Scientists estimate that if index fossils were deposited during a certain time frame, then the entire rock layer was also deposited at the same time. A scientist finds Trophite fossils. According to the chart above, in what era and period was this rock layer deposited? (a)  

• Mesozoic era; Triassic period
• Cenozoic era; Tertiary period
• Paleozoic era; Permian period
• Paleozoic era; Mississippian period

Scientists discovered fossils of different organisms in some layers of rock. Organism 5 was discovered in the uppermost layer. The scientists wanted to determine if Organism 5 was related to other organisms found in older layers of rock. They compared physical traits and DNA similarities from all the fossils. Some of their results are shown in the table. Based on the table, which organism is MOST likely an ancestor of Organism 5?

• Organism 4

• Organism 1

• Organism 2

• Organism 3

Scientists theorize that the ancient animal on the left is related to the modern animal on the right and has gone through many changes over time. How did the scientists conclude that the animal changed over time?

• by examining fossil records

• by learning about natural selection

• by studying deposition of sediments

• by observing different types of rock formations

A scientist drew some diagrams of ancestors of elephants based on fossil evidence. Which is the BEST conclusion that can be made from comparing the diagrams?

• Elephant species have changed over time.

• Ancient elephants were better adapted than modern elephants.

• Elephant habitats have remained the same over time.

• Elephant fossil evidence is widespread and complete.

The picture shows an ammonite fossil on the left. On the right, it shows how the animal may have looked 160 million years ago. According to the ammonite’s characteristics, which modern animals would MOST likely be the relatives of ammonites? (a)  

• squids and octopi
• whales and porpoises
• lizards and turtles
• shrimp and crabs

This photograph of a canyon wall shows several layers as indicated by the arrows. Which distinction between these rock layers is indicated by the relative positions of the rock layers in the canyon wall?

• their rate of erosion

• their composition

• which types of organisms can live among them

• which forces of erosion are acting on them

The diagram shows the front limbs of four different members of the horse family, based on the fossil record. They are arranged from the oldest to the most recent. Which BEST describes how the front limbs of horses have changed over time?

• The toes have reduced in number.

• They have gained additional toes.

• The bones have become stronger.

• The bones have become shorter.

When two fish die, Fish A sinks to the bottom of a lake and Fish B washes up on the rocky lake shore. Why is a fossil more likely to form from the body of Fish A than from the body of Fish B?

• Sediments in the water will quickly cover the fish.

• Soft parts of the fish will decay more quickly in the water.

• Scavengers in the water will eat the remains of the fish.

• Currents in the water will move the fish.

Scientists have discovered a fossil skeleton of a whale-like creature that lived in the early Eocene epoch. The skeleton shows an organism with large fore and hind limbs with distinct toes. Fossil skeletons of closely related species from later periods show organisms lacking hind limbs. Which conclusion does this observation BEST support?

• Ancestors of whales may once have been able to walk.

• Ancestors of whales had fewer bones than modern whales.

• Whales and their ancestors have always been ocean dwellers.

• Whales and their ancestors have always been the largest living animals.

Brachiopods are marine invertebrates. The drawing shows fossilized brachiopods and modern brachiopods. The fossilized brachiopods lived thousands of years ago and have gone extinct. Modern brachiopods are alive today. What can be concluded by examining the drawings of the brachiopods?

• The fossil record provides evidence that species can change over time.

• Marine species change faster than freshwater species.

• Invertebrates become fossilized more readily than other types of organisms.

• Any change to the living conditions of an organism will cause its extinction.