The History of Evolutionary Thought

Aristotle (384-322 B.C.) Ladder of Life 2 types of animals – those w/ blood & those w/o Animals classified by their way of life Plants by structure Observation of various marine life anatomy was remarkably accurate Distinguished whales from dolphins

Carol von Linné (1707 – 1778) “Father of Taxonomy” Linnaeus was classifying organisms based on what they looked like. This made it difficult to classify organisms that seemed to share characteristics with both kingdoms that Linnaeus proposed, Plants and Animals. For example, fungi including mold and mushrooms do not move (or do they?) so they seem to be plants but, unlike plants…..?????

                                               Immutable Species???

Jean-Baptiste Lamarck (1744-1829) His name is associated merely w/ a discredited theory of heredity – he died in obscurity & poverty Darwin & Lyell give him great credit Law of use/disuse Law of acquired characteristics

LAMARCK’S THEORY

Charles Darwin (1809-1882) Voyaged around the world 1831-1836 Wrote On the Origin of Species which reveals his ideas on Evolution by means of Natural Selection

ACCORDING TO DARWIN…

Natural Selection Summarized: Darwin’s theory suggests that in a species: There is a tendency towards overproduction Variation exists Variations are inherited Individuals survive in their environments with varying degrees of success Best adapted, survive and pass favorable variation on to next generation In time, great differences arise, until a new species evolved from an old species

What is biological fitness???

Biological fitness: The contribution an individual makes to the gene pool of the next generation relative to contributions of other individuals Offspring should be fertile

Alfred Wallace (1823-1913) Studied the way geography limited or facilitated the extension of species range How ecology influenced the shaping of adaptations In 1858, shared with Darwin on the Theory of Evolution by means of Natural Selection

Genetic variation exists in sexually reproducing populations Different alleles are available in the population thus producing different phenotypes.

The Hardy–Weinberg principle states: Both allele and genotype frequencies in a population remain constant or are in equilibrium from generation to generation unless… Disturbing influences happen such as non-random mating, mutations, selection, limited population size, random genetic drift and gene flow. Genetic equilibrium is a basic principle of population genetics.

The Hardy-Weinberg principle is like a Punnett square for populations, instead of individuals.

Hardy-Weinberg Principle p2 + 2pq + q2 = 1; p + q = 1

Homologous Structures Structures that have different mature forms in different organisms but develop from the same embryonic tissues.

Homologous Structures