Today’s Topics

1. Today’s Topics • Early Earth’s History (Chapter 17) • Charles Darwin (Chapter 15) • Principles of Evolution (Chapter 16)

2. Chapter 17 – Earth’s Early History • 4.6 billion years old – molten lava • 500 mya – crust formed, patched with volcanos (expelled gases) • Atmosphere – due to gravitational field • H2O • CO2 • CO • HCN • N2 and H2 • Among others—no free oxygen! Water vapor Carbon dioxide Carbon monoxide Hydrogen cyanide Nitrogen and Hydrogen gas

3. Geological Time Scale • There are three eras: • Cenozonic (currently in) • Mesozoic (dinosaurs appear and disappear) • Paleozoic (beginning of body plans, gymnosperms) K-T Boundary – a layer of iridium (meteorite material) found between rock layers of the Cretaceous and Paleogene periods Important because scientist believe that this meteorite impact cause mass extinction (dinosaurs).

4. Fossils • Fossils are traces of past organisms. • Fossils must be 10,000 years old. • Biogeography - the branch of biology that deals with the geographical distribution of plants and animals.

5. Types of Fossils • Trace fossil • Molds and cast • Replacement • Petrified • Amber • Original material – preservation via mummification or freezing.

6. Steno • Nicolas Steno was the scientist that developed the law of superposition which states the oldest layer is the bottom and the newest is on the top. • Example of relative dating

7. Radiometric Dating • Decay of radioactive isotopes to measure the age of the rock. • Uses element’s half-life (time it takes for half of the element to decay) • Ratio of Uranium 238 to Lead 206 • Recent fossils (i.e. human remains) – Carbon 14

8. For now, Evolution can be defined by Darwin’s phrase descent with modification (see slide 21) Evolution can be viewed as both a pattern and a process Charles Darwin

9. Carolus Linnaeus - organismal adaptations as evidence that the Creator had designed each species for a particular purpose Father of taxonomy, the branch of biology concerned with classifying organisms He developed the binomial format for naming species (Homo sapiens)

10. Ideas About Change over Time • Fossils (Chapter 17)occur in layers called strata – oldest at the bottom • Cuvier – each boundary between strata represents a catastrophe that destroyed many species • Hutton (gradualism) – changes in Earth’s surface result from slow, continuous actions still operating today • Lyell (uniformitarianism) - changes in the earth's crust during geological history have resulted from the action of continuous and uniform processes. • Catastrophes included! • Malthus – studied how human populations have been maintained by war and disease

11. Figure 19.3 Younger stratum with more recent fossils Older stratum with older fossils

12. Lamarck’s Hypothesis of Evolution Lamarck hypothesized that species evolve through use and disuse of body parts and the inheritance of acquired characteristics No evidence!

13. Charles Darwin - The Voyage of the Beagle 5 year voyage Collected specimens of South American plants and animals He observed fossils resembled living species from the same region and living species resembled other species from nearby regions Famous stop at Galápagos Islands west of South America

14. Figure 19.5 Darwin in 1840, after his return from the voyage HMS Beagle at sea Great Britain EUROPE NORTH AMERICA ATLANTIC OCEAN The Galápagos Islands AFRICA PACIFIC OCEAN Pinta Genovesa Equator Malay Archipelago SOUTH AMERICA Marchena Equator PACIFIC OCEAN Santiago Daphne Islands Brazil Chile AUSTRALIA Pinzón Fernandina Andes Mtns. PACIFIC OCEAN Isabela Santa Cruz Santa Fe San Cristobal Argentina Cape of Good Hope Tasmania 0 40 20 Florenza Española Cape Horn New Zealand Kilometers

15. Darwin’s Focus on Adaptation Based on his observations, Darwin perceived adaptation to the environment and the origin of new species as closely related processes Darwin’s Finches – beaks adapted to specific diets A population is said to have adapted when it maintains the number of individuals with favorable traits

17. Figure 19.6 (a) Cactus-eater (c) Insect-eater (b) Seed-eater

18. In 1844, Darwin’s essay on natural selection: a process in which individuals with favorable inherited traits are more likely to survive and reproduce In June 1858, Darwin received a manuscript from colleague Wallace, who had developed a similar theory—prompted Darwin to publish!

19. Chapters 15 and 16 (ignore the rest of the numbers) 15.1 Darwin’s Theory of Natural Selection Darwin Continued His Studies • Darwin hypothesized that new species could appear gradually through small changes in ancestral species. • Got this idea from “artificial” selection (dog breeding)

20. Evolution Chapter 15 15.1 Darwin’s Theory of Natural Selection Four “mini” theories of Natural Selection • Individuals in a population show variations. • Variations can be inherited. • Organisms have more offspring than can survive on available resources. • Variations that increase reproductive success will have a greater chance of being passed on.

21. Evolution Chapter 15 15.2 Evidence of Evolution • Derived traits – newly evolved features, such as feathers, do not appear in the fossils of common ancestors. • Ancestral traits – primitive features, such as teeth and tails, do appear in ancestral forms. • Anatomically similar structures inherited from a common ancestor are called homologous structures. • Descent with Modification (Darwin)

22. Evolution Chapter 15 15.2 Evidence of Evolution • Analogous structures – not inherited from a common ancestor • Show that functionally similar features can evolve independently in similar environments

23. Will eventually be lost! Evolution Chapter 15 15.2 Evidence of Evolution Vestigial Structures • Structures that are the reduced forms of functional structures in other organisms.

24. Evolution Chapter 15 15.2 Evidence of Evolution Comparative Embryology • Vertebrate embryos exhibit homologous structures during certain phases of development, but become totally different structures in the adult forms.

25. Evolution Chapter 15 15.2 Evidence of Evolution Comparative Biochemistry • Common ancestry can be seen in the complex metabolic molecules that many different organisms share.

26. Evolution Chapter 15 15.2 Evidence of Evolution Geographic Distribution • The distribution of plants and animals that Darwin saw first suggested evolution to Darwin. • Mara is closely related to a rabbit, but lives in a different part of the world. Rabbit Mara

27. Evolution Chapter 15 15.2 Evidence of Evolution Types of Adaptation • An adaptation is a trait shaped by natural selection that increases an organism’s reproductive success. • Fitness is a measure of the relative contribution an individual trait makes to the next generation. Examples of increased fitness: • Camouflage • Mimicry

28. Evolution Chapter 15 15.3 Shaping Evolutionary Theory Mechanisms of Evolution • Population genetics • Hardy-Weinberg principle states that when allelic frequencies remain constant, a population is in genetic equilibrium.

29. Evolution Chapter 15 15.3 Shaping Evolutionary Theory • This equation allows us to determine the equilibrium frequency of each genotype in the population. • Homozygous dominant (p2) • Heterozygous (2pq) • Homozygous recessive (q2)

30. Evolution Chapter 15 15.3 Shaping Evolutionary Theory

31. Evolution Chapter 15 15.3 Shaping Evolutionary Theory Genetic Drift • A change in the allelic frequencies in a population that is due to chance • In smaller populations, the effects of genetic drift are much greater! • Founder Effect: Occurs when a small sample of a population settles in a location separated from the rest of the population

32. Evolution Chapter 15 15.3 Shaping Evolutionary Theory Bottleneck • Occurs when a population declines to a very low number and then rebounds

33. Evolution Chapter 15 15.3 Shaping Evolutionary Theory Gene Flow • Increases genetic variation within a population and reduces differences between populations Nonrandom Mating • Promotes inbreeding and could lead to a change in allelic proportions favoring individuals that are homozygous for particular traits

34. Evolution Chapter 15 15.3 Shaping Evolutionary Theory • Sexual selection operates in populations where males and females differ significantly in appearance.

35. Evolution Chapter 15 15.3 Shaping Evolutionary Theory Natural Selection • Acts to select the individuals that are best adapted for survival and reproduction • For polygenic traits, “typically” a bell-shaped curve (see dotted line)

36. Evolution Chapter 15 15.3 Shaping Evolutionary Theory • Stabilizing selectionoperates to eliminate extreme expressions of a traitwhen the average expression leads to higher fitness.

37. Evolution Chapter 15 15.3 Shaping Evolutionary Theory • Directional selectionmakes an organism more fit.

38. Evolution Chapter 15 15.3 Shaping Evolutionary Theory • Disruptive selectionis a process that splits a population into two groups. • Likely to form two species!

39. Evolution Chapter 15 15.3 Shaping Evolutionary Theory • Prezygotic isolationprevents reproduction by making fertilization unlikely. • Behavioral isolation (different mating songs) • Temporal isolation (not mating at the same time) • Mechanical isolation – see HW option D! Eastern meadowlark and Western meadowlark

40. Postzygotic isolationoccurs when fertilization has occurred but a hybrid offspring cannot develop or reproduce. Evolution Chapter 15 15.3 Shaping Evolutionary Theory • Prevents offspring survival or reproduction Liger

41. Can occur in a relatively short time when one species gives rise to many different species in response to the creation of new habitat or some other ecological opportunity Evolution Chapter 15 15.3 Shaping Evolutionary Theory Adaptive Radiation • Follows large-scale extinction events

42. Evolution Chapter 15 15.3 Shaping Evolutionary Theory Allopatric Speciation • A physical barrier divides one population into two or more populations. • Darwin’s finches being separated within the Galpagos Islands Kaibab squirrel Abert squirrel

43. Evolution Chapter 15 15.3 Shaping Evolutionary Theory Sympatric Speciation • A species evolves into a new species without a physical barrier. • Darwin’s finches competing over different types of food • The ancestor species and the new species live side by side during the speciation process.

44. Evolution Chapter 15 15.3 Shaping Evolutionary Theory Rate of Speciation • Evolution proceeds in small, gradual steps according to a theory called gradualism. • Applying these concepts back to those early theories! (Hutton) • Punctuated equilibrium explains rapid spurts of genetic change causing species to diverge quickly. • Lyell recognized this as part of uniformiarianism

45. Evolution Chapter 15 15.3 Shaping Evolutionary Theory

46. Things Mr. Koons wanted to circle back to… • Gene pool – all of the different genes for a particular trait in a population • Coevolution – two organisms evolving together (pollinating insect and its respective flower) • Endosymbiotic theory – eukaryotic cells arose from convergent evolution of two prokaryotes. *Pay attention to Amino Acid example on the Understanding Evolution Assessment!