Chapter 16: Darwin’s Theory of Evolution

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. 16-2 Ideas That Shaped Darwin’s Thinking 0 • 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!!

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5. 16-3 Darwin Presents His Case 0 • 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

6. 16-3 Darwin Presents His Case 0 • 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”)

7. 16-3 Darwin Presents His Case 0 • 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.

8. 16.4 Evidence of Evolution • Fossils • Anatomy • Analogous structures • Homologous structures • Vestigial structures • Embryology • Biochemistry • Direct observation

9. 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

10. 16.4 Evidence of Evolution 0 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

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12. 16.4 Evidence of Evolution 0 Anatomical Evidence – Analogous Structures • Analogous structures - used for the same purpose but are not due to a common ancestor • Ex: bird wing & insect wing

13. 16.4 Evidence of Evolution 0 • 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

14. 16.4 Evidence of Evolution 0 • Embryology – the more similar the embryos are at certain stages of development, the more closely related they are thought to be.

15. 16.4 Evidence of Evolution 0 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

16. 0 Significance of biochemical differences

17. 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