lec 8- homology Flashcards
during what era did the dinosaurs live?
Mesozoic era, “age of reptiles”
what are synapsids?
“mammal-like” reptiles
when did the synapsids mostly dominate the land?
during the permian period
what is included in the synapsid clade and what are some characteristics?
all living mammals and extinct relatives, one opening in the skull behind the eye (fenestra), and differentiated teeth
when did the small mammals evolve and what did the evolve together with?
they evolved during the early mesozoic and evolved together with early dinosaurs
what did mammals evolve from?
from the reptilian synapsids
what 3 bones of the synapsids skull are homologous with the 3 inner ear bones of mammals?
The quadrate, articular, and angular
did the 3 jaw bones of synapsids shrink over time?
yes
why did these 3 bones in the jaw shift into ear bones?
because the way of hearing changed from listening to vibration in the ground to vibrations in the air
what are the 3 ancestral jaw bones that turned into ear bones called in humans?
tympanic ring, malleus, and incus
during what time did the mammals diversify?
after the extinction of most dinosaurs, around 50 Ma during the eocene
what is homology and homeoplasy?
-homology is when a species gains traits from a common ancestor
-homoplasy is when unrelated species that do not share a common ancestor evolve similar traits (convergent evolution) due to environmental influences
what is exaptation and give an example?
-when a trait evolves to serve a new function, different from its original function
- e.g. panda “thumbs” are a modified radial sesamoid bone (wrist bone)
give an example of obvious homology and not so obvious homology:
-obvious: feet structure of humans compared to chimps
-not obvious: feet structure of elephants compared to humans
what evolved first, feathers or flight in theropods?
feathers
what happened to the 3 digits of dinosaurs in bird wings?
they fused together to allow for flight, they are called the phalanges
how did they learn that dinosaurs had feathers?
some well preserved bones like on the velociraptor had quill nodes
did compsognathus turn out to be archaeopteryx?
yes
where did many feathered dinosaurs get uncovered?
in china
what were dinosaur feathers used for?
sexual selection and insulation, wings were too short for flight and body was too big
how are the color of feathered dinosaurs like Archaeornis found out?
by looking at the melanosomes size and shape in feather cells
what bird has 3 clawed fingers?
baby Hoatzin, claws lost in adults
what is the largest living dinosaur?
the ostrich
how did Darwin view evolution?
as a branching process that grows to increase diversity
is the early history of the 3 domains of life more like a bush rather than a tree of life?
yes
