1. DARWIN’S THEORY
SC B-5: THE STUDENT WILL DEMONSTRATE UNDERSTANDING OF BIOLOGICAL EVOLUTION & THE DIVERSITY OF LIFE

2. Inquiry Activity Page 368 in book Page 35 in notebook work in pairs
When you have calculated your average length put it on board so class average can be calculated
Also record length of your shortest bean and longest bean: What is the range of the bean length?

3. CN: PAGE 112 NOTEBOOK
TOPIC: Darwin’s theory of Evolution
EQ: What inferences did Darwin make about Natural Selection from his observations?

4. DEFINITIONS
EVOLUTION: process by which modern organisms have descended from ancient organisms
THEORY: well-tested explanation that unifies a broad range of observations

5. Charles Darwin Englishman born in 1809
After graduating in 1831 from University took job as a naturalist on H.M.S. Beagle & traveled around the world

6. Darwin’s Voyage

7. Darwin
During his travels, Darwin made numerous observations & collected evidence that led him to propose a revolutionary hypothesis about the way life changes over time.

8. Darwin’s Observations
Plants & animals remarkably well-suited to their surroundings
Different organisms lived in same type of ecosystem Example: grasslands of Europe + rabbits but grasslands in Australia - rabbits

9. Fossils: preserved remains or evidence of an ancient organism

10. Darwin studied fossils from different continents & noted that some resembled organisms still living & some unlike any creature he had ever seen

11. Galapagos Islands Small group of islands off Ecuador
Climates varied from hot & dry to rain forest
Each had different flora & fauna

12. Galapagos Animals

14. Darwin’s Hypothesis
Darwin noticed that characteristics of many animals & plants varied noticeably among different islands and hypothesized that they had a common ancestor

15. Contemporary Ideas that shaped Darwin’s Ideas
1785: James Hutton 1st to present idea that Earth is much older than Bible would indicate
Looked at layers of sedimentary rock with fossils of sea creatures now on mountain top
Looked at geological processes that shape Earth
Reasoned that processes seen today same in past

16. Origins of Evolutionary Thought
Malthus: 1798
Predicted human population will grow faster than the space & food supplies needed to sustain it

17. Origins of Evolutionary Thought
Lamark: 1809
proposed hypothesis of inheritance of acquired traits:
if parent became very accurate with bow & arrow after years of practice  any child born after would also be very accurate with bow & arrow

18. Lyell: wrote Principles of Geology (Darwin read 1st vol
Lyell: wrote Principles of Geology (Darwin read 1st vol. while on the Beagle)
Said must explain past events in terms of processes observed now
Lyell’s work influenced Darwin 2 ways:
1. He asked himself: If Earth can change over time why not living organisms?
2. He realized it would take very long time for change to be obvious

19. Origins of Evolutionary Thoughts
Wallace: 1858
Naturalist working in Malaysia
wrote Darwin speculating on mechanism of evolution by natural selection  induced Darwin to publish Origin of the Species in 1859

21. The Origin of the Species
Darwin returned to England in 1836 and reviewed his observations & notes but did not publish his book for 25 yrs
Darwin proposed a mechanism for evolution that he called: natural selection

22. Artificial Selection
One of Darwin’s most important insights was that members of each species vary from one another in important ways.
Darwin argued that these small variations were very important using breeders as example

23. Artificial Selection
Humans choose the natural variations in a species that they found useful and used selective breeding to enhance the traits desired.

24. Evolution by Natural Selection
Struggle for Existence: members of each species compete for available food, living space, mates
Predators that are faster, better nourished, survive longer, more likely to reproduce more thus passing on those traits that made them faster
Prey that are slightly better at camouflage less likely to be eaten, more likely to reproduce

25. Survival of the Fittest
Darwin reasoned that a key factor in struggle for existence was how well-suited an individual is to its environment
Fitness: the ability of an individual to survive & reproduce in its specific environment

26. Adaptations
Adaptation: any inherited characteristic that increase’s an organisms chances of survival
Can be:
Anatomical (structure of organism)
Physiological (function of organism)
Behavioral

27. Adaptations

28. Survival of the Fittest
Darwin referred to survival of the fittest as natural selection
Over time the variants in traits that offer an advantage will have increasing incidence in population

29. Descent with Modification
Term used by Darwin to explain why species today look different from their ancestors:
A successful species will just reproduce, always with some variation in traits until a new stressor appears which will give an advantage to some variations and a disadvantage to others
Variations that give advantage will then become more prevalent in population; others will decrease in #’s

30. Common Descent
Descent with modification implies all living things have a common ancestor

31. Evidence of Evolution: 4 sources
1. Fossil Record
2. Distribution of Species
Dating & comparing fossil shows progression of species over long periods of time
Many species have disappeared
Continental Drift helps explain why similar organisms on different continents

32. Continental Drift

33. 3. Homologous Structures
Evidence of Evolution
3. Homologous Structures
Darwin noticed striking similarities in vertebrates (also seen in plants & algae)
Vestigial Structures: homologous structure that have been reduced in size, no longer serve a purpose (appendix)

34. Evidence of Evolution
4. Embryology
Many vertebrate embryos go through stage where they look very similar to another species

35. Summary of Darwin’s Theory
1. individual organisms differ & some of this variation is inheritable.
2. organisms produce more offspring than can survive & many that do survive don’t reproduce
3. because there are more organisms than can survive they must compete for limited resources
4. individuals best suited to their environment will survive & reproduce passing their successful traits on (causes species to change over time)
5. species today all descended from common ancestors

36. Darwin’s Theory Strengths Weaknesses
Most of Darwin’s hypotheses have been confirmed
Is considered by many to be the “grand unifying theory of life sciences”
Still does not explain how life began
New information always coming to light: theories change over time