6th Grade Q2 Review

Scientists theorize that hundreds of millions of years ago, all the continents that exist today were combined into one landmass called Pangaea. Which of the following provides evidence scientists can use to support the theory of Pangea?

• Pangea can be supported by the shapes of the continents.

• Pangea can be supported by the diversity of modern organisms.

• Pangea can be supported by water samples from every ocean on Earth.

• Pangea can be supported by the temperature changes on Earth over the last several decades.

Ted’s science teacher was reviewing Earth’s geologic history. She asked the class which example from the present provides the best evidence that Earth has changed over its geologic history. Ted responded with the correct answer. Which example did Ted choose?

• Example 1: Mitochondrial DNA of living organism

• Example 2: Data collected of volcanic eruptions this year

• Example 3: Genetic similarities between humans and apes

• Example 4: Fossils of tropical trees and dinosaurs found in Antarctic

The Theory of Plate Tectonics is based on the concept of continental drift developed by Alfred Wegener. Which statement best describes why this is a theory instead of a law?

• The theory describes how the tectonic plates move over time.

• The theory is only supported by the claim Alfred Wegener proposed.

• The theory explains how the tectonic plates have drifted apart over time.

• The theory predicts how the continents will be positioned 100 years from now.

Scientific laws are a description based on observed facts and patterns in nature. One scientific law is the Law of Superposition. This law states that older rock layers are beneath younger rock layers. The diagram below shows a sample of rock layers.

According to the diagram and the law of superposition, which layer of rock is the oldest?

• A

• B

• C

• D

Jacob learned that many fossils have been found in the Peace River in Florida. He does some additional research and finds out that both land and marine fossils have been found there. The bar graph shows the ratio of marine fossils to land fossils dating from 20 million years ago, and the ratio of marine fossils to land fossils dating from 1 million years ago.

Based on the graphs, what conclusion can you make about the Peace River?

• You can conclude that earthquakes have disturbed the layers of fossils in the Peace River.

• You can conclude that twenty million years ago, land animals lived on islands in Peace River.

• You can conclude that the area where Peace River now flows was part of a seafloor 20 million years ago.

• You can conclude that over time, the number of marine animals in the Peace River area increased as they preyed on land animals.

When soil becomes very dry, wind can cause huge dust storms that erode the soil. The roots of plants can reduce the drying out of soil and can help keep it in place. Which statement best explains how human activity could contribute to an increase in soil erosion?

• When people farm the land, it is impossible to avoid over-farming the soil such that it becomes polluted and new plants can’t grow there.

• When people use careful farming practices, it is possible to maintain healthy soil such that it will allow new plants to grow there, and thus avoid erosion.

• When people farm the land, it is possible to avoid over-farming the soil such that new plants can easily grow there, making it easier for soil to dry out and erode.

• When people farm the land, it is possible for desertification to occur such that new plants can’t easily grow there, making it easier for soil to dry out and erode.

Initially, the theory of plate tectonics was rejected by most scientists. Now, the theory of plate tectonics is widely accepted.

Which of the following most influenced how scientists think about plate tectonics?

• The speed and motion of tectonic plates has increased over time.

• New evidence was discovered that made scientists revise their thinking.

• More geologists have studied plate tectonics in recent years, than in the past.

• Scientists have mapped the location of tectonic plate boundaries across the world

Chandler’s earth science class went on a field trip to walk on a trail by a mountain with places next to the trail where they could see layers of rock that were different colors and different thickness. He remarked how easy it was to see which layers of rock were older than the others by which ones were higher. Chandler’s teacher responded that it can be hard to be sure that superposition is the appropriate way to date the layers of rock. Why did his teacher question the use of the Law of Superposition to date the rock layers?

• Forces such as weathering and erosion can change the location of rock layers, sometimes putting younger rocks above older rocks.

• Forces such as gravity and magnetism can change the location of rock layers such that older rocks are sometimes located above younger rocks.

• Forces such as tilting, folding, and strike slip faults can change the location of rock layers such that younger rocks are sometimes located above older rocks.

• Forces such as tilting, folding, and strike slip faults can change the location of rock layers such that older rocks are sometimes located above younger rocks.

The diagram below shows layers of Earth’s crust that contain different kinds of fossils.

Layers B and D have fossils of different ammonites, whose hard spiral shells fossilize easily. Diego was researching the relationship of ammonites and the rocks in which they were found to find physical evidence of how Earth has evolved over time. He always found ammonites with ridged shells and 3 coils in rock matching layer B, and ammonites with smooth shells and 5 coils in rock matching layer D. He also found that rock like layer D was always underneath rock like layer B. What can Diego conclude about how ammonites changed over time

• Ammonites have not changed over great periods of geologic time.

• Ammonites with smooth shells and 5 coils lived after ammonites with ridged shells and 3 coils.

• Ammonites with smooth shells and 5 coils lived before ammonites with ridged shells and 3 coils.

• Ammonites with smooth shells and 5 coils lived at the same time as ammonites with ridged shells and 3 coils.

Juan was visiting his friend Brandon’s ranch, where there were several grazing animals. Juan helped Brandon move the animals from one area to another periodically throughout his visit. When he asked Brandon why it was important to move the animals, Brandon said that it prevented overgrazing. Overgrazing is the process of animals eating too many natural plants in an area. Juan asked what problems were caused by overgrazing. Brandon replied that it could lead to desertification and wind erosion. Juan wasn’t completely sure how overgrazing causes desertification. What is the missing part of Brandon’s explanation?

• Overgrazing kills off plants whose roots are necessary to hold soil in place

• Overgrazing kills off plants whose leaves attract insects necessary for fertilizing crops

• Overgrazing often leads to uncovering new layers of rock that are then eroded into sediments.

• Overgrazing often leads to animals digging in the ground, which changes the flow of water over Earth’s surface.