Question 1

The time interval spanning four billion years across three eons is the

Accepted Answer

The time interval spanning four billion years across three eons is the Precambrian. The Precambrian era is the longest span of time in Earth's history, starting from the formation of Earth about 4.6 billion years ago and ending about 541 million years ago. It includes the Hadean, Archaean, and Proterozoic eons. Therefore, option E is the correct answer.

Question 2

Which of the following could not be dated by means of radioactive carbon?

Accepted Answer

Radiocarbon dating can only be used to date objects up to about 50,000 years old, so the Homo erectus skeleton estimated to be 800,000 years old is far beyond the limit of carbon dating.

Question 3

Which sample would not be appropriate for dating by means of radioactive potassium?

Accepted Answer

Potassium-argon dating is only effective for dating materials that are less than 2 million years old. The Homo erectus skeleton is much older than that, so it would not be appropriate for dating by means of radioactive potassium.

Question 4

The type of rocks that contain fossils are formed when grains accumulate at the bottom of bodies of water; they are called _______ rocks, and they can be dated relative to each other by a method called stratigraphy.

Accepted Answer

Sedimentary rocks are formed from the accumulation of sediments, including fossils, at the bottom of bodies of water. They can be dated relative to each other through stratigraphy, which involves analyzing the layers (strata) of the rock and the fossils contained within them. Igneous and deep rocks are not likely to contain fossils, and stromatolite and tertiary are specific types of sedimentary and time periods, respectively, but do not fully encompass the answer.

Question 5

The half-life of a particular radioactive isotope of element X is 100 years.If you know that 400 years ago a fossil contained 10 mg of this isotope, you would expect to find about _______ mg in that fossil today.

Accepted Answer

Since the half-life of the isotope is 100 years, we can calculate how many half-lives have elapsed since the fossil was created:

400 years / 100 years/half-life = 4 half-lives

Each half-life reduces the amount of isotope by a factor of 2, so after 4 half-lives the amount remaining would be:

10 mg / 2^4 = 10 mg / 16 = 0.625 mg

Rounding this to one decimal place gives us the nearest answer choice, which is C: 0.6 mg.

Question 6

The world's oldest recorded living tree is a 9,550-year-old spruce in the Dalarna province of Sweden.Scientists have also found cones from the same site that date back over 9,000 years and have the same genetic identity as the tree.These ages were determined using carbon-14 dating at a laboratory in Miami, Florida.If the ratio of ¹⁴C to ¹²C in the tree and the cone samples were compared, the ratio would be

Accepted Answer

The ratio of ¹⁴C to ¹²C would be lower in the cones because ¹⁴C is not replenished after death, hence the concentration of ¹²C would be relatively higher in the cones.

Question 7

In undisturbed sedimentary rock, strata from the _______ are immediately above rocks from the Ordovician.

Accepted Answer

In the geological time scale, the Silurian period follows immediately after the Ordovician period. Therefore, in undisturbed sedimentary rock layers, Silurian strata would be found directly above Ordovician strata.

Question 8

Refer to the graph showing the decay of a radioactive substance.  The half-life of this substance is _______ years.

Accepted Answer

The answer of Refer to the graph showing the decay...

Question 9

When Nicolaus Steno discovered that the relative ages of rocks can be determined by examining the position of fossils in separate layers of soil, he coined a process called

Accepted Answer

Nicolaus Steno's discovery led to the development of the field of stratigraphy, which involves studying the layers (or strata) of rocks to determine the relative ages of different deposits. By examining the position of fossils in these layers, scientists can determine the order in which different species lived and how they evolved over time. This technique is still used today to study the history of the Earth and the evolution of life on our planet.

Question 10

Refer to the graph showing the decay of a radioactive substance.  If this substance started decaying 280,000 years ago, and 4 mg of it remains, there was roughly _______ mg of the original substance.

Accepted Answer

The answer of Refer to the graph showing the decay...

Question 11

Which statement about carbon dating is true?

Accepted Answer

Carbon dating relies on the radioactive decay of carbon-14, which is balanced by its production from neutrons reacting with nitrogen-14 in the upper atmosphere. Option B is incorrect as dead organisms stop exchanging carbon compounds with the environment. Option C is also incorrect as carbon dating is only effective up to approximately 50,000 years. Option D is also incorrect as the half-life of carbon-14 is approximately 5,700 years. Option E is irrelevant as carbon-14 does not decay into argon.

Question 12

If the half-life of a radioactive substance is 600 years, what fraction of the original material would be left after 1,800 years?

Accepted Answer

After 1,800 years, which is three half-lives (1,800 / 600 = 3), the fraction of the original material left would be (1/2)^3 = 1/8.

Question 13

The half-life of ¹⁴C, a radioactive element of carbon, is 5,700 years.The ratio of ¹⁴C to ¹²C in a fossil 28,500 years old would be about _______ that of a living organism today.

Accepted Answer

Since the half-life of ¹⁴C is 5,700 years, in 28,500 years (5 half-lives), the amount of ¹⁴C in a fossil would be (1/2)^5 = 1/32 of what it was initially. Therefore, the ratio of ¹⁴C to ¹²C in a fossil 28,500 years old would be about 1:32 that of a living organism today.

Question 14

In the upper atmosphere, the bombardment of nitrogen-14 with neutrons varies somewhat over time.If in the past this rate had been higher, objects dated by _______ dating would now appear _______ than they really are.

Accepted Answer

The bombardment of nitrogen-14 with neutrons is a key part of the formation of carbon-14 in the atmosphere, which is used in carbon dating. If the bombardment rate had been higher in the past, there would be more carbon-14 in the atmosphere at the time, leading to objects appearing younger than they really are when dated using carbon dating.

Question 15

Which of the following was not known to eighteenth- and nineteenth-century geologists?

Accepted Answer

Radioactivity was not discovered until the late nineteenth century, so it was not known to eighteenth- and nineteenth-century geologists.

Question 16

The time interval characterized by a diverse multicellular biota is the

Accepted Answer

The Phanerozoic eon is the time interval characterized by a diverse multicellular biota, including the evolution of complex organisms such as plants, animals, and fungi. The Proterozoic and Archaean eons refer to earlier periods of Earth's history, before the evolution of complex life. The Hadean eon refers to an even earlier period, before the formation of the Earth's crust. The Precambrian is a term that encompasses the Proterozoic, Archaean, and Hadean eons, as well as the first part of the Phanerozoic eon before the Cambrian period.

Question 17

Which statement is true?

Accepted Answer

Radioisotope dating of rocks, combined with fossil analysis, allows geologists to determine relative and absolute ages of rocks and geological events. It is considered the most powerful method for this purpose.

Answer: C
 Geological periods are indeed divided into eras. The current era is the Cenozoic era, which is further divided into the Paleogene, Neogene, and Quaternary periods.

Answer: D
 To date igneous rocks, geologists typically search for locations where sedimentary rocks have intruded into igneous rocks, because the igneous rocks would have formed before the intrusion and therefore provide an older date.

Answer: E
 Radioisotope dating can be performed on any type of rock or material that contains radioactive isotopes, not just fossils.

Question 18

The half-life of carbon-14 is 5,700 years.If 10 percent of the original carbon-14 is left in a structure, that structure would be _______ years old.

Accepted Answer

The half-life of carbon-14 is 5,700 years, meaning the amount of carbon-14 halves every 5,700 years. If 10 percent is left, it means the carbon-14 has gone through more than three but less than four half-lives (since $1/2^3 = 12.5\%$ and $1/2^4 = 6.25\%$). Three half-lives equal 17,100 years and four half-lives equal 22,800 years, placing the age of the structure between 17,100 and 22,800 years.

Question 19

Which statement about Earth's history is true?

Accepted Answer

The answer of Which statement about Earth's history is true?
...

Question 20

Which statement about radioisotope dating is false?

Accepted Answer

The statement that isotopes in sedimentary rocks contain reliable information about their formation dates is false. Sedimentary rocks are formed through the accumulation of sediment, which can include rocks and minerals of various ages. This makes radioisotope dating of sedimentary rocks unreliable, as the age of the sediment does not necessarily reflect the age of the rocks within it. Igneous rocks, on the other hand, form from molten material and can be reliably dated using radioisotope methods. The decay of potassium-40 to argon-40 has been used to date many geological events, including the evolution of life. Paleomagnetic dating can be used to relate the ages of rocks to patterns in Earth's magnetism, and the age of igneous rocks can be used to estimate the age of adjacent sedimentary rocks.

Quiz 24: The History of Life on Earth

The time interval spanning four billion years across three eons is the

Which of the following could not be dated by means of radioactive carbon?

Which sample would not be appropriate for dating by means of radioactive potassium?

The type of rocks that contain fossils are formed when grains accumulate at the bottom of bodies of water; they are called _______ rocks, and they can be dated relative to each other by a method called stratigraphy.

The half-life of a particular radioactive isotope of element X is 100 years.If you know that 400 years ago a fossil contained 10 mg of this isotope, you would expect to find about _______ mg in that fossil today.

In undisturbed sedimentary rock, strata from the _______ are immediately above rocks from the Ordovician.

Refer to the graph showing the decay of a radioactive substance. The half-life of this substance is _______ years.

When Nicolaus Steno discovered that the relative ages of rocks can be determined by examining the position of fossils in separate layers of soil, he coined a process called

Refer to the graph showing the decay of a radioactive substance. If this substance started decaying 280,000 years ago, and 4 mg of it remains, there was roughly _______ mg of the original substance.

Which statement about carbon dating is true?

If the half-life of a radioactive substance is 600 years, what fraction of the original material would be left after 1,800 years?

The half-life of ¹⁴C, a radioactive element of carbon, is 5,700 years.The ratio of ¹⁴C to ¹²C in a fossil 28,500 years old would be about _______ that of a living organism today.

In the upper atmosphere, the bombardment of nitrogen-14 with neutrons varies somewhat over time.If in the past this rate had been higher, objects dated by _ dating would now appear _ than they really are.

Which of the following was not known to eighteenth- and nineteenth-century geologists?

The time interval characterized by a diverse multicellular biota is the

Which statement is true?

The half-life of carbon-14 is 5,700 years.If 10 percent of the original carbon-14 is left in a structure, that structure would be _______ years old.

Which statement about Earth's history is true?

Which statement about radioisotope dating is false?

Quiz 24: The History of Life on Earth

The time interval spanning four billion years across three eons is the

Which of the following could not be dated by means of radioactive carbon?

Which sample would not be appropriate for dating by means of radioactive potassium?

The type of rocks that contain fossils are formed when grains accumulate at the bottom of bodies of water; they are called _______ rocks, and they can be dated relative to each other by a method called stratigraphy.

The half-life of a particular radioactive isotope of element X is 100 years.If you know that 400 years ago a fossil contained 10 mg of this isotope, you would expect to find about _______ mg in that fossil today.

In undisturbed sedimentary rock, strata from the _______ are immediately above rocks from the Ordovician.

Refer to the graph showing the decay of a radioactive substance. The half-life of this substance is _______ years.

When Nicolaus Steno discovered that the relative ages of rocks can be determined by examining the position of fossils in separate layers of soil, he coined a process called

Refer to the graph showing the decay of a radioactive substance. If this substance started decaying 280,000 years ago, and 4 mg of it remains, there was roughly _______ mg of the original substance.

Which statement about carbon dating is true?

If the half-life of a radioactive substance is 600 years, what fraction of the original material would be left after 1,800 years?

The half-life of 14C, a radioactive element of carbon, is 5,700 years.The ratio of 14C to 12C in a fossil 28,500 years old would be about _______ that of a living organism today.

In the upper atmosphere, the bombardment of nitrogen-14 with neutrons varies somewhat over time.If in the past this rate had been higher, objects dated by _______ dating would now appear _______ than they really are.

Which of the following was not known to eighteenth- and nineteenth-century geologists?

The time interval characterized by a diverse multicellular biota is the

Which statement is true?

The half-life of carbon-14 is 5,700 years.If 10 percent of the original carbon-14 is left in a structure, that structure would be _______ years old.

Which statement about Earth's history is true?

Which statement about radioisotope dating is false?

The half-life of ¹⁴C, a radioactive element of carbon, is 5,700 years.The ratio of ¹⁴C to ¹²C in a fossil 28,500 years old would be about _______ that of a living organism today.

In the upper atmosphere, the bombardment of nitrogen-14 with neutrons varies somewhat over time.If in the past this rate had been higher, objects dated by _ dating would now appear _ than they really are.