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CH's 25-26 Concept Map (The History of Life on Earth (CH 25) (Fossil…
CH's 25-26 Concept Map
The History of Life on Earth (CH 25)
Conditions on Earth made the Origin of Life Possibles
cells have been produced by four steps
step 1: abiotic synthesis of small organic molecules
step 2: joining of small molecules to make macromolecules
step 3: packing molecules into protocells
Protocells: droplets of liquid contained in a membrane that is chemically different from the outside world
step 4: origin of self replicating molecules that made inheritance possible
Synthesis of Organic Compounds on Early Earth
for the first 0.6 billion years of Earth's history, it was hit by many asteroids
Earth's first atmosphere was very thick with water vapor and had little oxygen
once earth cooled, the water vapor condensed and made oceans
made primarily of nitrogen and carbon dioxide
Oparin and Haldane came up with the primitive soup idea in the 1920's
tested in 1953 by Stanley Miller and Harold Urey
one hypothesis states that early life came from deep sea vents
Alkaline Vents
Hydrothermal Vents
Another hypothesis states that organic molecules came from meteorites
Abiotic Synthesis of Macromolecules
the abiotic synthesis of RNA can occur spontaneously
Heat can also spontaneously begin the process of RNA synthesis
Protocells
self-replicating molecules and a metabolism may have existed in protocells
Protocells: droplets of liquid contained in a membrane that is chemically different from the outside world
Can reproduce and grow without dilution
Self-Replicating RNA
RNA was most likely the first genetic material
ribosomes = RNA catalysts
RNA can be many shapes
this leads to faster replication with fewer errors
all life may have originally been RNA based
RNA may have provided the template for DNA which is more stable and accurate in replication
Fossil Record
sedimentary rocks have the most fossils
therefore, the fossil record is based on sediment layers (strata)
information can also be provided by amber and ice
an incomplete record of evolution
many are destroyed
not all organisms die at the right time or place
gaps are always being filled by new discoveries
How They're Dated
radiometric dating: based on the decay of radioactive molecules
Half-life = rate of decay
is limited because organisms don't contain elements with long half-lives
Origins of New Groups of Organisms
new features developed over time
think of how the mammalian jaw developed
Key Events
fossils have helped establish a geologic record
divides Earth's history into four eons and other subdivisions
Hadean + Archean + Proterozoic = 4 billion years
Phanerozoic = 0.5 billion years
most of the time that animals have existed
3 Eras
Paleozoic
Mesozoic
Cenozoic
1st single-celled organisms
Prokaryotes were the first organisms and were the only ones for 15. billion years
Photosynthesis and the Oxygen Revolution
oxygen was introduced because of photosynthetic prokaryotes
the O2 saturated the water and rusted the iron 2. billion years ago
this had a devastating impact on anaerobic prokaryotes and wiped many of them out
1st Eukaryotes
the oldest eukaryotic organism fossil is 1.8 billion years old
evolved by way of endosymbiosis
prokaryote engulfed a mitochondria
evidence of endosymbiosis
inner membranes have enzymes and transport systems
mitochondria replicate using a similar process to bacterial replication
mitochondria have cellular machinery
mitochondrial ribosomes and bacterial ribosomes are similar
Origin of Multicellularity
Early Multicellular Eukaryotes
oldest = 1.8 billion years old
large diverse multicellular eukaryotic organisms appeared 600 million years ago
Cambrian Explosion
535-525 million years ago
sudden appearance of many fossils
large animals didn't have to be soft-bodied anymore
Colonization of Land
began 500 million years ago
arthropods are the most diverse and widespread animal group
first to colonize land 450 million years ago
Speciation and Extinction
rise and fall of any group is related to speciation and extinction rates
Plate Tectonics
the continents move over time because plate tectonics float on Earth's mantle
this process is called continental drift
consequences of continental drift
alters habitats
allopatric speciation
mass extinctions
most of the species that ever existed are now extinct
5 of them over the past 500 million years
Permian Extinction
252 million years ago
due to volcanic eruptions, rising CO2 levels, and a warmer climate
wiped out 96% of marine life
Cretaceous Extinction
66 million years ago
wiped out the dinosaurs
asteroid
6th Extinction????????
species are going extinct 100-1000 times faster than usual
Consequences of mass extinctions
changes the course of evolution
recovery time = 5-10 million years
Adaptive Radiations: periods of evolutionary change in which many new species are formed
worldwide adaptive radiations
most mammals were very small until the dinosaurs went extinct
large predators evolved in the Cambrian Explosion
regional adaptive radiations
the islands of Hawaii are the most impressive example of this
Major Bodily Changes = Changes in Genes
Effects of Developments Genes
tiny genetic changes can lead to huge morphological changes
the result of heterochrony
heterochrony = timing of development
Paedomorphosis = retaining juvenile ancestral features after reaching sexual maturity
the result of changes in spatial patterns
homeotic genes determine where body parts are placed
Evolution of Development
Changes in Gene Sequence
origin of morphological change = new developmental genes arising after duplication
Changes in Gene Regulation
change in nucleotide sequence = change in gene expression
therefore, major changes come from regulatory genes
There is Not a Goal for Evolution
As new species form, novel and complex structures gradually change and evolve
Think about the development of eyes
Evolutionary Trends
some show a trend from smaller body to larger body
can result from natural selection
evolution is the result of interaction between organisms and their environments
aka, its based in the current environment, which can change
Phylogeny and the Tree of Life (CH 26)
Phylogenies = Evolutionary Relationships
Phylogeny= evolutionary history of a species
Taxonomy= how organisms are classified and named
Binomial Nomenclature = a name with two parts
the system was made up in the 18th century by Carolus Linnaeus
The name format is:
Genus species
Hierarchical Classification
Linnaen System
Domain
Kingdom
Phylum
Class
Order
1 more item...
Does NOT reflect evolutionary history
Taxon= taxonomic unit
How are Classification and Phylogeny Related?
Evolution is tracked using a phylogenetic tree
many new systems have been suggested for classifying organisms
one system recommends classifying organisms based on evolutionary relationships
What is and isn't to be learned from phylogenetic trees?
Is to be learned
hypothesis on evolutionary history
common ancestors
root ancestor
basal taxon= the first to diverge
Isn't to be learned
phenotypic similarity
ages of the taxa
Applications of Phylogenies
inferring species identity
Phylogenies are inferred from morphological and molecular data
Morphological and Molecular Homologies
Homologies= phenotypic and genetic similarities caused by shared ancestry
Homology vs Analogy
Analogy= convergent evolution
convergent evolution is the result of similar conditions in different places
Homology= shared ancestry
Evaluating Molecular Homologies= comparing DNA
Shared characteristics are used to construct phylogenetic trees
Cladistics= common ancestry is used to classify organisms
Taxon = clade if and only if it's monophyletic
Monophyletic= contains ancestral species and all descendants
Is not a taxon if species is para or poly phyletic
Shared Ancestral and Derived Characteristics
Shared Ancestral Characteristic = character that originated in a taxon
Shared Derived Characteristic = evolutionary character unique to a certain clade
Inferring Phylogenies
derived characters are used to determine evolutionary relationships
Outgroup= a species that is closely related by not part of the group of species that is being studied
determined by morphology, paleontology, embryonic development, and genetic sequences
Ingroup= the group of species being studied
Phylogenetic Trees with Proportional Branches
Branches can show times or amount of evolutionary changes
time is usually calculated using fossils
Max Parsimony and Max Likelihood
Maximum Parsimony= looks for the simplest explanations (Occam's Razor)
Max Likelihood= looks for the most likely explanation given DNA
Phylogenetic Trees as Hypotheses
best hypothesis= best fits all available data
modified as new data comes out
Evolutionary history is documented in the genome
having genetic information helps us build phylogenies
DNA changes more slowly than RNA
Gene Duplications and Gene Families
gene duplication increases the number of genes in the genome
Gene Families= related genes within a genome
two types of homologous genes
orthologous genes= result of a speciation event
paralogous genes= results from gene duplication
Genome Evolution
lineages that diverged long ago have many orthologous genes
Molecular clocks help track evolutionary time
Molecular clock= measured by a few genes who have a constant rate of change
not a perfectly accurate system
Differences in Clock Speed
caused by mutations that a selectively neutral (not beneficial or detrimental)
neutral mutations= slow change
detrimental mutations= fast change
Problems with using molecular clocks
don't run smoothly
assumes that change has been constant
can go back billions of years
The tree is always changing
2 kingdoms -> 3 domains
originally it was just 2 kingdoms: plants and animals
Now there are 5: Monera, Protista, Plantae, Fungi, Animalia
There were problems with the 5 kingdom system so they added 3 domains: Bacteria, Archaea, and Eukarya
Horizontal Gene Transfer= when genes are transferred from one genome to another
tree of life is based on rRNA genes
Monera is no longer a taxon