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Environment Forum

Latest Posts

Definition of living?

Posted by Sean Bone Tuesday, 13th September 2016

Thank you for your answer to my previous question about 'abiotic' and 'biotic'. How do we know then if something is 'living'?

Posted by Andrew Bone Tuesday, 13th September 2016

The definition of 'living' may vary, but most scientists are agreed that living things:


- are not necessarily capable of independent movement. A common definition beginner students use for life is 'that it moves on its own', or that it 'grows'. A plant is living, but does not 'move on its own', except perhaps through growth. However, many non-living processes, such as the formation of crystals, involve movement and 'growth' as well.

- living things are capable of reproduction. Sometimes 'self-replicates' is used, but care should be taken here: crystals will grow through a process which could be described as self-replication.

- living things are organisms. These fall into the kingdoms of cellular life: Bacteria, Archaea, and Eukarya. There are also organisms which are non-cellular: viruses and viroids (a simple form of virus with a single strand of RNA and only about 15% as many nucleobases).

Posted by Andrew Bone Thursday, 13th October 2016

Cellular organisms have cell membranes, DNA and capacity for reproduction in common, but otherwise there is a great variety of possible organelles, including the option of a nucleus. Viruses are where the clarity on what is living and what is not gets a little less clear: viruses do not carry all the reproduction equipment of their own, so have to hijack the DNA of a eukaryote to reproduce.

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