Transcript 3.5 billion years ago.

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.
Arthropod
predator
Trilobite
Sponges
Burgess Shale
fossil samples
Bivalve Crustacean
Carnivorous worm
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 extinctions
1. 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 eruptions
2. 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)
Kingdom
Phylum
Class
Order
Family
Genus
Species (most specific)
Example:
Domain Eukarya
Kingdom Animalia
Phylum Vertebrata
Class Mammalia
Order Primates
Family Hominidae
Genus Homo
Species 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