Download Science Starter 1. Evolution is as much a fact as the fact

6/10/13
Science Starter
! I  ndicate whether each
statement is true or false, in
terms of your current
understanding of evolution.
!  We will go over them together.
2. Evolution is something a
person should either believe
in, or not believe in.
1. Evolution is as much a fact
as the fact that planets go
around the Sun.
!  True!
!  Has extensive evidence and
no evidence against it
3. Evolution is a process that
includes the origin of life.
!  False!
!  It’s based on science, not
faith
!  False!
!  It only deals with the origin of
species, not the origin of life
4. Evolution was first
proposed and explained by
Charles Darwin.
5. Evolution is also known as
"Natural Selection".
!  False!
!  Others proposed it first,
Darwin used extensive
research to support it
!  False!
!  Natural selection is one way
evolution happens
1
6/10/13
6. Evolution is something that
happened in the past; it is not
happening now.
7. Evolution is something that
happens to individual
organisms.
!  False!
!  It’s still happening, we create
new dog breeds and new
species are still evolving
!  False!
!  Populations evolve and adapt
8. Evolution is a totally
random process, a series of
accidents.
9. In order to accept evolution
as a real process, you cannot
believe in God.
!  False!
!  The environment and mate
selection put limits on it.
!  False!
!  Evolution is neutral, God is
not required or eliminated, for
all we know, evolution could
be God’s creation
10. Evolution is only a theory.
Evolution
!  False!
!  A theory is a scientific fact,
just like the theory that the
Earth revolves around the
Sun, and the theory of gravity
! T
  he process by which new
species arise from earlier
species by accumulated
changes
!  Genetic differences are
passed down from parent to
offspring
2
6/10/13
How does Evolution Happen?
1.  Mutations
!   Mutations introduce new genes
2.  Migration
!   Traveling individuals can introduce
new genes
3.  Genetic Drift
!   Some just do better just by chance
4.  Natural Selection
!   A gene increases survival
Fitness
! T
  he ability to pass on your
genetics
!  Having offspring
!  Does not mean the
strongest or fastest
Darwin (1809-1882)
Darwin’s Four Principles of
Natural Selection
1.  Individuals in a population have
variations (they are different)
2.  Variations are inherited
3.  Living things overproduce
4.  Variations that increase fitness will
be more common in the next
generation
Lamarck (1744-1829)
Believed that . . .
!  Life changed over time
!  Changes in organisms were due to
wants or needs
!  Unused body parts would disappear
!  Those changes were passed onto its
offspring
Types of Natural Selection
!  Used research to support theory
!  Wants and needs have no effect
!  Those organisms with traits better
suited to their environment did better
!  Had more offspring
!  Passed on their genes
!  Those not so well off, died off or had
less offspring
3
6/10/13
Stabilizing Selection
! T
  he extremes of certain traits are
disadvantageous and eliminated.
Disruptive Selection
! S  election favors the extremes for
particular traits rather than the mean,
which is selected against.
!  This often results in divergence into
two new species
How does Evolution Happen?
1.  Mutations
!   Natural or environmental
2.  Migration
!   Gene flow
3.  Genetic Drift
!   Founder Effect
!   Genetic Bottleneck
4.  Natural Selection
Directional Selection
!  One extreme for certain traits are
disadvantageous and are selected
against. The other extreme is
selected for.
Sexual Selection
!  When males or females select a
mate based on secondary sexual
characteristics like flashy colors or
long antlers.
!  These traits are often harmful and not
helpful for survival but they increase
the chance of breeding.
Mutations
! M
  utations are random and can
be caused by a copying mistake
or by the environment.
!  Example: Antibiotic resistant
bacteria
4
6/10/13
How does Evolution Happen?
1.  Mutations
!   Natural or environmental
2.  Migration
!   Gene flow
3.  Genetic Drift
!   Founder Effect
!   Genetic Bottleneck
4.  Natural Selection
How does Evolution Happen?
1.  Mutations
!   Natural or environmental
2.  Migration
!   Gene flow
3.  Genetic Drift
!   Founder Effect
!   Genetic Bottleneck
4.  Natural Selection
Effects of Genetic Drift
! Y
  ou can by chance, lose a trait
because it wasn’t inherited
!  This happens faster in a small
population
Migration (gene flow)
! W
  hen individuals migrate, they
introduce new genes and
genetic variation where they go
!  This increases genetic variation
and is a good thing
Genetic Drift
! S
  ome individuals may, by
chance, have more offspring and
pass on their genes
!  They were “lucky” not better or
healthier
Genetic Bottleneck
! O
  ccur when a population’s size is
reduced for at least one
generation
!  This reduces the genetic variation
and the population can lose traits
5
6/10/13
Founder Effect
! O
  ccurs when a new colony is
started by a few members
!  There is reduced genetic
variation
!  The colony is a non-random
sample and can be missing traits
1. Allopatric Speciation
(Geographic Isolation)
! A
  physical barrier divides one
population into two or more
!  Mountain range, river, lava, island
! A
  fter a long period of time, the
two populations will be separate
species
3. Coevolution
! T
  wo species can evolve
together
!  Example: Flowers have
marking that guide bees to
nectar
! T
  he bees gather nectar, they
pollinate the flower
Speciation
! O
  ccurs when a population
reproduces in isolation
1. 
2. 
3. 
4. 
Allopatric Speciation (Isolation)
Adaptive Radiation
Coevolution
Convergent Evolution
2. Adaptive Radiation
! O
  ccurs when one species
evolves in a short period of
time into a number of new
species
!  Can occur when a species
evolves a new, useful trait, or
arrives in a new habitat
4. Convergent Evolution
!  Unrelated organisms in different
places evolve to resemble one
another
!  Can produce organisms with similar
physiology and behavior even though
they are unrelated
!  Example: Porcupines and hedgehogs
6