Evolution: A Remodeling

processSection 15.2

Refinement of Existing Adaptations

Any living organism may have many adaptations.

A complex structure may have evolved from simpler structures.

Ex: Camera –like eye of mammals has evolved from simpler eye types

Adaptation of Existing Structures to New Functions

Flippers of Penguins modified wings

Development Feet in various salamanders Salamanders vertebrates closely related

to frogs, live in land or water, but some live in trees

Tree dwelling ones have feet adapted to climbing

Ground Dwelling Tree Dwelling w/ more webbing

Fossil records

Section 15.3

Formation of FossilsFossil Records and the Geologic Time Scale

Dating FossilsContinental DriftMass Extinction

Fossil Records and the Geologic Time Scale

Most Recent Layers: Top Oldest Layers: Bottom

Geologic Time Scale

Distinct Ages in Earth’s HistoryPrecambrianPaleozoicMesozoicCenozoic

See fig 15-18 p337

Dating Fossils

Relative DatingAbsolute DatingRadioactive Dating

Relative Dating

Determines the Order in which events occurred

Not Actual Age

Absolute Dating

Determines how long ago an event occurred: Actual Age

Radioactive Dating

Based on measurement of certain radioactive isotopes.

Used to determine the absolute ages of rocks and fossils

Measured in Half-Life

Half-LifeTime required for a

radioisotope to lose ½ of its radioactivity.

Ex: Carbon-14: ½ life ~ 5730 yrs. decays into Nitrogen-14

Carbon-14 is produced in the atmosphere fairly constant rate

14C is constant in all living things. When an organism dies, it no longer picks up 14C.

By comparing the activity of a sample with the activity of living tissue time an organism has been dead

Continental Drift

Land masses on different plates change positions as a result of movement

Mass Extinction

Long periods of relative stability broken by comparatively brief episodes of species loss

5 or 6 over the last million years