Which of the following was probably the least important factor in bringing about the Cambrian explosion? a. the emergence of predator-prey relationships b. an increase in the concentration of atmospheric oxygen c. the movement of animals onto land d. the origin of Hox genes

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1. Identify the time period of the Cambrian explosion, which occurred around 541 million years ago, marking a significant increase in the diversity and complexity of life forms.
2. Analyze the options given: the emergence of predator-prey relationships, an increase in atmospheric oxygen, the movement of animals onto land, and the origin of Hox genes, and consider how each could influence the diversification of life during the Cambrian period.
3. Understand that the emergence of predator-prey relationships and the origin of Hox genes both played crucial roles in the development of complex body structures and behaviors, which are characteristic of the Cambrian explosion.
4. Consider the role of increased atmospheric oxygen, which would have supported more complex metabolic processes and larger body sizes, contributing to the diversification seen during the Cambrian explosion.
5. Evaluate the timing of animals moving onto land, which is generally accepted to have occurred in the Ordovician period, following the Cambrian. This suggests that the movement of animals onto land did not directly influence the events of the Cambrian explosion.

Key Concepts

Cambrian Explosion

The Cambrian explosion refers to a significant period in Earth's history, approximately 541 million years ago, when a rapid diversification of life forms occurred. This event marked the appearance of most major animal phyla and is characterized by the development of complex organisms with hard body parts, leading to a more complex ecosystem. Understanding this event is crucial for analyzing the factors that contributed to the rapid evolution of life.

Hox Genes

Hox genes are a group of related genes that determine the body plan and organization of an organism during embryonic development. They play a critical role in the segmentation and differentiation of body structures in animals. The origin and evolution of Hox genes are believed to have been pivotal in enabling the complexity seen in Cambrian organisms, influencing their morphology and diversity.

Predator-Prey Relationships

Predator-prey relationships are ecological interactions where one organism (the predator) hunts and consumes another (the prey). The emergence of these relationships during the Cambrian period likely drove evolutionary adaptations, leading to increased diversity and complexity in animal forms. This dynamic interaction is essential for understanding the ecological pressures that may have contributed to the Cambrian explosion.