1. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. CHAPTER 26 LECTURE SLIDES

2. The Tree of Life Chapter 26

3. Origins of Life Cell is the basic unit of life Today all cells come from pre-existing cells The Earth formed as a hot mass of molten rock about 4.5 billion years ago (BYA) –As it cooled, chemically-rich oceans were formed from water condensation Life arose spontaneously –Ocean’s edge, hydrothermal deep-sea vents, or elsewhere 3

4. 4 Fundamental Properties of Life Cellular organization Sensitivity Growth Development Reproduction Regulation Homeostasis Heredity

5. Panspermia –Earth may have been “infected” with life from some other planet –Meteor or cosmic dust may have carried complex organic molecules to earth –Kicked off evolution of life Frozen water found on Mars 5

6. Conditions on Early Earth Seems likely that Earth’s first organisms emerged and lived at very high temperatures First organisms emerged between 3.8 and 2.5 BYA Early atmosphere composition not agreed on –May have been a reducing atmosphere –Would have made it easier to form carbon-rich molecules 6

7. In 1953, Miller and Urey did an experiment that reproduced early atmosphere –Assembled reducing atmosphere rich in hydrogen with no oxygen gas –Atmosphere placed over liquid water –Temperature below 100ºC –Simulate lightning with sparks 7

8. 8

9. Found within a week that methane gas (CH 4 ) converted into other simple carbon compounds –Compounds combined to form simple molecules and then more complex molecules Later experiments produced more than 30 carbon compounds including amino acids –Adenine also produced 9

10. RNA may have been first genetic material –Ribozyme activity Amino acids polymerized into proteins Metabolic pathways emerged –Primitive organisms may have been autotrophic – built what they needed Lipid bubbles could increase the probability of metabolic reactions –Leads to cell membranes Other innovations contributed to diversity of life 10

11. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Periods Eons Eras Quaternary Tertiary Cretaceous Jurassic Triassic Permian Carbonife- rous Devonian Silurian Ordovician Cambrian Present 50 MYA 100 MYA 150 MYA 200 MYA 250 MYA 300 MYA 350 MYA 400 MYA 450 MYA 500 MYA Cenozoic Mesozoic Paleozoic Phanerozoic Appearance of humans First primate Bird radiation Mammal radiation Pollinating insects Diversification of flowering plants First flowering plants, birds, marsupial mammals First dinosaurs First gymnosperms First reptiles First amphibians Bony fish, tetrapods, seed plants, and insects appear Early vascular plants diversify Invertebrates dominate First land plants Cambrian explosion; increase in diversity North and South America joined by land bridge. Uplift of the Sierra Nevada. Worldwide glaciation. Gondwana begins to break apart; interior less arid. Pangea intact. Interior of Pangea arid. Climate very warm. Supercontinent of Laurentia to the north and Gondwana to the south. Climate mild. Gondwana Laurentia Gondwana 11

12. 12 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Periods Eons Eras Late Middle Early Late Middle Early 500 MYA 1000 MYA 1500 MYA 2000 MYA 2500 MYA 3000 MYA 3500 MYA 4000 MYA 4500 MYA Proterozoic Archaean Hadean Precambrian Appearance of animals and plants First multicellular organisms Oldest definite fossils of eukaryotes Appearance of oxygen in atmosphere Cyanobacteria Oldest fossils of prokaryotes Molten-hot surface of Earth becomes somewhat cooler Oldest rocks Formation of Earth Supercontinent of Gondwana forms. Oceans cover much of North America. Climate not well known. Most of Earth is covered in ocean and ice.

13. Classification of Organisms More than 2000 years ago, Aristotle divided living things into animals and plants Later, basic units were called genera –Felis (cats) and Equus (horses) In the 1750s, Carolus Linnaeus instituted the use of two-part names, or binomials –Apis mellifera the European honeybee –Genus name capitalized, all in italics 13

14. Taxonomy is the science of classifying living things –A classification level is called a taxon Scientific names avoid the confusion caused by common names 14

15. The Linnaean Hierarchy Taxa are based on shared characteristics –Domain → → → Species Early taxonomists not aware of distinction between derived and ancestral traits –Many hierarchies now being re-examined Categories at the different levels may include many, a few, or only one taxon Limitations –Many higher ranks are not monophyletic –Linnaean ranks not equivalent in any meaningful way 15

16. 16

17. 17

18. 18 Grouping Organisms Carl Woese proposed a 6-kingdom system Prokaryotes Eukaryotes

19. 6-kingdom system –4 eukaryotic kingdoms Plantae Fungi Animalia Protista – did not fit into 3 other kingdoms –Probably paraphyletic –2 prokaryotic kingdoms Archaea Bacteria 19 Each fundamentally different Each probably monophyletic

20. 3 domain system –Domain Archaea –Domain Bacteria –Domain Eukarya –Each of these domains forms a clade 20 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. Domain Bacteria (Bacteria) Domain Archaea (Archaebacteria) Domain Eukarya (Eukaryotes) Common Ancestor

21. 21 Tree based on rRNA analysis Archaea and Eukarya are more closely related to each other than to bacteria

22. 22

23. Bacteria Most abundant organisms on Earth Key roles in biosphere –Extract nitrogen from the air, and recycle carbon and sulfur –Perform much of the world’s photosynthesis Responsible for many forms of disease Highly diverse Most taxonomists recognize 12–15 different groups 23

24. Archaea Shared characteristics –Cell walls lack peptidoglycan (found in bacteria) –Membrane lipids are different from all other organisms –Distinct rRNA sequences Divided into three general categories –Methanogens –Extremophiles –Nonextreme archaea 24

25. Methanogens –Use H 2 to reduce CO 2 to CH 4 –Strict anaerobes that live in swamps and guts Extremophiles –Thermophiles – High temperatures (60–80ºC) –Halophiles – High salt –Acidophiles – Low pH (pH = 0.7) Nonextreme archaea –Grow in same environments as bacteria –Nanoarchaeum equitens – Smallest cellular genome 25

26. Eukarya Prokaryotes ruled the earth for at least one billion years Eukaryotes appeared about 2.5 BYA Their structure and function allowed multicellular life to evolve Eukaryotes have a complex cell organization –Extensive endomembrane system divides the cell into functional compartments 26

27. Mitochondria and chloroplasts most likely gained entry by endosymbiosis Mitochondria were derived from purple nonsulfur bacteria Chloroplasts from cyanobacteria 27

28. ArchaebacteriaAnimaliaFungiProtistaPlantaeBacteria Brown algae Photosynthetic protists Thermophiles Halophiles Methanogens Ancestral eukaryotic cell Purple bacteria Photosynthetic bacteria Other bacteria Chloroplasts Mitochondria Red algae Green algae Nonphotosynthetic protists Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 28

29. Key Eukaryotic Characteristics Compartmentalization –Allows for increased subcellular specialization –Nuclear membrane allows for additional levels of control of transcription and translation Multicellularity –Allows for differentiation of cells into tissues Sexual reproduction –Allows for greater genetic diversity 29

30. 30

31. 31

32. Viruses Are literally “parasitic” chemicals –DNA or RNA wrapped in protein Cannot reproduce on their own Not considered alive – cannot be placed in a kingdom Viewed as detached fragments of a genome Tobacco mosaic virus (TMV) first discovered in 1933 32

33. 33 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. T4 bacteriophage Ebola virus 100 nm Vaccinia virus (cowpox) Influenza virus Tobacco mosaic virus (TMV) Herpes simplex virus HIV-1 (AIDS) Rhinovirus (common cold) Adenovirus (respiratory virus) Poliovirus (polio)

34. Making Sense of the Protists Represents tension between traditional classification and use of evolutionary relationships Eukaryotes diverged rapidly as atmosphere shift from anaerobic to aerobic –May never be able to sort out relationships during this time Protist is a catchall for eukaryotes that are not plant, fungus, or animal 34

35. 35 6 main branches of protists are current working hypothesis –At least 60 protists do not fit into these groups New kingdom called Viridiplantae would include all green algae and land plants

36. Origin of Plants Land plants arose from an ancestral green alga only once during evolution Green alga consist of 2 monophyletic groups –Chlorophyta –Streptophyta Composed of seven clades, including land plants –Kingdom Viridiplantae would include Chlorophyta and Streptophyta 36

37. Mesostigma represent the earliest Streptophyte branch Charales is the sister clade to land plants –Split 420 MYA 37

38. 38 Some land plants show evidence of horizontal gene transfer Amborella has some mitochondrial genes from moss Close contact with epiphytes increases the probability of HGT

39. Sorting Out the Animals Origins of segmentation –Used in the past to group arthropods and annelids close together –rRNA sequences now suggest that these two groups are distantly related –Segmentation likely evolved independently in these two groups, as well as in chordates 39

40. Division based on embryonic development –Protostomes develop the mouth before the anus in embryonic development Annelids and arthropods among others –Deuterostomes develop the anus first Chordates including humans Protostomes divided further into –Lophotrochozoans Flatworms, mollusks, and annelids –Ecdysozoans Roundworms and arthropods 40

41. Segmentation is regulated by the Hox gene family –Hox ancestral genes already present in ancestor to all groups –Members were co-opted at least three times 41

42. 42 Within the arthropods, insects have traditionally been separated from the crustaceans – Uniramous vs. biramous appendages However, molecular data is questioning this classification – Distal-less, a Hox gene, initiates development of both types of appendages

43. The Mammalian Family Tree Over 90% of mammals are eutherians or placental mammals –Now divided into four major groups First major split occurred 100 MYA when Africa split from South America 43

44. 44 Origin of whales and hippos debated for 200 years –Whales thought to be relatives of pigs based on skull and teeth –DNA sequences reveal a close relationship between whales and hippos –Some adaptations to aquatic origins had a common origin –Recent fossil finds confirm the artiodactyl origin

45. 45 Understanding evolutionary relationships among organisms accomplishes these things –Provides an orderly and logical way to name organisms –Allows researchers to ask important questions about physiology, behavior, and development using information already known about a related species –Provides insights in understanding the history of major features and functions