1. AP Biology 2/28/13 Chp.25 ~ Phylogeny & Systematics (& Chp.26~Review the Origin of Life, Dating Fossils)

2. Phylogeny: the evolutionary history of a species Systematics: ◦the study of biological diversity in an evolutionary context The fossil record: ◦The ordered arrangement of fossils (generally within strata of sedimentary rock)

3. The fossil record Sedimentary rock: rock formed from sand and mud that once settled on the bottom of seas, lakes, and marshes Dating: Relative~ geologic time scale; sequence of species Absolute~ radiometric dating; age using half-lives of radioactive isotopes

4. Review: The Origin of Life Early earth atmosphere ◦CO 2, CH 4, NH 4 ◦Very little oxygen ◦Water ◦Lightning

5. Miller-Urey Experiment (1953) Simulated early earth conditions and added electricity (“lightning”) Successfully created organic compounds (amino acids)

6. RNA World Hypothesis It is believed that RNA was present before DNA ◦RNA can replicate itself ◦RNA can catalyze reactions ◦Therefore, RNA could have existed as an early form of life before DNA After RNA was present, any organisms who developed the ability to use DNA and proteins would have been selected for, since they are superior to RNA

7. The First Cells The first cells were probably ◦Prokaryotic ◦Primary heterotrophs (eat their food) OR ◦Maybe simple autotrophs (make their own food) By the time of the first cell, there would have been many organic compounds in the environment for the cells to “eat”

9. Biogeography: the study of the past and present distribution of species Pangaea-250 mya Geographic isolation-180 mya

10. Extinctions Extinctions are always occurring at a low rate (background rate) Occasionally, mass extinction events will happen when many more species will go extinct than normally Example: ◦Permian ( 250 million years ago):  90% of marine animals; Pangaea merge ***Human Impact on Ecosystems & Species Extinction Rates***

11. Mass extinction Cretaceous (65 million years ago): death of dinosaurs, 50% of marine species; low angle comet (maybe?) (maybe?)

14. Phylogenetics The tracing of evolutionary relationships (phylogenetic tree) Use Linnaean Classification Binomial nomenclature ◦Homo sapiens

15. Phylogenetic Trees Cladistic Analysis: taxonomic approach that classifies organisms according to the order in time at which branches arise along a phylogenetic tree (cladogram) Clade: each evolutionary branch in a cladogram

16. 0 = character is absent 1 = character is present Analyzing the distribution of these derived characters can provide insight into vertebrae phylogeny

17. Phylogenies Types: 1. Monophyletic: single ancestor that gives rise to all species in that taxon and to no species in any other taxon; legitimate cladogram 2. Polyphyletic: members of a taxa are derived from 2 or more ancestral forms not common to all members; does not meet cladistic criterion 3. Paraphyletic: lacks some descendants of the common ancestor; does not meet cladistic criterion

19. Constructing a Cladogram Sorting homology vs. analogy... Homology: ◦likenesses attributed to common ancestry ◦(shared ancestry) Analogy: ◦likenesses attributed to similar ecological roles and natural selection (convergent evolution)

20. Convergent Evolution Convergent evolution: ◦species from different evolutionary branches that resemble one another due to similar ecological role  Does not show an evolutionary relationship When species develop similar adaptations because of similar environments ◦Dolphins and sharks ◦Flying insects and birds

21. Analogy – Convergent Evolution These structures are analogous, because they did not come from a common ancestor but were evolved separately

22. Patterns of Evolution Coevolution ◦Species evolve together because of some relationship  Predator/Prey or Parasite/Host: ◦ “Evolutionary arms race”  Symbiotic relationships ◦ Flowers (Plants ) and pollinators (insects, bats, birds)

23. Human Evolution Human Evolution Humans and chimpanzees last had a common ancestor about 6 million years ago The genus Homo evolved approximately 2 million years ago and included several species (although only Homo sapiens is still alive) species Anatomically modern human is approximately 200,000 years old

24. Human Traits (not exclusive to Homo sapiens) Bipedalism (walk upright) ◦“Lucy” – nearly complete skeleton of Australopithecus afarensis – 3 million years ago Large brain, good reasoning skills, tool- making (not exclusively human) Extended childhood Speech (hyoid bone)

25. According to this phylogeny, humans are most closely related to chimpanzees (Genus Pan). (split ~ 6 mya) The ancestor of gorillas branched off earlier in evolution (~8 mya). Pongo = Orangutan Hylobates = gibbons

30. Homo ergaster Ancestor or subspecies of H. erectus Lake Turkana, Kenya (“Turkana Boy”) discovered by Richard Leakey Used tools

31. Phylogenetic Trees/Cladograms Practice

32. Mass Extinctions