Question about rocks (biotic or abiotic)...
My daughter is working on her 4th grade science homework, and her teacher is claiming that shells are abiotic, as well as dirt. I understand her reasoning for saying so, but I'm wondering at what point organic material like shells (once part of a living creature) and dirt (decomposing plant matter) goes from biotic to abiotic. The way I'm thinking about it is that I am thinking most rocks, especially sedimentary and metamorphic, would technically be biotic because they're made from biotic material...
Posted Apr 13, 2020, 3:38 PM UTC
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It depends on the school, but the main factor to mark the difference is whether it's alive or not. Biotic is everything that's alive and abiotic everything that's not (some define biotic as living beings and their remains after death, which includes decomposing organic matter or non-fossilized remains).
But lets stick that living things are biotic and non-living objects are abiotic.
The same with dirt, which is not decomposing plant matter (exclusively), but one of multiple definitions is: a thin layer of material in the earth's surface composed of unconsolidated mineral material product of rock alteration + living beings and their products/remains.
About the sedimentary and metamorphic rocks, biochemical sedimentary rocks are formed from organic processes that involve living organisms producing the sediments (example: carbonate shells). When those rocks go through processes that destroy that original structure (metamorphism causes the carbonate shells to recristalize and become mineral calcite or other carbonate minerals) they stop being biochemical rocks.
TL;DR: biotic is living beings and abiotic non-living objects, the difference is life/death
Biotic: bacteria, plants, animals Abiotic: shells, decomposing organic matter (dead bodies/remains), rocks, water, bones, teeth
Thank you for the response. That all makes sense... I'm confused then why the teacher would say a feather and a leaf are considered biotic because they're no longer connected to the living thing... That would be like calling nail clippings biotic...