Correction of Evolution Misconception…

Evolution = humans came from monkeys

Evolution really means…

• CHANGE OVER TIME! • Think about it…– Over 4.6 Billion years there have been LOTS of

changes– Life as we know it has survived despite many

obstacles– How? • Life ADAPTS to survive!

“Evolve” Means to Change Over Time • The belief that life on Earth has changed over time is

quite old

• To be considered science, this belief requires a great deal of evidence

The Development of Evolutionary Theory Naturalists have always wondered at the diversity of

living things………• Great varieties in shape, size, and ecological role• Estimated 3 million to 20 million different living species• Much of the natural world’s biodiversity has vanished

through extinction99% of all species that ever lived are now extinct.

Development of Evolutionary Theory

What could cause such great diversity, and why have so many species died out?

Charles Darwin offered an explanation based on careful observations.

Development of Evolutionary TheoryDarwin Concluded:• Physical traits and behaviors enable organisms to

survive and reproduce (called Fitness )• Fitness results from adaptations• Darwin reasoned that adaptations result from

natural selection and result in evolution

Evolution is the process by which living things change and diversify over time

Development of Evolutionary Theory• These ideas were widely challenged until a

tremendous amount of evidence was gathered to support evolution!

• Now…The Theory of Evolution is the Cornerstone of Biology

• Explore the Evolution Revolution

Anatomy and Comparative Anatomy• Vestigial Organs– Organs inherited but not used by modern

organisms– Present but greatly reduced in modern

organisms– Hip bone in python– Appendix in human– Tail bone (cocyx) in human

Anatomy: Homologous Structures• Similar parts of different organisms, often

quite dissimilar in purpose, that developed from the same ancestral body parts.

• Divergent evolution

Anatomy: Analogous Structures• Similar in purpose, but not inherited from a

recent common ancestor• Environment selected for trait– Wings of birds and insects

• Convergent evolution

Natural Selection and Speciation

Charles Darwin

• Studied Medicine and Theology• Excelled in Geology and Biology• In 1831 Darwin joined the H.M.S. Beagle on

a trip around the world to make maps• He was the ship’s naturalist.

The Voyage of the Beagle: Ports of Call

Noted that populations of organisms were slightly different from place to place

Each group was modified to their specific environment

The Galapagos Archipelago

Land Iguana

Marine Iguana

Evolution Through Natural Selection• There is variation in populations caused by genetics • Many more offspring are produced than can survive.

Many die through predation or starvation.• Some variations are favorable and help organisms

compete to survive and reproduce.• Over time, the organisms with favorable variations

become plentiful. The ones without favorable variations become rare or extinct.

Speciation

• Natural Selection modifies populations. Some evolutionary changes are so great that some organisms can no longer interbreed with the original population

• A new species results.• Species– An interbreeding population of organisms that can

produce healthy, fertile offspring