Early Earth and the Origin of Life

3A Test review

Protobionts

Very simple first cells - not officially living but resemble living cells and can perform simple cell functions

Prokaryotic heterotrophs

Simple single celled organisms with no nucleus that get nutrients by eating other cells and performing anaerobic respiration

Prokaryotic autotrophs (Cyanobacteria)

Simple single celled organisms with no nucleus that get nutrients by performing photosynthesis

Simple eukaryotes

Single celled organisms with a nucleus and other organelles including mitochondria. Get nutrients by eating other organisms and performing aerobic respiration

Prebiotic Soup Hypothesis

Atmospheric gasses in the ocean reacted to form the first organic molecules. Oceans were very hot and organic molecules could have formed from inorganic molecules

Panspermia Hypothesis

Life began elsewhere and came to earth on an asteroid

Outer Space hypothesis

Organic molecules formed elsewhere and came to earth on an asteroid

Iron-Sulfur World Hypothesis

Hydrothermal vents on the ocean floor with iron sulfide deposits could produce organic molecules

RNA First Hypothesis

Suggests RNA was the first macromolecule to form. RNA can function to store information. catalyze reactions, and carry out protein synthesis

Spontaneous Generation

Claimed that living organisms can arise from nonliving matter. (Maggots “arise” from rotting meat, Dust “creates” fleas).

Biogenesis

A living thing comes from another living thing, particularly of the same type. (Maggots come from flies)

Autogenic Theory

Organelles formed from the cell folding in on itself, forming vesicles and membrane-bound structures that later specialized into organelles

Endosymbiosis Theory

Certain organelles were once separate prokaryotes that were engulfed and not digested

Primary endosmybiosis

A larger early eukaryote had engulfed a smaller prokaryote(s), eventually forming organelles with specialized functions

Law of superposition

In general, older rock strata are covered by more recent rock strata. Deeper the strata, the older the rock and the older the fossil.

Great Oxygenation Event

2.5 BYA. Prokaryotic cells evolve the ability to perform photosynthesis. Carbon dioxide levels decreased in the atmosphere. Mass extinction of anaerobic life.