1. Lesson Overview
16.4 Evidence of Evolution

2. Biogeography
study of where organisms live now and where they and their ancestors lived in the past.
Two biogeographical patterns are significant to Darwin’s theory.
a pattern in which closely related species differentiate in slightly different climates.
Ex. variation in shell shape among the giant land tortoises that inhabit the Galápagos islands.

3. Species Vary Globally
2. a pattern in which very distantly related species develop similarities in similar environments.
Ex. similar ground-dwelling birds (rheas, ostriches, and emus) inhabit similar grasslands in Europe, Australia, and Africa.
Rheas
emu.
ostriches

4. Homologous Structures
Structures shared by related species and that have been inherited from a common ancestor are called homologous structures.
Darwin proposed that animals with similar structures evolved from a common ancestor
Biologists test whether structures are homologous by (1)studying anatomical details the way structures develop in embryos,
(2)the pattern in which they appeared over evolutionary history.

5. Homologous Structures
Ex. the front limbs of reptiles and birds are more similar to each other to than either is to the front limb of an amphibian or mammal.
Scientists say that this similarity is used to show that the common ancestor of reptiles and birds lived more recently than the common ancestor of reptiles, birds, and mammals.

6. Analogous Structures
Another example used by scientists are analogous structures  body parts that share a common function, but not structure.
Ex. The wing of a bee and the wing of a bird are analogous structures.

7. Vestigial Structures
inherited from ancestors, but have lost much or all of their original function due to different selection pressures acting on the descendant.
Ex. The hipbones of bottlenose dolphins
Pelvic bone of a whale

8. Other Examples of Vestigial Structures
The wings of a flightless cormorant
The legs of an Italian three-toed skink
cormorant
three-toed skink

9. Embryology
Some scientists use the similar patterns of embryological development as evidence that organisms have descended from a common ancestor.

10. Life’s Common Genetic Code
Some scientists believe that the strongest evidence supporting evolutionary theory comes from genetics.

11. Life’s Common Genetic Code
This genetic code is nearly similar in almost all organisms, including bacteria, yeasts, plants, fungi, and animals
This compares a small portion of the DNA for the same gene in three animals—a mouse, a whale, and a chicken.