Exam 2 Flashcards
Why did organisms move onto land?
- new food sources (insect radiation in the Carboniferous period)
- avoid high predation
- move from one drying pond to another (ex. lungfish)
- basking in the sun to elevate body temp (increased activity)
- dispersal of juveniles away from natal site (less competition)
Sarcopterygian synapomorphies
- fins supported by small bony, muscular lobes
- cosmine on dermal bones and scales
- intracranial joint between anterior and posterior portions of braincase
Coelacanthimorpha
- primarily marine, large, deep water fish
- once believed to have gone extinct in the Mesozoic
- unique rostral organ (electroreception)
- internal fertilization, viviparous
- sister group to lungfish and tetrapods
- part of Class Sarcopterygii
Dipnomorpha
- 6 species (Australia, Africa, South America)
- first evolved ~400 mya
- estivate in burrows during the dry season, mucus secretions seal burrow
- part of Class Sarcopterygii
Dipnomorpha synapomorphies
- holostylic jaw (palatoquadrate is fused to the cranium)
- duraphagous apparatus (broad teeth plates lining the palate, reduction in jaw bone)
- well developed lungs
(Part of Class Sarcopterygii)
Tetrapods
terrestrial vertebrates descended from common four-legged ancestor, possess chiridium
chiridium
muscular limb with well-defined joints and digits
Tetrapodomorphs
group of extinct fish closely related to extant sarcopterygians
Eusthenopteron
- tetrapodomorph
- Late Devonian sarcopterygian fish
Traits Shared w/ Early Tetrapods - enamel coated teeth (labrynthodont teeth)
- rudimentary humerus, radius, ulna
- more robust vertebrae (enlarged introcentrum)
Tiktaalik
- tetrapodomorph
- late Devonian sarcopterygian most similar to tetrapods
- good shallow water predators with eyes on top of head, and no dorsal/anal fins
Traits Shared w/ Early Tetrapods - loss of bony operculum (skull is not connected to pectoral girdles which allows the head to raise above the water)
- forelimb with metacarpals
- ribs projecting more ventrally to support body out of water
How are tetrapodomorphs still fish-like?
- retain distinct caudal fins and fin-like limbs
- retain a fusiform body with undifferentiated epaxial and hypaxial muscles
- poorly ossified vertebrae
- retain well developed gills
Stem tetrapods
Acanthostega and Ichthyostega
Fish-like traits of Acanthostega
- fin rays on large caudal fin and fin-like limbds
- weak zygapophyses
- internal gills (operculum)
- evidence of lateral line system
Tetrapod-like traits of Acanthostega
- some differentiation in vertebral column
- limbs are well defined (chiridium, 8 digits)
- robust pelvic and pectoral girdles
More derived traits of Ichthyostega
- robust ribs (support thorax on land)
- stronger zygapophyses
- smaller caudal fin
- highly differentiated thoracic and lumbar vertebrae
Benefits of limbs in aquatic predators?
- can climb underwater vegetation
- allows for rapid ambush in shallow water
Where did caecilians evolve from?
Stereospondyles
Where did frogs and salamanders evolve from?
Dissorophoidea
What are reptilomorphs?
Stem amniotes
Extinct non-amniote tetrapods
- Stereospondyles
- Dissorophoidea
- Reptiliomorphs
Stereospondyles
- mostly larger forms
- flat skulls with long snouts
- two occipital condyles for rotating head
Dissorophoidea
- smaller forms
- short snout and large eyes
- large tympanum for hearing
- some fossils have a combination of salamander and frog traits
Reptiliomorphs
- mainly terrestrial with terrestrial limb structures
- domed skull
- 5 digit feet
- likely ancestor of amniotes
Amniotic Egg
- leathery or rigid shell (some permeability)
- albumin
- yolk
- 4 extra-embryonic membranes
albumin
(in amniotic eggs) source of water and protein, acts as a protective layer
yolk
(in amniotic eggs) primary energy source (lecithotrophic)
What are the four extra-embryonic membranes in the amniotic egg?
- yolk sac
- chorion
- amnion
- allantois
Yolk sac
- made of embryonic endoderm and mesoderm
- surrounds yolk
- develops into the gut
Amnion
- made of embryonic ectoderm and mesoderm
- inner membrane that surrounds the embryo
Chorion
- made of embryonic ectoderm and mesoderm
- outer membrane that surround the entire embryo and yolk
Allantois
- made of embryonic endoderm and mesoderm
- nitrogenous waste site
- respiratory organ during later development
Benefits of amniotic egg?
- allantois allows storage of nitrogenous waste
- tough shell for support on land (avoid drying out)
- larger egg allows for larger hatchlings which increases survival
- respiration is possible through the semi-permeable shell
Synapomorphies of amniotes
- amniotic egg
- keratin derived dermal features (scales, hair)
- costal ventilation
- lateral flange on pterygoid bone aids in chewing
- more complex brachial plexus innervating forelimbs
costal ventilation
use of ribs to ventilate lungs (results in less water loss to environment)
temporal fenestration
major openings in temporal region of skull, used to divide amniotes into major groups
anapsids
group of amniotes that lack fenestra (primitive amniotes and turtles)
synapsids
group of amniotes with lower temporal fenestra only (mammals)
diapsids
group of amniotes with upper and lower temporal fenestra (extant reptiles and birds)
Evolution of temporal fenestration
- ancestral condition = anapsid (large, flat skulls, buccal cavity was used for ventilation, closed jaws)
- costal ventilation allowed for more variability in head shape
- less robust skull allowed for formation of fenestra (abductor mandibullae splits into 2 muscles = temporalis on temporal and parietal and the masseter on the zygomatic arch
- more complex jaw musculature allows for isometric contractions resulting in more oral processing
Land v Water (oxygen)
- higher concentration of O2 in air than water
- high concentration of O2 in fresh water than salt water
- higher temperatures reduce O2 concentration in water
density and viscosity
- water is 800x more dense than air
- water has greater viscosity than air
- both influence locomotion and respiration
Impact of density and viscosity on respiration
- less energy is needed for respiration in air than water
- tidal ventilation. (bidirectional flow) is possible in air
Gills
- unidirectional flow
- methods include buccal pumping and ram ventilation
- 2 rows of filaments per branchial arch
- upper and lower row of lamellae on each filament (counter current exchange)
buccal pumping
skeletal muscle pumps water in buccal cavity and out through the opercular cavity
ram ventilation
mouth is always open, swimming forces water across the gills (only works in highly active fish)
lamellae
site of gas exchange in gills
countercurrent exchange
blood flow is opposite of water flow which ensures the concentration of oxygen is always greater than the partial pressure in the blood along the entire length of the gill, this also allows for more O2 to be absorbed
Lungs
- bidirectional flow
- lungs contained within thoracic cavity
- negative pressure breathing
negative pressure breathing
inhalation: diaphragm and external intercostals contract while internal intercostals relax
exhalation: diaphragm and extern intercostals relax while internal intercostals contract
aortic arches
pass through the gills between the branchial arches
Circulatory system: Chondrichthyes
- 4 chambers in series (sinus venosus, atrium, ventricle, conus arteriosis)
- afferent artery, gill arch, efferent artery, body, heart
- 6 aortic arches (first is reduced to supple spiracle and second is reduced to supply head)
- single circuit
- single pressure
advantage of single pressure
high pressure at the gills helps facilitate (and prioritize) gas exchange
disadvantage of single pressure
low pressure system in capillaries, results in less efficient gas exchange in body tissues
Circulatory system: dipnoi
- 3 chambers in series (atrium, ventricle, conus arteriosus)
- septum partially divides halves of atrium and ventricle
- conus arteriosis is homologous with bulbs arteriosus in teleosts
- vestigial spiracle, lost first arch but retains second
- double circuit - pulmonary and systemic
- pulmonary artery branches off 6th aortic arch
- ductus arteriosus (shunt used to bypass lungs when under water)
Circulatory system: amphibians
- 3 chambered heart (2 atria, 1 ventricle
- 1st/2nd aortic arches are lost, 6th becomes the pulmonary artery
- single pressure heart
- double circuit with spiral valve
- deoxygenated blood going towards pulmocutaneous circuit
- oxygenated blood going toward systemic circuit
Circulatory system: reptiia
- 3 chambered heart (2 atria, 1 ventricle) with partial separation of ventricles by horizontal septum
- only arches 3, 4, and 6 remain (arch 3=carotid arteries, arch 4=left/right systemic arch, arch 6=pulmonary artery)
- single pressure with some separation
- double circuit
Circulatory system: aves
- 4 chambered heart (2 atria, 2 ventricles)
- portions of arches 3, 4, 6 remain
- only right systemic arch retained
- double circuit and double pressure (left = oxygenated, right=deoxygenated)
Circulatory system: mammalia
- 4 chambered heart (2 atria, 2 ventricles)
- portions of 3, 4, 6 remain (3=carotid, brachiocephalic, right subclavian, 4=aorta, 6=pulmonary trunk)
- only left systemic arch retained (aortic arch and dorsal aorta)
- part of right systemic arch is brachiocephalic artery
- double circuit with double pressure
Cane Toad
- Amphibia
- introduced to AUS from Hawaii to control sugar cane pests
- rapidly extending range
- eat native wildlife and damage the ecosystem
Subclass Lissamphibia
first observed in Permian, radiated during Jurassic, with approximately 7600 species
Synapomorphies of Lissamphibia
- permeable, glandular skin used for gas exchange
- columella-opercular complex: unique ear bones
- carnivory
- pediciliate teeth
- green rods
- levator bulbi muscle
columella
derived from hyoid, detects high frequency sound
opercular
part of dermatocranium, detects low frequency sound
carnivory
refers to the behavior of eating whatever can be caught and swallowed
pedicilate teeth
crown and based on teeth are made of dentine, they are separated by a weaker, fibrous layer
green rods
unique retinal cells that have sensitivity to blue light and can detect color in the dark
levator bulbi muscle
used to bulge eyes outward
Order Caudata
- part of Class Amphibia (salamanders and newts)
- ancestral mode: elongate body and tail
- some paedomorphosis
- large species include Chinese giant salamander
- cave species with reduced eyes and pigmentation (Texas blind salamander)
feeding specializations of Plethodontidae
- hyobranchial apparatus – specialized throat bones and musculature for protruding tongue
- good vision – eyes large and moved forward for binocular vision
hyobranchial apparatus
specialized throat bones and musculature for protruding tongue (not compatible with buccal pumping due to lack of lungs, and not compatible with suction feeding because there is no larval stage)
paedomorphosis
retention of juvenile traits in the adult form (failed to release TSH)
reproductive biology of salamanders
- fertilization via spermatophore
- pheromones released from hedonic glands
- maternal care
spermatophore
large packet of lipid and sperm used for fertilization in various ways
- male pushes spermatophore into female’s cloaca
- female picks up spermatophore with cloaca (internal fertilization in most species)
- female deposits eggs on spermatophore
Rough skinned newt
releases pheromones from hedonic glands by rubbing chin on the female’s nostrils
Plethodontid salamanders
releases pheromones from hedonic glands by slapping the gland on his chin onto the female’s nostrils
two-lined salamander
releases pheromones from hedonic glands by using enlarged teeth to scrape the skin on the female’s head
smooth newt
releases pheromones from hedonic glands by using his large tail to waft pheromones towards the female
maternal care of salamanders
aquatic species lay eggs in water as a gelatinous mass, terrestrial species lag eggs in damp soil, some species will guard the eggs, there are also a few viviparous species
Caecilians
- part of Order Gymnophiona
- legless, burrowing, aquatic
- eye covered by skin or bone flap, some lack eyes
- annuli: dermal folds overlaying segments bordered by ribs
- pair of protrusible tentacles near eyes
- feed on insects and earthworms
reproductive biology of caecilians
- internal fertilization via male intromettenti organ
- some are oviparous and female guards the eggs
- most species are viviparous and matrotrophic
Caecilians methods of matrotrophy
young can be 30-60% of female’s body length
- fetuses scrape oviduct using embryonic teeth to release uterine milk
- dermatophagy in which young peel off out layer of mother’s skin
Order Anura
- frogs and toads, 7350 species everywhere but Antarctica
modes of locomotion
Order Anura
- hoppers - jump 5-10x body length, tend to be widely foraging predators (toads, horned frogs)
- jumpers - jump 10-20x body length, tend to be sit-and-wait predators (frogs)
- leapers - jump over 20x body length, tend to be arboreal sit-and-wait predators (tree frogs have toe disks for climbing and have wet adhesion)
specializations for jumping
- elongated hindlimbs (tibia and fibula are fused)
- caudal and sacral vertebrae are fused into urostyle
- semi-membraneous muscle adapted for max power
permanent pools in reproduction
- prolonged breeders
- longer breeding season
- males arrive first and claim territories
- high reproductive skew (few males get most matings)
- high competition
- ex. green frogs and leopard frogs
temporary pools in reproduction
- explosive breeders
- short breeding season
- males and females arrive at the same time
- low reproductive skew (most males get similar mating opportunities)
- scramble competition favors ability to rapidly find a mate
- ex. wood frogs and spring peepers
advertisement calls
used to attract mates, identify species, sex, and condition of the male (females become responsive to the male’s call only during breeding season)
Costs of vocalization
- increased predation risk (by bats)
- energy costs
- increased competition, risk of disputes with other males
- satellite strategy
- ex. Tungara frog: females prefer males with loud chuck calls but this also attracts bats, honest signal (only males with good survival traits will be successful)
modes of reproduction: anurans
- amplexus: male clasps female with fore or hind legs until she lays eggs
- foam nests: float on water surface and tadpoles fall into water as they hatch
Strawberry poison frogs
lay eggs in pools, unfertilized eggs feed tadpoles
midwife toad
carries eggs on male’s back
surinam toad
female carries in her back where they metamorphose into small toads
Darwin’s frog
embryos develop in male’s vocal sac
Turtle synapomorphy
shell (upper is the carapace, lower is plastron), results in limited species diversity
Turtle phylogenies
- anapsid = ancestral condition
- anapsid is an evolutionary reversal (turtles are more closely related to modern lizards)
- anapsid skull is a several and turtles are a highly derived diapsid
Cryptodires
- 255 species
- on all continents except Antarctica and Australia
- retract head by bending in vertical S
- trochlear process is formed by the otic capsule
Pleurodires
- 93 species
- found in Australia, South America, and New Guinea
- retract head by bending horizontally
- trochlear process is formed by pterygoid process
