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’
When and why did Ichthyosaurs go extinct?
~95 mil yrs ago
couldn’t evolve fast enough to deal with global warming
What did early forms of reptiles probaby feed on?
Invertebrates = little competition
When and why did the plesiosaurs, pterosaurs and dinosaurs go extinct?
~65 mil yrs ago
Potentially:
Mammals outcompeted
Massive volcanic eruption
Massive asteroid impact
= Most likely due to climate change, triggered by asteroid ash blocking sunlight
→ only 4 orders survived this
Which order do turtles, terrapins and tortoises belong to?
Chelonia
Describe the Chelonia
Includes marine (turtle), freshwater (terrapin) and terrestrial (tortoise) forms
Teeth replaced by sharp horny plates
No fenestra = weaker jaws
Bony dermal plates fuse to form carapace (top shell) and plastron(bottom shell)
Tortoises have retractable neck and limbs to protect against predators
Which order do lizards and snakes belong to?
Squamata
Describe snakes
Loss of limbs, elongate body form
Probably evolved from a burrowing lizard-like ancestor (convergent evolution with earthworms)
Eyelid lost, spectacle clear
Jaws extremely flexible, moveable joints for large prey
Which order do alligators and crocodiles belong to?
Crocodillia
Describe Crocodilia
Adapted for life in water
Broad flattened tail = powerful propulsion
Eye, ear, nose openings on the top of the flat head
Most closely related group to the dinosaurs
How are crocodilia adapted for life on water?
Broad flattened tail = powerful propulsion
Eye, ear, nose openings on the top of the flat head
Describe the differences between ailligators and crocs
Difference between alligators and crocs:
Alligators lower teeth not visible when mouth is shut
Crocs lower teeth stick up (always 4th one)
Alligators: prefer freshwater
Crocs: prefer saltwater
Crocs: more aggressive
What order does the Tuatara belong to?
Sphenodontia
Describe the Tutara
2 species, both in NZ
Very slow growing, 35 yrs to reach full size
Mean lifespan 60yrs, one male reproduced successfully at 111 yrs
Some biologists predict that in captivity they could live up to 200 yrs
What are birds defined by?
Defined by presence of feathers
Describe birds modifications to flight
Hollow bones with cross struts
Reduced organs (e.g females have 1 ovary)
No teeth, food ground in gizzard
Lightweight keratin bill
Large pectoral muscle anchored to keel (enlarged sternum)= gives power for flight
Describe a birds wing
Aerofoil shaped wing
Pentadactyl limb
What are a birds feathers held together by?
held together with barbs and hooked barbules = link together to give continuous flat mat of feathers
what are a birds feathers made from?
Keratin = not living
What are the 5 types of feathers on a bird?
Filoplumes
Down
Flight
Contour
Describe filoplume feathers
hair-like structures, accompany contour feathers, suggested sensory function
Describe down feathers
lie under contour feathers, lack barbules, long fluffy barbs. Trap air for insulation
Where are flight feathers on the wing?
posterior
Describe contour feathers
overlay body and give bird outershape, cover anterior edges of wings
Flight carries a high energetic requirement, what does this necessitate?
Necessitates endothermy, fat and feather circulation
Efficient circulation, 4 chambered heart
Birds have larger brains than reptiles, give some examples of what this facilitates
Complex behaviours: courtship, flight, navigation
Some capable of learning and solving problems
Colour vision
Describe the kind of dinosaur birds evolved from
Bipedal theropod dinosaur
What are 3 hypothesis for possible origins of flight?
1: Ancestors chased insect prey
Feathers aided running, jumping then gliding
2: Wings and feathers aided running up inclines, then gliding
3: Ancestors were climbers, feathers evolved as an adaptation for gliding to the ground
What does ratite mean?
Any bird with a flat breastbone
→ Cassowary & emu, kiwi, ostrich, rhea
Describe the ratites
Lack keel but wide sternum, suggests lost flight
Vestigial wings, large powerful legs
Has evolved at least 4 times → not monophyletic
Give some examples of carinates
Penguins, waders, raptors
