Question

Which of the following types of fossils are formed when mineral replaces all parts of the organism and the entire animal is transformed into stone?
A. Petrified fossils
B. Mould and cast
C. Actual remains
D. All of the above

Answer 1

Hint: Fossils are the remains of past life forms that have been preserved by natural processes. The size ranges from the largest organisms to the smallest ones. There are different types of fossils. The process in which organic matter exposed to minerals over long periods of time gets turned into a stony substance is known as petrification.

Complete answer:
Moulds are the type of fossils that are imprinted on rocks. For example, a shell pattern could appear on a rock after the crustacean dies and gets buried in the mud. It is formed when the sediments in the mud fill both the inside and outside of the dead organisms.
Cast is a type of fossil which is made when the organism dies and their flesh decays. Then their bones decompose because of chemical reactions and the minerals enter into the cavities. This results in the formation of casts.
Actual remains are the real body parts of the organisms, but the soft parts of the plant or animal decay and disappear. These are also the most common types of fossils.
In the process of petrification, first the solutions of carbonates, silicates, iron, other minerals enter deep inside the body of the organism and get filled in the spaces between the cells covering them. Then these solutions slowly replace the cells as well. As time passes by the minerals get deposited into the body of the organisms and replace all the organic matter and finally form a petrified fossil.

Hence, the correct answer is option A, petrified fossils.

Note:
There are different processes of preservation. Based on these processes’ fossils are classified into five categories. They are Permineralization, Moulds and Casts, Recrystallization, Carbonization, and Bioimmuration. Apart from these categories there are other types of fossils as well. The most common type is actual remains.