Download 2/17

More Evolution:
who, what, how
•Exam key posted on
class webpage
•Check out Bonuses on
class webpage
Evolution: A
species’ genetic
component
changes as the
individuals
reproduce.
These changes
are based on
how the DNA
changes and
who
reproduces.
Reproductive success = evolutionary success
Evolution can occur via several processes.
One common process is
Natural Selection:
Individuals that are most successful at
reproducing will pass on more of their genetic
information.
Natural Selection can only occur when
both of these conditions are met:
•Genetic diversity gives rise to individuals
with different traits
and
•Not all individuals can reproduce equally
Evolution: A
species’ genetic
component
changes as the
individuals
reproduce.
These changes
are based on
how the DNA
changes and
who
reproduces.
Individuals are selected…
But species evolve via changes in DNA during
reproduction.
Who evolves?…Species.
A. harrisi
A. leucurus
•A population that can produce fertile offspring
•A population that does reproduce
**A population sharing genetic information**
Fig 24.6
X
Horse
Donkey
=
Mule
X
Horse
=
Mule
(sterile)
Donkey
So…horses and
donkeys are not
the same species.
Who evolves?…Species.
A. harrisi
A. leucurus
•A population that can produce fertile offspring
•A population that does reproduce
**A population sharing genetic information**
Fig 24.6
Fig 22.19
How does evolution occur?
Fig 22.19
Divergent Evolution
Fig 22.20
Convergent
Evolution
Evolution has no goal...no ultimate life form
wrong
right
Natural Selection:
Individuals that are most
successful at reproducing will
pass on more of their genetic
information.
Environmental
changes drive
evolution.
250 mya
Fig 25.13
135 mya
Plate Tectonics
65 mya
180 mya
current
The environment is in constant flux
Fig 24.5
Changing environment can separate populations
and lead to new species…
Separation does not
need to be geographic
Fig 24.9
Flies raised in different
environments prefer to
mate with individuals
from the same
environment...
Flies raised in different environments prefer to mate
with individuals from the same environment...
Fig 24.9
Three basic types of selection…
• Directional
• Stabilizing
• Disruptive
Next even more
Evolution:
Types of Selection
and Randomness
•Exam key posted on
class webpage
•Check out Bonuses on
class webpage