More Than An EyeWitness

Evidence for Evolution

Sources of Evidence

• From the fossil record

• From studies of anatomy

• From studies of embryology

• From studies of DNA/biochemistry

• From observation

Transitional Organisms

• If evolution has occurred in the past there should be evidence of transitional organisms in the fossil record.

Archeopteryx

• Archeopteryx shows evidence of the evolution of birds from reptiles….there is evidence of feathers, a characteristic of birds, and claws, a characteristic of reptiles.

Identify how each organism uses its forelimb

Frog Lizard Bat Human Cow Whale bird

balance Walking flying Multiple

uses

walking swimming flying

Anatomical Studies show

• Homologous parts – similar in structure but not necessarily function – evidence of evolution from common ancestor

Anatomical studies show...

• Name two other organisms that have the ability to fly but have wings very different than those of the bird or the bat?

Analogous structures

• Butterflies or insects have wings but they are very different from the birds. These organisms do not have a common ancestor but have adapted to a similar environment. Again evolution explains the similarities.

Anatomical studies show

• Vestigial parts – why does a whale have a pelvis and femur bones if it has no hind limbs?

Vestigial structures

• Why does this salamander have eyes if it never sees the light of day?

Vestigial structures

Ear muscles Wisdom teeth Appendix

Human vestigial structures

Why do these structures occur?

• May be homologous to useful structures in other organisms and thus suggest evolution from an ancestor in which they do have a use.

Modification of anatomy

• The stinger of the wasp is not an entirely different structure but a modified ovipositor.

Anatomical Studies

• Anatomical studies of cells show a commonality in structure of the cell membrane among almost all living things. Does this suggest a common ancestor for all life?

Embryology Studies

• Even though it may not be apparent at this stage these three organisms are very different when born. Why do they look so similar now?

Embryology Studies

• The organisms are:– Fish

– Bird

– Human

– Why would these three, so different looking organisms at birth, look so similar before birth?

Studies of Biochemistry/DNA

Species Sequence of Amino Acids in the Same part of the Hemoglobin Molecule

Human Lys-Glu-His-Iso

Horse Arg-Lys-His-Lys

Gorilla Lys-Glu-His-Lys

Chimpanzee Lys—Glu-His-Iso

Zebra Arg-Lys-His-Arg

Which organisms appear to be more closely related to each

other?Human and chimpanzee have no

differences in their amino acid sequence suggesting their close evolutionary

relationship, they have a more recent common ancestor. Their DNA would be

similar because DNA determines the sequence of amino acids in proteins.

Observations of Evolution in modern organisms

• Mosquitoes resistance to insecticides

• Bacteria resistance to antibiotics

• New strains of influenza viruses (?)

• New strains of malaria causing Plasmodium

• New strains of TB (tuberculosis)

• Peppered moth

• Darwin finches

Has and Does Evolution Occur?

• Scientists do not dispute that evolution does occur. Evolution is a FACT.

• How evolution occurs is not completely understood.• Charles Darwin explained how evolution occurred

through natural selection. Natural selection is a well documented THEORY uniting all of biology.

• Modern evolutionary theory uses ideas of genetics, particularly mutations, to help explain how evolution may occur. (Darwin didn’t know about mutations.)