1. Evolution and
Natural Selection
How species change
over time

2. Evolution and Natural
Selection
 GSE’s
 Genetic variations are passed on
through reproduction
 Evidence for evolution illustrates how
organisms are related
 Natural selection leads to evolution
 Our understanding of evolution has
changed over time

3. Evolution
The theory that
organisms today
developed from more
simple life forms and
have changed (evolved)
over time

4. Natural Selection
The theory that states
that those organisms
best adapted to their
environment have a
better chance of
surviving and
reproducing

5. Evolution
Pre-Darwin Beliefs
 Earth was only a few thousand years
old.
 We now know it is billions of years
old.
 Neither the planet nor the species that
inhabited it had changed since the
beginning of time.
 We now know the planet has changed

6. Evolution
Pre-Darwin Beliefs
 Jean Pierre Lamark believed that organisms
can change their traits during their lifetime
by use or disuse.
 He thought that these traits are passed on to
offspring. Over time this would cause
change in a species.
 Larmark was
wrong

7. Charles Darwin
1809 - 1882
 Scientistcredited with the
Theory of Evolution & Natural
Selection
 Voyage of the HMS Beagle –
a 5 year voyage to South America and the
South Pacific, collecting specimens,

8. Voyage of the Beagle
What did Darwin find?
 Thefinches on each island in the
Galapagos had different types of
beaks.

9. Voyage of the Beagle
What did Darwin find?
The tortoises on each island in the
Galapagos had different types of
shells.

10. What was Darwin’s
hypothesis?
 Darwin hypothesized that organisms
had a common ancestor, but had
adapted to their particular
environments and changed over time.
 Darwin published his
research in 1859

11. Natural Selection
 For natural selection to occur,
there must be at least two
varieties of a species.
 For example: the peppered moth

12. Peppered Moths
 Atthe beginning of the Industrial
Revolution in England, coal burning
produced soot that covered the
countryside in many areas

13. What do you think
happened?

14. Evolution/Natural
Selection
 White moths became easier to see, while the
black moths became harder to see. The
black moths were more likely to survive
and pass on the gene for dark color to their
offspring.
 Over time, the black moths

15. Evidence for Evolution:
Common Ancestry
 Common Ancestry: If species evolved from a
common ancestor, then they should share
common anatomical traits
 Hawaiian Honeycreeper: family of
birds in Hawaii that have similar
skeletons and muscles, indicating
they are closely related.
 Over time, their common ancestor evolved
into several species, each with a specialized
bill for eating certain foods. Just like
Darwin’s finches on the Galapagos!

16. Evidence for Evolution:
Homologous Structures
 Ifanimals evolved from a
common ancestor, then they
should share common structures
– and they do!
 These are called
homologous structures

17. Evidence for Evolution
Embryo Development
 What do you notice? List 2
observations

18. Evidence for Evolution:
Vestigial Organs
 Some organisms have structures
or organs that no longer have a
useful function.
 These structures or organs may
have been useful to the ancestors
of a species, but over time have
evolved into what we term
vestigial organs.

19. Examples of Vestigial
Organs
 Kiwi (flightless bird)
 Whales (hind leg bones)
 Humans (tailbone, appendix)

20. Evidence for Evolution
Fossils
 Fossils provide a look
into the past
 Scientists can trace how
a species has evolved
by studying fossils

21. Wrap Up the Evidence
 Common Ancestry
 Homologous Structures
 Vestigial Organs
 Embryonic Development
 Fossils

22.  Any Questions?