Q32.4-3CC. MAKE CONNECTIONS Based on the ph... [FREE SOLUTION]

Chapter 32: Q32.4-3CC. (page 682)

MAKE CONNECTIONS Based on the phylogeny in Figure 32.11 and the information in Figure 25.11, evaluate this statement: 鈥淭he Cambrian explosion actually consists of three explosions, not one.鈥�

Short Answer

Expert verified

The two phylogenetic trees provided in the figures explain how the Cambrian explosion occurred three times and not only once. This is because the fossil records that have been provided explain that Molluscs were found on Earth ten million years before the Cambrian explosion.

It indicates that organisms were evolving through evolutionary changes to give rise to Ecdysozoa and Deuterostomia.

Step by step solution

Cambrian explosion

The Cambrian explosion occurred 541 million years ago. During this period, multiple organisms belonging to different phyla came into existence. This event is significant in biological history as it leads to biodiversity on Earth.

The main element that triggers the Cambrian explosion is the abundance of oxygen in the atmosphere.

Information obtained from the phylogenetic trees

Figure 32.11 explains that molluscs belong to the group Lophotrochozoa which is a subgroup of bilaterians. Figure 25.11 explains that these organisms were found much earlier than the Cambrian explosion. This explains that organisms evolved independently.

The Cambrian explosion occurred three times

Figures 32.11 and 25.11 clearly indicate that the Cambrian explosion did not occur only once. Before the Cambrian explosion could occur, molluscs were already found invading the land.

Additionally, even after the Cambrian explosion occurred, several organisms evolved independently, leading to Dueterostomia and Ecdysozoa. Therefore, the explosion occurred three times, that is, with Lophotrochozoa, Deuterostomia, and Ecdysozoa.