1. Descent with modification
Evolution
Descent with modification

3. I. Biological Evolution = observable fact
A. Change in species over time
B. Change in gene frequencies from generation to generation
C. A Process of change

4. II. Proposed Mechanism for evolution
A. Natural Selection – Requires
1. Genetic diversity
2. some genes increase fitness
3. best genes get passed on more often

5. III. Pre-Darwin Ideas A. Fossil Evidence– 1. rock laid down in layers
2. oldest at bottom
3. fossils in layers show when organisms lived:
order of appearance
4. Older fossils less similar to modern
5. species appear and disappear

6. B. Lamarck ( )
1. one of many to propose that life evolves as environments change
2. first to propose mechanism
3. compared fossils showing lines of descent
a. Change caused by use or disuse(not genes)
b. inheritance of acquired traits
c. striving to become ‘ideal’

7. IV. Darwin’s Contemporaries
A. Charles Lyell ( 1797 – 1875)
1. Geologist
2. Theory of Uniformity
3. Natural processes observed today are the same as processes acting in the past
4. The rate of processes today mirror those of the past
5. contradicted young earth theory

8. B. Alfred Wallace ( )
1. first to publish Natural Selection as a mechanism for evolution
2. ideas nearly identical to Darwin’s
C. Charles Darwin ( 1809 – 1882)
1. Origin of Species
2. extensive evidence of
natural selection
3. Lylle, Darwin & Wallace
convinced most scientists with in 10 years

9. Origin of Species Three Main Ideas
1) Unity of Life: shared characteristics come from common ancestor
2) Diversity of Life: due to natural selection
3) Match between organisms and environments: due to adaptation

10. IV. Darwin’s main observations/Inferences
Observations in blue
Followed by associated Inference
Inferences in yellow

11. A. Artificial selection: selective breeding
can produce visible change over a life-time
A. If artificial selection can produce rapid change….then natural selection could produce dramatic change given enough time
* Lyell suggested a time line of millions of years

12. B. Organisms produce more offspring than can survive
B. Some survive some do not

13. C. members of a population vary in Inherited
traits
C. If only some organisms survive then
the best fit more likely to survive
So good genes accumulate in population…
Genetic make-up of population ∆ over time =
Evolution!

14. VII. Theory of Evolution
A. speciation – one species branches into 2 new species
B. Adaptive radiation –1 species gives rise to many species (common after mass extinctions)
1. individuals spread out to new environments
2. adapting to new environment causes them to change

15. C. Universal Common Ancestor – all started from some single celled organisms
1. ‘the unity of life’
2. same DNA, RNA
3. shared genes
4. Semiconservative replication
5. transcription/translation (Met)

16. VIII. Main Branches of Evidence
A. Direct observation – species change over time
1. Bacteria develop antibiotic resistance

18. 2. Weeds develop resistance to roundup
Figure 1. Number of weed species with glyphosate resistant populations and number of states with glyphosate-resistant weed populations.
Source: Heap, 2009.

19. 3. Grant’s finch research
a. recorded beak depth of all finches on an island over 30 years

20. B. Homology: similarities resulting from
common ancestor
1. Homologous Structures
a. anatomical features
b. same underlying structure
c. may have adapted to different function

21. d. embryo homology may be lost in adult
1. gill slits– all vertebrates
2. tail – all vertebrates

22. e. Vertebrate limbs : same bones just different shape due to different function of appendage

23. 2. Vestigial Structures : inherited from ancestor but no longer used
a. explains presence of useless structures
b. pelvic girdle & femur in whale & snake

24. 3. molecular homologies: same DNA/ protein
a. all organisms homologous DNA structure
b. Many homologous DNA genes
1. some have developed a new function
2. some still same function
3. some genes vestigial

25. C. Fossil Record
A. document formation of new species by sequential fossils