Chapter 15 Evolution Section 1: Darwin s Theory of Natural Selection In this section, you will learn about the series of events leading to Charles Darwin forming his Theory of Evolution.
Chapter 15 Evolution 15.1 Darwin s Theory of Natural Selection Darwin on the HMS Beagle Darwin s role on the ship was as naturalist and companion to the captain. His job was to collect biological and geological specimens during the ship s travel.
Chapter 15 Evolution 15.1 Darwin s Theory of Natural Selection The Galápagos Islands Darwin began to collect mockingbirds, finches, and other animals on the four islands. He noticed that the different islands seemed to have their own, slightly different varieties of animals.
The Birds Darwin Observed
Tortoises Observed
What did Darwin s Travels reveal The diversity of living species was far greater than anyone had previously known! These observations led him to develop the theory of evolution.
Chapter 15 Evolution 15.1 Darwin s Theory of Natural Selection Almost every specimen that Darwin had collected on the islands was new to European scientists. He wondered if populations from the mainland had changed after reaching the Galápagos due to different environmental pressures.
Chapter 15 Evolution 15.1 Darwin s Theory of Natural Selection Darwin Continued His Studies Darwin hypothesized that new species could appear gradually through small changes in ancestral species. Darwin inferred that if humans could change species by artificial selection (like making corn bigger, see photo), then perhaps the same process could work in nature.
As you look at the following photos of bird beaks, try to Identify which type of food it is most suited to eat. Identify advantages for eating this particular kind of food. Predict how this beak may change if the food source is altered.
Chapter 15 Evolution 15.1 Darwin s Theory of Natural Selection Four Principles of the Theory of Natural Selection Individuals in a population show variations (physical traits AND/OR behavioral traits. Variations can be inherited. Organisms have more offspring than can survive on available resources. Variations that increase reproductive success will have a greater chance of being passed on.
Chapter 15 Evolution 15.1 Darwin s Theory of Natural Selection EVOLUTION = change Natural Selection = how change happens Darwin s theory of natural selection is not synonymous with evolution. It is a means of explaining how evolution works.
Homework Assignment Select one modern thing and show how it has changed over generations. Ideas: cell phone, coke bottle, barbie, one type of car, music devices, computer, game system, golf club, basketball shoes, football helmet, etc. Select something unique something that you have an interest in. (no drug or weapon related items)
Natural Selection and Species Fitness Over time, natural selection results in changes in the inherited characteristics of a population. It DOES NOT change a living individual into a better suited individual during its lifespan! These changes increase a species fitness (survival rate)
Descent with Modification Each modern living species has descended from an ancestor changes over time lead to a more fit species Multiple changes (different beaks) within a species could lead to multiple new species (speciation)
Summary of Darwin s Theory 1. Organisms in a population differ; variation is inherited 2. Organisms produce more offspring than can survive 3. Organisms compete for resources 4. Organisms with advantages survive to pass those advantages to their children 5. Species alive today are descended with modifications from common ancestors
Chapter 15 Evolution 15.1 Formative Questions What was Darwin s term for selective breeding? A. evolution B. speciation C. artificial selection D. natural selection 1. A 2. B 3. C 4. D, A, 0%, B, 0%, C, 0%, D, 0%
Chapter 15 Evolution 15.1 Formative Questions What did Darwin infer from his observations of artificial selection? A. Animal breeders could create new species. B. A similar process could work in nature. C. Reproductive success could be increased. D. Variation in a species could be produced. A B 1. A 2. B 3. C 4. D 0% 0% 0% 0% C D
Chapter 15 Evolution 15.1 Formative Questions What is the relationship between the terms natural selection and evolution? A. They mean the same thing. B. Evolution works against natural selection. C. Evolution explains how natural selection works. D. Natural selection explains how evolution works. 1. A 2. B 3. C 4. D 0% 0% 0% 0% A B C D