Transcript Reptile Derivatives

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
or to chase insects?
Mammal lung = dead end –
incomplete exchange of Oxygen
Bird lung – one way movement =
flow through and current counter
current = greater efficiency and
lighter weight.
Hespirornis = toothed, flightless,
loon like diving bird
Rattites = worldwide, ancient flightless
birds.
7 is Vega island, off of James Ross Island at tip of
Antarctic Peninsula.
Vega Island, Antarctic Peninsula
Pleisiosaur front arm (fin)
Vegavis, from Vega
Island in Western
Antarctica – Cretaceous
in age (pre-meteor)
A ‘duck’
Origin of Modern birds (Neornithes) before end of Cretaceous
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.
Unexpected relationships
Hawks, falcons not related
Penguins – albatrosses
Flamingos – grebes !!!
Ducks and
grouse
ratites
Origin of Mammals
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.
Synapsids = mammal like reptiles
Pelycosaurs = Dimetrodon
Function of “sail”
Camoflage?
Swimming?
Thermoregulation
Note: nasty
carnivore
Therapsids
How to make a Mammal
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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
Hair, tooth regionalization, forward pointed toes of same length, limbs
under body,
Reptilian scales with sensory papillae in between.
Papillae become hair – for insulation
A definition of mammal = three
bones in middle ear, one bone in
lower jaw
Mammals; monotremes, platypus and echidna
Lay eggs.
Echidna – egg in pouch,
Hatches in 9 days – young
in pouch for 12 weeks. Gets
milk.
Marsupials and
Placentals –
Parallelism
And no shelled
eggs
Marsupial and placental reproduction;
clevage total and equal - blastula forms with inner cell
mass
Inner cell mass forms layers of cells
inside blastula
Embryo implants into uterine wall
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
Marsupial pouch with ‘baby’
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)
Human origins – arboreal nocturnal monkey
Arboreal diurnal monkey
Terrestrial monkey to terrestrial ape
To human , with what does the change correlate ?