evidences of organisms changing over timewhs.rocklinusd.org/subsites/biology/documents/biology/ls 4...
TRANSCRIPT
Evidences of organisms changing over time
Fossils• Fossil = any remnant of prior life on earth
(bone, tooth, imprint, etc.) • Found in sedimentary rock, ice or tar! • Only 0.01% of all species can be found in
fossil record!!! • What it tells us:
– Organisms existed before but may not now
Determining Age of Fossils
• Relative Age/Dating = based on location in rock relative to other fossils. – Law of Superposition – new
rock on top, old rock on bottom!
• Absolute Age/Dating = specific age using radioactive ½ life of atoms.
Molecular Biology – Comparing Macromolecules
• DNA – nucleotide sequences are compared
• Proteins – amino acid sequences are compared
• What it tells us: – The more closely related
organisms are, the more similar their DNA/protein sequences are
• They must share a common ancestor!
Comparative Anatomy• Homologous Structures
• Similar structure, Different Function
• What it tells us: – These organisms share a
common ancestor
• Analogous Structure • Different structure,
same function • What it tells us: – Different organisms can
adapt to the environment in similar ways
Comparative Anatomy – Vestigial Structures
• Vestigial Structure • seem to have no
useful function, but has a function in a similar or ancestral organism
• What it tells us: – Organisms share a
common ancestor
Comparative Embryology
• In early developmental stages, related organisms have very similar embryos
• What it tells us: – These organisms have
very similar genes – Organisms share a
common ancestor
Biogeography• The geographic
distribution of species
• What it tells us: – Organisms can
migrate from a place of origin and evolve into new species.