CHAPTER 13: EVOLUTION – Evidence of Change

The Diversity of Life Biodiversity: the diversity of living organisms Darwin realized that the great number of species was

an indication of just how old the Earth really is ! Fitness: the physical traits and behaviors that enable

an organism to survive and reproduce in its environment.

Darwin believed fitness arose through two processes: Common descent: species have descended from

common ancestors. Adaptation: this enabled organisms to be better

suited to their environment and better able to survive and reproduce.

The Age of the Earth

Fossils are the preserved remains of ancient organisms. This provided evidence for the changes that occurred over millions of years.

The record in the rocks helped to form the Geologic Time Scale

Relative Dating was used to compare layers of rocks and their fossils to determine the approximate ages

Radioactive dating is a more precise technique to determine the age of a fossil. It uses radioactive elements and their half-life value. It’s also known as absolute dating.

The Fossil Record Most fossils are found in sedimentary rock when small

particles, as well as dead organisms, are deposited on lake or ocean bottoms.

The record is incomplete due to the quality of fossil preservation and the completeness of the sample (weathering processes and location)

The record tells us the history of organisms and the changes that occurred.

Evidence from Living Organisms1. Similarities in Early Development: embryos show striking

similarities during the early stages of development p. 283.

2. Homologous structures: are structures that have a different function but a similar build ie leg of a dog and flipper of a whale. p.284

3. Vestigial organs: parts that resemble small legs, tails or other structures indicating a change took place. Snakes have tiny bones that resemble legs… over years they perhaps were reduced.

4. Similarities in Chemical compounds: all organisms share the same DNA make up as well as ATP and other proteins.

5. Fossils

6. Biogeographical: species were derived in the same location.

7. Mutations/DNA: change in the DNA structure.