Reptile Overview & Chelonians Flashcards
Give the ancestral group that have rise to the amniotes
Early Labyrinthodont amphibian
Sister clade to living amphibians
Why did amniotes evolve ?
Due to the reproductive constraints placed on amphibians
Have to return to water for egg laying. (shell less eggs)
What does the amniotic egg provide ?
An aquatic environment in the egg for offspring
Amniotes still have a larval stage in life cycle
True or False ?
False, offspring hatch from the egg as mini adults.
Describe the amniotic eggs of reptiles, birds and mammals.
Birds- calcareous
Reptiles- Leathery and flexible
Mammals- no longer egg shell, develops within the mother
List the 4 extra-embryonic membranes of amniotic eggs.
Amnion
Chorion
Allantois
Yolk sac
What is the purpose of the Amnion ?
A membranous sac surrounding the embryo in fluid.
Give protection
What is the purpose of the Chorion ?
An outer membrane than surronds the embryo and yolk sac.
Allows gas exchange between embryo and air.
What is the purpose of the Allantois ?
Outgrowth of the hindgut
Storage of nitrogenous waste (
What is the purpose of the yolk sac ?
Surronds the yolk, giving an extensive blood supply to embryo
Give the disadvantages of the amniotic egg
Air is more thermally variable than water- Parental care to maintain temperature
Must have internal fertilisation, Require organs for this to occur
Energetcially costly for fewer offspring.
Substances required have to e consumed. i.e CaCO3
When did the divergence of synapsids (mammals) and reptiles occur ?
285 million years ago
How could the early amniotes be distinguished ?
By the number of fenestra in the skull
How would you identify…
Anapsid
Synapsids
Diapsids
Anapsid- No fenestra
Synapsids- 1 fenestra
Diapsids- 2 opening
What were the parareptiles ?
Permian and Triassic reptiles
Large stocky quadrupeds
Plates on skin
Died 200 million years ago
What are the chelonians ?
Turtles and tortoises
Which ancestral amniote group did the chelonians evolve from ?
Modern day research suggests the diapsids (2 fenestra)
Give the Chelonian adaptions to…
Seawater
Freshwater
Terrestrial
Seawater- Flippers for propulsion
Fresh- Webbed feet
Terrestrial- lost aquatic adaptions
What is the benefit of webbed feet for a chelonian in a freshwater system ?
Chelonians will spend more time at the bottom of the water system hunting for food rather than swimming (flippers)
Give the diet of Chelonians.
Carnivorous and Herbivorous
Give the name for the top and bottom shell of a chelonian
Top- Carapace
Bottom- Plastron
Give the 2 groups of Chelonian
Cyrptodires
Pleurodires
What organisms are found witihin the Cryptodires ?
Most living turtles
Hidden neck turtle
Neck retracts in S shape into shell
What organisms are found within the Pleurodies ?
Few species
Side necked turtle
Neck does not retract into shell
