Download Ch. 14.2 - Brunswick City Schools

Evolution has left
much evidence
Ch. 14.2
The Fossil Record
• We use the past to help gather
information about our present
• FOSSILS  preserved remains or
markings left by organisms.
– Found in sedimentary rock
• In sedimentary rock, younger rock is
found near the top layers, older rocks
near the bottom
– LAW OF SUPERPOSITION
• FOSSIL RECORD  chronological
collection of life’s remains in the rock
layers
• Fossil record proves Earth’s changing
life
• Oldest fossil evidence is from 3.8 billion
years ago!
• Fossils of ancestral life forms link the
past and the present
– i.e. whales evolving from land dwelling
ancestors that had 4 limbs
Geographic Distribution
• Geographical distribution of organisms
serve as a clue to how modern species
may have evolved
Similarities in Structure
• Certain structural similarities provide clues to
evolutionary history
– i.e. forelimbs of all mammals have same skeletal
parts
• however, FUNCTION differs!
• HOMOLOGOUS STRUCTURES  similar
structures of species sharing a common
ancestor
• Evolution is a REMODELING process
• VESTIGIAL STRUCTURES 
remnants of structures that may have
had important functions in an ancestral
species, but have no clear function in
some of the modern descendants
Similarities in Development
• Embryos of closely related organisms
have similar stages in development
– i.e. all vertebrates have pouches on the
sides of their throats (could form fish, frogs,
snakes, birds, or primates)
• Supports evidence of homologous
structures
Molecular Biology
• Comparing DNA sequences to relate to
species
• Closer related have similar DNA, more
differences in DNA show they don’t
share a common ancestry