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Chapters 25 & 26 (The History of Life on Earth (The Origin of Life…
Chapters 25 & 26
The History of Life on Earth
The Origin of Life
abiotic synthesis
the abiotic synthesis of RNA monomers experiment in 2009
macromolecules
Stanley Miller and Harold Urey early atmospheric experiment in 1953
protocells
natural selection favored the proliferation of stable protocells with self-replicating, catalytic RNA
fastest replicating RNA has the most descendants
self-replicating molecule
the first genetic material was most likely RNA, not DNA
RNA functions as an enzyme-like catalyst called a ribozyme
primitive soup - J B S Haldane
Major Events in the History of Life on Earth
Precambrian era (4.5 billion-541 million years ago)
Hadean
Archean
Proterozoic
prokaryotes and early atmosphere -- single-celled eukaryotes and multi-cellular animals
Paleozoic era (541 million-252 million years ago)
colonization of land
Mesozoic era (252 million- 66 million years ages)
Triassic
Jurassic
Cretaceous
(Age of the Reptiles)
Cenozoic (66 million- present)
earth started to warm up
Rise of the Mammals
humans
Continental Drift, Mass Extinctions, and Adaptive Radiations
Pangea
theory of plate tectonics: the continents are part of bigger plates of Earth's crust that float on the hot, underlying portion of the mantle
Earth's plates have formed a supercontinent 3 times: 1 billion, 600 million, and 250 million years ago
continental drift
alters the habitat in which organisms live
climate change
allopatric speciation
explains the geographic distribution of extinct organims
mass extinctions
Ordovician-Silurian (439 million years ago, 86% of life)
late devonian (364 million years ago, 75% of life)
Permian-Triassic (251 million years ago, 96% of life)
Triassic-Jurassic (199-214 million years ago)
Cretaceous-Paleogene (65 million years ago, 76% of life)
The Evolution of Complex Structures
changes in spatial pattern
changes in gene sequence
changes in gene regulation
new genes/mutation
heterchrony: developmental timing
Phylogeny and the Tree of Life
Phylogenies Show Evolutionary Relationships
phylogeny: the evolutionary history of a species or group of species
constructed using systematics
a phylogeny of lizards and snakes indicates that both the eastern glass lizard and snakes evolved from lizards with legs, but their legless conditions evolved separately
systematics: a discipline focused on classifying organisms and determining their evolutionary relationships
Linnean system of classification
binomial nomenclature: two-part format of the scientific name
Genus species
(Latin)
invented by Carolus Linnaeus in the 18th century
hierarchical classification: hierarchy of increasingly inclusive categories
kingdom, phylum, class, order, family, genus, species
phylogenic tree: represents the evolutionary history of a group of organisms in a branching diagram
A phylogenic tree represents a hypothesis about evolutionary relationships that are depicted as a series of two-way branch points called dichotomies
some parts of phylogenic trees aren't accurate to evolutionary history though
birds (class Aves) would be a subgroup of Reptilia because they evolved from a group of reptiles
legless lizards don't go in the same group as snakes because they aren't related
phylogenic trees are intended to show patterns of descent, not phenotypic similarity
sometimes taxonomists make a mistake and place a species within a genus that it is not most closely related based on it phenotypic features
the reason it may not look like its relatives is the species may have lost a key feature shared by its close relatives
if DNA or other evidence shows that an organisms has been misclassified, the organism mat be reclassified to accurately reflect its evolutionary history
legless lizards and snakes are in separate groups
taxonomic terms
sister taxa: groups of organisms that share an immediate common ancestor that is not shared by any other group
chimpanzees and humans
basal taxon: a lineage that diverges from all other members of its group early in the history of the group
fish diverge early from others in phylum chordata
polytomy: nodes with more than two descendant lineages
The Construction of Phylogenic Trees
clades: groupings of organisms that infer phyloogeny from homologous patterns
monophyletic: consists of an ancestral species and all of its descendants
paraphyletic: consists of an ancestral species but not all of its descendants
polyphyletic: group that includes distantly related species but no their most recent common ancestor
shared ancestral character: a character that originated in an ancestor of the taxon
mammals have backbones but it doesn't distinguish them from vertebrates because all vertebrates have backbones
shared derived characteristic: an evolutionary novelty unique to a clade
hair is a characteristic shared by all mammals but not found in their ancestors
ingroup: the group of species being studied
outgroup: a species or group of species from an evolutionary lineage that is closely related to but not part of the ingroup
maximumm parsimony: investigate the simplest explanation that is consistent with the facts
maximum likelihoods: identifies the tree most likely to have produced a given set of DNA data, based on certain probability rules about how DNA sequences change over time
ex: the underlying probability rules could be based on the assumption that all nucleotide substitutions are equally alike
genes and genetic sequences show the similarities between two species; homologous sequences in two species would show common ancestry
orthologous genes: homologous genes that result from a speciation event and occurs between gens found in different species; one copy in one genome
paralogous genes: homologous genes that rslut from gene duplication; multiple copies of these genes have diverged from one another within a species; multiple copies in one genome
Morphological and Molecular Homologies
homology: phenotypic and genetic similarities due to shared ancestry
similarity in the number of bones in the forelimbs of mammals is due to their descent from a common ancestor with with the same bone structure
ex: whale and human bones
analogy: similarity between organisms that is due to convergent evolution
convergent evolution occurs when similar environmental pressures and natural selection produce similar adaptations in organisms from different evolutionary lineages
ex: Australian "mole" and African golden mole look similar, but their internal anatomy, physiology, and reproductive systems are dissimilar, and they have no common ancestry
bird and bat wings
they are homologous because they both have vertebrae forelimbs and evolved from a common ancestor
they are analogous because their wings developed separately to adapt to their separate environments
molecular clocks
molecular systematics: a way to measure the absolute time of evolutionary change based on the observation that some genes and other regions of genomes appear to evolve at constant rates; they measure the rate of mutations
determined from graphing the number of genetic dufferences against the dates of branches that come from the fossil record
it is inconsistent because every organism changes at a different rate