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?

EARTH’S EARLY HISTORY Chapter 17-2

Evidence for Early Life

• Chapter prevents what is currently known

• Hypotheses are based on very little evidence

• You may have a different opinion

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, CO2, CO, nitrogen, hydrogen sulfide, H2O vapor

• 3.8 billion years ago

– cooled enough to permit water to exist as a liquid

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

MILLER AND UREY’S EXPERIMENT

Experiments were eventually proved inaccurate, but provided hypothesis and techniques that stimulated further investigation that came up with more accurate models.

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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

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

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

ENDOSYMBIONT THEORY

Evidence for this theory comes from modern eukaryotic cells.

Evidence for Early Life?

• http://www.earthinstitute.columbia.edu/news/vostok/vostok.swf

• http://rt.com/news/antarctic-million-secrets-lake-583/

Chapter 19 Bacteria and Viruses

19-1 Characteristics of Prokaryotes

WHAT ARE BACTERIA? Single-celled prokaryotic

microorganisms

First… Some Clarifications Prokaryote = Bacteria

Two Basic Kinds of Cell

• Prokaryotes “Before Kernel”

FOCUS of this CHAPTER

• Eukaryotes “New Kernel”

Next CHAPTER

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

Just How Small?

http://learn.genetics.utah.edu/content/begin/cells/scale/

BA

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Bacterial Classification

• Little fossil evidence

• Two ancient groups

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

MORNING GLORY POOL,

YELLOW STONE NATIONAL PARK

Color comes from massive colonies of archaebacteria

Halophiles,

salt loving bacteria evaporation ponds

at the abandoned

Pittsburgh Plate Glass Company in

Bartlett, CA

Ways to Classify Eubacteria

1. Cell shape – 3 common shapes

2. Cell wall composition

3. Nutrition

4. Respiration

Shape Classification

Round = Cocci

Rods = Bacilli

Spirals = Spirilla & Spirochete

E. coli

Anthrax in lung

Staph. bacteria

Salmonella

Bacteria in human brain

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

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

Bacterial Respiration

• Aerobic

– Uses oxygen

• Anaerobic

– NO oxygen

based on the whether or not they need oxygen to make cellular energy

Bacteria grow

near surface

where oxygen

is available

Bacteria grow

at bottom

where oxygen

is not

available

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

Parasitic Bacteria each have

limitations for

“ Host Range”

Only certain Species

Only certain Tissues

Bacteria

can be free-living or parasites

Bacterial Reproduction

• Can be

Sexual

or

Asexual

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

Binary Fission – Asexual Reproduction

– Not very complicated

– Happens very quickly

Bacterial Life Cycles

• Growth

– Increase in the

number of individuals

in a colony

– NOT an increase in

cell size

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

Other Forms of Genetic Exchange

• Transformation

– Living bacterial

cells take up

DNA from dead

bacterial cells

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?

19-2 Viruses

BIG IDEA

Viruses are non-living particles that depend on living things to replicate

What are Viruses?

• Viruses

– non-living, infectious particle

– very simple structure

– organized into specific parts

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

Why did it take so long to discover viruses?

They are submicroscopic!

Let’s take a look.

Just How Small?

http://learn.genetics.utah.edu/content/begin/cells/scale/

HOW MANY REASONS CAN YOU COME UP WITH?

Why do you think scientists with the CDC are interested in studying viruses?

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

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

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

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

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

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

Lytic Cycle

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

Lysogenic Cycle

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

Host Classification

• viruses infect cells

– host cell infection can be specific or broad

– are specific to major groups of cells

• animal

• plant

• bacterial

Host Classification

examples:

Polio

only humans

Rabies

any mammal

Host Specificity

• capsid and envelope proteins must match receptors on cells to be infected

no recognition, no viral nucleic acid injected

Viral Replication

• Depends on:

– type of nucleic acid

– type of participating enzymes

– location of replication within the host cell

Origin and Diversity of Viruses

BIG IDEA

Compare and Contrast Methods of Viral Classification

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,

Shape

• arrangement of capsid proteins determines

the four main shapes

– Filovirus

– Binal

– Polyhedral

– Helical

Filovirus Examples

Ebola

Marburg

Binal Examples

Only found in bacteriophages

(viruses that infect bacteria)

Polyhedral (Icosahedral) Hedral = Having a

specified kind or

number of surfaces

Icosa = twenty

Helical

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.