EVOLUTION THE EVOLUTION OF EVOLUTIONARY THEORY BEFORE DARWIN

EVOLUTION THE EVOLUTION OF EVOLUTIONARY THEORY

BEFORE DARWIN • CREATIONISM = first explanation of diversity observed = separate creation of each organism by a supernatural being • Scientists however historically have sought natural causes for the origin of species

HISTORY OF EVOLTION • HOW TO DISTINGUISH A SPECIES? o Differences in appearance Reproductive isolation o Today’s Definition of SPECIES: a population of organisms that are capable of interbreeding under natural conditions

GREEK PHILOSOPHERS • PLATO – “Ideal Form” = object on earth were created by God in their ideal form and do not change, although minor variations do occur due to the imperfections of our world • ARISTOTLE – “Scala Naturae” = ladder for classifying and naming nature in which each species had a place that had been given to it by God

EVOLUTION BEFORE DARWIN & WALLACE • BEFORE 1700’S – Creationism was unchallenged • LEAVING EUROPE- observed a greater diversity and variety within species and started to think about the possibility that species could change over time • DISCOVERY OF FOSSILS – William Smith discovered that fossils in lower rock were more primitive and changed to more advanced forms as well as some fossils of extinct forms

EVOLUTION BEFORE DARWIN & WALLACE • BUFFON – original creation of a few species that evolved over time producing the modern species • CATASTROPHISM – catastrophes produced layer of rock and made species extinct and after each catastrophe, new species were created • UNIFORMITARIANISM – the same forces (wind, water , volcanoes) that change geology also produced the rock layers and the ever changing earth

LAMARCK • Organisms evolved through the INHERITANCE OF ACQUIRED CARACTERISTICS • IE. Giraffe stretch to reach trees, therefore pass on longer necks to offspring • Not scientifically supported

DARWIN & WALLACE • Independently, both provided evidence that the diving force behind evolution is natural selection

EVIDENCE OF EVOLUTION P. 283 -285

• When scientists speak of evolution as a theory they do not mean that it is a mere speculation. It is a theory in the same sense as the propositions that the earth is round rather than flat or that our bodies are made of atoms are theories. Most people would consider such fundamental theories to be sufficiently tested by empirical evidence to conclude that they are indeed facts. As a result of the massive amount of evidence for evolution accumulated over the last two centuries, we can safely conclude that evolution has occurred and continues to occur. All life forms, including people, evolved from earlier species. Furthermore, all still living species of organisms continue to evolve today. We now understand that there a number of different natural processes that can cause evolution to occur. These are presented in later lessons.

FOSSILS • progressive series of fossils leading from an ancient, primitive organism to a modern form • even though the fossil record is not complete we can form a picture from the fossils we do have. Some animals are better represented than others - like the horse

COMPARATIVE ANATOMY • Evolution predicts that organisms that evolve in similar environments will develop similar structures (even if these organisms are not related) - basically that natural selection will drive species to develop structures best suited for the environment

COMPARATIVE ANATOMY • Convergent Evolution - where two unrelated species have similar forms (a whale and a shark) • Analogous structures - the outwardly similar structures, like the wings of a fly and the wings of birds

SIMILARITIES IN EARLY DEVELOPMENT • Embryos of many different animals look similar • this shows that similar genes are at work

SIMIALR BODY STRUCTURES • HOMOLOGOUS STRUCTURES - have similar underlying makeup, though different functions. The similarity is due to having derived from the same common ancestor. Ex. the forelimbs of various mammals

STRUCTURES • Structures that have no apparent purpose, like the pelvic bones of whales, the appendix in humans

BIOCHEMICAL & GENETIC ANALYSIS • Similarities between organism's DNA and protein structures show relationships. Gene sequencing can help us determine what organisms are more closely related than others.

ARTIFICIAL SELECTION EVOLUTION CAN BE OBSERVED! • Artificial selection is the process of breeding domestic plants and animals to produce specific desirable features in a population. • All dog breeds have been created via artificial selection • Cows have been breed over the years to produce more milk and become larger

RIGHT BEFORE OUR EYES • Natural Selection can also be observed today! · peppered moths · insects become resistant to pesticides · bacteria become resistant to antibiotics

PEPPERED MOTHS • Peppered moths in Britain showed a shift in coloration after the industrial revolution. Moths were generally light colored to match the background of lichens on trees. Soot from factories turned the bark of trees to a darker coloration, darker colored moths increased in number because they were better camouflaged on the dark trees.

ADDITIONAL NOTES • The variations upon which natural selection works are produced by chance mutations • Natural selection does not produce increasing degrees of perfection, it produces organisms best suited for a particular environment. • It is a common misconception the evolution will produce better and better organisms - its simply not true. A seal is adapted for water, but its not a good design for a prairie. When an environment changes, many populations can go extinct because they are no longer suited to an environment (dinosaurs)

MONKEYING AROUND • It is also a common misconception that if humans evolved from earlier primates, then we shouldn't have monkeys at all (since they would have all evolved to humans) - again this is erroneous, monkeys aren't "driven" to become humans, as long as their suited for their environment, the process of natural selection won't facilitate any major changes, there a variety of primates, just like there is a variety of cats - but more on human evolution later.