The document discusses several ways that natural selection can lead to speciation and the evolution of new species. It provides examples of giraffes, peppered moths, seaside sparrows, and sickle cell anemia to illustrate how genetic variations within populations allow some individuals to better adapt to their environments, leading to reproductive isolation and the emergence of new species over time.

1. The Process of Speciation

2. How Natural Selection Causes
Evolution
 Key factor= environment
 The environment “selects” which
organisms will survive.

3. Giraffes
 Variation is the raw
material for natural
selection.
 Living things face a
constant struggle for
existence.
 Only some individuals
survive and reproduce.
 Natural selection results
in genetic change
 Species adapt to their
environment.

4. Giraffe Notes

5. Kettlewell & Peppered Moths
 Step 1
 Adaptation- an inherited
characteristic that increases and
organisms ability to survive and
reproduce in its specific
environment.
 knew- coloration is an inherited
trait.
 Raised moths in lab
 Marked and released.
 Set traps to capture live moths

6. Kettlewell & Peppered Moths
 Found that 2/3 of the recaptured moths were
dark (released in a polluted area)
 Moths that matched the trees were more
likely to survive.
 Step 2
 Using the same procedure Kettlewell
released moths in an unpolluted forest.
 2/3 of the recaptured moths were white.
 Moths matched the color of the trees.

7. Kettlewell & Peppered Moths
 Step 3
 Kettlewell set up hidden cameras in
the forest to record the capture of
moths by birds.
 Results: birds are more likely to
capture moths that do not match the
color of the tree trunk.

8. Sickle Cell Anemia
 Homozygous recessive individuals die at an
early age.
 Heterozygous individuals will live a normal
life span.
 Central Africa 1:500 has the sickle cell trait
 Advantage of having a sickle cell allele– are
not likely to contract malaria
 Person more likely to die of malaria than
sickle cell.

9. Sickle Cell Anemia
 Balancing selection-
two opposite forces
affect the allele in a
population.
 Sickle cell allele
lethal=decrease
 Sickle cell allele protects
against malaria =
increase

10. Sickle Cell Anemia cont
 Balancing selection-
– Situation in which natural selection for an allele
is balanced by selection against it, and remains
at the same frequency.
• Sickle cell causes anemia
• Sickle cells prevents malaria
 Directional Selection-
– Situation in which selection for or against an
allele in a population is unopposed
• Sickle cell is less likely to occur in the US because it
has no advantage.

11. Seaside Sparrows
 There are many different types of seaside
sparrows. They have adapted to better fit
into their environment. The are not different
enough to be considered their own species
but they have taken the first step.
 Divergence- an accumulation of differences
between species or populations

12. Selective Breeding aka Artificial
Selection
 Choosing an organism with a
desirable trait and breeding it with
another organism with that same
trait. Goal to produce offspring with
that trait.
 Example:

13. Extinct vs. Endangered
 Extinct-
the
population of a
species drops to
zero.
 Endangered- the
population is so
small reproduction
may be difficult.
Gene pool is
decreased.

14. Geographical Isolation
 Mating does not occur because of a
separation of egg and sperm.
 Caused by physical barriers
– Rivers, mountains, or other bodies of
water.
 Createsa subspecies. If both
species can still interbreed they are
the same species.

15. Speciation
 The evolution of a new species.
 Occurs when a population of
interbreeding individuals is split into
separate populations.
 Over time these populations become
a new species. (can’t interbreed)