Evolution Essential ?s• How & why have species changed with time?

• What is the benefit & value of evolution?

• How can the theory of evolution be applied to today?

• What evidence & thought have contributed to the theory of evolution?

Evolution Change in genetic make-up over

time Process by which modern

organisms have descended from ancient organisms

The History of the Development of Evolutionary

Thought

1st HypothesisUse & Disuse

Jean – Baptiste Lamark

1809

French naturalist

• Tendency Towards Perfection & Complexity• organisms continually change to become better

adapted to their environment & improve survival

• Use & Disuse of Organs • structure that are used frequently will become

larger and be more developed during a lifetime

• structures not used will become weaker or disappear (vestigial organs) during a lifetime

• Inheritance of Acquired Traits• newly acquired traits can be passed on to offspring

Evaluation of Lamark’s Theory• Incorrect because…..

• acquired traits (those gained during an organisms

lifetime) are NOT inherited

• acquired behaviors CANNOT develop heritable characteristics

• Correct because….• organisms adapt to their environment overtime to

increase survival

2nd HypothesisNatural

SelectionCharles Darwin

1831

Voyage on the H.M.S. Beagle The Trip around the World

• Observed many various organisms

• Researched their patterns of diversity

• Studied living organisms & fossils

• Concluded that the earth is constantly changing

The Galapagos Islands• Most influential location to Darwin’s

development of the theory of evolution• 13 small islands off the

West coast of South America by Ecuador

• Close proximity• Extremely diverse

climates & environments• Isolated from each other

• Organisms on each island vary greatly in characteristics to be specialized & better adapted to their diverse environments

Darwin’s Theory of Evolution

Published in 1931 “The Origin of Species”

Natural Selection • Organisms varying in inheritable characteristics(mechanics of genetics was unknown at this time!)

• Large population size causes competition for resources & restricts survival rate

Natural Selection

• Organisms with traits that are better “fitted” or adapted to their environment survive and reproduce more successfully passing on their superior genes to the next generation

• Fitness • resulting adaptations that

increase the survival of an organism

• Adaptations • any inherited

characteristic that increases an organism’s survival

“Survival of the Fittest”

Descents with Modification• Over many successive generations:

• pressures of natural selection • change traits of a population • increase overall fitness of the population

• Species evolve:• differences in structures & niches • resulting in the formation of a new species • remaining related to each other by a

common ancestor

3 Types of Natural Selection

Stabilizing Natural Selection• Nature eliminates both extreme traits

• Nature favors average traits

• Graph narrows increasing the number of species with the average trait

Directional Natural Selection• Nature eliminates only 1 extreme trait • The other extreme trait is favored • Graph & population diversity shifts toward

favored trait

Distributive Natural Selection• Nature eliminates the average trait & favors

the extreme traits

• Graph & population diversity shifts towards the 2 extreme traits

• Possibly leading to creating2 new species

Finches of the Galapagos IslandsDarwin’s most famous discoveries came from his observations on the variations of finch species on

the Galapagos Islands

which had extremely diverse and extensive gene pools, supporting his theory of evolution

• All of the Finches from the Galapagos Island evolved from the same founder species

• The Finches were separated to different islands over several years

• On each island they experience different natural pressures

• Finches on each island developed variations to make them better adapted to their different environments of each island

• Eventually the Finches became specialized and different from each other becoming separate & new species on each island

Finch’s of the Galapagos Islands