Soal Latihan dan Jawaban Reading Comprehension 69
Anyone who has handled a fossilized bone knows that it is usually not exactly like
its modern counterpart, the most obvious difference being that it is often much heavier.
Fossils often have the quality of stone rather than of organic materials, and this has led
to the use of the term “petrifaction” (to bring about rock). The implication is that bone
(5) and other tissues have somehow been turned into stone, and this is certainly the
explanation given in some texts. But it is a wrong interpretation; fossils are frequently
so dense because the pores and other spaces in the bone have become filled with
minerals taken up from the surrounding sediments. Some fossil bones have all the
interstitial spaces filled with foreign minerals, including the marrow cavity, if there is
(10) one, while others have taken up but little from their surrounding. Probably all of the
minerals deposited within the bone have been recrystallized from solution by the action
of water percolating through tem. The degree of mineralization appears to be determined
by the nature of the environment in which the bone was deposited and not by the
antiquity of the bone. For example, the black fossil bones that are so common in many
(15) parts of Florida are heavily mineralized, but they are only about 20,000 years old,
whereas many of the dinosaur bones from western Canada, which are about 75 million
years old, are only partially filled in. under optimum conditions the process of
mineralization probably takes thousands rather than millions of years perhaps
(20) This amount of change that has occurred in fossil bone, even in bone as old as that of
dinosaurs, is often remarkably small. We are therefore usually able to see the
microscopic structure of the bone, including such fine details as the lacunae where the
living bone cells once resided. The natural bone mineral, the hydroxyapatite, is
virtually unaltered too-it has the same crystal structure as that of modern bone.
(25) Although nothing remains of the original collagen, some of its component amino acids
are usually still detectable, together with amino acids of the noncollagen proteins of
Reading Comprehension 69
The composition of fossils
The location of fossils in North America
Determining the size and weight of fossils
Procedures for analyzing fossils
The marrow cavity gradually fills with water.
Spaces within the bone fill with minerals.
The organic materials turn to stone.
Bone tissue solidifies with age.
Many colorful crystals can be found in such a fossil.
Mineralization was complete within one years of the animal's death.
It was exposed to large amounts of mineral-laden water throughout time.
It was discovered in western Canada.
The location of the bone in the animal's body
The type of animal the bone came from
The age of the fossil
To prove that a fossil's age cannot be determined by the amount of mineralization.
To explain why scientists are especially interested in Canadian fossils.
To discuss the large quantity of fossils found in both places.
To suggest that fossils found in both places were the same age