Chapter 25: The History of Life on Earth

macroevolution

the broad pattern of evolution above the species level

protocells

droplets with membranes that maintained an internal chemistry different from that of their surroundings

hydrothermal vents

areas on the seafloor where heated water and minerals gush from Earth’s interior into the ocean

alkaline vents

deep sea vents that release water with a high pH (9-11) and a warm temperature, rather than hot

ribozymes

RNA catalysts that function like enzymes

radiometric dating

a technique used to determine the age of a fossil, which is based on the decay of radioactive isotopes

half life

the time required for 50% of the parent isotope to decay

tetrapods

animal group that has 4 limbs

stromatolites

layered rocks that form where certain prokaryotes bind the films of sediment together

endosymbiosis

when a prokaryotic cell engulfed a small cell that would evolve into an organelle found in all eukaryotes, the mitochondrion

serial endosymbiosis

states that mitochondria evolved before plastids through a sequence of endosymbiotic events

cambrian explosion

phenomenon that explains many present day animal phyla suddenly appearing in fossils formed around 535-523 million years ago

plate tectonics

theory that claims that the continents are part of great plates of Earth’s crust that essentially float on the hot, underlying portion of the mantle

continental drift

plates move over time due to the movements in the mantle

pangaea

a supercontinent from 250 million years ago, brought together by separated landmasses

mass extinction

when large numbers of species become extinct worldwide

Permian mass extinction

mass extinction which defines the boundary between the Paleozoic and Mesozoic eras

Cretaceous mass extinction

mass extinction that extinguished more than half of all marine species, including all dinosaurs. Characterized by 66-million year old crater

adaptive radiations

periods of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological roles in their communities

heterochrony

an evolutionary change in the rate of timing of developmental events

paedomorphosis

a condition in which the development of reproductive organs accelerates in comparison to that of other organs, and the sexually mature stage of a species may retain body features that were juvenile structures in ancestral species

homeotic genes

master regulatory genes that determine basic features, like where a pair of wings and legs will develop on a bird