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Charles Darwin’s Theory of Evolution. Introduction. Charles Darwin was a biologist who lived during the 1800s Scientific thinking was shifting (biology & geology) Evolution = the process of change over time
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Introduction • Charles Darwin was a biologist who lived during the 1800s • Scientific thinking was shifting (biology & geology) • Evolution = the process of change over time • Darwin developed a theory that explains how modern organisms evolved over long periods of time through descent from common ancestors.
Darwin’s Observations • Darwin was invited to sail aboard the HMS Beagle’s 5-year journey • The captain and crew were mapping the coastline of South America • Darwin was collecting animal and plant specimens and making notes about the biological diversity (species) he observed • They visited South America, remote islands, New Zealand, Australia, and the southern tip of Africa
Examples • Birds: • Rheas are similar to ostriches but live on separate continents • Finches on the Galapagos Islands were similar but each species had a differently-shaped beak • Marsupials are found only on Australia • Fossils • Many fossils that Darwin collected resembled living species.
Other Scientists’ Ideas • James Hutton and Charles Lyell (Geologists) • Concluded that the Earth is extremely old • The processes that changed Earth in the past were still operating in the present. • Jean-Baptiste Lamarck (Biologist) • Suggested that organisms could change by using or not using parts of their bodies • Thomas Malthus (Economist) • Studied factors that limited population growth
Artificial Selection • Plants and animals are bred for certain characteristics • Cows that produce more milk • Horses that run faster • Plants that produce better fruit • Dogs that possess certain skills (dog breeds) • Artificial selection = nature provides the variations in a species, but humans select those that they find useful. (Darwin had NO idea how heredity worked)
Darwin’s Conclusions • Organisms struggle to survive • They compete for limited resources • Some variations are more beneficial than others (adaptations) • Individuals with these variations were more likely to reproduce and pass them on to offspring. • “Survival of the fittest” • An organism’s fitness describes how well it is able to survive and reproduce in its environment
Natural Selection • The process by which organisms with certain variations are more likely to survive and produce more offspring. • The natural environment determines fitness • Natural selection exists when organisms compete for resources, possess variations, and there are different levels of fitness among individuals in a population.
Evidence for Evolution 1. Biogeography – Patterns of species distribution • Closely related but different = variations among populations that resulted in the development of different species • Distantly related but similar = species that are similar and live in similar environments but in different locations 2. Fossils • The geologic record of organisms that have lived in the past • Some extinct organisms are similar to living species.
3. Anatomy and Embryology • Homologous structures = structures that are anatomically similar but have different uses • Ex: arm bones of amphibians, reptiles, bird wings, and mammals • Vestigial structures = traces of structures • Ex: hip bones in marine mammals, tailbones • Embryos of different species show similar development patterns 4. Genetics and Molecular Biology • All organisms share the same basic genetic code
