Origin of Life
on Earth
Classification of
Life
I. Origin of Life on Earth
A. Earth’s early atmosphere
1. Probably contained
• Hydrogen cyanide
• Carbon dioxide
• Carbon monoxide
• Nitrogen
• Hydrogen sulfide, and
• Water
**No free oxygen
B. Earth formed 4.5 bya & life
started 3.5 bya
C. Miller-Urey Experiment
1. Stanley Miller & Harold Urey:
conducted experiment to
recreate how life started
2. They & others made:
• Amino acids
• Building blocks of DNA, RNA,&
ATP
Miller-Urey
Experimental
Apparatus:
D. First organisms on Earth were
prokaryotes
1. Archae: means “old” or “ancient”
• First appeared 3.5 billion years
ago
• Called extremophiles because
the live in extreme environments
similar to conditions of early Earth
• High salt, high temp., dean ocean
• Some live in non-extreme
environments
2. True Bacteria were next organisms
• Live all around and in us.
• Cyanobacteria: made first free
oxygen on Earth; began the type
of photosynthesis that splits water
& makes free oxygen
• Three common shapes:
― Round: called coccus
― Rod-shaped: called bacillus
― Corkscrew shaped called spiral
The Importance of Classification
Taxonomy – grouping and naming organisms
by their characteristics and evolutionary
history.
I. Aristotle – first to classify organisms
A. Organisms were either plant or
animal
1.
2.
Animals were put into land, water, or air
dwellers.
Plants were put into three categories
based on stems.
B. After a period of rapid discovery,
new organisms were found that were
neither plant nor animal
C. Common names, such as the robin or
fir tree were used for more than one
species depending on the country.
•
The Great Britain robin is a different bird
than the N. American robin.
D. Also, common names did not
accurately describe the organisms.
•
A jellyfish is not a
fish made of jelly!
II. Carolus Linnaeus (1700’s)
A. Classification System based on
morphology (form or structure of
organisms)
1. Developed 7 levels of organization
•
Kingdom (plant or animal)
•
Phylum
•
Class
•
Order
•
Family
•
Genus
•
Species
B. Binomial Nomenclature – process of
naming organisms
Bi = two Nomial = name
1. Every organism has a scientific name.
• 1st part is the organism’s genus
(Capitalized)
• 2nd part is the species identifier, a
descriptive word that matches the
species the organism belongs to (not
capitalized)
• Latin
• Ex: Homo sapiens
2. There are some species that have shown
great variation. Botanists sometimes split
plant species into varieties. Zoologists split
animal species into subspecies.
3. Modern taxonomists still consider
morphology (like Linnaeus), but also
consider phylogeny (evolutionary history)
when classifying organisms.
III. Cladograms – diagrams that show
the evolutionary relationships among
a group of oganisms
• Identify the organism in the table that
is least closely related to the others.
• Use the information in this table to
construct a cladogram of these
animals.
IV. Now we classify on similarities in DNA
& RNA & Proteins
A. The genes of many organisms show
important similarities at the
molecular level.
B. Similarities in DNA can be used to
help determine classification and
evolutionary relationships.
C. Molecular Clock –
uses DNA
comparisons to
estimate how long
ago 2 species
shared a common
ancestor
V. Today’s version of Linnaeus’s
Classification System
•
•
•
•
•
•
•
•
Domain = recognizes differences in cell type
Kingdom = 6 kingdoms in 3 domains
Phylum = many phyla per kingdom
Class
Order
Family
Genus
Species = unique group of organisms that
can only breed with each other
Kingdoms & Domains
I. Updating Classification Systems
A. Linnaeus’s 2 Kingdom System
1. Plantae & Animalia – very few species
were known at this time.
2. Sponges used to be classified as plants,
but with knew knowledge and
technology, they are classified as
animals.
B. From 2 to 5 Kingdoms
1. In the 1800’s, there was an explosion of
discovery.
2. First, the Protista Kingdom was added for
unicellular organisms.
3. When eukaryotic and prokaryotic cells
were noticed, Kingdom Monera was
added.
4. By the 1950’s, 5 Kingdoms were used:
Monera, Protista, Fungi, Plantae,
Animalia
C. Six Kingdoms
1. In the 1990’s, Kingdom Monera came
into question as genetic data showed
there were 2 groups of prokaryotes.
2. Kingdom Monera was split:
Kingdom Eubacteria and
Kingdom Archaebacteria
II. Three (3) Domain System
A. Major Characteristics of Organisms
1. Cell Type – prokaryote
or eukaryote
2. Cell Walls – cells either
have or don’t have
3. Body Type – unicellular
or multicellular
4. Nutrition – autotroph or heterotroph
5. Genetics – unique system of DNA, RNA
(rRNA), & Proteins
B. The 3 Domains – developed by Carl
Woese of the University of Illinois (did
work on RNA of all major organism
groups)
1. Domain Bacteria – strong cell wall &
unique genetic system; same as
Kingdom Eubacteria
2. Domain Archae – chemically unique cell
wall, membranes, & genetic system;
same as Kingdom Archaebacteria
3. Domain Eukarya – all organisms made of
eukaryotic cells; Kingdoms Protista, Fungi,
Plantae, & Animalia
III. The 6 Kingdoms
A. Archaebacteria
•
•
•
•
•
Unicellular
Prokaryote
Auto- or Heterotrophic
Live in Harsh Conditions: Sulfurous hot
springs, salty lakes, anaerobic (no O2),
your intestines
Archae = ancient; modern
Archaebacteria resemble 1st organisms
on Earth
B. Eubacteria
•
•
•
•
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•
Eu = true
Unicellular
Prokaryote
Auto- or Heterotrophic
Most bacteria that affect our lives –
cause tooth decay, illnesses, curdle
dairy, etc.
Largest # of organisms than any other
kingdom
C. Protista
•
•
•
•
•
Eukaryotes
Mostly unicellular (some multicellular like
giant kelp and some algae)
Auto- and Heterotrophic
Reproduction varies between species
Examples: Euglena, Amoebas, Giant
Kelp, Algae
1. Classification Problem
• Some move with flagella, pseudopods or
cilia
• Animal-like, plant-like & fungus-like groups
2. Ecological Importance
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Important foundation in food chain
Produce a lot of oxygen
Decomposition
Symbiotic relationships: mutualistic,
parasitic
Medicinal & Industrial uses
D. Fungi
Eukaryote
Unicellular, Multicellular
Heterotrophic (absorption)
- feed on decaying organisms
• Examples: mushrooms, puffballs,
mildews, molds
•
•
•
1. Ecological Importance
• Decomposers
• Symbiotic
- parasitic: on plants and animals
- Mutualistic: lichens (fungi & algae) and
mycorrhizae (fungi & plants/roots)
E. Plantae
•
•
•
•
•
Eukaryote
Multicellular
Mostly Autotrophic
Sexual Reproduction
Examples: mosses, ferns, conifers,
flowering plants
1. Three Traditional Groupings
• Bryophytes (mossy plants) –
nonvascular, seedless
• Tracheophytes (ferns) – vascular,
seedless
• Seed Plants
• Gymnosperms – cone-bearing plants
• Angiosperms – flowering plants
2. Importance to Humans
• Food source – Wheat, grains, fruits,
vegetables
• Medicine – Aspirin, cancer treatments,
stimulants
• Industry – Agriculture, wood products,
cotton
F. Animalia
•
•
•
•
•
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Eukaryotic
Multicellular
Heterotrophic
Symmetrical Bodies, Move
Invertebrates: 97% of Animal Kingdom,
no backbone
Vertebrates: internal skeleton (bone or
cartilage)
1. Invertebrates
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Sponges
Cnidarians: jellyfish
Worms
Mollusks: snails, clams, octopus
Arthropods: insects, crustaceans
Echinoderms: starfish, sea cucumber
2. Vertebrates = Chordates
• Fish
- Agnatha (jawless fish/lamprey)
- Chondrichthyes (sharks, skates, rays)
- Osteichthyes (bony fish: bass, tuna,
salmon)
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Amphibians
Reptiles
Birds
Mammals