How old is Earth?
4.6 billion years old
When did the First Life Forms Appear on Earth?
3.8 billion years ago
How did Life Arise?
Abiotic synthesis of small organic molecules
Joining of these small molecules
Packing of the molecules into protocells
Origin of self replicating molecules (RNA)
What were the First Catalysts?
Ribozymes (RNA)
RNA both helped in self replicating and catalyzing
Early Atmosphere
It was a reducing environment (as opposed to an oxidizing atmosphere)
These conditions favored a synthesis of organic compounds
Soup Analogy
Ingredients = Oparin and Haldane
Oven = Energy such as lightning and UV radiation
Miller and Urey
They provided conditions similar to earths early atmosphere and tested the Oparin-Haldane hypothesis
Simulated conditions in a lab
Produced amin acids
What does the Fossil Record Reveal?
It reveals the changes in history of life on earth and it shows the kinds of organisms on Earth overtime
Sedimentary Rocks
Deposited into layers called strata and are the richest source of fossils
Where are Older Fossils?
Older fossils are farther down in the earth
Newer ones are nearer the top
Stromatolites
The oldest known fossils
They are rocks formed by the accumulation of sedimentary layers on bacterial mats
They are layers of single cell organisms on top of each other
When do Stromatolites date back to?
3.5 billion years ago
How long were Prokaryotes the only Inhabitants of Earth?
1.5 billion years
Oxygen Revolution
O2 accumulated gradually in the atmosphere from about
2.7 to 2.4 billion years ago
Proof of Oxygenic Revolution
Branded iron formation of rocks
The iron reacted with the oxygen to rust
Consequences of the Oxygenic Revolution
Many prokaryotic groups could not adapt to increased atmospheric O2 levels
Some groups survived and adapted using cellular respiration to harvest energy
When do the Oldest fossils of Eukaryotes Date back to?
1.8 billion years ago
Endosymbiont Theory
The theory proposes that mitochondria and plastids (chloroplasts and related organelles) were formerly small prokaryotes living with in larger host cells
Endosymbiont
A cell that lives within a host cell
Serial Endosymbiosis
Mitochondria evolved before plastids through sequence of endosymbiotic events
ATP for the host cell was the rent that the mitochondria paid
Evidence of the Endosymbiotic Theory
Have two membranes
Utilize electron transport enzyme
Has its own DNA
Have ribosomes
Prokaryotic Ribosome
50S subunit
30S subunit
70S ribosome
Eukaryotic Ribosome
60S subunit
40S subunit
80S ribosome
When did the Second Wave of diversification Occur?
When the multicellularity evolved and gave rise to algae, plants, fungi, and animals
Cambrian Explosion
The sudden appearance of fossils resembling modern animal phyla in the Cambrian period (535-535 millions years ago)
When was the Land Colonized?
Fungi, plants and animals began to colonize land about 500 million years ago
What Evolved from lobe-finned Fish and When?
Tetrapod’s about 365 millions years ago
What Evolved from Tetrapod’s and When?
The human lineage evolved around 6-7 million years ago
When did Modern Humans Originate?
195,000 years ago
What does the Rise and Fall of Groups of Organisms Reflect?
It reflects the differences in speciation and extinction rates
What can Extinction be Caused by?
Can be caused by changes to a species biotic and abiotic environment
Mass Extinction
The rate of extinction is increased dramatically
Adaptive Radiation
The rapid evolution of diversity adapted species from a common ancestor
What May Adaptive Radiation Follow?
Mass extinctions
The evolution of novel characteristics
The colonization of new regions
Taxonomy
Ordered division and naming of organisms
Linnaeus (18th Century)
Published a system of taxonomy based on resemblances
2 Key Features of Linnaeus’s System
Utilize binomial nomenclature: Genus + Specific epithet
Utilizes Hierarchal classification
Taxonomic Groups from Broad to Narrow
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
Taxon
A taxonomic unit at any level
Phylogeny
Evolutionary history of a species or group of related species
Systematics
Classifies organisms and determines their evolutionary relationships
Use fossil, molecular, and genetic data to infer evolutionary relationships
What does Phylogenetic Tree Represent?
It represents a hypothesis about evolutionary relationships
Branch Point (Node)
Divergence of two species from a common ancestor
Sister Taxa
Groups that share an immediate common ancestor that is not shared by any other group
Sisters not cousins
Rooted Tree
Includes a branch to represent the last common ancestor of all taxa in the tree
Basal Taxon
Diverges early in the history of a group and originates near the common ancestor of the group
Polytomy
A branch from which more than two groups emerge
What do Phylogenetic Trees Show?
Pattern of descent
What do Phylogenetic Trees not Show?
When or how much genetic change has occurred in a lineage
Can Taxa be Rotated Around Nodes and still Depict the same Relationships?
Yes
Monophyletic Group
Consists of all the descents of a single common ancestor
Paraphyletic Group
Consists of some, but not all descendants of a single common ancestor
Polyphyletic Group
Does not include the common ancestor of all descendants (excludes at least one monophyletic group)
3 Ways of Making a Phylogeny
Character Table
Phylogenetic tree
DNA
How to Make a DNA Phylogeny?
Start with the first hypothesis
Map all the changes onto the tree and count the number of events
Do the same for other Phylogenetic hypothesis
The tree with the fewest number of events is the best tree
The first tree is the most parsimonious
Parsimony
The fewest number of evolutionary steps
Phylogenetic Bracketing
Allows for us to predict features of an ancestor from features of its descendants
What are the Best Hypotheses for Phylogenetic Trees?
The trees that fit the most data:
Morphological, molecular, and fossil
How Many Kingdoms did Early Taxonomists Have?
2
Plants or animals
The 5 Kingdoms
Monera (prokaryotes)
Protista
Fungi
Plantar, and Animalia
Monera
Archaea and bacteria prokaryotes
Small
Lack internal Organelles
Simple genetic information
Important in nutrient cycling, agents of disease
Protista
Single celled eukaryotes
Most artificial of kingdoms
Have flagella and cilia
Have true organelles
Range from algae to animal- and fungal-like heterotrophs
Almost all are aquatic and aerobic
Plantae
Multicellular photosynthetic autotrophs
All terrestrial, secondary specialization -Adapts to prevent dying
Fungi
Multicellular
Heterotrophic - Obtain nutrients by absorptions
Degrade organic matter majority of lifecycle spent in haploid state
Animalia
No cell walls
Separate tissues
Cell fate is determined
Most complex organisms with many feedback and control systems
3 Domain System
Bacteria
Archaea
Eukarya
Which of the 3 Domains are more Closely related to Each other?
Eukaryotes and Archaea
What does a typical Prokaryotic Cell Contain
Fimbriae
Nucleoid
Ribosomes
Plasma membrane
Bacterial chromosome
Cell wall
Capsule
Flagella
Most Common Shapes of Prokaryotic Cells
Coccus
Bacillus
Spiral
Prokaryote Cell Wall
Peptidoglycan
Are Eukaryotes or Prokaryotes Bigger?
Eukaryotes
Capsule
A polysaccharide and/or polypeptide layer covers many prokaryotes
Sits on top of the cell wall
Viscous and gelatinous
Functions of the Capsule
Contribute to virulence
Resists drying
Resists engulfment
Enables adhesion
Streptococcus Mutans
Plaque develop and produce acid, which dissolves tooth enamel
Fimbriae
Hair like appendages that allow prokaryotes to stick to their substrate or other individuals in a colony
All over the cell
Small and thin
Solid structure
Pili
Involved in motility (gliding and twitching motility)
Conjugation pili involved in DNA transfer from one cell to another
Function of Cell Wall (Prokaryote)
Maintain cell shape
Physical protection
Prevents the cell from bursting in a hypotonic environment
Gram Positive Characteristics
Thicker peptidoglycan
No outer membrane
Purple circle
Gram Negative Characteristics
Thinner peptidoglycan
Outer membrane
Pink rod
Gram-Positive Bacteria
Alcohol dehydrates peptidoglycan
CV-I crystals do not leave
Gram Negative Bacteria
Alcohol dissolves outer membrane and leaves holes in peptidoglycan
CV-l washes out; cells are colorless
Safranin added to stain cells
Cell Wall in Eukaryotes (Plants)
Plant cells walls made of different polymers
Cellulose, hemicellulose, pectin, lignin
Cell Wall in Eukaryotes (Fungi)
Fungal cell walls made of chitin, glucans
Internal Organization in Prokaryotes
Prokaryotic cell usually lack complex compartmentalization
However some prokaryotes do have specialized membranes that perform metabolic functions
Prokaryotic Flagella
Flagellin
Used for propulsion
Have a motor (4 rings) and a hook
Allow bacteria to move toward or away from stimuli by “running and tumbling”
Fluid structure
3 Types of Taxis (Stimuli)
Chemotaxis
Phototaxis
Magnetotaxis
Monotrichous
1 flagella on 1 end
Amphitrichous
2 flagella 1 per each end
Lopotrichous
4 flagella at 1 end
Peritrichous
Flagella surrounding everywhere
Amphilophotrichous
Tuft of flagella at both ends
Magnetotaxis
Small magnets inside of bacteria used to move around
Eukaryotic Flagella
Tubulin based
9 microtubules around and 2 in the middle
Whip like motions
Prokaryotic Chromosome
DNA is in a nucleoid region
Usually a circular chromosome
Less DNA than the eukaryotic genome
DNA is supercoiled
Eukaryotic Chromosome
Large linear with several copies
Why is DNA Packaged into Chromosomes
Compact the DNA to fit into the cell
Protect the DNA from damage
Transmit all DNA to daughter cell when the cell divides
Extra chromosomal DNA in Prokaryotes
Bacteria can carry smaller rings of DNA called plasmids
They replicate independently and carry genes that are useful in stressful condition
Plasmid
Small circular, independent double-stranded DNA molecule
They can be frequently transmitted from one bacterium to another
Extra Chromosomal DNA in Eukaryotes
Mitochondria or the chloroplast (have their own DNA)
Endosymbiosis
Cell Division in Prokaryotes
Reproduce quickly by binary fission
Ranges from 20 minutes to 24 hours
Can have multiple copies of the plasmid in the cell
May be divided into 2 offspring by chance