Lesson 22 Test AB - 2

How do models represent the history of Earth.

Models of Earth are used to show how little the humans have been on earth compared to other era and history. Includes other things that have happened on Earth.

How was the Earth formed?

4.6 bya the cloud became smaller, denser and began to spin and clump due to gravity. Sun and planets formed from this.

What is scientific law?

A description of a natural phenomenon that has been repeatedly tested and appears to be without exception. Scientific law only describes what happens, whereas a scientific theory explains why. Ex: Laws of Conservation.

What is a model?

A representation of an object or process that makes important aspects easier to observe.

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 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 absolute dating?

Absolute dating is the process of determining the approximate age of a rock, fossil, or event. In absolute dating scientists look at radioactive elements in rocks and fossils which change to other elements over time.

What era do humans live in?

Cenozoic Era.

How can you explain the evidence of the major extinctions in the geologic timeline using rock strata?

Certain major events in Earth's history can also be useful for matching up the ages of rocks from different parts of the world, found in rock strata. Example: 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.

How was the Earth formed in sections from past to present time?

Cloud of Dust and Gas, Solar System Formation, Spinning Disc, Early Solar System, Solar System Today.

What is scientific evidence?

Data, or information, that either supports or counters a scientific theory or idea.

What Era did Dinosaurs live in?

Dinosaurs lived in the Mesozoic Era.

What is the divisions in the geologic time scale from largest to smallest?

Eons, Eras, Periods, Epochs.

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 a half-life and how do you calculate it?

Half-lives are the time it takes for 50% of the element to turn into another element. Example: 700 million yrs for 50% of Uranium-235 to turn to Lead.

How long have humans been on earth and what are their scientific names?

Homo sapiens have lived on Earth only for about 300,000 yrs.

What is an index fossil?

Index fossils are fossils of widely distributed organisms that lived during only one short period of time.

How long did the Paleozoic Era last?

It lasted 300 million years.

What and when was the first evidence of a single celled fossil was found?

Oldest fossils were found to be 3.7 bya, called Stromatolites (which are produced by living bacteria).

What is rock strata and how is it formed?

Rock strata are layers of rock and are formed by different kinds of sediments being deposited, and these form the distinct layers.

How old is the Earth?

Scientists have evidence that Earth is 4.6 billion years old.

What is the law of superposition?

States that older layers of rock are found below younger layers of rock.

What is the Geologic Time Scale and why do scientists use it?

The Geologic Time Scale is a model used to study the history of Earth that divides this history into blocks of time such as geologic eras and geologic periods. Scientists use it to date history, events, fossils, strata, and what happened during that time.

What period were early humans from?

The Neogene Period.

What period are modern humans from?

The Quaternary Period.

What is gravity?

The attraction of matter (objects that have mass and take up space) to other matter.

What is relative dating?

The process of determining whether one rock, fossil, or event is older or younger than another.