1. Evolutionary Patterns Chapter 23

2. PHYLOGENY 23.1 A phylogenetic tree is a reasoned hypothesis of the evolutionary relationships of organisms. Phylogeny: history of descent with branching/modification and the accumulation of change over time Node: represents the common ancestor from which the descendent species divergent; can be rotated without changing evolutionary relationships

3. PHYLOGENY OF VERTEBRATES The order of branches indicates the sequence of events in time

4. SISTER GROUPS Sister groups: 2 groups that share a common ancestor not shared by any other group

5. MONOPHYLETIC, PARAPHYLETIC, AND POLYPHYLETIC GROUPS Only monophyletic groups reflect evolutionary relationships Only they include all descendents of a common ancestor

6. CLASSIFICATION Taxonomic classification: Domain (most general) Kingdom Phylum Class Order Family Genus Species (most specific; called binomial nomenclature) 3 Domains (Superkingdoms) of life: Eukarya, Bacteria, Archae

7. HOMOLOGOUS AND ANALOGOUS FEATURES 23.2 A phylogenetic tree is built on the basis of shared derived characters. Shared derived characters: Anatomical Physiological Molecular features that are in common Homologies: similarities based on shared common ancestor Analogies: similarities based on independent adaptations

8. HOMOLOGOUS VS ANALOGOUS Homologies: similarities based on shared common ancestor Analogies: similarities based on independent adaptations

9.  Fish and dolphins have many traits in common, including a stream-lined body and fins. Are these traits homologous or analogous? QUICK CHECK

10.  The traits are analogous, the result of convergent evolution.  Both animals are adapted for swimming in water and converged independently of their traits.  However, they are only distantly related, as one is a fish and the other is a mammal. ANSWER

11. SYNAPOMORPHIES Synapomorphies: are shared derived characters Useful in constructing phylogenetic tree because the homology is shared by some, but not all, of the members of the group. Cladistics: phylogenetic reconstruction based on synapomorphies

12. CONSTRUCTION OF A TREE

13. DETERMINING THE BEST FIT

14. USING MOLECULAR DATA TO BUILD PHYLOGENETIC TREES

15. PRACTICAL USES OF PHYLOGENETIC TREES

16. 23.3 The fossil record provides a direct glimpse of evolutionary history  Paleontology: The branch of biology that reconstructs evolutionary history by collecting and evaluating fossils  Fossils: preserved remains or impressions left by organisms from the past 1.Allow us to calibrate phylogenies in terms of time 2.Provides a record of extinct species 3.Places evolutionary events in context with Earth’s history PALEONTOLOGY

17. FOSSILS Fossils only preserve the mineral-rich hard parts of an organism

18. FORMATION OF THE FOSSIL RECORD

19. TRACE/MOLECULAR FOSSILS 1.Tracks and trails 2.Molecular fossils: DNA, proteins, lipids

20. BURGESS SHALE Preserved the deep seafloor of 505 mya

21. MESSEL SHALE

22. GEOLOGIC TIMESCALE Relative dating: The order in which fossils appear in strata (layers) of sedimentary rock indicates relative age of fossil Lower fossils: older Higher fossils: more recent Compare to index fossil…shells of marine organisms

23. RADIOACTIVE DECAY Absolute dating: Uses radioactive isotopes to give the age of fossil, with <10% error, in wood and bones Compare half-life of isotope in living organism to ratio of same isotopes in fossil Half-life: number of years for half (50%) of the original sample to decay

24.  Grouped into 3 eons, 3 eras, then periods, then epochs  The 1 st two eons (the oldest) lasted about 4 billion years and is referred to as the Precambrian eon…….the age of ancient life  Origin of Earth: 4.6 bya  First prokaryotic cell: 3.5 bya (fossils)  Origin of eukaryotes: about 2 bya GEOLOGICAL TIME SCALE

25.  Phanerozoic eon: last 500 million years  Most of the time that multicellular eukaryotes have existed  Divided into 3 eras  Paleozoic era: age of ancient eukaryotic life  Cambrian period: 544-505 mya; Cambrian explosion= sudden increase in diversity of many animal phyla  Permian period: 286-245 mya; Permian extinction= mass extinction of many marine and terrestrial organisms  Mesozoic era: age of reptiles  Jurassic period: dinosaurs abundant/diverse; NOTE: dinosaurs existed for 200 million years!  Cretaceous period: 144-65 mya; Cretaceous extinction= many groups of organisms became extinct, including dinosaurs PHANEROZOIC EON

26.  Cenozoic era: age of mammals (newest era)  Paleocene epoch: 65-54 mya; mammals flourished  Pliocene epoch: 5-1.8 mya; ape-like ancestors of humans appear; Australopithicus africanus  Pleistocene epoch: 1.8 million -10,000 years ago; Ice ages; human- like hominids appear; Homo erectus. Homo Neanderthal  Holocene epoch: 10,000 years to present age; age of Homo sapiens PHANEROZOIC EON (CONTINUED)

27.  Biogeography: Geographical distribution of species  Continental drift: drifting of continents  Results from movement of plates of crust/upper mantle that float on Earth’s molten core  Called “plate tectonics”  Where 2 plates meet, many important geological phenomena occur; i.e. earthquakes, volcanoes BIOGEOGRAPHY

28. PANGAEA Formation of Pangea……”all land” Occurred at end of Paleozoic era (250 mya) Supercontinent Had tremendous environmental impact…..possibly Permian extinction?

29. BREAKUP OF PANGEA Occurred during Mesozoic era (180 mya) Pangea broke into northern (Laurasia) and southern (Gondwana) land masses About 65 mya S. America split from Africa; India moved north; Australia split from Antarctica; Laurasia split into N. America and Eurasia The final split occurred in the Cenozoic era between North America and Eurasia, which led to present distribution of continents

30. DINOSAUR AND BIRD PHYLOGENY Archeopteryx is a fossil organism that demonstrates the bird-dinosaur transition.

31. FISH TO TETRAPOD VERTEBRATES Tiktaalik is a fossil organism that demonstrates the fish-tetrapod transition.

32. MASS EXTINCTIONS  The history of life is characterized by rare mass extinctions.  There have been 5 major mass extinctions over the past 500 my, including: Permian Extinction: 250 mya Eliminated >90% marine life Cretaceous Extinction: 65 mya Dinosaurs became extinct Impact Hypothesis: an asteroid or comet struck Earth while extinction was already in progess

33. PHYLOGENY AND FOSSILS TOGETHER 23.4 Phylogeny and fossils provide independent and corroborating evidence of evolution.

34.  Biogeography  Geographic distribution of species  First suggested common descent to Darwin  Different geographic regions, different mammalian “brand  Fossil Record  Shows that prokaryotes are ancestors of ALL life  Fish…amphibians….reptiles….birds…..mammals  Have found transitional fossils linking past and present  Comparative Anatomy  Homologous structures….likeness due to common ancestry  The higher the amount of homology, the more closely related the species  i.e. forelimbs of mammals  i.e. humans and chimps share 98% of same genome EVIDENCE OF EVOLUTION

35.  Vestigial Structures: remnants of features that served important functions in organism’s ancestors  i.e. skeletons of some snakes show vestiges of pelvis/leg bones of walking ancestors  Comparative Embryology  May see anatomical homologies nor visible in adult organisms  i.e. ALL vertebrate embryos have a post-anal tail  Molecular Data  Shows similarity of DNA and proteins between closely related species  i.e. all organisms use same genetic code EVIDENCE OF EVOLUTION (CONTINUED)