I. Beginning of Prokaryotic life

A. The oldest fossils

1. Evidence suggests that Earth is about 4.6 billion years old

2. Fossil evidence indicates that life existed about 3.5 billion years ago.

a. These fossils are found in dome-shaped rocks called stromatolites – rock composed of thin layers of sediment pressed tightly together (layers of an onion)

b. These fossils resemble photosynthetic prokaryotes living today in salt marshes.

c. More simpler life is believed to have existed 3.9 billion years ago.

Stromatolites are found in hot salty lagoons in Western Australia. Inside the rocks are: Cyanobacteria chains Heterotrophic bacteria Sand, silt, and clay particles Calcium carbonate

B. How did life begin? In a nutshell:

Simple molecules present (carbon monoxide, water vapor, nitrogen, carbon dioxide)

Small monomers form (amino acids, monosaccharides, nucleotides, fatty acids)

Polymers form (proteins, polysaccharides, lipids, DNA/RNA)

Polymers copy self (RNA)

Polymers became packaged within membranes (protobionts)

C. How did life begin? The nutshell explained

1. Origin of small organic molecules (monomers)

a. years ago, Earth contained carbon monoxide, carbon dioxide, nitrogen, and water vapor (there was little to no oxygen) – geologic evidence shows this

b. years ago, active volcanoes, lightning, and UV radiation from the sun were more intense than today (all energy sources)

c. Stanley Miller designed an experiment (1953) that simulated conditions on Earth. Gases in a flask, electric sparks produced a variety of organic molecules such as amino acids.

d. since then, scientists have tried other gas scenarios and energy sources and have been able to produce all 20 amino acids, sugars, lipids, nitrogenous bases in DNA and RNA, and ATP.

2. Formation of Organic Polymers (proteins, polysaccharides, large fats, DNA/RNA)

a. Solutions of monomers were dripped onto surfaces of hot sand, clay, or rock.

b. The above experiments show that polymers could easily form under the conditions found on Earth years ago.

3. What was the original process of copying hereditary info?

a. In lab, short RNA molecules copy themselves in solutions containing nucleotides without enzymes or cells present (maybe the first genes were short

strands of RNA)

4. Formation of Protobionts – nonliving and do not have the properties of cells

a. Experiments show that proteins can come together to form microscopic, fluid filled spheres

b. If lipids are included in the solution, they form selectively permeable membranes similar to those of cells

Lab experiments cannot prove that the sequence above is how life began. They only show that such events could have taken place. Debates still go on about the beginning of life.

I. The fossil record chronicles life on Earth

A. Geologists have established a geologic record of Earth’s

history 1. Origin of Earth (4.6 billion)

2. Oldest fossils of cells (prokaryotes) (3.5 billion)

3. Oldest fossils of single celled Eukaryotes (2.1 billion)

4. Origin of multicellular Eukaryotes (1.5 billion)

5. Colonization of land

Marella, the most abundant Burgess Shale organism.

Sponges

Trilobite

Arthropod predator

Carnivorous wormBivalve Crustacean

Burgess Shale fossil samples

II. Mechanisms of Macroevolution A. Continental Drift

1. Formation of Pangaea a. effects:

2. Breakup of Pangaea a. effects:

3. Mountain ranges, volcanoes, eathquakes

a. effects:

B. Mass extinctions1. The Permian Extinctions a. 251 million years ago b. claimed about 96% of marine animals and took toll on terrestrial animals c. a lot of volcanic eruptions2. The Cretaceous Extinctions a. 65 million years ago b. all dinosaurs gone…except for one lineage – birds c. Meteorite d. layer of clay enriched with iridium (element that is rare on earth, but common in meterorites e. large crater, “Chicxulub crater”, found in the Caribbean Sea near the Yucatan Peninsula of Mexico

II. Modern Taxonomy reflects evolutionary history

A. What is Systematics?

1. Identification, naming, and classification of species

2. Goals of taxonomy

a. to assign a universal scientific name to each known species.

b. to organize the diversity of life by classifying species into larger groups of related species.

B. The Linnaean System of Classification

1. Created by Carolus Linnaeus (1707-1778)

2. Two main characteristics

a. Two-part Latin name for each species

b. A hierarchy, ordering, of species into broader groups

3. The Two part name – “binomial”

a. The “first” name is the genus the organism belongs to

b. The “last” name is the species the organism is

c. Examples:

Panthera pardus (leopard)

Panthera leo (lion)

Notice the “first” name is capitilized and the “last” name is not. It is also written in italics (or underlined if writing, not typing)

4. The grouping a. Domain (most general)

KingdomPhylum

Class Order Family Genus

Species (most specific)

Example: Domain EukaryaKingdom AnimaliaPhylum VertebrataClass MammaliaOrder PrimatesFamily Hominidae

Genus HomoSpecies sapien

C. Classification and Evolution

1. Phylogenetic Tree – diagram that reflects evolutionary relationships (has a branching pattern)

a. scientists construct these “trees” from homologous structures, DNA analysis, protein analysis

D. Dichotomous Keys

1. Used to identify an unknown organism

2. Based on physical features that are used to classify the organism

3. Uses a one question, two answer (yes, no) method

E. Domains

1. Domain Bacteria: Prokaryotic

2. Domain Archaea: Prokaryotic

3. Domain Eukarya: Eukaryotic

F. Kingdoms within Domain Eukarya

1. Protista – single celled

2. Fungi – multicelled, cannot make own food, cell wall made of chitin

3. Plantae – multicelled, can make own food, cell wall made of cellulose

4. Animalia – multicelled, cannot make own food, does not have a cell wall

Protista

Fungi

Mold

Plants Animals