1. Chapter 25: Evolution
Biology: Mrs. Neistadt

2. Changes Over Time:
 *Most species change over time. This
slow, gradual change is called
Evolution
____________________.
 Evidence shows the first living creatures
were single-celled organisms living in the
oceans 3 billion years ago.
 *Many species have become extinct.
Extinct species were once living, but no
longer exist.

3. Jean Baptist Lamarck
 In the 1800s scientists were studying and
discovering __Fossils .
 A fossil is the remains of an organism that
lived long ago.
 Jean Baptist Lamarck proposed one of the
first theories of evolution.
 He thought organisms developed traits by
using or not using parts of their body.
 Example: Giraffes
Incorrect!

4. Charles Darwin
 In 1831 an Englishman named Charles Darwin took
a trip on the HMS Beagle.
 He was to map the coast of South America.
 He stopped on the Galapagos Islands where he
began a study that would turn scientific study in a
new direction.
 Darwin discovered the various Galapagos Islands
had different species of animals.
 He noticed 13 species of finches. Each finch had a
different beak, specialized to find food on its
island.

5. Charles Darwin
 Charles Darwin spend 20 years thinking
about his discoveries.
 *In 1859, Darwin wrote the book, “The
Origin of Species” to explain his theories
on evolution.

6. *Four Points to Darwin’s Theory:
*Overproduction
*Competition
*Variations or Adaptations
*Survival of the Fittest

7. Charles Darwin

8. Genetic Variations:
 Darwin did not know HOW genetic traits
were passed on.
 *A gene pool is the combined genetic
information of all members of a
population.
 By studying the gene pool of a
population, scientists can see how
variations in traits are passed to offspring.

9. *Events That Can Cause
Evolution:
*Natural
Selection
*Evolution can
only occur when
*Mutation an event causes
changes in the
gene pool.
*Genetic Drift

10. Natural Selection
 *Natural Selection is the way that
organisms best suited to an environment
survive

11. Mutation
 *Mutation: If a mutation is harmful the
organism may die before passing on the
gene. If the mutation is helpful, the
organisms live and pass the gene on.

12. Genetic Drift
 Genetic Drift is changes within a gene pool
that occurs due to random events, or
when individuals leave or join the
population.

13. 3 Types of Evolution:
Divergent Convergent
Coevolution
Evolution Evolution
Different
Types of
Evolution

14. Your turn…
Create a graphic organizer to
Compare the 3 types of evolution:
Divergent
Convergent
Coevolution
Use Internet research and/or your
textbook Pg398 to help you.