4d Evolution review

Scientists find a fossil (Fossil A) in a deep layer of sedimentary rock. They determine that Fossil A is the remains of a species never seen before. A few years later, other scientists discover a similar fossil (Fossil B) in a layer of sedimentary rock closer to Earth’s surface. Fossil A and Fossil B share some characteristics, but it is determined that Fossil A is a different species. One hundred years later, scientists discover another similar fossil (Fossil C) in a layer of sedimentary rock between those in which Fossils A and B were found. Upon examining all three fossils, scientists reach the conclusion that all three fossils represent related species.

A model of the layers were the fossils were found is shown below. Which of the following interpretations is best supported by the data in this situation?

• Fossil A is the oldest because it was discovered first, and Fossil C is the most recent because it was discovered most recently. Using the order of discovery, scientists can determine that Fossil A evolved from Fossil B, and Fossil B evolved from Fossil C

• Fossil A is the oldest because it was discovered first, and Fossil C is the most recent because it was discovered most recently. Using the order of discovery, scientists can determine that Fossil C evolved from Fossil B, and Fossil B evolved from Fossil A

• Fossil A is the oldest because it is found in the lowest layer, and Fossil B is the most recent because it is found in the uppermost layer. Using the ordered rock layers, scientists can determine that Fossil A evolved from Fossil C, and Fossil C evolved from Fossil B

• Fossil A is the oldest because it is found in the lowest layer, and Fossil B is the most recent because it is found in the uppermost layer. Using the ordered rock layers, scientists can determine that Fossil B evolved from Fossil C, and Fossil C evolved from Fossil A

Which explanation can best be supported by the horse fossil record?

Echippus is an early ancestor to modern horses that lived 40 million years ago. The organism had a short neck and tail and also feet with four toes. After ten million years, the tail and neck became longer and one of the toes disappeared as seen in the Mesohippus. Evolution of these organisms continued 20 million years up to the present day with the organisms having longer necks and one solid hoof.

Which explanation can best be supported by the horse fossil record?

• The fossil record shows that the mammals gradually evolved so that their toes became one large hoof so this variation must have been more useful for survival than many toes

• The fossil record shows that the mammals rapidly evolved so that their toes became one large hoof so this variation must have been more useful for survival than many toes

• The fossil record shows that the mammals gradually evolved so that their toes became one large hoof so this variation must have been less useful for survival than many toes

• The fossil record shows that the mammals rapidly evolved so that their toes became one large hoof so this variation must have been less useful for survival than many toes

A science class takes a field trip to a rock formation known for the many fossils it holds. A student finds a fossil that shows a plant with leaves similar to those of a plant that grows nearby. The student tells his classmates that the plants must be an ancient species that has not changed much over time.

Which statement BEST describes the student’s claim?

• The claim is not reasonable because fossils are records of organisms that lived long ago

• The claim is reasonable because fossils are records of organisms that lived long ago

• The claim is reasonable because plants do not change over time

• The claim is not reasonable because plants must change over time