards' and snakes)
2. archosaurs (dinosaurs, birds + crocodiles)
38
describe the anamniote egg
- permeable vitelline membranes (to allow direct exchange with the environment)
- must be deposited in water to prevent drying out
- ex. frog
39
describe the amniote egg
- semi permeable shell (allows gases to pass but keeps fluids inside)
- extra embryonic membranes (for protection + gas transfer)
- ex. chick
40
what are the extra embryonic membranes within the amniote egg?
1. amnion (surrounds embryo with water)
2. chorion (surrounds embryo and yolk sac)
3. allantois (fills with waste as yolk proteins are used) (waste storage)
41
how did the amniote egg change species' way of life?
- allowed for entire development of organism on land, loss of larval stage
- more efficient gas exchange (allowed egg/embryo to grow larger before hatching compared to aquatic species)
- required internal fertilization
42
describe the major derived characteristics of amniotes
1. low skin permeability to prevent desiccation
(thickened keratinized stratum corneum) (presence of lipid)
2. lung ventilation aided by ribs
(allowed for a long neck as they could draw in air through the trachea) (space for elaboration of forelimb nerves)
3. body support + locomotion
(increased gravity on land needed stronger/stiffer skeletons)
43
describe the amniote axial skeleton
- expanded regionalization of the vertebral column
(cervical, thoracic, lumbar, sacral, caudal vertebrae)
- lumbar ribs lost in some amniotes
(allows for hindlimb forward movement, easier limb oscillation, rapid locomotion)
44
describe the changes in the atlas + axis cervical vertebrae in amniotes
- atlas + axial have reduced centrum + processes
- addition of skull atlas joint
(allows for vertical nodding + horizontal tilting of head)
- addition of atlanto-axial joint
(allows for twisting movement)
(maintains strength of neck while allowing cranial movement)
45
how did limb posture change for amniotes?
- limbs are often situated under the body in mammals for increased efficiency of limb swing
- digits + limbs are rotated inwards for a forward thrust during locomotion
46
how did skull fenestration change during the evolution of amniotes?
- in anapsids, no temporal fenestration
(earliest amniotes + turtles)
- in synapsids, one lower temporal fenestra
(extinct synapsids + mammals)
- in diapsids, two temporal fenestrae
(modern reptiles + birds)
- in euryapsids, one upper temporal fenestra
(derived from diapsid pattern in extinct marine reptiles)
47
describe the main characteristics of turtles
- present 230 MYA
- hard shell + solid (anapsid) toothless skull
- ventral plastron (covers belly) + dorsal carapace made up of fused bony elements covered by keratin scutes
48
what are the main components of the turtle body plan?
- skeletal + dermal (keratinized osteoderms) bones
- position of scapula inside of rib cage
49
what are the two hypothesis for the evolution of the turtle body plan?
hypothesis 1 - classic transformationist view (gradual mod. of pre-existing features
hypothesis 2 - emergentist view (rapid evolution due to changes
50
what are the two main groups of lepidosaurs?
1. sphenodontids (tuatara, a single extant species that branched early)
2. squamates ('lizards' + snakes) (lizards evolved first)
51
describe the skull adaptations in squamates
- loss of temporal bars in fenestrae (lower absent in lizards, both absent in snakes)
- opening of skull (allowed for improved jaw mobility + swallowing ability)
- transcranial joint across the top of the skull (front of orbit in snakes) (rear of orbit + back of skull in lizards)
- ability of quadrate bone to rotate around dorsal connection w/ braincase)
52
how did cranial kinesis alter movement and adapt feeding in lizards?
- when jaws open, snout tips up
- when jaws close, snout tips down
- allows for equal perpendicular force of both jaws on food, limits preys ability to escape
53
how did cranial kinesis alter movement in snakes?
- lower jaw is loosely hinged
- the two sides of mandible are only connected by muscle + skin, allows for sides to separate during feeding
54
describe locomotion in limbless species
- main type is lateral undulation
- wave movements connect with environmental contact points to gen. reaction forces to propel forwards
55
what are the main groups of archosaurs?
- crocodilians
- pterosaurs (extinct)
- dinosaurs (ornithiscians + saurischians) (extinct)
- birds
56
what are the main characteristics of crocodilians?
- aquatic ambush predatory lifestyles (eyes, nostrils + ears on top of head, transparent eyelids, bony throat flaps)
- regulates body temp by lying with mouth open
- four chambered heart
- offspring sex determined by nest temp.
57
what are the main characteristics of pterosaurs?
- first vertebrae group to evolve powered flight
- used membranous wings + elongated forelimbs
- early forms had long tails + elongated forelimbs
- later forms lost tail + teeth, but had a crest on the back of head
58
what are the main groups of dinosaurs and how are they distinguished?
saurischian = pelvic girdle w/ forward pointing pubis (lizard-hipped), herbivorous + carnivorous
ornithischian = pelvic girdle w/ backward-pointing pubis (like bird hips), only herbivorous
59
how did giant dinosaur's skeletons adapt?
- shortened, robust, pillar-like limbs (weight support)
- elongated necks with more, lighter cervical vertebrae
- presence of soft pads in limbs
- reduction of wrist/fingers + ankle/toes
60
how did dinosaurs outcompete crurotarsans?
by luck
- crurotarsans had larger range of phenotypes and similar evolutionary rates but died by chance in mass extinction
61
when did dinosaurs go extinct?
the KT mass extinction
- the cretaceous tertiary mass extinction
62
how did birds skeletally adapt?
skull - reduced # of bones
- thinner bones
- no teeth to reduce weight
neck - heterocoelous cervical vertebrae (exceptionally flexible)
backbone - very rigid to minimize the # of muscles needed to maintain streamlined body during flight (reduces energy consumption)
pelvic girdle - fused w/ synsacrum
- no symphysis of pelvic bones so larger outlet for big eggs
62
how did bird's synsacrum adapt?
- fusion of vertebrae w/ pelvic girdle allows for rigidity + support of hindlimbs
63
how did bird's sternum adapt?
- ossified + pronounced keel to provide attachment for flight muscles
64
describe reptile integument
- relatively few mucous glands (dry skin)
- species specific glands for producing poison or pheromones
- keratinized scales
65
describe reptile keratinized scales
- continuous folds of epidermis
- protection from desiccation
- provides snakes w/ grip during locomotion
- sheds regularly in lizards + snakes
66
describe bird integument
- large gland (uropygial gland) produces oily secretion to coat feathers for waterproofing
- have epidermal derivatives (claws, scales in absence of feathers, tooth-like perturbances in beak, feathers)
67
What are synapsids?
mammals and mammal-like reptiles
68
What are Pelycosaurs?
Basal synapsids that arose in the Carboniferous period
-have a single temporal fenestrae
-carnivorous or herbivorous with palatal teeth
69
What are Therapsids?
Advanced synapsids that evolved from Pelycosaurs in the early Permian period.
-have an enlarged temporal fenestrae
-reduction of palatal teeth
-the dominant species until the Triassic period
70
What are Cynodonts?
Mammal-like reptiles that arose in the late Permian period.
- developed jaw musculature for chewing
- double occipital condyles for neck mobility
- no palatal dentition
- nasal turbinates for regulating heat and water exchange
71
What are features of the first mammals?
Evolved in the late Triassic period from cynodonts.
- small insectivores
- use endothermy
- enlarged brain for better hearing and smell
- lower jaw is a single bone (dentary)
- teeth have specialized functions and vary between species
72
What are the three living groups of mammals?
- Monotremata (monotremes)
- Metatheria (marsupials)
- Eutheria (placentals)
73
What are the four modern mammal specialized glands in their integument?
- Sebaceous glands (alveolar glands)
-> oily sebum secreted with hair follicle to 'waterproof' hair and protects skin from drying
- Sweat glands (tubular glands)
-> secrete water, salts and urea, can be used for thermoregulation
- Mammary glands
-> provide nutrition for young offspring
- Scent glands
-> derived from sweat or sebaceous glands and are used for defence or sexual selection
74
What are four mammal characteristics?
- feed young milk from mammary glands
- extended parental care of young
- large brain/body size ratio
- hair (derived from integument)
75
What are some monotreme features?
Ex. platypus, echidna
- lack nipples, external ears and teeth as adults
- embryos develop in leathery eggs
76
What are some marsupial features?
Ex. kangaroo, opossum
- give birth to tiny young who suckle until they grow larger, often in a mothers pouch
77
What are some placental features?
Ex. fox, elephant
- most widespread group of mammals
- prolonged gestation of enbryo in uterus with placenta
78
What four groups did eutheria diversity give rise to?
- Afrotheria (evolved in Africa)
- Xenarthra (evolved in South America)
- Euarchontoglires (evolved in northern supercontinent of Laurasia)
- Laurasiatheria (evolved in northern supercontinent of Laurasia)
** Euarchontoglires and Laurasiatheria are under the Boreoeutheria clade**
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