EVOLUTION SBI3U/3C M. St Denis Charles Darwin An English Biologist Fascinated by different species and fossils. Traveled around the world on the BEAGLE and headed to the FAMOUS GALAPAGOS ISLANDS GALAPAGOS ISLANDS The Galapagos islands are isolated encrusted with lava and home to the worlds most bizarre creatures found nowhere else on Earth Tortoises that reach giant sizes Land dwelling lizards that take to the sea Vampire finches that suck the blood of other birds rather than eating seeds. GALAPAGOS ISLANDS The unusual species on the island have long fascinated biologists. Once such biologist was the young Charles Darwin, who visited the Galapagos as part of his remarkable 5 year journey on the ship the beagle On this trip, Darwin collected specimens and made observations. What is Evolution? Evolution is: the relative change in the characteristics of populations that occurs over successive generations Diversity of Life Diversity is the cornerstone of evolutionary biology Not all individuals of a species are exactly alike Differences between individuals are not always immediately visible Diversity is important for the long term survival of a species Biodiversity Differences in characteristics between individuals may be: Advantageous Harmful Neutral Characteristic may not give an individual an advantage now, but may become critical for survival later if the environment changes What controls the characteristics of individuals? Genes!! There are different versions of genes, known as alleles, in a population which is the basis of biodiversity. Gene pool total of all genes in a population What is Evolution? Evolution is the relative change in the characteristics of populations that occurs over successive generations any shift in the gene pool of a population ratio of characteristics in a population change over successive generations Who can evolve? Individuals cannot evolve! Individuals cannot change their genes. Populations are the smallest unit that can evolve. Populations can have a shift in their gene pool. Why would populations evolve? So that a population becomes better suited to its habitats. Increased survival Better chance of passing on characteristics to offspring. Takes place over many generations. How does a population evolve? A shift in the gene pool so that a higher ratio of individuals have a particular adaptation. Adaptation a particular structure, physiology or behaviour that helps an organism survive and reproduce in a particular environment. e.g. camouflage, superb sense of smell, bill shape Example of a population that evolved: Peppered moths in England The Peppered Moth The peppered moth has two colour forms: A light form and a dark form Moth color is an inherited characteristic. Many moths are eaten by birds, which usually select the moths that differ most in colour from the trees on which the moths rest. Thus, in regions where soot darkens the bark of trees, moth populations evolve to consist mostly of dark moths. What did Darwins 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!! 3.How did tortoises and birds differ among the islands of the Galapagos? Each island had its own type of tortoises and birds that were clearly different from other islands Galapagos Turtles Evolution is when organisms change over time. So, modern organisms descended from ancient ones Geologists: Hutton and Lyell Fundamentalists said that the earth was around 6000 years old Hutton and Lyell argued that the earth is many millions of years old b/c layers of rock take time to form processes such as volcanoes and earthquakes shaped the earth and still occur today Lamark Theory of acquired characteristics Lamark said organisms acquired traits by using their bodies in new ways These new characteristics were passed to offspring Lamark was totally wrong! Evolution is a Theory Just like Gravity! Evolution is a well supported explanation of phenomena that have occurred in the natural world A theory in science is a well tested hypothesis, not just a guess Malthus Reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone There will be a struggle for survival between the members of the population Individuals with advantageous variations will breed and produce more offspring Darwin finally published his ideas in 1859 Other naturalists were developing the same theory that Darwin did. Even though he was afraid of the Churchs reaction to his book he wanted to get credit for his work. Artificial Selection nature provides variation, humans select variations that are useful. Example - a farmer breeds only his best livestock Natural Selection The traits that help an organism survive in a particular environment are selected in natural selection Natural Selection and Species Fitness Overtime, natural selection results in changes in the inherited characteristics of a population. These changes increase a species fitness (survival rate) Descent with Modification Each living species has descended with changes from other species over time Summary of Darwins Theory 1. Organisms differ; variation is inherited 2. Organisms produce more offspring than 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