Who came up with the theory of evolution, what does the theory postulate?
Darwin
- explains how new species come into existence, how organisms become adapted to their environments and why specific groups of organisms share specific traits
- all life on Earth is related and shares a single common origin
What are the three basic characteristics of life that Darwin noticed?
- if unchecked, organisms produce more offspring that can be sustained by the environment
- organisms tend to resemble their parents because parent organisms pass on some or all of their genetic code to their offspring
- occasionally, organisms are produced that have novel traits or have trait variations
What are the four principles of life?
- many traits of an organisms are heritable: a trait must be heritable in order for that trait to evolve
- some organisms have heritable traits that are new: usually caused by random genetic mutation; in order for natural selection to occur on any given trait, there must be variation in that trait in a population
- an organism’s traits affect how successfully that organism is able to reproduce: trait affects the organism’s ability to survive; one variation of the trait must provide an advantage/differential success over other variations for evolution to occur
- natural environments must have limited resources: competition for these resources leads to only some organisms being able to reproduce before they die; some version of the trait must be selected out for evolution to occur
What is natural selection?
competitive selective process by which detrimental traits are selected against and advantageous traits are selected for/retained
what does it mean to be ‘heritable’?
the trait is part of an organisms’ genetic code and has a chance to be copied to the organisms’ offspring
What clade are ornithischians and sauropods apart of?
dinosauria
How can we determine the most recent common ancestor of two organisms?
by studying characters
What is a character?
any heritable trait that can be described and labeled
What is a shared derived character? What’s another term for this?
a character that’s present in at least two groups + their common ancestor, but isn’t present in more distantly related groups
synamorphy
What is the biggest challenge to determining evolutionary relationships?
convergent evolution
Spinosaurus and ouranosaurs share one common character, what is it? Is it a synamorphy and an example of convergent evolution?
common character = long processes on the vertebrae to form a sail
spinosaurs are a theropod while ouranosaurs are iguanodonts, therefore, it is likely that the sails evolved independently –> convergent evolution
Why does convergent evolution occur?
results when two lineages must adapt to be similar environments and models of life
Describe how the wings of pterosaurs, birds, and bats demonstrate convergent evolution?
pterosaurs: have wing made of a membrane supported by one long finger
birds: have a wing made of feathers and have fused the hand bones into a single unit
bats: have a wing made of membrane supported by several fingers
What is parsimony?
the simplest answer is probably the right one?
How do paleontologists identify evolutionary relationships?
Computer analyzes a list of characters/character matrix that is compiled by the researcher. Based on the character matrix, the computer program applies the principles of parisimony to arrange the organisms is a sequence that requires the fewest instances of convergent evolution. Results in the production of a phyolgenetic tree
What does a node represent?
the point where two lineages shared a common ancestor
What is a clade?
must contain the ancestor of a group and all of its descendents
Who is Huxley?
one of the earliest advocated for the theory of evolution and first scientist to recognize that birds evolved from dinos
Why did Huxley cite Archaeopteryx as the missing link between birds and dinos?
- long wing feathers and tail feathers –> bird
- teeth, clawed fingers, and a long series of tail vertebrae –> dino
What was a major character that was observed in Sinosauropteryx that helped bring more attention to the relationship between dinos and birds?
first non-avian dino to be discovered with feathers - it’s feathers are simple and used for insulation
What are the possible uses of feathers?
- sexual display
- thermal insulation
- protection from the elements like rain
- flying
what does the clade aves include?
includes all living birds + extinct taxa like the dodo
What odes the clade avialae include?
include extinct species that looked very similar to modern birds (including Archaeoptyrex)
What are the 4 definitions of what a bird is? what are the limitations and which definition is favoured?
- Archaeoptyrex and all of its descendants: problem = new phyolgenetic analyses sometimes show that Archaeoptyrex is more closely related to the dromaeosaurid theropods that to modern birds
- feathered dinos: problems = as more and more feathered dino fossils, like Yutyrannus are found, more dinos are being included in this definition (e.g. tyrannosaurs would be considered birds)
- flying dinos: problem = it is difficult to determine exactly which dinos were capable of flying as opposed to gliding
- crown dino* (the last common ancestor of all extant birds and its descendants): problem = fails to recognize many feathered theropods and flying dino that are more closely related to modern birds than to Archaeoptyrex as birds
