ch. 23/24.1 origins of life and extinction

adaptive radiation

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

geologic record

A standard time scale dividing Earth's history into time periods grouped into four eons—Hadean, Archaean, Proterozoic, and Phanerozoic—and further subdivided into eras, periods, and epochs.

half-life

The amount of time it takes for 50% of a sample of a radioactive isotope to decay.

heterochrony

Evolutionary change in the timing or rate of an organism's development.

homeotic gene

Any of the master regulatory genes that control placement and spatial organization of body parts in animals, plants, and fungi by controlling the developmental fate of groups of cells

macroevolution

Evolutionary change above the species level. Examples of macroevolutionary change include the origin of a new group of organisms through a series of speciation events and the impact of mass extinctions on the diversity of life and its subsequent recovery.

mass extinction

The elimination of a large number of species throughout Earth, the result of global environmental changes.

paedomorphosis

The retention in an adult organism of the juvenile features of its evolutionary ancestors.

Pangaea

The supercontinent that formed near the end of the Paleozoic era, when plate movements brought all the landmasses of Earth together.

plate tectonics

The theory that the continents are part of great plates of Earth's crust that float on the hot, underlying portion of the mantle. Movements in the mantle cause the continents to move slowly over time.

radiometric dating

A method for determining the absolute age of rocks and fossils, based on the half-life of radioactive isotopes.

stromatolite

Layered rock that results from the activities of prokaryotes that bind thin films of sediment together

extremophile

An organism that lives in environmental conditions so extreme that few other species can survive there. Extremophiles include extreme halophiles (salt lovers) and extreme thermophiles (heat lovers).

ribozyme

An RNA molecule that functions as an enzyme, such as an intron that catalyzes its own removal during RNA splicing.

protocell

An abiotic precursor of a living cell that had a membrane-like structure and that maintained an internal chemistry different from that of its surroundings.

abiotic synthesis experiment

Stanley Miller experiment that made amino acids under reducing conditions - used METHANE- which is not thought to be in early earth's atmosphere

RNA world

RNA can function as ribozymes which can make organic molecules - very improbable due to abiotic synthesis of RNA

clay synthesis

dripping of amino acids and RNA onto hot sand/clay/rock polymers can be made

vesicles

fluid filled sacs that can form abiotically when lipids are mixed with water - can reproduce on their own and uptake RNA

iron - sulfide model

pyrite crystals in black smoker chimneys can bind RNA precursors which can replicate when crystals grow

inter-planetary dust particles

interplanetary dust particles- float to earth with organic molecules from comets and asteroids - seeding life on earth

glaciation

a period of global cooling during which continental ice sheets and mountain glaciers expand Ordovician and Devonian mass extinction

Sulfur Dioxide (SO2)

can contribute to global cooling by forming sulfate aerosols in the atmosphere, which reflect sunlight back into space, effectively acting as a "cooling agent" when released in large quantities, primarily from volcanic eruptions

Meteor Impact Theory

Theory suggesting a meteor caused dinosaur extinction. Triassic/Cretaceous extinctions

Siberian Traps

large igneous province formed about 250 million years ago, causing the Permian Extinction- massive volcano eruptions caused global warming