in the beginning…
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In The Beginning…. The Origin of Life. Chapter 17 The Origin and Evolution of Microbial Life: Prokaryotes and Protists. Chapter 17.1. Life Began on a Young Earth. Chapter 17.2. How Did Life Originate?. Chapter 17.3. - PowerPoint PPT PresentationTRANSCRIPT
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.