reptile derivatives
DESCRIPTION
Reptile Derivatives. Birds and mammals. Archaeopteryx = “first” bird. Reptilian features teeth, tail, pelvis – no sternum skull features Avian (bird) features feathers, longer front limbs. Why feathers ?; insulation. Why fly?: to glide from tree to tree - PowerPoint PPT PresentationTRANSCRIPT
Reptilian features
teeth, tail, pelvis – no sternum
skull features
Avian (bird) features
feathers, longer front limbs.
Mammal lung = dead end – incomplete exchange of Oxygen
Bird lung – one way movement = flow through and current counter current = greater efficiency and lighter weight.
Vega Island, Antarctic Peninsula
Use of DNA
• Gives relationship
• Distance in time (if mutation at constant rate)
• Does not use whole DNA but rather segments that evolve with time
• Different authors use different DNA seqments.
ratites
Ducks and grouse
Unexpected relationships
Hawks, falcons not related
Penguins – albatrosses
Flamingos – grebes !!!
1. synapsids, leading to mammals are the first group of reptiles
2. Based on differences from all reptiles and birds, mostly in features of soft anatomy.
• ventral aorta leaves heart, splits into aortic arches to gills
• in amphibians , single vessel leaves heart, then splits to left and right sides to form dorsal aorta
• in mammals and birds, same system in embryo, but in adults, ventral aorta splits back to the heart so the arches come directly off heart, one to lungs, others to body. In mammals and birds, finally reduced to a single arch
• in reptiles, the split involves a twist. In mammals it does not, so the remaining aortic arch in on different sides in reptiles and birds vs mammals.
How to make a Mammal
• Develop for carnivory = active
• Hair – warm bloodedness
• Limbs; under body, toes of equal length
• Teeth; regionalization, multi roots, cutting
• Lower jaw – one bone
• Not there – change in reproduction
On plate inside embryo – primitive streak forms
Get chorion, amnion, allantois and yolk sac
Placenta = chorion plus yolk sac in marsupials
Placenta = chorion plus allantois in placentals
opossum young on nipple.
Marsupials not primitive, but different
Designed for an unpredictable environment – can dump kid to save mother.
The Path leading to humans: choices along the way.
• bilateral symmetry
• internal skeleton
• active life – carnivore, omnivore? warm blooded, good senses
• daylight living – visual shape perception = brains for memory storage
• tropical climate – k species strategy
• social organization – based on?? Food sources? Defense?
This gets us to monkeys or squid. Now what to lead to humans?
Suggested, upright, tools, social structure, none correlated to big brain
probably speech – (no direct fossil record)