Chapter 14 The History of Life
I. Fossil Evidence of Change
-provides _________ of _________ in organisms over time.
A. Early History
- Earth was formed approximately ___________ years ago
- the ________ was formed from gases expelled from volcanoes
- gases present were ___________(steam), CO2, SO2, ______, H2S, HCN, N2 and H2
- Earth's atmosphere had little or no _________
- Earth cooled, H2O vapor condensed into _________
- Earliest life appeared 3.5 billion years ago
-Clues were left behind in ________
- A _________ is any preserved evidence of an organism.
- See table 1, pg 393 for types of fossils
- fossils form in _____________ rock
- Most organisms ___________before they have a chance to become fossilized.
- The ______________ build up until they _________ the organism’s remains.
- Minerals __________ the organic matter or fill the empty pore spaces of the organism.
- A ___________________ is a scientist who studies fossils
1. Dating fossils
a. ________________ is a method used to determine the age of rocks by
comparing them with those in other layers.
b. Radiometric Dating
- Uses the ________ of radioactive isotopes to measure the age of a rock
- Uses ____________ which is the amount time that it takes for half of the
isotopes to decay
- Radioactive isotopes that can be used for radiometric dating are found
only in ___________ or _________________ rocks.
B. The Geologic Time Scale
-The _______________________________- is a model that expresses the major
geological and biological events in Earth’s history.
- The geologic time scale is divided into the __________________ time and the
Phanerozoic eon .
- _______ of the Phanerozoic eon include the Paleozoic, Mesozoic, and Cenozoic eras.
- Each era is divided into one or more ______________.
1. Precambrian Eon
- Nearly _____________ of Earth’s entire history (the first __________________)
- Stretches from the ________________ of Earth to the beginning of the Paleozoic era
about 542 million years ago
- Earth formed and life appeared
- Eventually _________________ prokaryotes added ______________- to the
atmosphere
- _________________ appeared
-The first _____________ appeared
2. The Paleozoic Era
- began about 542 million years ago
-The ancestors of most major animal groups diversified in what scientists call the
Cambrian explosion.
- Life in the oceans continued to evolve at the end of the Cambrian period.
- Fish, land plants, and insects appeared during the Ordovician and Silurian periods.
- The first tetrapods (land vertebrates) appeared in the Devonian.
- A mass extinction ended the Paleozoic era at the end of the Permian period.
- Between 60 and 75 percent of the species alive went extinct, 90 percent of the marine
organisms disappeared
3. The Mesozoic Era
- Began about _____ million years ago
- ___________ and ___________ first appeared late in the Triassic period
- ____________ plants evolved from nonflowering plants.
- _________ evolved from a group of predatory dinosaurs in the middle of the Jurassic
period.
- ____________ were the dominant life form in the late Mesozoic
- About _________ years ago, a meteorite struck Earth.
- Created what scientists called the ________ boundary in the rock layers
- Dinosaurs _____________ along with _________ percent of all other life on earth (on
land, everything larger than a cat disappeared)
II. The Origin of Life
A. Early Ideas
- __________________________ is the idea that life arises from nonliving matter
- Francesco Redi, an Italian scientist, tested the idea that ______ arose spontaneously
from rotting meat.
- The theory of ___________ states that only ________ organisms can produce other
_________ organisms.
- Louis Pasteur designed an experiment to show that biogenesis was ______ even for
microorganisms.
B. Modern Ideas
- Life originated through a series of ____________ events early in Earth's history
- The ________________________ was an early hypothesis about the origin of life.
*Organic molecules could have been synthesized from simple ______________.
*Energy probably came from ______ (UV light), electric discharge in __________, and
volcanic heat
- Stanley Miller and Harold Urey were the ________ to show that simple organic
molecules could be made from inorganic compounds.
- Later, scientists found that hydrogen cyanide could be formed from even simpler
molecules in simulated early Earth environments.
1. Making Proteins
- Life requires __________.
- One possible mechanism for the formation of proteins would be if amino acids were
bound to a clay particle.
2.Genetic Code
- Some _______ sequences appear to have changed very little through time.
- Many biologists consider RNA to have been life’s ________ coding system.
-Other researchers have proposed that clay crystals could have provided an initial
template for RNA replication.
C. Cellular Evolution
- First cell did not leave fossils
- Earliest fossils were about _______ billion years old
- Scientists hypothesize that the first cells were ______________.
- Many scientists think that modern prokaryotes called __________ are the closest
relatives of Earth’s first cells.
- Scientists believe that soon after Archaea came ______________ prokaryotes called
cyanobacteria
- ___________ evidence of cyanobacteria has been found in rocks as old as 3.5 billion
years.
- By about _______ billion years ago there was enough oxygen to add oxygen to the
atmosphere.
- Oxygen was around long ___________ 1.8 billion years, but enough had to be
produced to oxidize the free iron before it could accumulate in the atmosphere.
- Cyanobacteria eventually produced enough oxygen to support the _____________ of
the ozone layer.
D. The Endosymbiont Theory
- Eukaryotes appeared by about 1.8 billion years ago
- One ________________ began to live __________ another prokaryote (either digested
or entered as a parasite)
- The "eaten" prokaryote then became an ____________ and eukaryotic cells appear
- This theory explains the _____________ of chloroplasts and mitochondria (these
organelles have their own DNA, prokaryote membranes and ribosomes and they replicate
by themselves