Download Natural Selection and Evolution

Natural Selection and Evolution
Jean Baptiste de Lamarck—theory of acquired characteristics.
Traits acquired during life that increase survival are passed on to
future generations. The traits change by use or disuse.
Charles Darwin
 in 1830’s was a naturalist on a worldwide voyage of the HMS
Beagle.
 published a controversial book, The Origin of Species (1859).
 credited with the theory of evolution (over Alfred Russell Wallace).
 believed evolution was the result of natural selection.
What led to Darwin’s theory?
1. Knowledge of Geology—Darwin read Sir Charles Lyell’s book
explaining the age of the Earth and many changes through time.
2. Artificial Selection by farmers—Darwin marveled at how complex
traits could intentionally be selected for.
3. Theories of Thomas Malthus—Malthus observed that humans
are born faster than they die. Darwin applied this idea to plant
and animal populations. He realized the significance of the large
number of offspring and natural death of weaker individuals.
4. Personal observation— knew of natural (genetic) variety in all
organisms and noted how slight differences in similar species
help them survive.
Natural selection is the “survival of the fittest.” Any variation in a
trait that benefits a species will be passed on to future generations,
traits that make a species weaker will not. Variations that are
passed on are often called adaptations.
Adaptations are any trait that enhances the survival of an organism.
Adaptations are a result of natural selection. Generally the traits
studied are unusual. Examples:
 Coloration or appearance: camouflage, warning coloration,
imitation of defensive behaviors. Mimicry is common.
 Physical defense: poisons, thorns, stingers, etc.
 Escape behavior: running fast and traveling in schools or herds.