Lecture 23 Vertebrates - Tetrapods & Amphibians Flashcards
Tetrapod means
Four footed
Tetrapods include (4)
-amphibians
-reptiles
-birds
-mammals
Lateral line system is
A sensory system used for organisms in an aquatic environment, present in amphibian larvae but lost during metamorphosis
Like modern amphibians, many ancestral tetrapods were
Aquatic as juveniles and terrestrial as adults
Tetrapods adapted to a terrestrial existence through (2)
-limbs, pelvis, and pectoral girdle (ossified, fusion of bones)
-vertebral column with larger articulations to avoid sagging
Modern amphibians represent
An intermediate in the transition from water to land
Modern amphibians arose from the
Labyrinthodonts
Acanthostega (6)
-four footed fish
-late Devonian period (~365 Mya)
-radial fins supporting a tail fin
-defined limbs with digits (8)
-weight bearing girdles
-internal gills
Digits arose before
The transition to land
Three orders of amphibians include
-Anura (frogs and toads)
-Urodela/Caudata (salamanders and newts)
-Gymnophiona/Apoda (caecilians)
Modern amphibians arose about
200 million years ago in the Jurassic Period
____ most closely resemble ancestral amphibians
Salamanders
Metamorphosis from aquatic larvae to terrestrial adults results in (3)
-lose of lateral line system
-lungs that replace gills
-development of legs
How many species of amphibians are there worldwide
~3000
Amphibians utilize ____ respiration
Cutaneous
Cutaneous respiration is (2)
-gas exchange occurring in capillary beds within the epidermis
-large surface area to body mass ratio
Modern amphibians have a very thin _____ which means
Stratum Corneum
-limited protection from abrasion and dehydration
Amphibians have ___ digits on hind limbs and ___ in forelimbs
5, 4
Articulate processes of amphibians (3)
-make up the vertebrae
-interlock
-provide rigidity and support out of water
The pectoral girdle of amphibians is (2)
-no longer joined at the skull
-contains a cervical vertebrae (able to move head)
The pelvic girdle of amphibians contains
Urostyle: ilium, ischium, and pubis
Mucous glands in amphibians (2)
-are continuously secreted
-help prevent dehydration
Granular glands are
Poison glands, often toxic if ingested or injected
Chromatophores are (3)
-mostly found in the dermis
-produces coloration as a warning to predators
-creates a noxious skin secretion
Eyelids and tear glands of amphibians are developed at
Metamorphosis
In frogs and toads, fertilization is (2)
-external
-occurs in or near water
In caecilians, fertilization is
-internal
-male and female press cloaca together and sperm is deposited into female’s cloaca
In salamanders, fertilization is
-Internal
-male produces a spermatophore (cap of sperm on a gelatinous stalk) that is picked up by the female’s cloaca
The evolution of ____ facilitated the success of vertebrates on land
Amniotic egg
Amniotic egg contains (4)
Extraembryonic membranes:
-amnion
-allantois
-chorin
-yolk sac
Amniotes include
-reptiles
-birds
-mammals
Amnion (3)
-encloses embryo
-fluid filled
-protects embryo from mechanical shock
Allantois (2)
-contains fetal urine
-contributes to placenta in eutherian mammals
Two parts of the amniotic egg that contribute to placenta are the
-allantois
-chorion
Yolk sac
Source of nutrition for the embryo
Chorion (2)
-outer envelope
-contributes to placenta in eutherian mammals
In birds and reptiles, the amniotic egg is enclosed by a
Calcareous or leathery shell which prevents desiccation
Eutherian mammals form a
Placenta
Marsupials (therian mammals) deliver
Altricial young
Monotremes have retained the
Egg shell
Cotylosauria (2)
-“stem reptiles”
-basal group of amniotes
Two major lineages in the evolution of amniotes include
-sauropsida (dinosaurs, birds, reptiles)
-synapsida (mammals)
Sauropsids include
Dinosaurs, reptiles, and birds
Amniotes can be grouped according to
The anatomy of the temporal region of the skull (ie. number of temporal fenestrae)
Three types of skulls:
-anapsid
-diapsid
-synapsid
Anapsid Skull (3)
-no fenestrae
-ancestral amniotes
-turtles and tortoises
Diapsid Skull (2)
-two fenestrae
-dinosaurs, lizards, snakes, crocodiles, tuatara, birds
Synapsid Skull (2)
-one fenestrae
-mammals
