The historical context of Darwin’s life and ideas
James Hutton Charles Lyell Changes in Earth’s surface can be caused by slow, continuous changes; Earth has to be more than a few thousand years old
Georges Cuvier & Paleontology <ul><li>Cuvier largely developed field of paleontology </li></ul><ul><li>Study of fossils </li></ul><ul><li>History of life is recorded in strata containing fossils </li></ul>
Formation of sedimentary rock & deposition of fossils
Malthus was a British social scientist who made these observations about humans: Darwin based his theory on his own observations and the writings of Thomas Malthus. People have more children than are able to survive. There are built-in population checks: disease, famine, and war.
Lamarck <ul><li>Placed fossils in evolutionary context </li></ul><ul><li>Use/ disuse </li></ul><ul><li>Inheritance of acquired characteristics </li></ul>
The Galapagos Islands lie 500 miles west of Ecuador in the Pacific Ocean, directly on the equator. Many of Darwin’s conclusions were based on observations of wildlife in the Galapagos Islands. “ Galapagos” means turtle.
In particular, Darwin observed something odd about the finches: they all looked like a bird he had seen on the South American continent. Galapagos finches
Darwin hypothesized that some of the birds from South America migrated to the Galapagos Once on the islands, the birds must have changed over the years.
1. All species have genetic variation. Every species is different, even within itself.
2. Organisms produce more offspring than can survive . Many that survive do not produce offspring. The female green sea turtle lays a clutch of about 110 eggs. She may lay several clutches. It is likely that less than 1% of the hatchlings will ever reach sexual maturity.
3. Since more organisms are produced than can survive, there is competition (struggle for existence) . Competition exists WITHIN and AMONG species. Within and Among Species for And Within a Species for food water mates shelter space
The constant struggle for survival is affected by short-term natural disasters (drought, fires, floods, snowstorms, hurricanes, and tornadoes) The constant struggle for survival is also affected by long-term changes in the environment (ice ages, biome shifts, etc)
4. Survival of the fittest Some organisms are more suited to their environment as a result of variations in the species. Individuals that are fit to their environment survive and leave more offspring than those who aren’t. Fitness: the ability of an individual to survive and reproduce in its specific environment. Fitness is a result of adaptations. He who spreads the most genes wins! 1st
5. Descent with modification : Living species today are descended with modifications from common ancestral species that lived in the past. Over time, genes for less favored characteristics will be eliminated from the gene pool. Characteristics of fit individuals increase in a population over time.
Natural Selection: Survival of the Fittest An adaptation is any inherited characteristic (a genetic variation) that can increase an organism’s chance of survival. An organism does not change because of need or desire to survive. The organism either already has the variation that enables it to survive or it dies. the variation exists first. the environment changes. a variation may give an advantage to survive environmental change.
<ul><li>CLADOGRAM: diagram that shows the evolutionary relationship among a group of organisms. </li></ul>What organism belongs at each branch? Amino Acid Difference in Hemoglobin Compared with Human G F E D C B A Common ancestor Where would the common ancestor be? Species Difference Gorilla 1 Monkey 8 Mouse 27 Chicken 45 Frog 67 Lamprey 125 Number of Amino Acid Differences 150 100 50 0 40 20 30 10
<ul><li>HOMOLOGOUS STRUCTURES </li></ul><ul><li>structures with similar structure but different function </li></ul><ul><li>(ex: turtle, alligator, bird, mammal) </li></ul>Turtle Alligator Bird Mammal
<ul><li>Homologous structures show </li></ul><ul><li>Similar genes </li></ul><ul><li>Descent from a common ancestor </li></ul>Turtle Alligator Bird Mammal Ancient lobe-finned fish
<ul><li>VESTIGIAL STRUCTURES </li></ul><ul><li>organs so reduced in size that they are nonfunctioning </li></ul><ul><li>ex: human tailbone, appendix, whale pelvis </li></ul><ul><li>Show relationship with other organisms that have similar organs that are still functioning </li></ul>
BIOGEOGRAPHY <ul><li>Biogeography </li></ul><ul><ul><li>Geographic distribution of species </li></ul></ul><ul><ul><li>Closely related species tend to come from same area </li></ul></ul><ul><li>Endemic species </li></ul><ul><ul><li>Only found in a certain location </li></ul></ul>
The evolution of fruit fly ( Drosophila ) species on the Hawaiian archipelago
Essay <ul><li>Evolution is one of the unifying concepts of modern biology. Explain the mechanisms that lead to evolutionary change. Describe how scientists use each of the following as evidence for evolution: </li></ul><ul><li>1) Bacterial resistance to antibiotics </li></ul><ul><li>2) Comparative biochemistry </li></ul><ul><li>3) The fossil record </li></ul>