Evidence for Evolution Among Organisms

1
Evidence for Evolution Among Organisms

• Indirect and Direct Observations
• Does not prove evolution, but gives evidence that
  there was a common ancestor at some point in time

2
Comparative Anatomy

• Study comparison of the body parts of different
  species
• Skeletons are similar even though the limbs have
  different functions
• Forelimbs of various vertebrates humerus
• Examples
• Bird forelimbs flight
• Whale forelimbs swimming
• Alligator forelimbs moving on land
• Human forelimbs grasping

3
Homologous Structures

• similar in structure and embryonic development
  but have different functions
• Seems to indicate that they came from a common
  ancestor

4
More
One of the classic examples of a homologous
structure is the pentadactyl ( five digit) limb.
5
Analogous Structures

• Different structure and embryonic origin, but
  have similar function
• Both the bat wing and the insect wing are used
  for flight

6
Embryological Evidence
All vertebrates share a common embryology but
become progressively different as they develop
7
Vestigial Structures

• Certain body parts do not have a function that we
  know of.
• Example humans
• Appendix, body hair, muscles to move ears, and
  caudal vertebrae (tail bone)
• Other examples
• Flightless birds still have wings
• Cavedwelling fish still have eyes, but are blind

8
Direct ObservationsCan Evolution be Observed?

• Evolution is difficult to prove since it happens
  over a very long period of time.
• Change in the genetic makeup of an organism is
  transmitted during reproduction
• Species with short life spans more easily show
  changes
• Examples bacteria and insects

9
Bacteria and Antibiotics

• Strains become resistant to drugs and then
  antibiotics doesnt work
• Some bacteria will grow and reproduce even in the
  presence of the drug while others will die out
• Examples E. Coli streptomycin
• Other examples insects and DDT