Topic 16 - History of Life on Earth Flashcards
Abiotic
Not alive (e.g., air, water, and some components of soil)
Adaptive radiation
Rapid evolutionary diversification within one lineage, producing many descendant species with a wide range of adaptive forms.
Biotic
Living, or produced by a living organism.
Cambrian Explosion
The rapid diversification of animal body types and lineages that occurred during a 50-million-year period about 541 mya at the start of the Phanerozoic eon.
Cenozoic era
Recent life. The most recent interval of geologic time, beginning 66 million years ago, during which mammals became the dominant vertebrates and angiosperms became the dominant plants.
Continental drift
The movement of Earth’s continents relative to each other over geologic time.
End-Cretaceous extinction
Happens at the transition between the Mesozoic and Cenozoic eras. Triggered by the impact of an asteroid, after which 60 to 80% of multicellular species were extinct.
End-Permian extinction
Happens at the transition between the Paleozoic and Mesozoic eras. 90% of species were extinct. Possible explanation involves volcanism, increase in CO2 and SO2 in the atmosphere, intense global warming, acid rains with devastation of plants and fungi, anoxic oceans, among other things.
HOX genes
A class of genes found in most animal phyla, including vertebrates, that are expressed in a distinctive pattern along the anterior-posterior axis in early embryos and control formation of specific structures. Hox genes code for transcription factors with a DNA-binding sequence called a homeobox.
Mass extinction
The extinction of a large number of diverse organisms around the world during a relatively short period of geologic time (about 1 million years). May occur due to sudden and extraordinary environmental changes.
Mesozoic era
Middle life. The interval of geologic time from 252 million to 66 million years ago, during which gymnosperms were the dominant plants and dinosaurs the dominant vertebrates. Ended with the extinction of the dinosaurs (except birds).
Oxygen
This gas was virtually absent from the atmosphere until around 2.5 billion years ago, when the first cyanobacteria started photosynthesizing. At first it was mostly dissolved in water, and then it diffused in larger amounts to the atmosphere and allowed for the formation of an ozone layer. Its concentration reached a peak at the second half of the Paleozoic era, when extensive fern forests covered a good part of land masses.
Paleozoic era
Ancient life. The interval of geologic time from 541 million to 252 million years ago, during which fungi, land plants, and most animal lineages first appeared and diversified. Began with the Cambrian explosion and ended with the extinction of almost all multicellular life-forms at the end of the Permian period.
Precambrian
The interval between the formation of the Earth, about 4.6 billion years ago, and the appearance of most animal groups about 541 million years ago. Unicellular organisms were dominant for most of this era, and oxygen was virtually absent for the first 2 billion years.
