Biology 3B Test
Chapter 25: History of Life on Earth
Know the brief history of life as discussed in class.
Know what the spontaneous generation is. (life comes from nonliving things)
Aristotle's postulate, obsolete theory regarding the origin of life from inanimate matter.
What’s biogenesis? (life comes from living things.
The process of lifeforms producing other lifeforms, e.g. a spider lays eggs, which develop into spiders.
Know the 4 hypothesized stages for the origins of life.
The abiotic (nonliving) synthesis of small organic molecules (monomers).
The joining of monomers into polymers.
The packaging of these molecules into protobionts, droplets with membranes that maintained a distinct
The origin of self-replicating molecules that eventually made inheritance possible.
Protobionts is a collection of abiotically produced molecules surrounded by a membrane-like structure that
can carry simple reproduction and metabolism. processes. It could have formed spontanously, when a
mixture of organic ingredients includes lipids, droplets called liposomes, becamomes surrounded by a lipid
bilayer. If enzymes is added, it can carry out a simple metabolic reactions.
Know the general makeup of the early atmosphere – was it a reducing or oxidizing atmosphere & why?
Oparin and Haldene proposed that a reducing atmosphere, lightning and intense UV radiations favored the
synthesis of organic compound from inorganic compounds. Afterwards, Miller and Urey tested their
hypothesis by applying sparks to flask water and H2O, H2, CH4, NH3, they found variety of organic
molecules. Growing evidence suggest that early atmosphere was made up primarily of nitrogen and carbon
dioxide and was neither reducing nor oxidizing. Perhaps, it is likely that small "pockets" of early atmosphere
were reducing. 1st organic compound may be formed near volcanoes and deep-sea vents, where hot water
and mineral gush from Earth's interior.
What was the first genetic material and why?
The first genetic materials is RNA, not DNA. The discovery of ribozyme, an RNA molecule that
function as an enzyme, catalyzing reactions during RNA splicing. Ribozymes can make
complementary copies of parts of RNA sequence. Natural selection has observed with RNA in
which the most stable and autocatalytic will prevail in population. Differential reproductive
success of RNA's offspring would have accumulated metabolic and hereditary improvements
creating a more stable molecule, DNA.
What are ribozymes and how they work?
An RNA molecule that functions as an enzyme, catalyzing reactions during RNA splicing.
RNA catalysts, called ribozymes, remove their own introns and modify tRNA molecules to make them fully
functional. Ribozymes also help catalyze the synthesis of new RNA polymers. Ribozyme-catalyzed reactions
are slow, but the proteins normally associated with ribozymes can increase the reaction rate more than a
What are protobionts?