Evolution 4 Flashcards
What discovery heralded a new epoch for the origin of humans?
Lucy’s skull which was an intermediate species between primates and humans.
How many species and families does the primate order contain?
233 species in 13 families.
What features do primates have?
Flattened faces and forwardly directed orbits-associated with stereoscopic vision.
Opposable pollex and hallux.
Unfused and highly mobile limb bones - radius and ulna - tibia and fibula.
Pentadactyl hands and feet.
Presence of a clavicle.
Enlarged cerebrum.
What clade do humans belong to?
Same clade as the apes.
What are the synamorphies between the ape descendent’s and their ancestor?
Large brain No tail More erect posture Hip/ankle/wrist/thumb Flexibility
What are the autapomorphies between the terminal group of apes?
Elongated skulls
Larger brow ridges
Short canine teeth
Reduced hariness
What life are primates adapted to?
An arboreal life but not all specimens live in trees.
What group do humans and apes belong to?
Hominoids.
What are hominids?
Hominids are the members of the biological group Hominidae (the great apes) which includes extant species of humans, chimpanzees, gorillas and orangutans.
What are molecular clocks?
When species diverge, amino acid sequences in corresponding proteins begin to change. So the molecular clock records the passage of time by substitution of amino acids.
In molecular clocks, what does the rate of substitution depend on?
Generation time of species and the selection pressure operating.
How can changes in amino acids be linear overtime if the rate of substitution depends on generation time and selection pressure?
Because some DNA substitutions do not change the amino acid sequence because the genetic code is redundant - most amino acids are coded by more than one triplet of RNA.
What are synonymous substitutions?
Substitutions that do not alter the amino acid sequence.
What rate do synonymous substitutions proceed at?
A uniform rate across a wide range of DNA sequences.
Why don’t nonsynonymous substitutions proceed at a uniform rate?
Because of natural selection.
