Concept that biological organisms have changed since the origin of life - origin of new species or groups from ancestral species or groups

Ideas on evolution began to emerge during 18th and 19th centuries - generated periodic controversies due to perceived conflicts with religious beliefs

Darwinian evolution - concepts proposed by Charles Darwin (On The Origin of Species -1859) revolutionized biology - has become a core theme of modern biology

Aristotle (384-322 BC) - Greek philosopher -believed that organisms were perfectly adapted and could be arranged like "rungs" on a ladder ("scale of nature") - opposed any concept of evolution - his ideas dominated science for more than 2,000 years

Natural theology - dominated science in Europe and North America during 18th and early 19th centuries - organisms created in their present form - goal of science is to discover Creator’s plan - Carolus Linnaeus - father of taxonomy - developed system of binomial nomenclature

Georges Cuvier - catastrophism

James Hutton - gradualism

Charles Lyell - uniformitarianism

Jean Baptiste Lamarck (1744-1829) - inheritance of acquired characters

Alfred Russel Wallace (1823-1913) - independently developed a theory of natural selection that was essentially identical to that of Darwin’s theory

Published On the Origin of Species in 1959 - one of most important works in history of science

Developed ideas on evolution during round-the-world voyage of the HMS Beagle (1831-6)

Proposed two concepts - that our extant (present) species evolved with modifications from ancestral species ("descent with modification") and the theory of natural selection (the mechanism or "driving force" of evolution)

Now accepted by most scientists

Natural selection essentially means differential success in reproduction - because of certain heritable traits, certain individuals within a population are more likely to survive and reproduce than others - their genes eventually become predominant in the population

Tends to increase adaptation of populations to changes in the environment

Natural selection can amplify or diminish only heritable variations

A population is the smallest unit that can evolve

An adaptation that is advantageous in one situation may be useless or detrimental in another environment - i.e., the specifics of natural selection are situational

Natural selection involves differential reproductive success - operates without man’s direct intervention

Artificial selection - genetic changes direct result of man’s intervention - e.g., plant breeders select desirable cultivars from wild stock through series of generations