Major Transitions in Earth History Flashcards
(19 cards)
life has 1 origin
random features, such as L isomers of amino acids and DNA, are ubiquitous
origin of life
methane, ammonia, hydrogen gas, water + electricity -> spontaneously generate simple compounds -> organic molecules -> self-replicating polymers
RNA world
all organisms had self-replicating RNA at first
single strand was unstable
double stranded DNA probably allowed
development of larger genomes
cell origin
macromolecules within a cell membrane allowed genes to co-evolve within a genome
cells only evolved once
origin of eukaryotes
bacterial-archaeal symbiosis -> became an endosymbiont (bacteriam within an archaean) -> became an organelle (mitochondria)
only happened once; some eukaryotes don’t have mitochondria because they lost them
origin of meiosis
probably only happened once because molecular mechanisms of sexual reproduction are always the same
unclear if it originated from bacterial transformation, or mitosis
similar to DNA repair
multicellularity
evolved many times
cell adhesion -> cell signaling and intercellular bridges for communication and sending resources
evolved to offer size benefit or to divide labor
origin of eusociality
many origins
societal structure benefits organisms through division of labor + size advantage
origins of mutualism
evolves frequently
ex. endosymbionts
Hadean eon
4.6 BYA
Earth forms, lots of asteroids, some bringing the water of
our oceans. Moon forms. Dynamic plate tectonics, small protocontinents.
Archean eon
4 BYA
RNA protocells (life!), prokaryotes (3.8 bya). Bombardment
slows. Archaea, microbial mats (3.5 bya). Phototropic bacteria (3.2 mya)
Earth’s surface stabilizes (2.8 bya)
Proterozoic eon
2.5 BYA
Cyanobacteria produce oxygen boom (2 bya). Eukaryotes (1.8 bya).
Algae, fungi (1.6 bya).
Marine algal communities (1.2 bya).
Terrestrial algal mats (1 bya), animals (720 mya), terrestrial fungi.
First jellyfish, bilateria (635 mya), but origins of outgroups to bilateria are murky.
Phanerozoic eon
500 MYA
Establishment of present day phyla. Paleozoic era (insects
and marine invertebrates dominate, origin of vertebrates); Mesozoic era
(dinos and non-flowering plants dominate, origin of mammals); Cenozoic
era (mammals and flowering plants world).
unicellular sisters to animals
choanoflagellates; look just like sponge choanocytes (fluid exchange structures)
history of oxygen on Earth
cyanobacteria start making oxygen
soaks into ocean and seabed
gases out of ocean, gets absorbed into land and the ozone layer
oxygen gas accumulates once the ocean, land, and ozone are filled
paleozoic era
539 MYA
Cambrian explosion! Crustaceans, jawless vertebrates, molluscs, echinoderms, cephalopods, lots of marine diversity. Ozone layer forms. Vascularized plants, terrestrial arthropods, jawed fish. Oxygenated air and organic soil. Ferns, seed plants, trees, first terrestrial vertebrates, winged insects. Amphibian diversification. Lots of extinctions wipe out
lots of insects and marine life; amniotes and reptiles are favored.
Mesozoic era
252 MYA
Dinosaurs and non-flowering plants expand, complicated
insects, small mammals. Birds, lizards, snakes, turtles, crocs. Flowering plants take over at the end. K/Pg extinction kills all non-avian dinos and most mammals, except monotremes, marsupials, and placental mammals.
Cenozoic era
66 MYA
Large birds and mammals expand. Fish and marine
mammals. Continents settle to present orientation, though glacial cycles
change land bridges and selective pressures.
12 Kya - climate stabilizes and agriculture begins. Industrial CO2 increases. On track for 75% species extinction in 250-900 years.
