Theory of Evolution

Evolution Definition: the change in allele frequencies in a population over time Alleles are the different variations/forms of a particular genetic trait. Allelic frequency deals with how often a particular allele appears in a population.

Jean Baptiste Lamarck French Naturalist 1809 - published ideas on evolution

Lamarck’s Hypothesis During organism’s lifetime, physical features  size b/c use or  size b/c disuse Organisms pass down acquired traits to offspring

Examples Short-necked vs. long-necked giraffes Body builders

Thomas Malthus - 1798 Human population increasing faster than supply of resources Pop. growth limited by disease, famine, war

Charles Lyell – 1830s Leading geologist of Darwin’s time. Surface of Earth changed slowly over long periods of time

Charles Darwin 22 yrs old HMS Beagle naturalist Spent 5 yrs observing & collecting 1000s of plants & animals from jungles, grasslands, desert, etc.

Darwin noticed… Unique animals & plants on islands looked similar to those on mainland but w/some differences

Darwin’s Finches Collected 13 types finches – looked like different species

After the Voyage… Spent 20+ years studying collections Results: variations w/in same species enable some to survive & reproduce, while those w/other variations do NOT survive or reproduce

Also studied… Farmers’ breeding of plants & animals with more desirable traits Artificial selection - selective breeding of plants/animals w/desirable traits

Artificial Selection Lots of change can be achieved in a relatively short time Darwin reasoned that natural selection could change species over 100s or 1000s of generations

Origin of Species 1859 - published his book, The Origin of Species by means of Natural Selection.

Natural Selection Organisms w/favorable variations for a certain environment will survive, reproduce, & pass these variations to offspring “Survival of fittest” Fitness – ability of an organism to survive & reproduce in its specific environment

For example… If a rabbit lived in an environment where it snowed all the time—what color of fur would be more advantageous? Why? Environment determines which traits are an advantage.

Main points of Darwin’s theory Genetic variations in populations Overproduction of offspring Struggle for existence Organisms w/favorable variations will survive, reproduce, & pass traits to next generation Ex. Hummingbirds w/longer beaks