Biology 171!
Your Instructor: Brett (KVO) Klaassen van Oorschot
Lab website: www.howbiologyworks.com
About me:
Evolution via natural selection
What would happen if all of the trees
and dinosaurs were the same size?
Individual variation is necessary for
natural selection to occur.
What would happen if all the dinosaurs
produced just one offspring?
Differential fitness is necessary for
natural selection to occur.
What would happen if offspring never
resembled their parents?
Parents:
Offspring:
✖
Traits must be heritable for natural
selection to occur
Parents:
Offspring:
✖
Conditions required for natural
selection to occur:
Individual variation: members of a species differ in
their characteristics
Differential fitness: some individuals leave more
offspring than others due to their special inherited
traits
Mode of inheritance: parents pass on some of their
traits to their offspring
Organisms do not “try” to change. It happens by random chance!
Change in population
occurs because of
differences in reproductive
success.
Total offspring + future
generations = “fitness”
Organisms do not evolve
because they want or need
to change.