62 Clues About Evolution

1
6-2 Clues About Evolution
2
Clues from fossils

• Paleontologists are scientists that study earths
  history by collecting and examining fossils.
• Organisms that are covered with mud or sediment
  can turn to fossils if everything is just right.

3
Types of fossils

• Fossils are the remains, imprint or trace of long
  dead organisms.
• Most fossils are found in sedimentary rock.
• Fossils provide evidence that living things have
  evolved.

4
Determining a Fossils Age

• Two main methods of finding the age of a fossil
  are relative dating and radiometric dating.
• Relative dating compares the layers of rock,
  does not give an age in years.
• Radiometric Dating uses the radioactive elements
  present in all living things to the amount of
  non-radioactive elements

5
Fossils and Evolution

• The fossil record is incomplete because not
  everything turns into fossils.
• Fossils show that simple things were on the earth
  first and more complex things developed later.
• Fossils can only give ideas about the organisms
  that were once here.

6
More Clues about Evolution

• Direct observation of evolution is a very strong
  case of proof.
• One example is of bacteria that become resistant
  to penicillin
• There are other indirect evidences such as embryo
  structure, chemical makeup, and growth to adult
  forms.

7
Embryology

• This is the study of embryos and how they
  develop.
• Tails, gills, or gill slits are found in the
  embryos of most vertebrates.
• The tail of the human embryo disappears before
  birth.

8
Homologous Structures

• These body parts are similar in structure and in
  what the developed from.
• These structures can have similar function.
• The structures show that the animals probably
  shared a common ancector.

9
Vestigial Structures

• These structures dont seem to have any function.
  
• These structures are things that at one time
  served some purpose but are no longer needed by
  the organisms.
• The pelvic bones of some snakes are examples of
  Vestigial structures.

10
DNA

• All living things on earth contain the same
  heredity information.
• Comparing the differences in the DNA can
  determine how long ago two organisms diverged.