Charles Darwin and Natural Selection Objectives: 1) To explain Darwin’s theories of evolution by natural selection 2) To discuss descent with modification

I. Darwin’s Ideas Influenced by: A. Lamarck’s Theory of Evolution B. Voyage on the Beagle ( )

Lava lizard Swimming Lizard

Green Iguana – S. America Land Iguana - Galapagos Marine Iguana - Galapagos

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Influences on Darwin…

TIME was very important to Darwin’s theory C. Geologists James Hutton and Charles Lyell 1. Earth is much older than a few thousand years 2. Processes shaping Earth have occurred for millions of years

D. Thomas Malthus, Economist 1. Human population is increasing; competition for food, water, space 2. War, famine and disease prevents this

E. Artificial Selection 1. Breeders select best traits to produce next generation

II. Darwin’s Theory of Evolution by Natural Selection A. Over time, the number of individuals that carry advantageous traits will increase in a population B. Occurs in 4 steps…

Darwin’s Theory of Evolution by Natural Selection 1. Living things overproduce

Darwin’s Theory of Evolution by Natural Selection 2. There is variation among offspring

Darwin’s Theory of Evolution by Natural Selection 3. There is a struggle to survive

Darwin’s Theory of Evolution by Natural Selection 4. Those that survive are most fit

C. Natural Selection: “Survival of the Fittest” 1. Fitness = ability to survive and reproduce 2. Fitness is the result of adaptations – inherited characteristics that increase an organism’s chance of survival

Adaptation

III. Descent with Modification A. Over time, natural selection produces organisms with different structures B. Today’s species look different from their ancestors C. Each species descended with changes over time

FORD MUSTANG

Descent with Modification D. Implies that all living things are related to one another E. COMMON ANCESTOR