Evolution by Natural Selection

Source: http://www.salem.k12.va.us/staff/jwright/vocabulary/cladogram.html

Evolution

• Process in which significant changes in genetic makeup of a species occurs over time

• Evolution is fact; natural selection is a theory

• Evolution was not first described by Charles Darwin

Source: http://darwiniana.org/horses.htm

Who was Charles Darwin?

• Man who developed theory of natural selection

• Was hired as a naturalist on an expedition to South America in 1831.

• Keen observer of the natural world and collected many different species

• Kept meticulous notes of his observations.

Voyage of the Beagle

• Darwin collected specimens of all kinds of species, fossils, and took detailed notes

• Darwin used his collections and findings along with evidence from others to piece together natural selection

What Darwin Found• Fossils of extinct animals that

resembled animals present today

• Noticed that continents separated by large distances had entirely different species occupying similar ecological niches or habitats

What Darwin Found Con’t

• different species of finch; different species on each island

What Darwin Found Con’t

• Homologous structures: common origin but different functions

• Analogous Structures: similar function but different origin

Other Evidence

• Artificial selection: selecting and breeding for desirable traits

Source: http://www.teachers.ash.org.au/monkweb/10chap8/evolution.htm

Idea’s from Lyell & Malthus

• Lyell – “Principles of Geology” Idea that earth’s surface has and continues to change through similar and gradual processes

• Malthus – “Essay on the Principle of Population” – In nature both plants and animals produce more offspring than are able to survice

Theory of Natural Selection

• Darwin’s Observations:1. Individuals within a species vary

2. Some variability can be inherited

3. More individuals are born than can survive

4. Populations of species tend to remain stable in size

• Darwin’s Inferences:1. Members of same species compete for survival

2. Individuals with favorable traits are more likely to survive and mate

3. These individuals will contribute more offspring to future generations therefore increasing favorable trait

Example of Evolution by Natural Selection

• Industrial melanism by peppered moth as a result of industrial revolution

• Melanism – development of dark pigmentation (opposite of albinism)