a. The age of the earth is 4.5 billion years old.

b. Geological history of the earth is divided into eras, periods, and epochs.

c. Fossil record provides relative dating of rock layers; top layers of rock are younger than lower layers.

EVOLUTION: Geological Time Scale

d. Absolute dating method uses radioactive isotopes.

(1). Isotopes each have a particular half-life or time it takes for half of the isotope to decay and become nonradioactive.

(2). Carbon-14 is used to date organic matter; half decays to Nitrogen-14

each 5,770 years.

EVOLUTION: Geological Time Scale

Absolute dating continued:

(3). Half of potassium-40 decays to argon-40 each 1.3 billion years; it is

used to estimate the age of younger rocks.

(4). Half of Uranium-238 decays to lead 206

every 4.5 billion years; it is used to estimate the age of older rocks.

EVOLUTION: Geological Time Scale

a. Fossils are remains, traces or other direct evidence of past life forms.

b. Most fossils form from burial of plants and animals in sediment; soft parts are more often consumed or decomposed but may leave imprints if buried rapidly.

c. Most fossils are embedded in sedimentary rock . Which are weathered particles that provide strata from lower older layers to upper newer layers.

EVOLUTION: Fossil Evidence

d. Paleontologists study the fossil record based on boundaries between strata, where one mix of fossils gives way to another.

e. Transitional links are intermediate between major groups.

Example: Archeopteryx has features intermediate between primitive reptiles and birds.

EVOLUTION: Fossil Evidence

Archeopteryx fossil

Archeopteryx drawing

a. Many organisms share a unity of plan; for example, vertebrate forelimbs contain the same sets of bones used for different functions in bat wings, whale fins, etc.

b. The simplest explanation is having a common ancestor whose basic forelimb plan was modified in succeeding groups as each continued along its own evolutionary pathway.

EVOLUTION: Anatomical Evidence

c. Homologous structures are similar structures derived through descent from a common ancestor.

d. Analogous structures have similar functions but differ in anatomy and did not derive from the same ancestral structure; for instance, an insect wing and a bird wing.

EVOLUTION: Anatomical Evidence

EVOLUTION: Anatomical Evidence

e. Vestigial structures are reduced and functionless anatomical features that are fully developed and functional in other ancestral groups.

Vestigial structures are evidence of an organism's evolutionary history.

(1). Flightless birds have vestigial wings.

(2). Snakes have remnants of a pelvic girdle.

(3). Humans have a tail bone but no tail.

EVOLUTION: Anatomical Evidence