8: Evolution Flashcards
Charles Darwin
Theory of evolution
British
Evolution is based on four basic principles of life
the differential success of certain variations of a heritable trait, because of competition for limited resources leads to the change over time of that trait in a population
heritable
trait is part of the organism’s genetic code
a trait must be heritable in order for that trait to evolve
variation
variation in traits in a population
random genetic mutations
advantage/differential success
a trait must provide an advantage over other variations in order for evolution to occur
competition
natural environments have limited resources and competition for these resources permits only some organisms to successfully reproduce before they die
Is evolution a random process?
No! It is based on how well each trait improves an organism’s reproductive success
T/F: Most random mutations are more likely to diminish than they are to improve an organism’s success
T
Natural Selection
the competitive selection process by which detrimental traits are competitively discarded and advantageous traits are retained
Organisms are grouped together based on their most recent…
shared common ancestors
character
a heritable trait that can be described and labelled
shared derived character
a character that is present in 2 or more groups and their common ancestor, but is not present in any more distantly related groups
ex. predentary of ornithischians
Synapomorphy
aka: shared derived character
Convergent evolution
the evolution of similar traits in 2 different lineages
Parsimony/Occam’s razor
All there things being equal, the simplest answer is usually the right one
A Clade
a group of species that share a common node
no size limits
must contain the ancestor of a group and all of its descendants
phylogenic tree
family tress composed of nodes and branches
node
where two branches diverge, and shows the point at which two lineages shared a common ancestor
Linnean Hierarchy
Classifies organisms as belonging a Kingdom, Phylum, Class, Order, Family, Genus, Species
Class Mammalia, Aves, and Amphibia are all…
subsets of the class Pisces (now called Osteichthyes)
Thomas Henry Huxley
advocate for theory of evolution
First scientist to recognize that birds evolved from dinosaurs, cited Archaeopteryx as fossils of a “missing link” between dinosaurs and birds
Archaeopteryx
“missing link” between dinosaurs and birds
Huxley
had teeth, clawed fingers, and long series of tail vertebrae like a dinosaur, and the long-wing and tail feathers of a bird
Sinosauropteryx
the first non-avian (non-bird) dinosaur to be discovered with feathers
Birds are classified as _______ dinosaurs
theropod
the only clade of dinosaurs alive today
birds
Bird definition 1: Archaeopteryx and all of its descendants
Problem: new phylogenic analyses sometimes show that Archaeopteryx is more closely related to the dromeosaurid theropods than to modern birds
Bird definition 2: feathered dinosaur
Problem: as more and more feathered dinosaur fossils, like Yutyrannus, are found, more dinosaurs are included in this definition. ex. Tyranosaurs would now be considered birds
Bird definition 3: Flying dinosaurs
Problem: it is difficult to determine which dinosaurs were capable of flying (as opposed to simply gliding
Definition 4: Crown dinosaurs
This a technical term that means the last common ancestor for all extant birds and its descendants
Problem: this fails to recognize many feathered and flying dinosaurs that are more closely related to modern birds than to Archaeopteryx as birds
This definition is favoured by scientists
We use the term Avialae for the clade containing Archaeopteryx and all of its descendants
