Evidence of Evolution

"Nothing in biology makes sense except in the light of evolution"

Theodosius Dobzhansky

#1: The Fossil Record

• different layers of rock (gradual change)

• Similar forms suggest gradual modification

#2 Geographical Distribution• Galapagos Finches – different islands, slightly

different characteristics• Species on different continents descended from

different ancestors but share features in common due to similar environmental conditions

#3: Homologous Body Structures

• Similar structures, different function

• Arms, wings, legs, flippers

Homology

bird wing bat wing

human arm

Analogous Structures

•Different structure, similar functions

•Butterfly vs. bat wing

Homology vs Analogy  Homology (shared ancestry) versus  Analogy (convergent evolution)

bird wing butterfly wing

bat wing fly wing

#4: Vestigial Organs• Serve little or no function

–Human appendix useless yet in other mammals, it is necessary to aid in digestion of high cellulose diet

–May play role in immune response

Other Examples:

– Human wisdom teeth vestigial compared to other primates

WISDOM TEETH

• Third molars

• When human diets consisted of mostly raw and unprocessed foods that required the extra chewing and grinding power

• Today they are not needed for chewing and, because they can crowd other teeth, are often removed.

Other Vestigial Examples

–Some snakes have skeletal limbs

–Boa: remnant of pelvic girdle

–Humans have tailbones and some babies occasionally have tails

Some Vestigial Structures May Be Adapted for a New Use

• Penguins: wing not used for flying but for swimming

#5: Similarities in Early Development

• Embryos of many animals with backbones are similar (especially in early stages)

#6: MOLECULAR BIOLOGY

• GENETIC SIMILARITIES

HUMANS vs. _________

# of Chromosomes

Similarity in DNA sequences

CHIMPANZEES 48 98.8%

GORILLAS 48 98.4%

BABOONS 42 93.4%

#7: Mimicry and Camouflage• Mimicry:

Frog Fish SpongeOwl Moth

Camouflage

Leaf-Tailed Gecko

Uroplatus Gecko

Toads