1. Chapter 16: Darwin’s Theory
of Evolution

2. 16-1 Darwin’s Voyage of Discovery
1831, Darwin set sail on HMS Beagle
Ship’s naturalist -observer/collector of plants, animals, & fossils
Left from England, sailed around South America, across Pacific, around Africa, and back to England
Most famous for observations made at Galapagos Islands
Biological evolution – change of populations of organisms over time

3. 16-1 Darwin’s Voyage of Discovery
Darwin noted 3 patterns of biodiversity:
Species vary globally – different, yet ecologically similar animal species inhabited separate, but ecologically similar, habitats around the globe (rheas, ostriches and emus)
Species vary locally – different, yet related animal species occupied different habitats within a local area (tortoise shell shape - Galapagos)
Species vary over time – fossils of extinct animals were similar to living species

4. 16-1 Darwin’s Voyage of Discovery
Darwin noted 3 patterns of biodiversity:
Species vary globally – different, yet ecologically similar animal species inhabited separate, but ecologically similar, habitats around the globe (rheas, ostriches and emus)

5. 16-1 Darwin’s Voyage of Discovery
Darwin noted 3 patterns of biodiversity:
Species vary locally – different, yet related animal species occupied different habitats within a local area (tortoise shell shape - Galapagos)

6. 16-1 Darwin’s Voyage of Discovery
Darwin noted 3 patterns of biodiversity:
Species vary over time – fossils of extinct animals were similar to living species

7. 16-2 Ideas That Shaped Darwin’s Thinking
Darwin was influenced by:
James Hutton - proposed that layers of rock form very slowly
Some rocks move up, while others are buried to create mountains and valleys.
Natural forces such as rain and temperature shaped the landscape
These processes happen very slowly over millions of years

8. 16-2 Ideas That Shaped Darwin’s Thinking
Charles Lyell – said earth was several million years old
Earth changed over time due to geologic forces (volcanoes, earthquakes, wind, erosion, etc.)
Darwin reasoned that if Earth changed, those who lived on it would have to adapt/change to survive.

9. 16-2 Ideas That Shaped Darwin’s Thinking
Jean-Baptiste de Lamarck suggested that organisms acquired traits during their lifetime to adapt to their environment and passed those acquired traits onto their offspring.
WRONG – only traits found on genes can be passed onto offspring!!

12. 16-2 Ideas That Shaped Darwin’s Thinking
Thomas Malthus – an economist that said the human population was limited by the supply of food and living space.
Darwin reasoned that the same limits could apply to organisms in nature.

13. 16-2 Ideas That Shaped Darwin’s Thinking
Natural Variation – differences among individuals of a species.
Farmers depend on natural variation for selective breeding
Only the largest hogs would be bred.
Artificial Selection – humans selected the variations that they find useful.

14. 16-3 Darwin Presents His Case
Darwin published his findings in 1859 in a book entitled The Origin of Species by Means of Natural Selection.
He was motivated to publish his book in 1859 because Alfred Wallace had independently come up with the same conclusions

15. Adaptations vs. Variations
16-3 Darwin Presents His Case
Adaptations vs. Variations
Variations – differences that exist within a population that may have no effect on fitness
Ex: length of your thumb
Adaptations – a variation that all members of a population have inherited because that trait improves fitness
Ex: an opposable thumbs

16. 16-3 Darwin Presents His Case
Sources of variation:
Mutations – individual genes change
Ex: ATC  AGC
Events during meiosis – during meiosis, chromosomes get mixed up (crossing over) in making eggs & sperm
Random fusion of gametes – which sperm fertilizes which egg – determined by chance

17. 16-3 Darwin Presents His Case
Three types of adaptations:
Structural – physical features of an organism
Ex: long tongue to get food, sharp teeth
Camouflage
Behavioral – actions an organism takes
Ex: migration, tracking prey, storing nuts, growing towards light
Physiological – functioning/biochemical processes
Ex: venom, ink of octopus, protein in web, respiration rate, digestive enzyme, blood clotting

18. 16-3 Darwin Presents His Case
Populations become modified through natural selection
Natural selection - the process by which environment acts on a population, determining which organisms are most “fit.” Those organisms who are most “fit” survive and reproduce more often than those who are not.
Fitness – reproductive success (“survival of the fittest”)

19. 16-3 Darwin Presents His Case
Darwin noticed similarities between species seen on mainland and island chains
Thought similarities could be explained by descent with modification – species came to new environment, then changed over time as the species adapted to its new environment.

20. 16.4 Evidence of Evolution Fossils Anatomy Analogous structures
Homologous structures
Vestigial structures
Embryology
Biochemistry
Direct observation

21. 16.4 Evidence of Evolution Fossil Evidence
Fossils - the remains of past life
Ex: shells, bones, teeth, imprints
Tell us age, habitat, diet, & lifestyle of organisms.
Record is incomplete – many organisms leave no fossils behind

22. Bones of vertebrate forelimbs
16.4 Evidence of Evolution
Anatomical Evidence – Homologous Structures
All vertebrate forelimbs contain the same sets of bones –suggests they evolved from a common ancestor.
Homologous structures - structures that are similar because they develop from same tissues early in development; may or may not have same jobs
Ex: frog, lizard, bird, whale, cat, bat, and human forelimbs
Bones of vertebrate forelimbs

24. Anatomical Evidence – Analogous Structures
16.4 Evidence of Evolution
Anatomical Evidence – Analogous Structures
Analogous structures - used for the same purpose but are not due to a common ancestor
Ex: bird wing & insect wing

25. Cormorant – flightless bird
16.4 Evidence of Evolution
Vestigial structures – have no function in the living organism but may have been used by its ancestors.
Ex: human appendix, python leg bones
Cormorant – flightless bird

26. 16.4 Evidence of Evolution
Embryology – the more similar the embryos are at certain stages of development, the more closely related they are thought to be.

27. 16.4 Evidence of Evolution Biochemical Evidence
Biochemical Evidence
Universal genetic code – organisms use the same triplet code and the same 20 amino acids in proteins
All organisms have certain organic molecules in common.
1.Hemoglobin - carries oxygen in blood
2. Cytochrome c - protein for cell respiration found in almost all living cells
3. Hox genes – control development

28. Significance of biochemical differences

29. 16.4 Evidence of Evolution
Direct observation – We’ve seen evolution occur in cases like:
The Grant’s studies of finches on Daphne Major in the Galapagos
Bacteria becoming resistant to antibiotics
Insects that become resistant to pesticides