Darwin and Natural Selection

Transcription

1 Darwin and Natural Selection Background: Students know Evolution is change over time Essential Question: What was Darwin s conclusion about his observations? (CIRCLE ans. ) Vocabulary: Highlight or underline the 5 facts of evolution Lamarck: I. Evolution A. variation is inherited, not acquired (Darwin): individuals have to stretch to reach leaves; figuring that a long neck is better, they produce offspring with long necks Darwin: Some individuals happen to be born with a long neck; they can reach food better, get stronger, produce more offspring --> trait will spread in the population B. Descent with Modification 1. change is based on the interactions between populations & pressure from the environment 2. is a change over time in the genetic composition of a population DO NOT COPY In (1859) Darwin published the book: On the Origin of Species by Means of Natural Selection as a mechanism for evolution Historical Process of Science DO NOT COPY The next slides Aristotle: -life-forms arranged on scale on increasing complexity (scala naturae) -he viewed species as unchanging - His ideas were supported for a long time Aristotle B.C. Until the 1700 s many scientists used the next two ideas to explain life on earth Old Testament - Creationism: Earth ~6000 years old; perfect species individually designed by God Natural theology: discovering Creator s plan by studying nature; to classify nature Carolus Linnaeus Linnaeus: founder of taxonomy; binomial nomenclature Classification based on anatomy & morphology -Thought patterns of similarity showed God plan Domain Kingdom Phylum Class Order Family - Genus Species Domains = Eubacteria, Archaea, Eukarya 1

2 Cuvier: Paleontologist studied fossils Deeper strata (layers) - very different fossils from current life Opposed idea of evolution Catastrophism He used this idea to explain the change in species from deeper strata He said catastrophe destroyed many living species, then repopulated by immigrant species George Cuvier ( ) Formation of sedimentary strata with fossils Hutton / Lyell: (Both used fossil record to show the earth was old) Gradualism -geologic change results from slow & gradual, continuous process James Hutton Charles Lyell Uniformitarianism = -Earth s processes same rate in past & present therefore Earth is very old -Slow & subtle changes in organisms big change Jean-Baptiste Lamarck Lamarck: Published theory of evolution (1809)» Importance: Recognized that species evolve, although explanation was flawed» Use and Disuse:» parts of body used lead to bigger, stronger characteristics» (eg. giraffe s neck)» Inheritance of Acquired Characteristics: modifications can be passed on Malthus: More babies born than deaths Consequences of overproducing within environment = war, famine, disease (limits of human pop.) Overpopulation leads to a struggle for existence Alfred Wallace: Independently conceived the theroy of evolution and published a paper in 1858 This prompted Darwin to publish his book on the idea in 1859 Thomas Malthus ( ) Alfred Wallace ( ) He is really considered a cofounder of evolution 2

3 II. Charles Darwin ( ) A. English naturalist B. 1831: joined the HMS Beagle for a 5-year research voyage around the world C. Collected and studied plant and animal specimens, bones, fossils D. Notable stop: Galapagos Islands Galapagos Islands Darwin set sail on the HMS Beagle around the world & found many new animals Do not copy Galapagos Islands in South America Some of the organisms that Darwin Studied Do not copy Darwin s Observations In the Galapagos Islands Darwin saw giant tortoises, fur-covered seals, lizards that ate cactus plants for food and water, and many birds. Darwin s Observations From his observations, Darwin inferred that a small number of different plant and animal species had come to the Galapagos islands from the mainland. Galapagos Islnd Mainland 3

4 Darwin s Observations Similarities & Differences Darwin reasoned that plants or animals that arrived on one of the Galapagos Islands faced conditions that were different from those on the mainland. Perhaps, Darwin thought, the species gradually changed over many generations and became better adapted to new conditions. Galapagos Islands Iguanas on the islands had large claws to help them stay on slippery rocks Mainland iguanas had small claws for climbing trees. Mainland Ecuadorian Jungle Island Similarities & Differences Similarities & Differences The cormorants on the mainland were able to fly those on the islands were unable to fly. Mainland Once the plants and animals reached the Galapagos Islands they reproduced. Eventually, through mutations in their genes, their offspring became different from their relatives on the mainland. Island *Remember mutations can be helpful, harmful or neither. 1. Darwin s Finch Collection from the Islands Darwin s Galapagos Finches a. The birds were all about the same size b. the shape and size of the beaks of each species were different. c. This was because each island had different food source 4

5 2. Giant Tortoise a. On each island the tortoise s had different shells. b. Travelers use the shape of the Tortoise shell to determine which island they were on. III. Darwin s Conclusion ( Based on his observations) A. Species were not created in their present form, but evolved from ancestral species. (descent with modification) B. Organisms with the best traits will survive changes to the environment and pass on their traits C. Natural selection is the major driving force for evolutionary change of a population 25 Two-Toed Sloth IV. Natural Selection is based on 5 facts A. Variation: Each individual in a species differs from the others. ** Natural selection requires genetic variation and variation must be inherited genetically B. Competition: Living things face a constant struggle for existence. **Since food, water, and living space are limited, the offspring must compete with each other to survive. Elk competing for females C. Overproduction: Too many individuals produced so food/resources are limited D. Survival of the fittest: Only those individuals that are best suited for their environment survive and reproduce **Individuals cannot adapt to their environment; they are adapted or are not; adapted individuals will survive and produce more offspring Migrating Wildebeest in Africa 5

6 Helpful variations add up, while unfavorable ones disappear. E. The genetic makeup of the population changes. Over time the population has adapted to their environment **Helpful variations add up, while unfavorable ones disappear. **This hare changes its coat two times a year, exchanging a thin brown summer coat for a heavy, white, fluffy winter coat. Snowshoe Hare in summer and winter V. Modes of selection A. Directional selection favors one of the extremes. 1. Example of Directional selection Example of Evolution 2. Pepper Moths -Known as Industrial Melanism a. Dark moths were once rare b. In the 1850 s, industries created lots of pollution, causing the trees to darken c. Dark moths were better able to survive. Because they were now camouflaged d. Lighter moths now stood out & were eaten by the birds Before pollution After pollution 6

7 B. Disruptive selection favors both extremes. C. Stabilizing selection acts against the extremes and favors the middle. Modes of selection: 7