Download Section 7-2

Section 7-2
Evidence of
Evolution
Evidence of Evolution
• There are four things we use to study
evolutionary relationships between species
– Body Structures
– Early Development
– DNA
– Fossils
Body Structures
• Homologous Structures
– Structures that organisms have in common
• Examples:
– Fish and reptiles both have backbones
– Cats and rabbits both have hair
– People and apes both have five fingers
Early Development
• Scientists look at embryos and study
relationships
DNA and Proteins
• Scientists look at DNA and amino acid
sequences
– Example: Chimp and Human DNA is 98% the same
Types of Fossils
• Molds
– A hollow area in rock in the shape of the organism (“iny”)
• Cast
– A solid copy of the shape of an organism (“outy”)
• Petrified
– When minerals replace the parts of an organism (usually wood)
• Trace
– Evidence of the organism (i.e. footprints)
• Preserved
– When the organism is kept from decay (i.e. frozen, amber, etc.)
• Carbon Film
– When only the carbon of an organism remains (looks like a photo
copy and are usually plants)
Theories of Evolution
• Gradualism
– Evolution occurs slowly and steadily
• Punctuated Equilibria
– Evolution occurs quickly in a few generations
• Most scientists think it is a combination of the
two