13.1 Spontaneous Generation
| Spontaneous generation - hypothesis that life could come from nonliving matter. |
| Redi's experiment made a convincing case for biogenesis. |
13.2 The Earth Before Life
| Evidence indicates that Earth was cold when first formed. |
| As done today, ancient volcanoes poured many gases into the primitive atmosphere. |
| It consisted of carbon dioxide (CO2), nitrogen (N2), ammonia (NH4), and methane (CH4). |
13.3 The Origin of the First Cells
| Oparin hypothesized that the conditions on ancient Earth caused chemical reactions in air and produce organic molecules. |
| Two factors are necessary for monomers to join into polymers. |
| One hypothesis is polymerization first occurred in small puddles of seawater. |
| The second hypothesis involves common clay. |
| Micropheres - protein and water bubbles look and behave like cell membranes. |
| RNA was probably the first molecule able to replicate itself. |
13.4 Early Life Forms
| Scientists agree the first cells were heterotrophic. |
| Stromatolites are fossilized remains of layered mats of bacteria and sediment. |
| About 1.5 billion years ago, the first eucaryotic cells evolved. |
13.5 The Evolution of Multicellular Life
| Era are divided into periods, and periods into epochs. |
| Rainfall and temperature patterns changed as continents split and drifted across the Earth's surface. |
13.6 The Fossil Record
| Paleontologists - scientists who study life thru fossil records. |
| Several reasons for gaps in the fossil record. |
| Soft bodies of organisms don't form fossils well. |
| Natural processes of erosion destroy many fossils. |
| Fossils are often buried in rock and very hard to find. |
| Half-life - time it takes for half the atoms in an element to undergo radioactive decay. |
| Potassium-argon dating - amount of argon (Ar) in rock compared to the amount of potassium (K) in rock. |
13.7 Evidence from Modern Organisms
| The more closely related two organisms are, the more recent the common ancestor. |
| Vestigial structures - inherited but unused structures. |
| They are homologous to leg and hip bones of other reptiles. |
| Analogous structures are similar in purpose but not inherited from a common ancestor. |