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16.4 – Evidence of Evolution
16.4 Evidence of
Evolution
16.4 – Evidence of Evolution
Biogeography
Biogeography - is the study of where organisms
live now and where they and their ancestors lived
in the past.
16.4 – Evidence of Evolution
Closely Related, but Different
 Same ancestor, but adapted to different environments.
 Black-tailed Jackrabbit
 Snowshoe Hare
 Classification = Same Genus (Lepus) – Different
Species
16.4 – Evidence of Evolution
Distantly Related, but Similar
 Different ancestors, adapted to similar environments
 Differences point to different ancestors
 Similarities caused by similar environments.
 Example: Rhea, Ostrich, & Emu
 Classification = Different Order, Genus & Species
16.4 – Evidence of Evolution
The Age of Earth
 Geologists now use radioactivity to establish the age of certain
rocks and fossils. = Radioactive Dating
 Earth is about 4.5 billion years old
16.4 – Evidence of Evolution
Fossil Evidence
 3.8 billion years: oldest fossil evidence
 Prokaryotes are the oldest form of life
 Location of eukaryotes in strata suggests they evolved from
prokaryotes
 Fossils link life forms from past and present (whales)
16.4 – Evidence of Evolution
Recent Fossil Finds
 One recently discovered fossil series documents the
evolution of whales from ancient land mammals.
16.4 – Evidence of Evolution
More Recent Fossil Finds
 Other recent fossil finds link:
 Dinosaurs and Birds
 Fish and four-legged land animals.
 The fossil evidence we do have suggests an
unmistakable story of evolutionary change.
16.4 – Evidence of Evolution
16.4 – Evidence of Evolution
Homologous Structures
 Homologous structures = Structures that are shared
by related species and that have been inherited from a
common ancestor.
 **Common structure, not common function.**
The bones in the
forelimbs of mammals all
have the same basic
pattern.
16.4 – Evidence of Evolution
Analogous Structures
 Analogous structures = Body parts that share a
common function, but not structure, and different
ancestry.
16.4 – Evidence of Evolution
Vestigial Structures
 Vestigial structures = are inherited from ancestors, but
have lost much or all of their original function in the
descendent.
 The hipbones of bottlenose dolphins
 Ear muscles, appendix, and
others in humans.
16.4 – Evidence of Evolution
Embryology
 Researchers noticed that the early developmental stages of
many vertebrates look very similar.
 Similar patterns of embryological development provide
further evidence for a common ancestor.
16.4 – Evidence of Evolution
Life’s Common Genetic Code
 All living cells use information coded in DNA and
RNA to carry information from one generation to the
next.
 It is nearly identical in almost all organisms,
including bacteria, yeasts, plants, fungi, and
animals.
16.4 – Evidence of Evolution
Homologous Molecules
 Homologous proteins share extensive structural and chemical
similarities.
 Cytochrome c, is a protein found in almost all living cells, and is
very similar in structure in all organisms.
 Ex. Bakers yeast and human cells
 Developmental genes called HOX genes are similar in
multicellular animals.
16.4 – Evidence of Evolution
Testing Natural Selection
 The Grant’s tested Darwin’s idea of natural selection.
 The data shows that individual finches with different-size beaks
have better or worse chances of surviving both seasonal
droughts and longer dry spells.
 Less food = Bigger beak greater chance of survival
16.4 – Evidence of Evolution
Testing Natural Selection
 The Grants’ data confirmed that competition and
environmental change drive natural selection.
 Without heritable variation in beak sizes, the finch
species would not be able to adapt to a change in
the environment.