TREE OF LIFE

Microevolution: changes in gene frequencies and trait distributions that occur within populations and species.
Macroevolution: large evolutionary change usually in morphology, typically refers to the evolution of differences among populations that would warrant their placement in different genera or higher level taxa.

• Observations on living organisms provide direct evidence of microevolution.
• Transitional fossil document the past existence of species displaying mixtures of traits what are today distinct group of organisms-evidence of macroevolution.

Vestigal Organs
Useless or rudimentary version of a body part that has an important function in other, closely allied species.

• Ex;coccyx or muscles attached to hair follicles.
• These characteristics can be seen at the molecular level as well.

Evidence from the Fossil Record

• Vast majority of fossils are unlike species that are living today argues that life has changed through time.
• The resemblance between living ans fossil forms in the same region suggests that living organisms are descended with modification from earlier species.
• Law of succession

Transitional Forms

• Many transitional fossils have been found.
• Archaeopteryx-intermediate form in between dinosaur and bird-modern feathers and dinosaurian skeleton.

Evidence of common ancestry

• Introduction to tree thinking.

Darwin's brilliant insight: evolution is a branching process
One of Darwin's brilliant insights was that all living things on Earth are related and can be depicted in a "Tree of Life"
Darwin's brilliant insight: evolution is a branching process
"As buds give rise by growth to fresh buds, and these, if vigorous, branch out and overtop on all sides many a feebler branch, so by generation I believe it has been with the great Tree of Life, which fills with its dead and broken branches the crust of the earth, and covers the surface with its ever branching and beautiful ramifications."-Darwin, 1859.
Phylogenies and phylogenetic trees
Phylogeny: the evolutionary history of a lineage or lineages (populations, genes, or species). Phylogenetic tree: a visual representation of a phylogeny.

A phylogeny is similar to a family tree

Reading a phylogenetic tree

• Nodes: represent common ancestors for all descendent lineages.
• Clades: a common ancestor and all of its descendants.
• Taxa can be rotated around nodes and still depict the same relationships.

Homology

• Study of likeness
• The same organ in different animals under every variety of form and function.

Molecular homolgy

• Genetic code.
• All organisms inherited their genetic code from a common ancestor.

Age of earth

• Relative dating-detemine how old each rock formation was relative to other strata- p69 in Evolutionary Analysis
• Radiometric dating- Isotopes decay-they change into different element or different isotopes of the same element.
• Half-life-each isotope decays at a particular and constant rate
• Amount of time it takes for 50% of the parent isotope present to decay into rts daughter isatope or any other environmental factor.
• The concept can be taken as natural clock.