Theories of Evolution

1. Theories of Evolution Charles Darwin Jean Baptiste de Lamarck Charles Lyell

2. The Old Belief • The Earth and all living things had been created in their present forms & were immutable (did not change). • Based on strong held religious beliefs (European perspective). • Between the 15th & 18th centuries, science led to a change in thinking.

3. The Seeds of an Idea • Studied anatomy. • Examined body structures of animals & considered their functions. • Wondered why some body parts seemed to have no purpose (i.e. Why do pigs have an extra toe that doesn’t reach the ground?). • Believed species were • changing over time. • Around the same time, other • scientists (i.e. Carl Linnaeus) • were proposing the same idea. • - Ideas remained speculation b/c there was no explanation (mechanism) for why living things were changing over time. Georges Buffon (Comte Georges-Louis Leclerc de Buffon) 1707-1788

4. Adaptation & Heredity • First to propose a possible mechanism for evolution. • Evolutionary change resulted from two principles: • 1) Use & disuse – structures of the body that were • used became larger & stronger, while those that were • became smaller & weaker (i.e. Muscles). • 2) Inheritance of acquired characteristics - individuals • could pass on to their offspring characteristics they had • acquired during their lives (i.e. Stretched giraffe necks). Jean-Baptiste de Lamarck 1744-1829

5. Lamarck’s contributions: • All species evolve over time. • A species evolves in response to its environment & becomes better adapted. • Changes are passed on from generation to generation. Flaws in the theory - many features do not change in response to use (i.e. Vision). - Features that do not change are not normally heritable (i.e. You can stretch your neck slightly, but this will not alter your DNA so your children are born with longer necks).

6. Fossils • Conducted first detailed studies of fossils. • Observations provided support for theory that life had evolved from simple to more complex forms. • Believed that species themselves did not change (still held old belief). • Proposed theory of Catastrophism • Global catastrophies (i.e. Floods) caused widespread extinctions of species on Earth. • Extinct species were replaced by newly created set of species. • - Theory did not account for why each layer of rock included progressively more complex forms. Georges Cuvier 1769-1832

7. Cuvier noticed the following: • Fossils of simple organisms are found in all depths. • Fossils of more complex organisms are found only at shallower depths, in younger rocks. • Fossils in shallower depths are more likely to resemble living species. • Rock layers contain fossils of many species that do not occur in the layers above. Youngest rocks Oldest rocks

8. Geology • Was studying rocks & fossils at same time as Cuvier, but came to opposite conclusions. • Proposed theory of Uniformitarianism • Earth has been changed by the same processes in the past that are occurring in the present. • Geological change is slow & gradual rather than fast & catastrophic. • Natural laws that influence these changes are constant & eternal, & they operated in the past with the same intensity as they do today. • These were radical ideas (i.e. Entire mountain ranges may have formed through extremely slow processes) • Suggested the Earth was extremely old and not the previously held belief that our planet was very young. Charles Lyell 1797-1875 “The Father of Modern Geology”

9. The stage was set! Charles Darwin 1809-1882

10. What is evolution? • Gradual Change in the inherited traits (genes) of a population of organisms from one generation to the next How do organisms evolve? • Individual organisms don't evolve. Populations evolve

11. In order for evolution to occur, the change must be at the genetic level and be passed on to the next generation What do genes have to do with evolution? • Recall: • DNA contains genes that carry the code responsible for building that organism in a very specific way. • Genes are passed from parent to offspring.

12. Who was Charles Darwin? • A Cambridge graduate (who thought about becoming a clergyman) • A shy and private wealthy landowner • A husband who married a devote Christian named Emma – she prayed for his soul • A geologist, a naturalist and a barnacle expert –he was meticulous • He was invited on the HMS Beagle as company for Captain FitzRoy • A reluctant rebel…

13. The voyage that changed the face of biology… • Darwin set sail on the H.M.S. Beagle (1831-1836) to survey the south seas (mainly South America and the Galapagos Islands) to collect plants and animals. • His observations of the geographical distribution of wildlife and fossils he collected on the voyage puzzled him. • Darwin conceived his theory of natural selection in 1838.

14. Darwin’s Theory is Based on Observations • Observation 1: Individuals within a population vary in their traits (Genetic variation). • Observation 2: More offspring are produced than can survive because of limited resources such as food and nesting sites. • Observation 3: Individuals with advantageous traits will survive and reproduce • Result: The more advantageous trait, that allows for more offspring to survive will become more common

15. Therefore: • The Theory of Natural Selection: • Individualswith heritable favorable traits results in a population that is better adapted to its current environment. • Adaptation: a structure, behaviour, or process that helps an organisms survive in a particular environment.