Origin of Life on EarthClassification of Life

I. Origin of Life on EarthA. 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 Experiment1. 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 ClassificationTaxonomy – grouping and naming organisms by their characteristics and evolutionary history.

I. Aristotle – first to classify organisms

A. Organisms were either plant or animal

1. Animals were put into land, water, or air dwellers.

2. 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 = name1. 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 & DomainsI. Updating Classification Systems

A. Linnaeus’s 2 Kingdom System1. 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 Kingdoms1. 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 Kingdoms1. 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 SystemA. 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 KingdomsA. 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• 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• 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• Eukaryotic• Multicellular• Heterotrophic• Symmetrical Bodies, Move• Invertebrates: 97% of Animal

Kingdom, no backbone• Vertebrates: internal skeleton (bone

or cartilage)

1. Invertebrates• 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)• Amphibians• Reptiles• Birds• Mammals