BISC 1112 Lecture Notes - Lecture 3: Stanley Miller, Radiometric Dating, Hydrothermal Vent
28 Aug 2016
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History of Life
Chapter 25: The History of Life on Earth
Lost Worlds
-macroevolution
•evolutionary change above the species level
•examples:
-the origin of a new group of organisms through a series of speciation events
-the impact of mass extinctions on the diversity of life and its subsequent
recovery
-the origin of key adaptations such as flight
25.1: Conditions on early Earth made the origin of life possible
-hypothesis: the chemical and physical processes could have produced simple cells
through a sequence of four stages:
•1) The abiotic (nonliving) synthesis of small organic molecules such as amino
acids and nitrogenous bases
•2) The joining of these small molecules into macromolecules, such as proteins
and nucleic acids
•3) The packaging of these molecules into protocells (droplets with membranes
that maintained an internal chemistry different from that of their
surroundings)
•4) The origin of self-replicating molecules that eventually made inheritance
possible
-Synthesis of Organic Compounds on Early Earth
•A.I. Opaline and J.B.S. Haldane
-Russian chemist and a British scientist
-independently hypothesized that Earth’s early atmosphere was a reducing
(electron-adding) environment in which organic compounds could have formed
from simpler molecules
•energy for this synthesis could have come from lightning and UV radiation
•Stanley Miller
-University of Chicago
-tested the Oparin-Haldane hypothesis by creating laboratory conditions
comparable to those that scientists at the time thought existed on early
Earth
•apparatus yielded a variety of amino acids found in organisms today, along
with other organic compounds
find more resources at oneclass.com
find more resources at oneclass.com
•Another hypothesis: organic compounds were first produced in deep-sea
hydrothermal vents
-hydrothermal vents
•areas on the seafloor where heated water and minerals gush from Earth’s
interior into the ocean
•some of these vents known as “black smokers” release water so hot that
organic compounds formed there may have been unstable
-alkaline vents
•release water that has a high pH (9-11) and is warm (40-90degrees
Celsius) rather than hot
•an environment more suitable for the origin of life
-Abiotic Synthesis of Macromolecules
•presence of small organic molecules, such as amino acids and nitrogenous bases,
is not sufficient for the emergence of life as we know it
-every cell has many types of macromolecules, including enzymes and other
proteins and the nucleic acids needed for self-replication
-Protocells
•all organisms must be able to carry out both reproduction and energy
processing (metabolism)
-DNA molecules carry genetic information, including the instructions needed
to replicate themselves accurately during reproduction
-Self-Replicating RNA
•first genetic material was most likely RNA, not DNA
-RNA plays a central role in protein synthesis
•can also function as enzyme-like catalyst
•ribozymes
-RNA catalysts
-some can make complementary copies of short pieces of RNA, provided that
they are supplied with nucleotide building blocks
•Natural selection on the molecular level has produced ribozymes capable of
self-replication in the lab
-unlike DNA, RNA molecules are single-stranded and assume a variety of
specific three-dimensional shapes maintained by their nucleotide sequences
25.2: The fossil record documents the history of life
-the fossil record opens a window into the world of long ago and provides glimpses
of the evolution of life over billions of years
-The Fossil Record
•sedimentary rocks are the richest source of fossils
find more resources at oneclass.com
find more resources at oneclass.com
-fossil record is based primarily on the sequences in which fossils have
accumulated in sedimentary rock layers called strata
•shows that there have been great changes in the kinds of organisms on Earth
at different points in time
•an incomplete chronicle of evolutionary change
-many of Earth’s organisms did not die in the right place at the right time to
be preserved as fossils
•the known fossil record is biased in favor of species that existed for a long
time, were abundant and widespread in certain kinds of environments, and had
hard shells, skeletons, or other parts that facilitated their fossilization
-How Rocks and Fossils Are Dated
•fossils are valuable data for reconstructing the history of life, but only if we
can determine where they fit in that unfolding story
•fossils in rock strata tells us the sequence in which the fossils were laid down
—their relative ages—it does not tell use their actual (absolute) ages
•radiometric dating
-one of the most common techniques to determine absolute age of a fossil
-based on the decay of radioactive isotopes
-radioactive “parent” isotope decays to a “daughter” isotope at a
characteristic rate
•rate of decay is expressed by the half-life (the time required for 50% of
the parent isotope to decay)
-each type of radioactive isotope has a characteristic half-life which is not
affected by temperature, pressure, or other environmental variables
-radioactive isotopes with longer half-lives are used to date older fossils
-The Origin of New Groups of Organisms
•some fossils provide a detailed look at the origin of new groups of organisms
-such fossils are central to our understanding of evolution
-they illustrate how new features arise and how long it takes for such change
to occur
•Origin of mammals
-mammals belong to the group of animals called tetrapods (having four limbs)
-have a number of unique anatomical features that fossilize readily allowing
scientists to trace their origin
-have a unique set of three bones that transmit sound in the middle ear
•the hammer
•anvil
•stirrup
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Chapter 25: the history of life on earth. Macroevolution: evolutionary change above the species level, examples: The origin of a new group of organisms through a series of speciation events. The impact of mass extinctions on the diversity of life and its subsequent recovery. The origin of key adaptations such as flight. 25. 1: conditions on early earth made the origin of life possible. Synthesis of organic compounds on early earth: a. i. Independently hypothesized that earth"s early atmosphere was a reducing (electron-adding) environment in which organic compounds could have formed from simpler molecules: energy for this synthesis could have come from lightning and uv radiation, stanley miller. Tested the oparin-haldane hypothesis by creating laboratory conditions comparable to those that scientists at the time thought existed on early. Earth: apparatus yielded a variety of amino acids found in organisms today, along with other organic compounds, another hypothesis: organic compounds were first produced in deep-sea hydrothermal vents.
