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Transcript
Theories of Evolution Objectives Define biological evolution Explain Lamarck’s theory of evolution Explain Darwin’s two theories of evolution Introduction Evolution is an orderly succession of changes Biological evolution is the change of populations of organisms over generations Lamarck’s Explanation Proposed by Jean Baptiste de Lamarck (17441829) First unifying hypothesis of species modification Similar species descended from a common ancestor Species changed by acquired traits that were passed on to offspring Acquired trait is one that is not determined by genes Acquired traits were a result of the organism's experience or behavior Modern Evolutionary Thought Charles Darwin (1809-1882) and Alfred Wallace (1823-1913) independently proposed the hypothesis that species were modified by natural selection Natural selection – organisms best suited to their environment reproduce more successfully than other organisms Over generations, the proportion of organisms with favorable traits increases in a population Charles Darwin Went on a 5-year voyage (1831-1836) on the H.M.S. Beagle to South America and the South Pacific Was the ship’s naturalist Job was to collect specimens and keep careful records of his observations Voyage of the Beagle While on the Beagle, Darwin read a geology book entitled Principles of Geology by Charles Lyell Book discussed the age of the Earth and the principles of uniformitarianism Uniformitarianism – the geological structure of the Earth resulted from cycles of observable processes Darwin concluded that organisms had to adapt to geological changes over time Voyage of the Beagle One of the most important stops that influenced Darwin’s theories was the Galapagos Islands The Galapagos Islands are geologically young (5 million years old) Each island has a different climate, so each island had different vegetation and animals Darwin’s Data Darwin spent several years in England analyzing his data Collected 13 similar but separate species of finches Each finch species has a distinctive bill adapted for a particular food source Darwin considered that all of the island’s finches had a common ancestor and descended from a single species Darwin’s Data Darwin also collected tortoises Tortoises varied in shell shape and neck length Shell shape and neck lengths could be used to identify which island the tortoise came from Origin of Species Darwin proposed his hypothesis of evolution by natural selection in 1858 Worked on his hypothesis for 21 years Published his book The Origin of Species in 1859 Darwin’s Theories Descent with Modification Newer forms appearing in the fossil record are actually modified descendants of older species All species descended from one or a few original types of life Darwin’s Theories Modification by Natural Selection How evolution works “Survival of the fittest” Adapt – to change genetically over generations to become more suited to the environment A favorable trait gives the individual that has it an adaptive advantage Fitness – a single organism’s genetic contribution to the next generation • An individual with high fitness is well adapted to its environment and reproduces more successfully than an individual with low fitness Notes Review Define biological evolution. Biological evolution is the change of populations of organisms over generations Notes Review Explain Lamarck’s theory of evolution. Similar species descended from a common ancestor Species changed by acquired traits that were passed on to offspring Acquired traits are not determined by genes but by an organism’s experiences or behaviors Notes Review Explain Darwin’s two theories of evolution. Descent with Modification • Newer forms appearing in the fossil record are actually modified descendants of older species • All species descended from one or a few original types of life Modification by Natural Selection • The more fit an organism is to its environment the more likely it is to survive and pass on its traits to the next generation