Question

The fossil record shows that the first mammals evolved 220 million years ago. The supercontinent Pangaea began to break apart 200 million years ago. Therefore, fossils of the first mammals should be found a. on most or all of the current continents. b. only in Antarctica. c. on only one or a few continents. d. none of the above

Short answer

a. on most or all of the current continents.

Step-by-step solution

Understand the Evolution Timeline

Recognize that the first mammals evolved 220 million years ago, which was before the supercontinent Pangaea began to break apart 200 million years ago.

Understand Pangaea's Breakup

Note that when Pangaea was whole, organisms, including early mammals, were distributed across one large landmass.

Impact of Pangaea's Breakup on Fossil Distribution

Since Pangaea started breaking up 200 million years ago, after the first mammals had already appeared, these mammals would have existed across the entire supercontinent prior to its fragmentation.

Fossil Distribution Today

Because the continents have drifted apart since the breakup of Pangaea, the fossils of the first mammals should logically be found on multiple current continents.

Choose the Correct Answer

Based on the understanding of the timeline and the distribution of landmasses, the correct answer is (a) on most or all of the current continents.

Key concepts

Evolution Timeline

The timeline of evolution is a fascinating subject. It helps us understand the sequence of events that led to the development of the diverse life forms we see today. In this exercise, we learn that the first mammals evolved around 220 million years ago. This was a significant milestone on the evolutionary clock. At this point, Earth’s ecosystem was vastly different from what we know today. Recognizing this timeline is crucial. It sets the stage for understanding how early mammals would have spread across the world's landmasses.

Early mammals weren't the first dominant creatures; they coexisted with dinosaurs during the Mesozoic Era. By marking the 220-million-year point, we can see how mammals underwent a long period of evolution, eventually leading to the diverse species we have now.

Attention to the timeline also helps us see how mammals adapted. Their early existence before Pangaea’s breakup indicates that these species were present on a single, vast supercontinent. This timing, just before continents started to drift apart, significantly influences our understanding of fossil distribution today.

Pangaea Breakup

Pangaea was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It was a massive landmass that included almost all of the Earth's land areas. About 200 million years ago, Pangaea began to break apart. This breakup was a slow and gradual process that eventually led to the formation of the continents we know today.

When Pangaea started splitting, the land sections drifted into different directions. This movement significantly altered Earth's geography. The landmasses we now recognize as separate continents were once connected. This is a crucial factor when studying the distribution of early fossils. Since the first mammals evolved 220 million years ago, they were widespread across Pangaea before its breakup began 20 million years later.

Understanding this breakup process helps explain why fossils of the early mammals can be found on most or all current continents. The movement of the landmasses separated the once unified populations, scattering their remains over vast areas. As a result, paleontologists have found these fossils in various parts of the world.

Fossil Record

The fossil record is a crucial tool for understanding the history of life on Earth. It is essentially the accumulation of all discovered fossils. This record provides evidence of different organisms that existed at various times. By studying fossils, scientists can trace back the evolutionary history of species, including the first mammals.

When it comes to the first mammals, we depend heavily on the fossil record. As they evolved 220 million years ago, the fossilized remains of these early mammals offer insights into their characteristics and habitats. Since Pangaea started breaking apart 200 million years ago, these mammals' fossils would be distributed across the large supercontinent.

After the breakup, pieces of Pangaea drifted into today's continents. Therefore, the fossil record shows evidence of early mammals on multiple continents. This broad distribution is a direct result of the supercontinent's division and the drift of its fragments. Thanks to the fossil record, we can piece together these incredible historical events and better understand the distribution of early life forms on Earth.