Charles Darwin and Natural Charles Darwin and Natural SelectionSelection

Objectives:Objectives:

1)1) To explain Darwin’s theories of evolution To explain Darwin’s theories of evolution by natural selectionby natural selection

2)2) To discuss descent with modificationTo discuss descent with modification

I. Darwin’s Ideas Influenced by:I. Darwin’s Ideas Influenced by:

A. Lamarck’s Theory of EvolutionA. Lamarck’s Theory of Evolution

B. Voyage on the Beagle (1831-1836)B. Voyage on the Beagle (1831-1836)

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 TIME was very important to Darwin’s theoryDarwin’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, EconomistD. Thomas Malthus, Economist

1. Human population is increasing; 1. Human population is increasing; competition for food, water, spacecompetition for food, water, space

2. War, famine and disease prevents this2. War, famine and disease prevents this

E. Artificial SelectionE. Artificial Selection

1. Breeders select best traits to 1. Breeders select best traits to produce next generationproduce 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 ModificationIII. Descent with Modification

A. Over time, natural selection produces A. Over time, natural selection produces organisms with different structuresorganisms with different structures

B. Today’s species look different from their B. Today’s species look different from their ancestorsancestors

C. Each species descended with changes C. Each species descended with changes over timeover time

1965 1975

1985 1995

2005

FORD MUSTANG

Descent with ModificationDescent with Modification

D. Implies that all living things are related to D. Implies that all living things are related to one anotherone another

E. COMMON ANCESTORE. COMMON ANCESTOR