Chapter 13 Outline
Evolution: Evidence of Change
I. Evolution and Lifes Diversity
1.Evolution- The process by which modern organisms have descended from ancient organisms is called evolution. Change over time.
A. Darwins Dilemma
1. Charles Robert Darwin (1809-1892)
Sailed on the HMS Beagle.
a. Contributed the most to the understanding of the process of evolution.
b. Witnessed countless wonders of nature on a cruise around the world. He needed to find an explanation. Looked 4 connections between organisms through behaviors and physical traits.
Wrote a Book- ORIGIN OF SPECIES
B. The Diversity of Life
1. The variety of living things is diversity of life. Many different shapes, sizes, and habits.
2. Darwin observed many different species when he traveled and realized there was an enormous amount of species that inhabit the Earth.
3. It is estimated that the range of species is from 3 million to more then 20 million different living species.
C. Fitness: To Survive and Reproduce
1. The physical traits and behaviors that enable organisms to survive and reproduce in their environment give them what Darwin called fitness.
2. Common descent-all species have shared or common, ancestors. Since species have descended from common ancestors.
3. Adaptation- the process that enables organisms to become better suited to their environment. Better able to survive and reproduce.
Survival of the Fittest
II. The Age of the Earth
A. Evidence in Stone
1. James Hutton in 1788 was the 1st geologist to argue that the Earth was much more then a few thousand years old.
2. Charles Lyell insisted that the only way the scientific method would work was that scientist had to explain past events in terms of events and process that they could observe.
^both helped support the old age of earth.
3. Fossils-the preserved remains of ancient organisms.
B. The Geologic Time Scale: A Clock in the Rocks
1. Biologists and geologists both date the Earths past with the help of a record in the rocks called the geologic time scale- record of the earths history from the rocks.
2. Relative Dating- a technique used by scientist to determine the age of fossils relative to other fossils in different layers of rock.
C. Radioactive Dating
1. Radioactive elements- decay, or break down, into nonradioactive elements at a very steady rate. Scientist measure this rate of radioactive decay in a unit called a Half-life.
2. Absolute Dating-researchers can calculate the actual age of a sample by radioactive dating which is called absolute dating.
3. Scientists have determined that the Earth is about 4.5 billion years old.
4. Eras- scientists have divided the 4.5 billion years into large units called eras.
5. Periods-are eras further divided
6. Epochs- are periods that have been divided.
III. The Fossil Record
A. How Fossils Form
1. Sedimentary Rock- where most fossils are found. Sedimentary Rocks are formed when exposure to rain, heat, and cold breaks down existing rocks into small particles of sand, silt, and clay.
B. Fossil Evidence: Problems in Assembling the Puzzle
1. The chancy process by which organisms are fossilized means that the fossil record is not as complete as we would like it to be. For every organism that leaves a proper fossil many die and vanish without leaving a trace.
2. The quality of fossil preservations also varies. Some fossils are preserved so perfectly that we can see the microscopic structure of tiny bones and feathers. Other fossils are not preserved as well and so raise fascinating questions about their meaning and importance.
Can also be found in ice, petrified rocks.
C. What the Fossil Record Tells Us
1. Paleontologist- scientists who study fossils.
2. Fossil Record- represents the preserved collective history of the Earths organisms. Worldwide collection of fossils over hundreds of years by paleontologists.
3. The fossil record shows that change followed change on Earth.
IV. Evidence from Living Organism
1. All living things carry within their bodies traces of the history that links them to their ancestors.
A. Similarities in Early Development
1. Scientists noticed that the embryos of many different animals looked so similar that it was difficult to tell them apart.
2. Embryos- are organism at early ages of development.
B. Similarities in Body Structure
1. As embryos mature, the limbs( of the once similar) grow into arms, wings, legs, and flippers that differ greatly in form and function.
2 Homologous structures-final Structures that enable the organism to survive in a different environment. Structures that develop from the same body parts are called homologous structures.
3. Vestigial organs-organs that seem to serve little or no purpose. These organs may resemble miniature arms, legs, tails, or other structures. Appendix.
C. Similarities in Chemical Compounds
1. All organism share many biochemical details.
2. All organisms use DNA and or RNA to carry information from one generation to the next and to control growth and development..
3. The DNA of all eukaryotic organisms always has the same basic structure from one species to the next.
Biochemical Similarities- comparing amino acid sequences or protein structure.
D. What Homologies Tell Us
1. The structural and biochemical similarities among living organisms are best explained by Darwin conclusion:
Living organisms evolve through gradual modification of earlier forms-descent from a common ancestor.