Chapter 4 Flashcards
What is Tiktaalik?
transitional fossil between fish and tetrapods
Define Phylogeny:
A visual representation of the evolutionary history of populations, genes, or species.
Define tips:
terminal ends of an evolutionary tree, representing species, molecules, or populations being compared.
Branches
Lineages evolving through time between successive speciation events.
Nodes
a point in a phylogeny where a lineage splits( a speciation event)
Internal Nodes
Nodes within a phylogeny representing ancestral populations or species.
Clade
An organism and all of its descendants.
Monophyletic
a group made of up of an organism and all its descendants.
Characters
Heritable aspects of organisms that can be compared across taxa.
Taxon (taxa)
A group of organisms that a taxonomist judges to be a taxonomic unit, such as a species or order.
Synapomorphy
A shared derived character.
Shared derived character
one that evolved in the immediate common ancestor of a clade and was inherited by all its descendants.
Cladistics
Phylogenetic methods that construct trees by grouping taxa into nested hierarchies (clades) according to their shared derived characters(synapomorphies).
Homoplasy
Character state similarity not due to shared descent. Produced by convergent evolution or evolutionary reversal.
Convergent Evolution
The independent origin of similar traits in separate evolutionary lineages.
Evolutionary Reversal
the reversion of a derived character state to its ancestral state.
Exaptation
A trait that originates performing one function, and which is later co-opted for a new function.
Australopithecine
any of a genus (Australopithecus) of extinct southern and eastern African hominids that include gracile and robust forms with near-human dentition and a relatively small brain
T or F: No current living species is ancestral to any other
T
Which term is not associated with tree-like depictions of evolutionary histories known as phylogenies?: Node, Seed, Branch, Root
Seed.
If you were looking at a phylogeny of living bird species, where could you find the name of a species of non-theropod dinosaur?
At the tip of a branch, as an out group or at the root of the tree.
What was Linnaeus’ system built on?
an understanding of structural similarities that was relatively basic compared with the tools of scientists today.
T or F: Clades are monophyletic groups
true
Which of the following is not a monophyletic group?: clade, reptilia, aves, amphibia
Reptilia
Based on your understanding of Carl Linnaeus’ classification system, how would you treat his conclusions?
Classification scheme could be used as a starting point for examining taxonomic relationships.
What would the most parsimonious tree be?
The most parsimonious tree is the one that requires the fewest evolutionary transitions from 0 to 1.
Is the ability to swim in dolphins and sharks a synapomorphy?
NO
What can lead to homoplasy?
The reversion of a derived character state to its ancestral state, the independent origin of similar gratis in separate lineages, evolution of wings in both birds and bats.
What are coelacanth fins homologous to?
Coelacanth fins are homologous to tetrapod forelimb
How did the tetrapod arm develop?
the humerus and wrist bones kept evolving.
what reptilian bones are homologous to mammalian inner ear bones?
Bones that once were connected to the jaw.
True or False: Feathers evolved before flight.
True
What were feathers originally used for?
Attracting mates via color and visual representation
What traits needed to evolve from African apes to humans?
Fossil record should document transition to to unique human traits
– Bipedality
– Larger brain size
– Smaller canine teeth
Explain the transition to bipedalism:
Appears to have evolved before larger brain
– Position of foramen magnum – Weight bearing stance
– Short, stiff toes
Ardipithecus traits:
Small head, large jaw, anchors for muscles in pelvis, four short toes. May have been bipedal.
What species made the 1.5 myo footprints?
Tracks made by Australopithecus afarensis (1.5 myo)
Why did the trait for walking upright succeed?
They might have lived in more open woodlands and needed to walk upright to obtain food.
Homo Erectus
1.9 mya, had a flatter face, legs well adapted to walking and maybe running. Larger brain as well 600-900 cc.
T or F: Living members of a clade may not reliably indicate origins of synapomorphies
T
What is our understanding of human evolution based on?
Our current understanding of human evolution is based on many specimens of 20 different species
How does including fossils in phylogenies of extant taxa affect the conclusions scientists can draw?
- Including fossils can change the hypothesis generated by the phylogeny
- Including fossils can define the timing of branching events
- including fossils can affect the understanding of common ancestors
- including fossils can generate new questions about clades.
What homologies do Tiktaalik and Acanthostega share?
weight-bearing elbows and lungs
Why are bird feathers considered an exaptation?
they first evolved under different conditions than those under which they are currently found.
Which choice below is NOT evidence that Ardipithecus radius spent much of its time walking on two legs?
Opposable big toes.
What clade do tetrapods belong in?
Lobe-fins, which includes coelacanths and lungfishes.
Why do scientists classify humans as therians?
- middle ear bones of humans are not fused to the jaw, they are separate.
- humans do not lay eggs
- humans share more synapomorphies with mammalian fossil Liaoconodon.
