vertebrates; tetrapods, amphibians and amniotes Flashcards
tetrapod means
4 footed
what does tetrapods include
amphibians, reptiles, birds and mammals
around when did vertebrates move onto land
400 MYA
many ancestral tetrapods, like modern amphibians were
aquatic as juveniles and terrestrial as adults
tetrapods had to adapt to land existence, give examples:
- limbs, pelvis and pectoral girdle; more ossified, fusion of bones
- vertebral column: larger articulations to avoid sagging
modern amphibians arose from
- labrynthodonts
- acanthostega; 4 footed fish
- radial fins rays supporting rail fin
what arose first: digits or transition to land
digits
3 orders of amphibians
1) anura: frogs and toads
2) urodela/ caudata: salamanders and newst
3) gymnophonia/apoda: caecilians (legless blind creatures)
what most closely resembles ancestral amphibians
- salamanders; long body, short legs, tail
amphibians; aquatic larva that metamorphose into terrestrial larva
- lose lateral line system
- lungs replace gills
- develop legs
ancestral amphibians had
scales; evolved from lobe finned fish
modern amphibians have a very thin
- stratum corneum
- limited protection from abrasion and dehydration
- cutaneous respiration
cutaneous respiration
- gas exchange
- capillary beds within epidermis
- large SA to body mass ratio
amphibian adaptations to terrestrial existence
- vertebrae; articular process
- pectoral girdle; no longer joined to skull
- pelvic girdle; ilium, ischium and pubis
- digits; 5 on hind, 4 on front
- mucous glands (continuous secretion)
- granular glands (poison)
amphibian chromatophores
noxious skin secretions often coupled w striking colour
- predominantly in dermis
when do amphibian eyelids and tear glands develop
at metamorphosis
amphibians; most return to ____ to reproduce
water
in frogs and toads fertilization is
external
in caecilians fertilization is
internal; cloacae pressed together
in salamanders fertilization is
internal; male produce spermatophore (a cap of sperm on a gelatinous stalk) female picks up with cloaca
amphibian brain
shows v little development from that of fish
lateral line (fish sensory system) present in aquatic larva and lost in terrestrial adults
evolution of the _____ facilitated the success of vertebrates on land
amniotic egg
amniotes inlcude
reptiles, birds, mammals
amniotic egg is characterized by
presence of several extra-embryonic membranes
presence of several extra-embryonic membranes in amniotic egg:
amnion
encloses the embryo; fluid filled and so protects the embryo from mechanical shock
presence of several extra-embryonic membranes in amniotic egg:
allantois
contains fetal urine; contributes to placenta in eutherian mammals
presence of several extra-embryonic membranes in amniotic egg:
chorion
outer envelope; contributes to placenta in eutherian mammals
presence of several extra-embryonic membranes in amniotic egg:
yolk sac
source of nutrition for embryo
in bird and reptiles the embryo and membranes enclosed by a
calcareous of leathery shell
eutherian and marsupial (therian) embryo and associated membranes
- have lost the shell
- eutherians form placenta
- marsupials deliver altricial young
do monotremes have egg shell
yes
basal group of amniotes
cotylosauria “ stem reptiles”
2 major lineages in evolution of amniotes
- sauropsids; dinosaurs, reptiles, birds
- synapsids; mammals
amniotes can be grouped according to anatomy of
temporal region of skull; number of temporal fenestrae
anapsid
- no fenestrae
- ancestral amniotes
- turtles and tortoises
diapsids
- 2 fenestrae
- dinos, lizards, snakes, crocs, tuatara, birds
synapsid
- one fenestra
- mammals
