Lecture 22: Reptiles & Birds Flashcards
how did reptiles perfect the transition to terrestrial life?
- new leg arrangements
- more efficient lungs and heart
- watertight coverings for skin and eggs
what are defining traits of reptiles?
- amniotic eggs
- dry skin
- thoracic breathing
- improved kidneys
who are the amniotes?
-all that have amniotic eggs (bird, reptiles, mammals)
what are the benefits of amniotic eggs?
- they’re independent and eliminate the need for water since they contain a food source
- have a watertight shell
- have 4 inter-membranes
internal fertilization
- amniotic eggs make external fertilization impossible
- sperm has to hit egg before the membrane forms
- some reptiles and birds have external gestation though
reptile skin
- not moist, made of keratin rich scales (not homologous)
- since not moist, they’re entirely dependent on their lungs and therefore have an increased lung capacity
thoracic breathing
-only limited to size of lungs so greatly increases gas intake
glottal breathing
-limits breath to size of mouth (how amphibians breathe)
ectothermy
- body temp changes with temp of environment
- i.e. can move in and out of sunlight to control body temp
endothermy
-maintain their temp using internal body functions (need to maintain this temp in order to survive)
benefits of reptile jaws
- very strong, more efficient
- categorized by the number of openings in the skull behind eyes
synapsids
- one opening in skull behind eye
- earliest reptiles
therapsids
- evolved from synapsids
- endothermic w/ a little bit of fur
- most of them died out when the dinosaurs came, except for mammals
diapsids
- 2 openings in skull behind eyes, led to birds
- contains all extant reptiles and extinct dinosaurs
archosaurs
- monophyletic group in diapsids
- 1st to walk on 2 legs
- had row of bony plates like modern crocodiles
lepidosaurs
-diapsids that aren’t archosaurs
tuataras
- lepidosaurs
- only 2 remaining species
- only found on a small group of islands
lizards and snakes
- squamates & lepidosaurs
- almost all carnivorous
- some have 2 peni
- most lizards walk on 4 legs
- snakes are limbless and can unhinge their jaws and some produce venom
turtles and tortoises
- neither individually are monophyletic, but together they are
- have no teeth and have protective shell which they are attached to
- marine ones have to return to land to lay eggs
crocodilians
- out-group to extinct dinosaurs
- large stealthy predators, mostly aquatic
- eyes and nostril on top of snouts
- enormous mother with strong neck muscles
- types: crocodiles, alligators, caimans, gavials
crocodilian parental care
- spend a lot of time with their young
- both parents will carry babies carefully in mouths
- moms even to teach them to hunt
who did birds evolve from?
archosaurs
theropods
- evolved feathers, gave rise to birds
- group of predatory dinosaurs
- all had bipedal stance, hollow bones, swiveling wrists, 3 fingered hands and feet, and backwards pelvises
- types: velociraptor
4 traits that birds share
- feathers
- flight skeletons
- improved lung design
- endothermy
facts about feathers
- they give lift for flight and provide heat
- they’re very flexible but strong bc secondary branches hook together with barbs
- large ones also have thin quills
- fan-like tail feathers stabilize the bird and down feathers keep it insulated
bird skeletons
- bones are thin and hollow to help with flying, many are also fused together
- gives it a rigid skeleton which gives it a sturdy frame to support flying muscles
- muscles connect to keel for powerful flight
bird lungs
- flight takes a lot of oxygen and energy
- bird lungs take in oxygen better than in any other organism
endothermy in birds
- body temp must be higher than in most mammals b/c it gives them good metabolism and ATP production
- all the energy used for flight leads to heat loss (that’s why their feathers are so insulating)
beak and foot morphology
- can tell a lot about a bird from its beak/feet
- types: you can tell a duck is aquatic from its webbed feet and filtering beak
general order of bird evolution
large flightless birds (ostriches) whose ancestors had flight (therefore flight was lost), after that you have water fowl, then owls/Swiffers/Woodpeckers, then Passeriformes.
passeriformes
- song birds
- most successful group of bird
- 1/2 of all birds are them
pelycosaurs
- gradually replaced amphibians
- had long, sharp teeth and could kill animals of their own size
- some of 1st synapsids
