IN THE BEGINNING….The Origin of Life

Chapter 17The Origin and Evolution of Microbial Life:

Prokaryotes and Protists

Chapter 17.1Life Began on

a Young Earth

Chapter 17.2How Did Life

Originate?

Chapter 17.3Stanley Miller’s

Experiments Showed That Organic Molecules Could Have Arisen on a

Lifeless Earth

Chapter 17.4 The First Polymers

May Have Formed on Hot Rocks or Clay

Chapter 17.5 The First Genetic

Material and Enzymes May Both

Have Been RNA

Chapter 17.6Molecular Cooperatives Enclosed by Membranes Probably Preceded the

First Real Cells

Chapter 17.7Prokaryotes Have

Inhabited Earth for Billions of

Years

Shadows

Chapter 17.8Archaebacteria and Eubacteria are the Two Main Branches

of Prokaryotic Evolution

Three Domains The current system, the Three Domain

System, groups organisms primarily based on differences in ribosomal RNA structure. Ribosomal RNA is a molecular building block for ribosomes.

Archaea, Bacteria, and Eukarya

Six Kingdoms of Life Animalia - humans, dogs, worms Plantae - trees, plants, most

algae Fungi - mushrooms, yeast Protista - amoeba, paramecium Eubacteria – most bacteria, blue-

green algae (domain bacteria) Archaebacteria – extreme

environment bacteria (domain archae)

Dom

ain

Euka

rya

• Eubacteria• Unique RNA

sequences• Simple RNA

polymerase• No Introns in

DNA• Peptidoglycan• Membrane

lipids unbranched

• Sensitive to antibiotics

• Archaebacteria

• RNA sequences match eukaryotes

• Complex RNA polymerase

• Introns in DNA• No

peptidoglycan• Membrane

lipids branched• Not sensitive to

antibiotics

Chapter 17.9Prokaryotes

Come in a Variety of Shapes

Chapter 17.10Prokaryotes Obtain

Nourishment in a Variety of Ways

Prokaryotic modes of nutritionNutritional

TypeEnergy Source

CarbonSource

Photoautotroph Sunlight CO2

Chemoautotroph

InorganicChemicals

CO2

Photoheterotroph

Sunlight OrganicCompoun

dsChemoheterotr

ophOrganic

Compounds

OrganicCompoun

ds

Chapter 17.11The First Cells Probably Used

Chemicals for Both Carbon and Energy

Two leading hypotheses for early energy metabolism:

Obtain ATP from the environmentTurn ADP into ATP using sulfur and ironcompounds

chemiosmosis

Antonie Van Leeuwenhoek Father of microscopy Perfected lens making

(1600’s) Calculus between teeth had

“little beasties” - no one believed

First to see bacteria

Robert Hooke Looked at cork - not alive

(1600’s) Only saw cell walls Looked like rooms monks

lived in Coined the word “cell” micrographia

Robert Brown Botanist - 1800’s First to see nucleus Nucleus was stained dark

The Cell Theory Theodor Schwann - zoologist Rudolf Virchow - physiologist Matthias Schleiden - botanist 1. The cell is the basic unit of life 2. All organisms are made of cells 3. Cells come from cells (life from

life)

Prokaryotes No membrane

bound nucleus DNA in circle DNA not

associated with proteins

No organelles except ribosomes

Eukaryotes Membrane

bound nucleus DNA is linear DNA wound

around spools of proteins

Membrane bound organelles

Prokaryotes

Many are anaerobes

All single celled

All Rxn occur in cytoplasm

Small cells

Eukaryotes All are

aerobes

Many are multicelled

Diverse Rxn in organelles

Many are large

Chapter 4.1Microscopes

Provide Windows to the World of the

Cell

3 types: 1. Light microscope (Phase/Contrast) 2. Transmission Electron Microscope (TEM) 3. Scanning Electron Microscope (SEM)

Magnification: The enlarging of an image.

Resolution: The power to show detail clearly. Resolving power is the ability to distinguish objects from one another.

Micrograph: Photograph of an image formed with a microscope.

Light Microscope:1. Refracted (bent) light rays magnify the image.2. Specimen must be thin enough for light to pass

through, used to see living cells.3. Can use stains but cell will die and sometimes

its structure is altered.4. Wavelengths of visible light (400-700 nm on

electromagnetic spectrum) limits resolution – maximum detail is only .2 μm.

5. Maximum magnification is about 2,000x.

Phase/Contrast Microscope:1. Same as light microscope only it converts small

differences in structure to large variations in brightness.

2. Also used to see living cells.3. Same magnification and resolving limits as a

regular light microscope.

TEM:1. Uses electrons with wavelengths of .005nm

(100,000x shorter than visible light)2. Magnetic field acts as a lens, diverting

electrons along defined paths and channels them to a focal point.

3. Electrons must travel in vacuum, thus cells must be dead.

4. Cells must be thin, electrons scatter in patterns according to density. The darker the area, the more dense.

TEM:1. High voltage excites electrons until they are

10x more energetic and can easily pass through specimen and show internal structures.

2. Cells must be stained with heavy metal dyes.3. Max resolution is .2nm.4. Max magnification is 2,000,000x.

SEM:1. Uses a narrow beam of electrons to scan the

surface of specimen.2. Specimen must be coated with a thin metal

layer (no living cells). Stops electrons from passing through specimen.

3. Metal responds by giving off some of its own electrons.

4. A television screen shows the image by detecting emission patterns.

SEM:1. Gives image of specimen depth, you get a 3D

image.2. Max resolution of 10nm.3. Max magnification of 50,000x.