Do all living things leave fossils?

Answer 1

Any species can leave a fossil. However, they only leave or become fossils in very rare conditions. First, the organism's remains or impressions must be immediately buried, so that they are not eroded, decomposed, or scavenged on. This usually only happens if they creature dies in a swamp or quicksand, or if it is buried after a flash flood.

Of course, this is rare. But even then, the remains must be exposed to so little air that they don't decompose (even under the soil, there are air pockets which allow bacteria to breathe). This, too, is rare.

If it survives these two stages, then over time rainwater will seep down through the soil, dissolving the organisms remains, and replacing the remains with other minerals. Over time, pressure turns these minerals into rocks.

Then, the organism is fossilized. However, because the plates are constantly moving, fossils may be destroyed by being turned into metamorphic rock, or by being pulled so deep under the crust that they melt.

In a nutshell, almost anything can, under the right conditions, be fossilized. However, the conditions that allow something to fossilize are very rare, so individuals are almost never fossilized. I hope this answers your question!