1. What is gradualism and punctuated evolution?
Agenda
Theories of Evolution Notes
Theories coloring worksheet
Darwin’s postulates worksheet

2. History of the theory
The idea of evolution was common among scientists in the early 1800s
Georges Cuvier – fossils in lower strata are more dissimilar than present-day organisms
James Hutton – Gradualism: major changes in Earth’s geologic history due to slow and continuous processes
Charles Lyell – Uniformitarianism: those continuous processes are STILL working today

3. Jean Baptiste de Lamarck
Use and Disuse – the more you use something, the greater it becomes; the less you use something, the more it deteriorates
Organisms acquire traits and then pass these traits on to their offspring
Acquired trait – a trait that arises during the lifetime of an organism

4. Lamarck

6. Lamarck’s Influence Incorrect Not all traits acquired get passed on
Important
Introduced change over time
Realized organisms are changing

7. Charles Darwin Naturalist Traveled on the HMS Beagle (1831-1836)
South America, Galapagos Islands, Australia
Wrote The Origin of Species

9. Galapagos Islands small group of volcanic islands
no land mammals or amphibians
Back in England he looked at his findings
Tortoises and Finches

10. Tortoises
Similar BUT tortoises on different islands had different shell morphologies
Could tell which island a tortoise came from just by looking at its shell

11. Finches Finches – collected 13 similar but separate species of finches
Each had a distinct bill (beak)
Observed finches doing very "unfinch-like things"
e.g. one behaved like a hummingbird, another like a flycatcher, another like a woodpecker
Conclusion: an ancestral group of finches colonized the islands and then, colonizers gradually changed into the specialized finches that he saw
Implied shared common ancestor

13. People influenced Darwin
Charles Lyell
Malthus
left unchecked, populations can growth exponentially
since they don’t, they must be limited by war, disease, or limited resources
This led to Darwin’s idea that there’s a struggle for existence

14. Darwin’s Theories Descent with Modification
Man changed domestic species (dogs)
Over time and generations traits with reproductive advantage become more common
All species descended from one or a few original types of life

15. Darwin’s Theory
Natural selection – organisms best suited for their environment reproduce more successfully than other organisms
Over several generations organisms with favorable traits increase

16. Darwin’s Theory

17. Variation within a population
Traits are inherited/passed on

18. More offspring are produced than can survive
Surviving offspring will be favored by the environment - "natural selection“

19. Those organisms that survive have favorable variations (known as adaptations)
Over time, these favored variations will accumulate -- this is "descent with modification" or evolution

20. 2 types of Adaptations
Camouflage and mimicry

21. Modification by Natural Selection
An organism’s genetic contribution to the next generation is fitness
Greater fitness = better adapted to env’t = reproduces more successfully
Favorable traits give organisms an adaptive advantage
Environment “selects” traits
Favorable traits depend on demands of env’t

22. Summary of Darwin
Natural Selection – organisms best suited/best adapted to the environment survive and reproduce
Adaptations
the population is the unit of evolution
individuals do not evolve during their lifetimes

23. Theory of Evolution
Evolution – change in the inherited traits of a population of organisms over time
NOT new species arising from pre-existing species
Part but not all of evolution

24. Cheetahs are able to run faster than 60 miles per hour when chasing prey. How would a biologist explain how the ability to run fast evolved in cheetahs, assuming their ancestors could run only 20 mph?

25. A long time ago, some cheetahs were faster than the others
The cheetahs that could run faster were able to catch their prey and were better able to survive
The slow cheetahs died off, or weren’t able to reproduce as successfully
The cheetahs that survived were the ones that could run faster

26. How did the heavy coat in polar bears evolve if their ancestors had thinner coats?
1. A long time ago, some polar bears had thicker fur than others
2. The thicker coat was favorable
3. The polar bears with thin coats died off.
4. The ones with thicker coats survived and reproduced.

27. Peppered Moths