2. 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!
3.
4. “Evolve” Means Earth has changed over time is
to Change Over Time
• The belief that life on
quite old
• To be considered science, this belief requires a great
deal of evidence
5. 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 extinction
99% of all species that ever lived are now extinct.
6. 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.
7. Development of Evolutionary Theory
Darwin 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
8. 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
9. 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
10. Anatomy: Homologous Structures
• Similar parts of different organisms, often
quite dissimilar in purpose, that developed
from the same ancestral body parts.
• Divergent evolution
11. 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
13. 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.
14. 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
21. 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.
22. 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
