Evolution and Natural Selection

1
Evolution and Natural Selection

• How species change over time

2
Evolution and Natural Selection

• GSEs
• Genetic variations are passed on through
  reproduction LS3-9a
• Evidence for evolution illustrates how organisms
  are related LS3 -9b
• Natural selection leads to evolution LS3 9d
• Our understanding of evolution has changed over
  time LS3 - 9e

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
EvolutionPre-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 and, through
  fossils, discovered organisms have changed, as
  well.

6
EvolutionPre-Darwin Beliefs

• Jean Pierre Lamark believed that organisms could
  change their traits during their lifetime by use
  or disuse.
• He thought that these traits could be passed on
  to offspring. Over time this would cause change
  in a species.
• Lamark was
• wrong

7
Charles Darwin1809 - 1882

• Scientist credited 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, making
  observations and keeping a scientific journal of
  his findings

8
Darwins Voyage
9
Voyage of the BeagleWhat did Darwin find?

• The finches on each island in the Galapagos had
  different types of beaks.

10
Voyage of the BeagleWhat did Darwin find?

• The tortoises on each island in the Galapagos had
  different types of shells.

11
What was Darwins 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

12
Natural Selection

• For natural selection to occur, there must be at
  least two varieties of a species.
• For example the peppered moth

13
Peppered Moths

• At the beginning of the Industrial Revolution in
  England, coal burning produced soot that covered
  the countryside in many areas

14
What do you think happened?
Before After
Before After
15
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
• have become more common.

16
Evidence for EvolutionCommon 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
• Darwins finches on the Galapagos!

17
Evidence for EvolutionHomologous Structures

• If animals evolved from a common ancestor, then
  they should share common structures and they
  do!
• These are called
• homologous structures

18
Evidence for EvolutionEmbryo Development

• What do you notice? List 2 observations

19
Evidence for EvolutionVestigial 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.

20
Examples of Vestigial Organs

• Kiwi (flightless bird)
• Whales (hind leg bones)
• Humans (tailbone, appendix)

21
Evidence for EvolutionFossils

• Fossils provide a look
• into the past
• Scientists can trace how
• a species has evolved
• by studying fossils

22
Wrap Up the Evidence

• Common Ancestry
• Homologous Structures
• Embryonic Development
• Vestigial Organs
• Fossils

23

• Any Questions?