Early History and Primitive Life. Unit 2: How do cells support life? Chapter: What are the origins of life? What are the simplest forms of life?

Transcription

1 Early History and Primitive Life Unit 2: How do cells support life? Chapter: What are the origins of life? What are the simplest forms of life?

2 Chapter 17-2 EARTH S EARLY HISTORY

3 Evidence for Early Life Chapter prevents what is currently known Hypotheses are based on very little evidence You may have a different opinion

4 Formation of Earth 4.6 billion years old based on geologic evidence Molten Earth rearranged itself according to density 4.0 billion years ago Cooling resulted in a solid outer and molten interior Less dense materials form the atmosphere Hydrogen cyanide, CO 2, CO, nitrogen, hydrogen sulfide, H 2 O vapor 3.8 billion years ago cooled enough to permit water to exist as a liquid

5 The First Organic Molecules Current Conditions Are not proper for formation of free organic molecules Recreating Prehistoric Conditions Miller and Urey s experiment Simulated early Earth s atmosphere in a closed system Applied an electric current to simulate lightning Produced simple organic compounds

6 MILLER AND UREY S EXPERIMENT p/itext/products/ /index.html Experiments were eventually proved inaccurate, but provided hypothesis and techniques that stimulated further investigation that came up with more accurate models.

7 The Puzzle of Life s Origin How did early single celled life originate? Formation of Microspheres Proteinoid microspheres Similar to cells in that they have a semipermeable membrane Have means of storing and releasing energy Evolution of RNA and DNA RNA is currently thought to have evolved first RNA may be able to direct the formation and replication of more complicated DNA molecules

8 Free Oxygen Regardless of HOW early organisms evolved 3.5 BYA early atmosphere did not have free oxygen early unicellular prokaryotes (bacteria) were anaerobic (an= no, aerobic = using oxygen) 2.2 BYA free oxygen begins to accumulate in the atmosphere photosynthetic bacteria were common and produced oxygen as a byproduct of photosynthesis oxygen combines with iron in the oceans and results in great deposits of iron on the ocean floor

9 Origin of Eukaryotic Cells 2 BYA Prokaryotic cells began to evolve internal cell membranes Thought to be the result of incorporation of prokaryotes into other prokaryotic cells Endosymbiont Theory

10 ENDOSYMBIONT THEORY Evidence for this theory comes from modern eukaryotic cells.

11 Evidence for Early Life? nstitute.columbia.e du/news/vostok/vo stok.swf /antarctic-millionsecrets-lake-583/

12 Chapter 19 Bacteria and Viruses

13 19-1 Characteristics of Prokaryotes

14 WHAT ARE BACTERIA? Single-celled prokaryotic microorganisms

15 First Some Clarifications Prokaryote = Bacteria

16 Two Basic Kinds of Cell Prokaryotes Before Kernel Eukaryotes New Kernel FOCUS of this CHAPTER Next CHAPTER

17 Two Basic Kinds of Cell Prokaryotes Before Kernel no nucleus no organelles single strand of DNA cell wall (not like a plant) small size THIS CHAPTER Eukaryotes New Kernel nucleus organelles multiple chromosomes cell wall (plants only) larger size Next Chapter

18 Just How Small?

19 BACTERIAL ANATOMY

20 Bacterial Classification Little fossil evidence Two ancient groups

21 2 Major Groups of Bacteria Archaebacteria Harsh environments Ancient life form Early form of life Types Methanogens Thermophiles Halophiles Eubacteria Cell wall with peptidoglycan Found in a variety of environments, not harsh Much newer form of bacteria Several types and ways to classify

22 MORNING GLORY POOL, YELLOW STONE NATIONAL PARK Color comes from massive colonies of archaebacteria

23 Halophiles, salt loving bacteria evaporation ponds at the abandoned Pittsburgh Plate Glass Company in Bartlett, CA

24 Ways to Classify Eubacteria 1. Cell shape 3 common shapes 2. Cell wall composition 3. Nutrition 4. Respiration

25 Shape Classification Round = Cocci Rods = Bacilli Spirals = Spirilla & Spirochete

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27 E. coli

28 Anthrax in lung

29 Staph. bacteria

30 Salmonella

31 Bacteria in human brain

32 Cell Wall Composition Gram Stain (developed by Hans Gram, 1884) Gram positive Look purple after staining Gram negative Look red after staining Important because antibiotics don t always work on gram negative

33 Bacterial Nutrition Autotrophs auto = self, troph = feeding make their own food from raw materials and an energy source do not need other organisms Photoautotrophs Chemoautotrophs Heterotrophs hetero = other, troph = feeding cannot make their own food, must consume other organisms need other organisms to survive Chemoheterotrophs Photoheterotrophs

34 Bacterial Respiration based on the whether or not they need oxygen to make cellular energy Aerobic Uses oxygen Anaerobic NO oxygen Bacteria grow near surface where oxygen is available Bacteria grow at bottom where oxygen is not available

35 Bacterial Respiration 3 Forms Obligate Aerobe Must use oxygen to produce energy Will die if oxygen is not present Obligate Anaerobe Must live in the absence of oxygen to produce energy Will die if oxygen is present Facultative Anaerobe Can live in the presence or absence of oxygen to produce energy

36 Bacteria can be free-living or parasites Parasitic Bacteria each have limitations for Host Range Only certain Species Only certain Tissues

37 Bacterial Reproduction Can be Sexual or Asexual

38 Conjugation Sexual Process of exchanging genetic information Requires cell-to-cell contact Bacterial DNA is transferred through pili BENEFITS TO BACTERIA Increases genetic diversity May help survival in changing conditions

39 Binary Fission Asexual Reproduction Not very complicated Happens very quickly

40 Bacterial Life Cycles Growth Increase in the number of individuals in a colony NOT an increase in cell size

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42 Bacterial Survival ENDOSPORES - resting stage for surviving poor conditions Has thick walls, copy of bacterial DNA Resists heat, drought, radiation Can remain for many years until conditions improve NOT ALL bacterial cells produce endospores

43 Other Forms of Genetic Exchange Transformation Living bacterial cells take up DNA from dead bacterial cells

44 Early History and Primitive Life Unit 2: How do cells support life? Chapter: What are the origins of life? What are the simplest forms of life?

45 19-2 Viruses BIG IDEA Viruses are non-living particles that depend on living things to replicate

46 What are Viruses? Viruses non-living, infectious particle very simple structure organized into specific parts

47 History of Viral Discovery Tobacco Mosaic Virus (TMV) historically causes severe damage to important cash crop 1892 Dimitri Ivanovsky (biologist) hypothesizes a very small particle causing the disease 1897 Martinus Beijerinck (biologist) TMV is replicated inside plant cells called infectious particle a virus Latin for poison 1935 Wendell Stanely (biochemist) was able to isolate and crystalize TMV

48 Why did it take so long to discover viruses? They are submicroscopic! Let s take a look.

49 Just How Small?

50 Why do you think scientists with the CDC are interested in studying viruses? HOW MANY REASONS CAN YOU COME UP WITH?

51 Viruses Today Virology is a recognized field of research viral identification and study is an important field of research, but why? ABILITY TO MUTATE RAPIDLY LETHAL NATURE OF VIRUSES COST ASSOCIATED WITH ILLNESS CROP DAMAGE AND LOSSES LIVESTOCK LOSSES

52 Viral Structure 2 main components of all viruses core of nucleic acid DNA or RNA outer coating of protein = capsid determines shape of virus protects nucleic acid

53 Additional Viral Component Component only found in animal viruses envelope carbs, lipids, proteins projections act like a secret-handshake to allow virus to attach to host cell

54 Viruses are Cellular Parasites Viruses replicate, do not reproduce replication = no cell division reproduction = cell division Replication requires a host cell host is hijacked to create cell parts host is usually a specific type of organism, group of organisms or cell type host provides all the raw materials and machinery for assembly

55 Two Paths for Replication 1) Lytic Cycle immediate replication by host active viral infection 2) Lysogenic Cycle no immediate replication by host inactive viral infection

56 Lytic Cycle Viral Replication Virus immediately begins to replicate Destroys the host cell Affected organisms show signs of disease Virus actively spreads to other organisms

57 Lytic Cycle

58 Lysogenic Cycle Viral Replication Virus inserts nucleic acid, BUT does not immediately take over cell function Viral DNA called a prophage, inserts itself into the cellular DNA Host cell copies viral DNA every time it reproduces Viral DNA only activates when an appropriate stimulus occurs

59 Lysogenic Cycle

60 Activating the Lysogenic Cycle Needs an environmental stimulus for viral DNA to separate and become active Once this happens it enters the lytic cycle Examples: HIV, can become AIDS Chicken Pox, can become Shingles Herpes, can periodically become active

61 Host Classification viruses infect cells host cell infection can be specific or broad are specific to major groups of cells animal plant bacterial

62 Host Classification examples: Polio only humans Rabies any mammal

63 Host Specificity capsid and envelope proteins must match receptors on cells to be infected no recognition, no viral nucleic acid injected

64 Viral Replication Depends on: type of nucleic acid type of participating enzymes location of replication within the host cell

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66 Origin and Diversity of Viruses BIG IDEA Compare and Contrast Methods of Viral Classification

67 Viral Classification Difficult because there are many different kinds of viruses Several ways to classify Shape = Capsid Structure, Presence of Envelope Host = Type of Cell Function = Nucleic Acid, Replication,

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69 Shape arrangement of capsid proteins determines the four main shapes Filovirus Binal Polyhedral Helical

70 Filovirus Examples Marburg Ebola

71 Binal Examples Only found in bacteriophages (viruses that infect bacteria)

72 Polyhedral (Icosahedral) Hedral = Having a specified kind or number of surfaces Icosa = twenty

73 Helical

74 Naked VS. Enveloped NAKED virus Only has a CAPSID made up of subunits called CAPSOMERES ENVELOPED virus Envelope is made from a combination of host cell membrane and viral components.