chapter 17 - The fossil record
Describe how most fossils are formed?
Most fossils are formed in sedimentary rocks. And the particles are carried by streams and rivers into lakes or seaswhere they eventually settle to the bottoms.
How do fossils form?
Most fossils form when organisms that die become buried in sediments.
index fossils
distinctive fossil used to compare the relative ages of fossils
mass extinction
event in which many types of living things become extinct at the same time
Cambrian period
from 544 million to about 500 million years ago
geologic time scale
scale used by paleontologists to represent evolutionary time
paleontologists
scientists who study fossils
periods
subdivisions of eras
what is the fossil record?
the fossil record provides evidence about the history of life on earth.it also shows how different groups of organisms,including species, have changed
Cenozoic era
the latest of the four eras into which geologic time is subdivided ; 65 million years ago to the present: sometimes called the age of the mammels.
convergent evolution
the process by which unrelated species become more similar as they adapt to the same kind of environment
Radioactive decay
the spontaneous disintegration of a radioactive substance along with the emission of ionizing radiation
half-life
the time required for one half of the atoms of a radioisotope to emit radiation an decay products
radioactive dating
the use of half-lives to determine the age of a sample
endosymbiotic theory
theory that eukaryotic cells formed from a symbiosis among several different prokaryotic organisms
Name two techniques that paleontologist use to determine the age of fossils.
...relative dating and radioactive dating
Why is the fossil record described as an incomplete record of life's history?
Because the formation of any fossil depends upon the precise combination of conditions. For every organism that leaves a fossil, many more die without leaving a trace.
Paleozoic era
Began 544 million years ago and is the period in which many vertebrates and invertebrates lived.
What two things do researchers compare to determine when an organism lived?
By comparing carbon 14 which begins to decay when a thing dies to carbon 12 which is not radioactive and does not decay, scientist can determine when a organism lived.
Identify the six periods that existed during the paleozoic era.
Cambrian Ordovician Silurian Devonian Carboniferous Permian
What geologic era is known as the age of mammals?
Cenozoic
How are eras and periods related?
Eras are subdivided into periods which range in lenght frim tens of millions of years toless than two million years.
How is sedementary rock formed?
It is formed when exposure to rain, heat, wind and cold breaks down existing rock into small particles of sand, silt, and clay.
what does the fossil record reveal?
It provides evidence about the history of life on earth. It also shows how different groups of organisms, including species, have changed over time.
What does geologic time represent?
It represents evolutionary time.
Identify three eras that geologist use to divide time?
Paleozoic Mesozoic Cenozoic
What does geologic time begin with?
Precambrian time which civers about 88% of the earths history.
Identify the two periods during the cenozoic era.
Quaternary Tertiary
What type of dating provides abosulte age for a given fossil?
Radioactive dating
what do paleontologist do?
They collect fossils and infer what past life forms were like.
what do paleontologist do when they study fossils?
They unearth the remains of entire organisms. Sometimes they reconstruct an extinct species from a few fossil bits, the look for anatomical differences and similarities between the fossil and the living organism.
Identify the three periods included in mesiozoic era.
Triassic Jurassic Cretaceous
fossil record
information about past life, including the structure of organisms, what they ate, what ate them, in what environment they lived, and the order in which they lived
proteinoid microspheres
large organic molecules that form tiny bubbles
macroevolution
large-scale evolutionary changes that take place over long periods of time
relative dating
method of determining the age of a fossil by comparing its placement with that of fossils in other layers of rock
microfossils
microscopic fossils of unicellular prokaryotic organisms that resemble modern bacteria have been found in rocks more than 3.5 billion of years old.
Mesozoic era
middle life (245-144 million years ago); rise of mammals and dinosaurs; the rise of birds; extinction of dinosaurs, rise of flowering plants
extinct
no longer existing or living
eras
one of several subdivisions of the time between the Precambrian and the present
punctuated equilibrium
pattern of evolution in which long stable periods are interrupted by brief periods of more rapid change
adaptive radiation
process by which a single species or small group of species evolves into several different forms that live in different ways; rapid growth in the diversity of a group of organisms
coevolution
process by which two species evolve in response to changes in each other
