CHAPTER 2 Evolutionary Theory
CHAPTER 2Evolutionary Theory
INTRODUCTION Evolution
What is your reaction to this term? Biological sciences Humans and Apes shared last common ancestor
5-8 million years ago.
HISTORY OF EVOLUTIONARY THOUGHT Discoveries came over a long time from a lot of
sources Charles Darwin
Alfred Russel Wallace Middle Ages
Thought processes were static Greek influence – Aristotle
Scientific Revolution Europe vs. Arabia and India
EARLY EVOLUTIONARY THINKERS John Ray (1627-1705)
Coined terms species and genus Carolus Linnaeus (1707-1778)
Fixity of species George-Louis Le Clerc de Buffon (1707-1788)
Change does occur in the universe Erasmus Darwin (1731-1802)
Charles Darwin’s Grandfather Jean-Baptiste Lamarck (1744-1829)
First to propose evolutionary process
EVOLUTIONARY THINKERS CON’T. Georges Cuvier (1769-1832)
Opponent of Lamarck Charles Lyell (1797-1875)
Wrote Principles of Geology Thomas Malthus (1766-1834)
English clergyman and economist Mary Anning (1799-1847)
Discovered a lot of fossils
LAMARCK
John Baptiste Lamack was the first scientist to produce an explanation for the evolutionary process.
He believed that species change was influenced by environmental change.
CUVIER
Georges Cuvier introduced the concept of extinction and the theory of catastrophism.
The view that the earth’s geological landscape is the result of violent cataclysmic events.
Cuvier promoted this view, especially in opposition to Lamarck.
THOMAS MALTHUS Thomas Malthus wrote
about the relationship between food supply and population increase.
His essay on the Principle of Population led both Darwin and Wallace to the principle of natural selection.
CHARLES LYELL
Charles Lyell developed the theory of uniformitarianism.
MARY ANNING
Discovered the first complete fossil of Ichthyosaurus, a large fishlike marine reptile.
She became known as one of the world’s leading “fossilists” and contributed to the understanding of the evolution of marine life over 200 million years ago.
CHARLES DARWIN (1809-1882) Ideas were formed while serving
as a naturalist on the voyage of the HMS beagle.
Darwin saw the importance of biological variation within a species.
Recognized the importance of sexual reproduction in increasing variation.
By 1844, Darwin had complete the work that he would publish fifteen years later.
ALFRED RUSSELL WALLACE(1823-1913) A naturalist who worked in South America and
Southeast Asia. Suggested species descended from other
species and new species were influenced by environmental factors.
Presented paper on evolution and natural selection to the Linnean Society of London jointly with Darwin.
DISCOVERY OF NATURAL SELECTION Charles Darwin (1809-1882)
Discovered first credible mechanism for evolutionary change
HMS Beagle Finches and barnacles
Alfred Russel Wallace (1823-1913) Developed own theory of natural selection Wrote letter to Darwin
THE PATH OF THE HMS BEAGLE
NATURAL SELECTION Darwin’s formulation included:
Potential for reproductive rates that outpace the rate of food supply
The presence of biological variation within all species
Constant competition among individuals for survival
Favorable traits = increase in reproduction Environment determines favorable traits Favorable traits passed to offspring Over long periods of time, successful variations
accumulate in populations Geographical isolation may result in new species
CONTRASTING VIEWS ON EVOLUTION
NATURAL SELECTION IN ACTION Peppered moth in the UK Galapagos birds and beak thickness
DOMESTIC DOG BREEDS
The variation exhibited by dog breeds has been achieved in a relatively short time through artificial selection.
EVOLUTIONARY CHANGE THROUGH NATURAL SELECTION1. A trait must be inherited if natural
selection is to act on it.2. Natural selection can’t occur without
population variation in inherited characteristics.
3. Fitness is a relative measure that changes as the environment changes.
4. Natural selection can only act on traits that affect reproduction.
CONSTRAINTS ON 19TH CENTURY EVOLUTIONARY THEORY No one knew source of variation that Darwin
explained Did not know how favorable traits were passed
down. Laws of heredity unknown – Mendel had not come
on the scene DNA was not discovered until 1953
OPPOSITION TO EVOLUTION Offensive to Christians because in conflict with
Biblical versions of creation Evolution considered to be a fact by most
scientists today Accepted in part by Catholic Church and most
Protestants Fundamentalists reject evolution
Creationism Intelligent Design
Debate topic: Should evolution be taught in public schools? If so
should Creationism also be taught?