Lesson 22: The History of Life On Earth :
How can you explain the evidence of the major extinctions in the geologic timeline using rock strata?
Meteorite collision and the demise of the dinosaurs. Scientists know that the iridium layer left over from the crash was deposited at the same time all over the world, they can use it to help match up the ages of rock strata.
What is an example of a scientific law?
Laws of Conservation
What is rock strata?
layers of rock
When was the first evidence of a single celled fossil found?
3.7 Billion years ago; they were called stromatolites
How long have modern humans been on Earth?
300,000 years
How old is the Earth?
4.6 billion years old
What is an example of half life?
700 million yrs for 50% of Uranium-235 to turn to Lead
What is a scientific law?
A description of a natural phenomenon that has been repeatedly tested and appears to be without exception.
How are models are used to represent the history of earth?
A model is a representation of an object or process that makes important aspects easier to observe. You can use a 12 hour analog clock to condense all of earth's history, so that it is easier to understand.
What is the geologic time scale?
A model used to study the history of Earth that divides this history into blocks of time such as geologic eras and geologic periods.
Why does a new era begin?
A sudden change in the types of fossils present, may mark the dividing line between different geologic time periods.
What is a scientific theory?
A well-tested explanation of scientific observations and experiments that is supported by a large amount of evidence. ex: Big Bang Theory
What is an index fossil?
Fossils of widely distributed organisms that lived during only one short period of time.
What is scientific evidence?
Data, or information, that either supports or counters a scientific theory or idea.
What are the divisions in the geologic time scale from largest to smallest?
Eons, Eras, Periods, Epochs.
What is an example of a new era beginning?
Extinction of dinosaurs; The Mesozoic Era changed to the Cenozoic Era.
How can you use fossils to compare rocks in different locations?
Fossils can help scientists determine the relative ages of rocks that are in different places.
What is half life?
Half-lives are the time it takes for 50% of the element to turn into another element.
What is the scientific name of the modern human species?
Homo Sapiens
What is the law of superposition?
It says older layers of rock are found below younger layers of rock.
How does rock strata form?
Over time, different kinds of sediments are deposited, and these form the distinct layers.
What era do humans live in presently?
The Cenozoic Era.
How did Earth form?
The cloud became smaller, denser and began to spin and clump due to gravity. Sun and planets formed from this.
What is absolute dating?
The process of determining the approximate age of a rock, fossil, or event.
What is relative dating?
The process of determining whether one rock, fossil, or event is older or younger than another.