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Adaptations and Natural Selection By: Mr. Lowe Important Vocabulary • Species = Group of organisms who share similar characteristics and can reproduce among themselves. • Evolution = Change in inherited (from DNA) characteristics over time. Theory of Acquired Characteristics (Jean Baptiste de Lamarck) • Traits or characteristics developed during an organisms lifetime are passed on to their offspring. The “tall” Giraffe would then have tall babies! No way dude!!!!! Charles Darwin (1809-1882) • Charles Darwin was a naturalist who sailed around the world in 1831. • One of the places he helped explore was the Galapagos Islands off the coast of South America. • On the Galapagos Darwin observed many, diverse, species of animals. • Darwin observed many types of finches that resembled a species from South America. • Each of these finches was well adapted for the local food source. • Darwin also observed different versions of the Giant Tortoise. They had also adapted to their environment. • Based on what he observed Darwin began to develop his Theory of Natural Selection… Important Vocabulary • Variation = DNA inherited trait that makes an individual different than others of its species. • Adaptation = Any variation that makes an organism better suited to its environment. Mimicry Camouflage Camouflage Camouflage Principals of Natural Selection 1.Organisms produce more offspring than survive. 2. Differences, or variations, occur among individuals of a species 3. Variations are passed to offspring. 4. Some variations are helpful. Individuals with helpful variations survive and reproduce. 5. Over time the offspring of individuals with helpful variations make up more and more of a population and eventually become a separate species. Clues About Evolution We have many clues that evolution has occurred and continues to occur with living organisms. Some of these clues are: • • • • • Fossils Embryology Homologous Structures Vestigial Structures DNA Fossils • Fossils = The exposed remains or imprints of long dead plants, animals, or other living organisms. • Most fossils are found in sedimentary rock. • This is rock formed from mud and silt from long dried up rivers and oceans. Age of Fossils • How do we know how old fossils are? a. Relative Dating: (How deep it’s buried) The deeper it is the older it is. b. Radiometric Dating: Radioactive elements in the rock are used to accurately date the contents of the rock. Embryology • Embryo = earliest growth stage of development. • Embryology = Studying the similarities in embryos of different species. Homologous Structures • Homologous structure = Similar in origin and structure. Common traits among many organisms. Vestigial Structures • Vestigial Structure = Structures that remain on the body, but have no apparent function. DNA • Similarities in DNA content and structure. • Ape = 24 pairs of chromosomes. • Human = 23 pairs of chromosomes. • Human and Chimpanzee = 96% identical DNA. Clues!!!! • No one thing states that evolution takes place! Many things do! • Indirect Evidence – “Clues” give us a picture of how living organisms might have changed (evolved) over million of years.