CBSE Class 9 Answered

When we burry dead bodies and dig the soil after 70 years, we see that the whole body with the bones have been broken down by bacteria, teeth may remain. Then why does fossils ever form? After 70 years we see that the body buried is fully decomposed, even the bones, then why after millions of years researchers find fossils? They shouldn't be there.

Asked by aryadutta2002 | 26 Jun, 2017, 04:35: PM

Expert Answer

Fossils are the remains or impressions of dead animals or plants which lived in the remote past. Usually, when organisms die, their bodies are decomposed by the action of microorganisms in the presence of oxygen, moisture, etc.
However, sometimes, due to unfavorable environmental conditions such as absence of oxygen or moisture, the bodies of the organisms do not decompose completely. Such bodies or body parts of an organism which do not decompose are obtained in the form of fossils on digging the Earth.
In many cases, the soft parts of the organisms get decomposed and what we get as a fossil is a skeleton of hard parts such as bones, teeth, etc. Even the soft parts of the plants and animals which usually get decomposed are sometimes preserved as fossils in the form of impressions inside the rocks.
For example, if a dead leaf gets caught in mud, it will not decompose quickly. The mud around the leaf will set around it as a mould, gradually harden to form a rock and retain the impression of the whole leaf.
Thus, we can see that sometimes, when decomposition of organisms does not occur, we get fossils which researchers obtain by digging the Earth.

Answered by Sheetal Kolte | 27 Jun, 2017, 10:24: AM