Ch. 25 History of Life

Four conditions for Origin of Life

Abiotic synthesis, macromolecule formation, protocell packaging, and self-replication.

Miller-Urey Experiments

Demonstrated that amino acids can be produced from non-living processes with an energy source.

Murchison meteorite

A meteorite containing both water and amino acids discovered in 1980 questioned earlier theories about how life may have originated on Earth.

Abiotic macromolecule formation

Simple RNA and polypeptide polymers form when monomers are placed on hot rocks or sand.

Protocells

Prebiotic lipid vesicles that isolate an internal environment to maintain homeostasis.

Ribozymes

RNA molecules capable of replicating short nucleotide sequences.

Absolute geologic dating

Determined using ratios of unstable isotopes and their predictable half-lives.

Earliest evidence of life

Stromatolites in Tanzania dating to 3.7 billion years ago (bya).

Oxygen Revolution

Oxygenic photosynthesis by prokaryotes increased atmospheric O2 and rusted ocean iron (~2.3-2.7 bya).

Origin of Eukaryotes

Arose from serial endosymbiotic relationships between early prokaryotic cells 1.8 bya.

First multicellular eukaryotes

Algae that arose approximately 1.2 to 1.8 bya, aided by increased oxygen.

Animal origins date

Molecular clock studies of sponges suggest animals first arose approximately 700 mya.

Cambrian Explosion

Massive radiation of animal phyla over 10 million years starting ~542 mya.

Earliest land plants

Evidence of plants with land adaptations dates from ~420 million years ago.

Plate tectonics rate

Continents continually float on the liquid mantle at a rate of ~2 cm/year.

Mass extinctions

Five events over the last 500 million years where at least 75% of species went extinct.

Mammalian adaptive radiation

Followed the 66 mya mass extinction, potentially aided by the advantage of endothermy.

Adaptive radiation triggers

Mass extinctions, colonization events, and novel adaptations.

Hox genes function

Homeotic genes whose mutations result in large modifications to body plans.

Evolutionary trends

Can build extreme complexity or trend toward fewer, more specialized characteristics.