At the end of the Cambrian Period, fossil evidence indicated that:
A.) a great adaptive radiation of amphibians occured
B.) amphibian species reached their greatest number
C.) most amphibian species became extinct
d.) amphibians first appeared
To answer this question, we need to first understand what the Cambrian Period was and what it represented in terms of the evolution of life on Earth.
The Cambrian Period was a geological period that occurred approximately 541 to 485 million years ago. It is often referred to as the "Cambrian Explosion" because it was a time when there was a significant diversification and proliferation of complex, multicellular organisms. This explosion of life forms resulted in the appearance of many new species and major evolutionary advances.
Now, let's discuss the options provided and explore how we can find the right answer:
A.) a great adaptive radiation of amphibians occurred: The term "adaptive radiation" refers to the rapid diversification of species from a common ancestor into a variety of ecological niches. However, during the Cambrian Period, amphibians were not yet present. Amphibians are vertebrates, and the Cambrian Period was dominated by invertebrate life forms. Therefore, we can rule out this option.
B.) amphibian species reached their greatest number: Since amphibians were not yet present during the Cambrian Period, it is impossible for them to have reached their greatest number. Therefore, we can eliminate this option as well.
C.) most amphibian species became extinct: Similar to the previous options, amphibians had not yet evolved during the Cambrian Period. Hence, they could not have gone extinct at that time. Thus, we can eliminate this option too.
D.) amphibians first appeared: This is the correct option. The Cambrian Period did witness the appearance of various new species, including the earliest amphibians. This marked an important step in the evolution of vertebrates from their invertebrate ancestors. Thus, option D is the correct answer.
In conclusion, at the end of the Cambrian Period, the fossil evidence indicates that amphibians first appeared.