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Adaptations Over Time Chapter 6 Ideas about Evolution Evolution-changes in inherited characteristics of a species over time. -A species is a group of organisms that share similar characteristics and can reproduce among themselves. Jean Babtiste Lamarck • Developed a hypothesis to explain how species change over time. • He traveled through the Galapagos Islands collecting data on species of animals and their acquired traits. Charles Darwin- model of Evolution • In December 1831 Charles Darwin, a young naturalist, sailed from England on a journey to South America on the HMS Beagle. He recorded observations on plants and animals. • He was amazed by what he found on the Galapagos Islands. • He observed the beaks of finches are related to its eating habits. • He also noticed the finches were similar to a finch species he had seen on the South American Coast. • He found they had to compete for food, and those with beak shapes that allowed them to eat available food survived. Darwin’s model of Evolution • He hypothesized that plants and animals on islands off the coast of South America originally came from central and South America. • He observed that the species of finches on the islands looked similar to a mainland finch species. • He reasoned that members of a population best able to survive and reproduce will pass their traits to the next generation; over time. Differences can result in separate species. • He published - THE ORIGIN OF SPECIES in 1859 Darwin’s hypothesis became known as the the theory of evolution by NATURAL SELECTION-organisms with traits best suited to their environment will more likely survive and reproduce How do Lamarck’s theory and Darwin’s theory differ? VARIATION- an inherited trait that makes an individual different from other members of its species • Adaptation- a variation that makes an organism better suited to its environment. • Many environmental factors can cause change in the source of genes. Geographic Isolation- can make two populations so different they become different species. Two models explain the speed of evolution 1. Gradualism- describes evolution as a slow, ongoing process 2. The Punctuated Equilibrium model says gene mutation can result in a new species in a relatively short time. CLUES ABOUT EVOLUTION Fossils found in Sedimentary rock show evidence that living things evolved. Fossil age can be determined by two basic methods. 1.Relative dating- looks at the fossil location in a particular layer or rock; older rock layers are under newer rock layers. • 2. Radiometric Dating- compares the amount of radioactive element with the amount of nonradioactive element in a rock Fossil records have gaps. • Incomplete rock record; most organisms do not become fossils • Enough fossils have been discovered for scientists to conclude that complex organisms appeared after simpler ones. • Most organisms that have ever existed are now extinct Direct evidence- such as the development of antibiotic resistance in bacteria; support evolution. Indirect evidence supporting evolution: 1. Embryology- the study of embryos and their development, shows similarities amongst all vertebrate species 2. Homologous body parts- body parts that indicate two or more species share common ancestors 3. Vestigial structures- structures that don’t seem to have a function but might have once functioned in an ancestor. DNA can provide evidence about how closely related organisms are. THE EVOLUTION OF PRIMATES PRIMATES- groups of mammals with: • 1. Opposable thumbs • 2. binocular vision • 3. flexible shoulders Hominids- appeared 4 to 6 million years ago and had larger brains then apes. • Fossils such as Australopithecus, point to Africa as the origin of Hominids. • Homo-habilis and Homo erectus are thought to be early human ancestors Lucy Lucy- australopithicus Homo- Sapiens- Began evolving 400,000 years ago Neanderthals – had short heavy bodies with thick bones, small chins, and heavy brow ridges. • Disappered about 30,000 years ago • Not thought to be direct ancestors of modern humans Cro –Magnon fossils date from around 10,000 to 40,000 years ago; are thought to be direct ancestors of early Homo Sapiens.