Evidence for Evolution

Fossil record

Comparative Anatomy Similarities in body structures

Comparative EmbryologySimilarities in early development

Comparative Molecular BiologySimilarities in DNA

BiogeographyGeographic distribution of living species

Fossil Record

• A relic or impression of an organism from the past, usually preserved in rock– Usually found in sedimentary rock

(sandstone, mudstone, shale, and limestone)– Hard parts of animals: teeth and bones – Thin tissues such as leaves can leave

imprints– Plant tissue can also be petrified– Imprints such as footprints are rare.

Fossil Record

• Stratification– The study of rock layers– Sedimentary rocks form in layers

• Dating– Relative = comparing fossils in a strata (can

not give age in term of years)– Radioisotopic = using isotopes of elements to

determine age in years• Carbon-14 used for dating recent fossils up to

50,000 yrs• Potassium-40 used to date rocks up to hundreds of

millions of yrs

Fossil Record

• Layers on the bottom are the oldest, find prokaryotes and eukaryotes

• Above them are multicellular organisms• Then trilobites and other invertebrates• Then vertebrates and fish• Amphibians and reptiles• Dinosaurs, crocodiles, birds, mammals…

Convergent Evolution

analagous (similar) structures in unrelated organisms that evolve independently when adapting to similar environments

Ex. Wings (Birds, bats, insects)

Comparative anatomy

Comparative Anatomy Homologous structures = structures that

have different mature forms in different organisms but develop from the same embryonic tissues

Homologous structures can be tricky

Does this suggest a lack of homology, or is there some other explanation?

Comparative anatomy

Some helpful terms for lab• Niche = the full range of environmental

conditions (physical and biological) under which an organism can exist– How a population responds to abundances of

resources and enemies• Grows when resources are present and

predators are scarce

• Adaptive radiation = species coming from a common ancestor have over time successfully adapted to their environment

Archaeopteryx 150-million-year-old fossil birdEvolutionary link between reptiles and birdsDiscovered 1862

Size of a crow Bird similarities:

WingsFeathers Skeletal

structures

Reptile similarities:

Reptilian teeth Long jointed tail

Comparative anatomy

Vestigial StructuresStructure that serves no useful function in an

organismSuggest a common ancestorDo not affect an organism’s ability to survive

Whale skeleton—why does it have pelvic bones?

Comparative anatomy

Comparative embryologySimilarities in early

development (embryos)Indicates same groups of

embryonic cells develop in the same order and patterns to produce the tissues and organs of all vertebrates

Produce the homologous structures discussed earlier

Comparative molecular biology

Similarities in DNA/genesInformation used to construct

genealogical trees

Organisms ranging from yeast to humans use an enzyme known as cytochrome C to produce high-energy molecules as part of their metabolism. The gene that codes for cytochrome C gradually has changed over the course of evolution.

Biogeographygeographic distribution of living species

Darwin’s finches came from mainland S. America, evolved differently on different islands in Galapagos