Natural selection is the gradual, non-random process by which biological traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution. The term "natural selection" was popularized by Charles Darwin who intended it to be compared with artificial selection, what we now call selective breeding.

1. Natural Selection

2. Charles Darwin
 On the Origin of Species
 Sailed with the HMS Beagle
 Observations made in the Galapogos
Islands
 These observations helped him form
the theory of how species change over
time called natural selection

3. What is Natural Selection?
 Natural selection is governed by the
principles of genetics.

4. Types of Adaptations
 Protective Coloring
– Camouflage
– Mimicry
 Physiological Adaptations
– Reproductive Changes
– Other changes
 Behavioral Adaptations

5. Evidence for Evolution
 Fossil
record
 Anatomy
– Homologous structures
– Analagous structures
 Vestigial
structures
 Embryology
 Molecular biology (DNA differences)

6. What is a Population?
 Populations evolve over many
generations, individuals don’t
 Populations are groups of interbreeding
individuals that live in the same place at
the same time
 Individuals in a population compete for
resources with each other

7. How Does Evolution Work?
 Populations produce more offspring
than the environment can support
 The unequal ability of individuals to
survive and reproduc leads to the
gradual change in a population over
many generations

8. Mechanism for change in a
population of organisms
 Animals who have greater fitness
survive in environment and live to
reproduce
 Random changes (mutations) can lead
to greater or less fitness
 Adaptations allow an organism to
survive better in their environment

9. Mutations & Variety Produced
by Sexual Reproduction Allow
for Diversity within a Population
 Genetic drift (caused by chance)
– Bottleneck
– Founder effect
 Genetic equilibrium
– Hardy-Weinberg law
– In H-W equilibrium, does not occur

10. Adaptations
 Canarise in response to environmental
pressures
– Temperature
– Antibiotic resistance in bacteria
– Pesticide resistance
– Morphological changes in peppered moths

11. How are new species created?
 Geographic isolation
 Reproductive barriers
 Change in chromosome numbers
 Adaptive radiation