Problem 3 - Campbell Biology

Question

Which of the following was probably an important factor in bringing about the Cambrian explosion? (A) the movement of animals onto land (B) an increase in the concentration of atmospheric nitrogen (C) the emergence of predator-prey relationships (D) the origin of bilaterian animals

Step-by-Step Solution

Answer

The origin of bilaterian animals (Option D) was probably an important factor in bringing about the Cambrian explosion.

Step 1: Understand the Cambrian Explosion

The Cambrian Explosion refers to a period around 541 million years ago when there was a rapid diversification of multicellular life forms. During this time, many major groups of animals first appeared in the fossil record.

Step 2: Evaluate Option A

The movement of animals onto land happened after the Cambrian period. Therefore, this is unlikely to be a factor in initiating the Cambrian explosion.

Step 3: Evaluate Option B

An increase in the concentration of atmospheric nitrogen did not have a significant role in the diversification of life forms during the Cambrian period. Thus, this option is also unlikely.

Step 4: Evaluate Option C

The emergence of predator-prey relationships could have driven natural selection, leading to rapid evolution and diversification of species. This fits well as a catalyst for the Cambrian explosion.

Step 5: Evaluate Option D

The origin of bilaterian animals, which are organisms with symmetrical body plans, is thought to have played a significant role in the Cambrian explosion. It allowed for more complex body structures and functions.

Step 6: Compare Options C and D

Both predator-prey relationships and the origin of bilaterian animals are plausible factors. However, the emergence of bilaterian animals is more directly linked to the anatomical and functional diversity seen in the Cambrian period.

Key Concepts

rapid diversification

The Cambrian Explosion is one of the most fascinating events in Earth's history. Around 541 million years ago, life on Earth underwent 'rapid diversification'. This period saw the sudden appearance of a variety of complex, multicellular organisms in the fossil record. Before the Cambrian Explosion, most life forms were simple and microscopic. During this period, however, many different animal phyla emerged, including arthropods, mollusks, and echinoderms. This rapid diversification led to the establishment of various new ecosystems and niches.
The causes for this event are still being explored, but several factors could have contributed:

• Increased oxygen levels in the ocean, giving an energy boost to multicellular life forms.
• Genetic innovations, such as the advent of new developmental pathways.
• Ecological interactions that accelerated evolution.

Understanding the Cambrian Explosion helps us appreciate the dynamic and rapidly changing nature of early life on Earth.

predator-prey relationships

The emergence of predator-prey relationships during the Cambrian period was a critical driver of evolution. As animals evolved to hunt others, it drove a 'natural selection' process where only the fittest survived and reproduced. This led to the development of various defensive mechanisms in prey species and more effective hunting strategies among predators.
These interactions could include:

• Development of protective shells and exoskeletons in prey species.
• Evolution of new sensory organs to detect predators or prey.
• Adaptations for speed and stealth in predators.

Predator-prey relationships create a dynamic and competitive environment, fostering rapid evolutionary changes. This shift in interactions likely contributed significantly to the biodiversity spike observed during the Cambrian Explosion.

bilaterian animals

One monumental factor during the Cambrian Explosion was the rise of 'bilaterian animals'. These organisms exhibit bilateral symmetry, meaning their body structure is mirrored on the left and right sides. This innovation allowed for more complex body plans and specialized organs.
Key features of bilaterian animals include:

• A head and tail region, allowing directional movement.
• Development of a central nervous system, including a brain.
• More efficient digestive systems and internal organs.

Bilaterian animals set the stage for the complexity we see in modern animals. Their diversified body structures enabled the exploitation of various ecological niches, contributing massively to the overall increase in biodiversity during the Cambrian Explosion.