Untitled Flashcards Set

The History of Life Miller Urey experiment – replicated chem of early Earth “primordial soup” Inorganic molecules -> important organic molecules Gene First Hypothesis – origin of life started with self-replicating RNA - Evolutionary forces - RNA organisms later utilized other macromolecules - DNA later became base for genetic code Metabolism first hypothesis – self-sustaining metabolic reaction formed first - Energy and components provided by the environment (Hydrothermal vents) - Other components came later to create more complex chem networks - Many metabolic reactions are cyclic -> self-sustaining, influence of evolution Extraterrestrial Hypothesis – life came from space (very questionable) - Important components of life came from space (less questionable) Homology – features that are the same/ similar due to common ancestry - Many specialized anatomical parts are just modifications of parts in other species Homoplasy – features that are the same/ similar not because of common ancestry - Convergent evolution! Embryology – homology among traits during developments (ancestral traits in embryos) Genetic information can be homologous – evolutionary history -> genetic similarity Pangea – ancient supercontinent Gondwana – Southern half Laurasia – Northern half Geographic distribution of organisms - flightless birds only in S. continents Fossil record -> largely incomplete - Changes a lot - No mammals (Jurassic) - No angiosperms (Triassic) - No gymnosperms (Carboniferous) - No fish (Cambrian) Geologic Timescales Eon > Era > Period > Epoch Phanerozoic Eon: present – 570 MYA - Cenozoic Era (present – 65.5 MYA) (Pretty eager old men play poker hard) • Holocene – Modern day, glacial retreat, worldwide expansion of human population, includes all recorded human history • Pleistocene - “Ice Age”, modern humans appear, Megafauna extinction of mammoths, mastodon, glyptodon, and giant ground sloths) • Pliocene – Australopithecus appears, “Great American Interchange” Panama rose from the sea and N/S America connected for the first time since Cretaceous • Miocene – grasslands appear, grazing animals more common, Hominins (bipedal apes) appear, Earth warms then cools again • Oligocene – Antarctica covered in ice, modern family of mammals present (Hominids and Apes), angiosperms more dominant, grass spreads away from waterside • Eocene – very warm, N/S poles covered in forests, ungulates (hooved mammals) prominent, whales diversify, grass appears, ends with Oi1 event (major cooling) • Paleocene – angiosperms expanding, forests rapid growth in absence of dinosaurs, mammals become dominant and grow larger - Mesozoic Era (65.5 MYA – 245 MYA) • Cretaceous – angiosperms become more common, some dinosaurs go extinct, new dinosaur groups appear, ends with KT or KPg extinction event (65% of all life dies and all non-avian dinosaurs die) • Jurassic – gymnosperms dominant, first angiosperms appear, first birds appear, dinosaurs get big, Pangea splits • Triassic – synapsids, crocs and dinosaurs compete for control after PT extinction (dinos win!), mammals appear, dinosaurs diversify - Paleozoic Era (245 MYA – 570 MYA) (Come over some day, maybe play poker) • Permian – gymnosperms appear and replace lycopsid and fern trees, synapsids become dominant (tetrapod with 1 hole in skull), first dinosaurs, ends with PT extinction (95% of life dies) • Carboniferous (Pennsylvanian and Mississippian) - amphibians diversify, first amniotes appear, lycopsid forests grow out of control, oxygen levels rise, giant terrestrial arthropods (centipedes) • Devonian - “age of fish”, rapid diversification of fish, fish become dominant, entire evolution of land walking tetrapod from jawed fish occurs • Silurian – appearance of bony (jaw) fish, first vascular plants appear (adapted to live on land), first fully terrestrial animals appear (Pneumodesmus) • Ordovician – Ordovician radiation (diversification), vertebrates, appearance of jawless fishes • Cambrian – Cambrian explosion (rapid diversification of multicellular eukaryotes), arthropods most dominant animal (some ventured on land) Proterozoic Eon: 570 MYA – 2500 MYA - Eukaryotes appear (end: multicellular organisms appear) - Increase in oxygen levels Pre-Cambrian - Hadean (oldest) eon -> no life on Earth - Archean (second oldest) eon -> prokaryotes appear Common ancestry, speciation, and extinction Phylogeny/ Cladogram shows evolutionary relationships Leaves – selected taxa Root – point where the tree connects back to the tree of life Node – hypothetical common ancestors (no organisms on nodes) Speciation – 1 species turns into 2 or more species - Allopatric speciation: new species appear in different areas -> vicariance (areas move) or migration (species move) - Sympatric speciation: new species appear in the same areas -> disruptive selection Species – a group of organisms that can interbreed and create viable, fertile offspring Prezygotic barrier prevents mating Postzygotic barrier prevents viable, fertile offspring Extinction – when all members of a species die off Mass extinction – when a large % of Earth’s species dies off at once - extinction sometimes opens niches that new species can inhabit Adaptive radiation – rapid rate of speciation -> ecological/ morphological diversity Gradualism – slow changes in speciation ex. Sharks Punctuated equilibrium – fast changes in speciation Speciation – extinction equilibrium – a constant state of biological diversity, when speciation rate = extinction rate Cladistics Pre-Cladistic Linnaean classification system: organisms grouped into hierarchies Kingdom, phylum, class, order, family, genus, species Binomial nomenclature – scientific name (genus name + species epithet) - Doesn't show how closely related organisms are Taxonomy – process of naming and classifying organisms based of phylogeny Monophyletic group – consists of 1 common ancestor and all the descendants Paraphyletic group – consists of 1 common ancestor but not all descendants Polyphyletic group – consists of distantly related organisms Synapomorphies – shared derived characters (informative!) Plesiomorphies – shared ancestral (old) characters (uninformative) Autapomorphies – unshared derived characters (uninformative) Outgroup – distantly related group that is used to distinguish synapomorphies from plesiomorphies Parsimonious analysis – least number of assumptions or evolutionary steps - Goal – maximize homology, minimize homoplasy Polytomy – when there is more than one most parsimonious result - Hard polytomy – results from evolutionary processes (real) - Soft polytomy – results from bad data (not real) Apomorphy-based clade: the ancestor to evolve a synapomorphy and all its descendants Node-based clade: the most recent common ancestor of two taxa and all its descendants (when both taxa living -> crown clade) Stem-based clade: all organisms more closely related to one taxa than to another DELTRAN – delayed - Prioritizes convergent evolution ACCTRAN – accelerated - Prioritizes losses/ reversals