Biodiversity 7: Reptiles and birds Flashcards
Describe the amniotic egg
A self contained waterproof chamber for development
Eliminates larval stage = freed ancestors from need to return to water to breed
What is the amniotic egg shell like in reptiles?
Leathery
What is the amniotic egg shell like in birds?
calcium carbonate (protected from drying out)
What are the 5 membranes present in the amniotic egg?
- Shell
- Amnion
- Chorion
- Yolk sac
- Allantois
Describe the shell of an amniotic egg
Shell is waterproof but allows gas exchange so embryo can get O2
Describe the amnion of an amniotic egg
fluid cushions and protects embryo
Describe the chorion of an amniotic egg
surrounds embryo and regulates gas exchange
Describe the yolk sac of an amniotic egg
surround egg yolk mass
yolk mass = accumulation of nutrients from mother
Describe the allantois of an amiotic egg
Stores nitrogenous waste (toxic to embryo)
What is a fenestra?
openings in the skull for attachment of jaw muscles, enables the jaw to open widely
Define anapsid
No fenestra
Extinct forms
Define synapsid
1 fenestra
Mammals
Define diapsid
2 fenestra
Birds and reptiles
Why did anapids go extinct?
probably due to poor bite power
‘reptiles are paraphyletic’
What does this statement mean?
multiple lineages, don’t have a single ancestor that distinguishes them from non-reptiles
Describe reptiles + examples
Lack a single defining characteristic:
Have amniotic eggs but no feathers (not birds)
Don’t have mammary glands/hair (not mammals)
E.g Turtles, lizards, snakes, crocodile, tuatara
Describe the features of reptiles
Heavier ossified skeleton, strong joints, clawed toes
Skin covered in keratinised scales or scutes
Ectotherm (cold blooded) → eat less: only need 10% of calories of an endotherm
Internal fertilisation, eggs laid on land
Efficient predators
What covers a reptiles skin and how are these adapted to life on land?
Skin covered in keratinised scales or scutes → prevent dessication
What type of fertilsation do reptiles use?
Internal, lay eggs on land
In which age were early reptiles dominant?
Mesozoic ‘Age of the Reptiles’