UNIT 5 Target IV: origins of life and early earth
conditions (ch. 25)
25.1 Conditions on early Earth made the origin of life possible


4 stages in chemical evolution:
1.) Abiotic synthesis of small organic monomers: amino acids and nucleotides
2.) Waves and lightning provide energy to join monomers to create polymers : proteins, nucleic acids,
polysaccharides, lipids
3.) Origin of self-replicating molecules: inheritance
4.) Package molecules within lipid semipermeable membrane: protobionts
Inorganic/abiotic -> organic -> organic macromolecules (has C and H) -> protobionts (first proteins) ->
inheritance and evolution
EARLY EARTH:
-
Earth was formed 4.6 million years ago
For millions of years, earth was hot and had MANY meteorites
Atmosphere made of CO2, CH4, NH3, H20 vapor, CO, N2, NO OXYGEN
Energy mostly came from lightning, meteors hitting, waves hitting (kinetic energy and gravitational pull
from the close moon, also made macromolecules)
SELF-REPLICATING RNA AND THE DAWN OF NATURAL SELECTION
-
RNA (organic macromolecules) was the first genetic material (self-catalytic, speed up creation of
themselves), makes proteins
Survival of the fittest; RNA molecules with certain base sequences and in certain environments were
more stable and could replicate faster with fewer errors ->greatest ability to replicate itself
Ribozyme- enzyme that is a RNA catalyst, make short copies of RNA, helps to replicate itself
PROTOBIONTS
-
Protobionts- nonliving collections of abiotically produced molecules surrounded by a membrane-like
structure, aka lipid bubble
- exhibit some properties of life, like simple reproduction, metabolism, and maintaining an
internal chemical environment different from that of their surroundings
DON’T FORGET…
…THE DOMAINS AND KINGDOMS!
-REMEMBER there is no
Kingdom Protista
anymore; just the 5
supergroups!
…THE KEY EVENTS IN LIFE’S HISTORY!
(25.3 Key events in life’s history include the origins of single-celled
and multicelled organisms and the colonization of land)
Origin of the Earth approxiamately
4.6 billion years ago.
Prokaryotes show up about 3.5
billion years ago
[Atmospheric oxygen] increases 2.7
billion years ago
Single-celled eukaryotes show up
about 2.1 billion years ago
Multicellular eukaryotes are found
1.5 billion years ago
Animal fossils appear .7 billion years
ago
Land is colonized about .5 billion
years ago
Humans join earth between 1.8-.01
million years ago (not long)