Evolution

1
Evolution

• Evidence Theory

2
The Fossil Record

• Many scientists studying Earths structure in
  1700s and 1800s.
• The fact that Earth is constantly changing,
  indicated that organisms change as well.

3
Geology

• Geologists studying layers of rocks found
  fossils.
• Fossils resembled organisms alive at that time,
  but many were different from modern organsisms.

4
So Much for Geology

• Fossils created questions that geologists
  couldnt answer.
• Paleontologists study fossils and try to
  determine their ages.

5
Dating Techniques

• Relative age compare fossils based on the layer
  they are found in. (superposition)
• Absolute age use radioactive dating to
  determine more accurate age.

6
The Fossil Record

• Paleontologists developed the fossil record which
  groups organisms into geologic time frames.

7
Theories of Evolution

• First scientist to propose the gradual change of
  species was Lamarck.
• Lamarck believed that organisms could change
  whenever they desired.

8
Acquired Traits

• Lamarck believed organisms could develop new
  traits during their lifetime.
• Believed acquired traits developed because of use
  or need.

9
Passing on Acquired Traits

• Lamarck believed that these traits were passed on
  to the next generation.
• As organisms acquired new traits, evolution
  proceeded.

10
Charles Darwin

• Darwin was intrigued by Lamarcks observation
  that organisms change over time.
• Instead of acquired traits, Darwin suggested his
  theory of Natural Selection.

11
Darwins Voyage

• Based on observations made on the HMS Beagle,
  Darwin gathered evidence for his theory.
• Published the very controversial The Origin of
  Species

12
Descent with Modification

• Darwin argued that all organisms have descended
  from one or a few common ancestors.

13
Modification by Natural Selection

• Describes how species change over time.
• Wondered why the Earth was not overrun with
  organisms.
• Thomas Malthus influenced Darwin with his
  theories of human populations.

14
Population Limitations

• Malthus argued that human population is kept in
  check by
• War
• Disease
• Limited resources

15
Survival of the Fittest

• Since populations are kept in check, Darwin
  reasoned that organisms better adapted would
  survive.
• Therefore, the more fitness an organism has, the
  better its chance to survive.

16
Fitness

• When an organism is better adapted, it has a
  better chance of reproducing.
• When it reproduces, it passes its fitness on to
  the next generation.

17
Examples

• Peppered moths soot on buildings caused moths
  with dark spots more fit.
• Bacteria a natural resistance to antibiotics
  makes some more fit.

18
Patterns of Change

• Environmental A change in the environment
  changes the desired fitness.
• Mutations a change in DNA that allows one
  organism to be more or less fit than another.

19
Summary of Darwins Theory

• All living species are descended from species
  that lived before.
• No 2 members of a species are exactly the same,
  this variation can be inherited.
• Far more individuals born than survive.
• Organisms compete with each other and nature to
  survive.
• The organism that is best fit, has the best
  chance of survival and reproduction.
• For the above reasons, organisms will evolve or
  change over time.

20
Evolution by Natural Selection

• The process is controlled by nature.