Chapter 19, Problem 29A

Summary Introduction

To determine:

The reason of having more fossils of diatoms, radiolarians, and foraminiferans that the other algae.

Introduction:

Fossils are the preserved or conserved remains of the plants, animals, and other organisms from the previous time period. They are very important evidences of evolution because fossils describe that the life on the earth was once distinct from the life present on the earth today.

Explanation of Solution

Diatoms are unicellular marine algae that have cell walls composed of opaline silica known as frustule. Foraminiferans are unicellular marine protists that contain a hard external shell of different forms and material. Their external shell is known as test. Chitin tests are the most primitive type of shells. Radiolarians are marine protozoans that produce complex mineral skeletons. They are found throughout the ocean as zooplankton and the remains of their skeletons make a big part of the ocean floor cover as siliceous ooze. Radiolarians also have external shells similar to the foraminiferans. The hard cell walls and hard outer shells of these organisms don’t get easily decompose and get fossilized in the form of sediments. This is the reason why there are more fossils of these organisms.

Conclusion

There are more fossils of diatoms, foraminiferans, and radiolarians than of other algae because these organisms have hard shell-like structure on their outer surface.