Activity 4 Darwin and the Development of a Theory
Read the Introduction. • Biological evolution or evolution is a change in the genetic composition of a population that gives rise to new life forms from common ancestors.
Challenge • How did Darwin build on his and others’ work to develop his ideas about natural selection and evolution?
Natural Selection and Evolution Competition for environmental resources needed for survival Heritable variation Changes in populations over time Differential reproduction +
Revisit the Challenge • How did Darwin build on his and others’ work to develop his ideas about natural selection and evolution?
Timeline of Ideas Leading Up To and Following Darwin’s Work An Essay on the Principle of Population: Malthus states increasing human population will need more food than available. Zoological Philosophy: Lamarck suggests evolution occurs in an individual organism—some organs used more, some less. Darwin is born. Principles of Geology: Lyell discusses the great age of the Earth, how small changes over long periods lead to change on a grand scale. 1798 1809 1830
Timeline of Ideas Leading Up To and Following Darwin’s Work, cont. Darwin joins the voyage of the H.M.S. Beagle as naturalist, reads Lyell’s first volume. H.M.S. Beagle returns. Naturalists help Darwin catalog his specimens. Farmers and pigeon breeders describe to him their efforts to improve crops and animals Sketch on Natural Selection: Darwin’s initial version of his theory of evolution; made public many years after his death. 1831 1836 1842
Timeline of Ideas Leading Up To and Following Darwin’s Work, cont. Alfred Wallace comes to the same conclusion as Darwin: natural selection is a driving force behind evolution. Linnaean Society presents the men’s work together. On the Origin of Species: Darwin explains his theory of evolution by natural selection. Austrian monk Gregor Mendel proposes the Laws of Heredity, based on his work with peas, mostly unnoticed until nearly 1900. 1858 1859 1866
Timeline of Ideas Leading Up To and Following Darwin’s Work, cont. Thomas Hunt Morgan’s work on eye color in fruit flies reveals the mechanism of mutation, the source of genetic variation. Systematics and the Origin of Species: Ernst Mayr gives examples of geographic isolation and how it leads to speciation. Francis Crick, Rosalind Franklin, and James Watson discover the structure of DNA. 1900 1942 1953
Key Vocabulary • biological evolution • evidence • evolution • natural selection • sexual selection • theory