ectotherms lecture 4 Flashcards
What is the fishbian sequence?
It is a sequence showing the transition of life from water too land where changes in the key limb bones (Ulna, radius and humerus) can be tracked
What are the fish characteristics of the tiktaalik?
Scales, Fins, Gills and Lungs
What are the tetrapod characteristics of the tiktaalik?
Neck, ribs, fin skeleton, flat skull, eyes on top of skull
What are the amphibian characteristics?
Bony Skeleton, varied body forms, usually 4 limbs, smooth moist skin (coated in glands), large mouth and small teeth, gaseous exchange occurs across gills, lungs and skin, 3 chambered heart, ectothermal (though tend to lack behavioural adaptation), separate sexes
What are the orders of amphibian?
Urodela (salamanders), Anura (frogs), Apoda (caecilians)
What are the unique features of the anura skeletons compared to the ancestral urodele skeleton?
The tail is lost, and the ilium is elongated there is also a urostyle which allows for the attachment of large jumping muscles
This specialises the skeleton for jumping
What are the unique features of the apoda skeleton compared to the ancestral urodele skeleton?
These skeletons have lost their leg
What is required for the amphibian life cycle?
There is a need for abundant water as this is required for the development of young and for respiration as the skin needs to be kept wet
How do amphibians reproduce?
The eggs are released into the water while the male clasps the female and releases sperm and a jelly coat swells
These eggs will require a moist environment, and for some species eggs are carried on the adults back, mouth or stomach
What occurs in the metamorphosis of amphibians?
The eggs hatch to swimming larvae which are herbivorous and have fish characters
This is followed by a thyroxin surge which triggers the metamorphosis leading to the growth of legs and tail regression to form an adult frog
What are the features of the amniotes?
They have an amniotic egg
Rib breathing, and they have abandoned skin breathing allowing further H2O conservation
What are the differences between the anapsida, synapsida and diapsida skulls?
Anapsida have no holes in their skulls whil synapsida have one and diapsida have two
What are the reptilian characteristics?
Bony with horny epidermal scales
Paired limbs usually with 5 toes
Ossified skeleton
Lungs not gills
3 chambered heart
Ectothermic with behavioural thermoregulation
Internal fertilization with separate sexes
Eggs covered in a shell with extraembryonic membranes
What are the reptilian orders?
Crocidylia (aquatic predators from the Mesozoic with the tail reverting to a swimming organ)
Testudines (ancient and successful, aquatic and terrestrial forms)
Squamata (developed from lizards, legs lost but vestigial in some species)
Sphenodonta (like tuatara)
What are the differences between a tuatara and a lizard?
A tuatara has two bony arches at the back of its skull while a lizard has one
The tuatara’s teeth are fused to its jaw bone while lizard teeth are attached to an inner surface of the jaw and replaced through out life
Tuataras have no external earhole or penis while lizards have both
Tuatara have a well developed parietal organ while lizards have a simple one
