Download Vocabulary Chapter 14

Vocabulary Chapter 14
• Fossil
• Paleontologist
• Relative dating
• Law of superposition
Fossil
 Any preserved evidence of an organism
 Formed in sedimentary rock
 Example fossil types: trace, molds, casts, replacement,
petrified, amber and mummification
 Plants, animals and bacteria can form fossils, but only
organisms that are buried rapidly in sediment are readily
preserved. Most organisms decompose before they have a
chance to become fossilized.
 Constant change of sediment in aquatic environments allows
for fossilization to occur more frequently
Paleontologist
 A scientist who studies fossils
 From fossil evidence, paleontologists
attempt to interpret the record of life left in
rocks
 They infer the diet of an organism and the
environment in which it lived and can
often create images of extinct
communities
Relative dating
 A method used to determine the age of
rocks by comparing them with those in
other layers
 Relative age scale for rocks all over the world –
from studies of rock layers (strata) geologists
inferred that all strata of the same age contained
similar collections of fossils
 Relative dating is based on the law of
superposition
Law of Superposition
 States that younger layers of rock are
deposited on top of older layers
 Process is similar to stacking newspapers in a pile
as you read them each day, unless disrupted, the
oldest ones will be on the bottom
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Do Chapter 14 Assessment Pages 411 – 412
Questions 1-10 and 17-24
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Vocabulary Chapter 14
• Radiometric dating
• Half-life
• Geologic time scale
Radiometric dating
 A method of dating rocks that uses the
decay of radioactive isotopes to measure
the age of a rock
 Scientists calculate the ratio of the parent isotope to the
daughter isotope to determine the age of the sample
 Radioactive isotopes used for radiometric dating are
found in igneous or metamorphic rocks, not
sedimentary rocks, so they can not be used to date
rocks that contain fossils but instead date rocks found
close by
Half-life
 The amount of time it takes for half
of the original isotope to decay
 For a radioactive isotope to be used to determine the
age of rocks by radiometric dating the half-life of that
isotope must be known
Geologic Time Scale
 A record of Earth’s history that identifies
major geological and biological events
 Geologic time spans more than 4 billion
years and it is subdivided to identify
how many millions of years ago (mya)
an event occurred
Vocabulary Chapter 14
• Epoch
• Period
• Era
• Eon
• Cambrian explosion
Epoch
Smallest units of
geologic time
Last several million
years
Period
Divisions of geologic time
consisting of two or more
epochs
Lasts tens of millions of years
Era
Unit of geologic time
consisting of two or more
periods
Lasts hundreds of millions of
years
Eon
Longest unit of time in the
geologic time scale
Can include billions of
years
Cambrian explosion
 A time period when the ancestors of most
major animal groups diversified, creating
a drastic change in the history of animal
life on Earth
 In the space of just a few million years,
started in Paleozoic era
Vocabulary Chapter 14
• K-T boundary
• Plate tectonics
• Spontaneous generation
• Theory of biogenesis
• Endosymbiont theory
K-T Boundary
 A layer of material that contains high levels of iridium,
between the rock layers of the Cenozoic era and ending
the Mesozoic era
 Iridium is rare on Earth but common in meteorites, which
indicates a meteorite impact
 Scientist relate this impact to the mass extinction wiping
out the dinosaurs
 The impact did not kill all species, but with the extreme
global climate change only species that could adjust to
the change survived including avian and reptilian
descendents, many marine invertebrates, and numerous
plant species
Plate tectonics
 Describes the movement of several large
plates that make up the surface of Earth
 Continental drift – continents sit on top of
these plates which have moved and
reshaped over millions of years
 Plates move atop a partially molten layer
of rock underneath them
Spontaneous generation
 Old idea that life arises from nonlife
 Disproved by Francesco Redi’s
experiment testing the idea that flies
arose spontaneously from rotting meat
 Not completely rejected until replaced
by theory of biogenesis
Theory of biogenesis
 States that only living organisms can
produce other living organisms
 Proved by Louis Pasteur’s
experiment which showed
microorganisms only grew in a flask
of broth that was exposed to the
enviroment
Endosymbiont theory
 States that the ancestors of eukaryotic cells lived in
association with prokaryotic cells
 The mutually beneficial relationship lead to the
prokaryotic symbionts to become organelles in
eukaryotic cells
 Proposed by Lynn Margulis
 Example: Mitochondria and chloroplasts have following
incommon to prokaryotes: contain there own DNA
(arranged in circular pattern), similar ribosome shape,
and reproduce by fission