Question

EVIDENCE OF EVOLUTION: What are the other means, besides entrapment in sedimentary rock, by which organisms can become fossils? Which of these is/are likely to preserve soft tissues and, thereby, DNA?

Answer 1

The preserved remains or evidence of living things are called fossils. The organism can be either a plant or an animal.T he soft parts that are exposed to air decompose quickly. Hard parts like bones, shells, or wood, don’t decompose as quickly. They have the greatest chance of becoming a fossil.

• Freezing, compression, drying and encasement, such as in tar or resin, can create whole-body fossils that preserve bodily tissues. These fossils represent the organisms as they were when living, but these types of fossils are very rare.
• Replaced Remains: Hard parts of plants or animals are replaced by minerals over time. The minerals are in the shape of the organism. This occurs when water containing minerals seeps through the plant/animal material. Petrified wood forms in this way.
• Molds and Casts: Impressions and copies. Molds are created as mud or sediment becomes rock around dead organisms.Casts are created as minerals get deposited into the molds and then harden. They make a copy of the fossil for e.g.cast of an ammonite.
• Both body and trace fossils are commonly found buried in sedimentary rocks.
• The process , which is called carbonization, or distillation, yields a detailed carbon impression of the dead organism in sedimentary rock.
• The most common method of fossilization is called permineralization, or petrification. In this organism's soft tissues decay in sediment but the hard parts particularly the bones are left behind. Water get into the remains, and minerals dissolved in the water seep into the spaces within the remains, where they form crystals. These crystallized minerals cause the remains to harden along with the encasing sedimentary rock.
• Not all organisms fossilise well, and there will be many fossils that have been destroyed by the movements of the Earth, or simply not yet been discovered.
• The study of the process of fossilization is called taphonomy.
• Soft tissues can be preserved by mineralisation. The fossilization of soft tissues with minerals requires the immediate presence of decay microbes. The most common minerals involved in fossilization are forms of silica, aragonite, calcite, dolomite, illite, pyrite, and apatite.