week 8 Flashcards
who first conceived the theory of evolution
darwin
define adaptation
an evolved trait that serves a certain function
define heritable trait
a characteristic within an organism’s genetic code that can be passed down to offspring
define evolution
theory that states the success of different heritable adaptations causes certain traits to be increasingly concentrated in a population, eventually changing the population over time
define natural selection
competitive selective process by which detrimental traits are lost and advantageous traits are kept within a population
Dinosauria. what is it
a group formed by ornithischians, saurischians, their most recent common ancestor, and all of its descendants
what are ornthischia
‘bird hipped’ group composed of hadrosaurs, ceratopsians, pachycephalosaurs, stegosaurs, and ankylosaurs, their most recent common ancestor, and all their descendants
what are saurischia
‘lizard hipped’ group formed by theropods, sauropods, and prosauropods, their most recent CA, and all their descendants
what is a character
any heritable trait that can be described and labelled. used mostly in taxonomy
what is a synapomorphy?
a character that stems from a common ancestor and is passed down to its descendants
what is convergent evolution
the independent evolution of similar structures by different lineages, due to organisms facing similar ecological or environ pressures
what are the four principles of natsel?
- a trait is heritable
- mutations can occur
- an organism’s trait impacts its survival, such that advantageous traits benefit it and disadvantageous traits harm it
- natural environ forces evolution virtue of having limited resources
is evolution random or directional?
directional - the processes behind evo are random, but evo itself is directional in that traits are selected for and against
what is a shared derived trait of ornithischia?
special bone in lower jaw that forms a beak (the predentary)
this character is unique to ornithischia
spinosaurus and ouranosaurus both have a big spine. are they related?
really really distantly. spinosaurus are theropod saurischians and ouranosaurus are hadrosaur ornithischians. would require one species completely rewriting its pubis, losing/developing predentary, etc
–> parsimony suggests its convergent evo
bats, birds, and pterosaurs all have wings. are they related?
no - they developed wings differently
bats: wing made of membrane stretching between five fingers
birds: wing made of feathers, w ‘hand’ bones fused into one bone
pterosaurs: wing made of membrane stretched from one elongated finger
phylogenetic trees contain nodes, branches, and clades. define
node: point at which two species diverge; indicates CA for the clade
branch: an independent lineage coming off a node
clade: a group of species that share a common ancestor, and implicitly some synapomorphies from said CA
who was the first dude to link birds to dinos? what evidence did he have? what is one problem he ran into?
huxley thought Arhceopteryx was the missing link, w long wing-like feathers and tail feathers similar to a birds, but w teeth, claws, and tail vertebrae of dinos
problem: birds have clavicles and dinos don’t. except on further analysis we realized they do, especially the theropods
what is a bird?
some say clade Avea, which is a clade of birds; some say clade Avialea, which is flying dinosaurs; some say any feathered dinosaur.
however there are problems w each (essentially, at what point do dinos become more birdlike than dino-like?)
tentatively we say crown birds, which distinguishes dinosaurs and birds by defining a bird as the last CA of all living birds. this includes some extinct species such as dodo birds, but excludes dinosaurs as well as some birds that were around at the time of dinos.
under this definition, Archaeopteryx is not a bird, but a dino
what is a hadrosaur example of synapomorphy?
lambeosaurus, corythosaurus, parasaurolophus all have crests but they appear to be different. however, that they have such crests is a synamopomorphy
what is the relevance of the ceratopsian syncervical?
an indicator of later ceratopsians that is not found in earlier ceratopsians
huxley thought birds came from dinos, but he has a problem. what was it
we’ve never found dino clavicles, but birds have them
except they actually did in the meat eating dinos, scientists just never noticed them