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A non-living thing in biology means any form without life, such as an inanimate body or object. Compared with the entity that has life, a non-living thing lacks the features that characterize a living thing. For instance, a non-living thing lacks the fundamental unit of life, a living cell that grows, metabolizes, responds to external stimuli, reproduces, and adapts. Instead of cells, a non-living thing is made up of elements or compounds that form from chemical reactions. Examples of non-living things are rocks, water, and air.
The word non-living is a combination of the Middle English non-, meaning “not”, “lack of”, or “failure to” and living from the Old English lifende, meaning “living” or “having life”. The term thing came from the Old English þing, meaning “entity”, “being”, “body”, or “matter”. Variant: nonliving thing. Synonym: inanimate (thing).
Non-living things vs. living things
How can we tell apart non-living things from living things? A living thing is one that manifests life; it is alive. But, how can we say that it is indeed alive? In essence, a living thing is one that moves, grows, and reproduces. Otherwise, we construe the object as inanimate or non-living. There are two depictions of a non-living thing. On one hand, a non-living thing pertains to an entity that previously had life and then became dead. On the other hand, a non-living thing is one that had not, has not, and will not ever have life. The latter is the stricter definition of a non-living thing. In a biological sense, the stricter definition of a non-living thing is more appropriate. A living thing, biologically speaking, encompasses both extant and extinct species.
The basic similarity between living and non-living things is that both of them pertain to that which exists. A thing is a distinct entity, being, matter, or object. A thing may be classified based on whether or not life is exhibited. A living thing is one that possesses or exhibits life as opposed to a non-living thing that lacks life.
Features of non-living things
Lack of cell organization
A non-living thing is not organized into cell(s); a living thing is. Although both non-living and living things are essentially made up of molecules of elements and compounds, a living thing would be made up of biomolecules organized into structures of a cell. The cell is the fundamental biological unit of a living thing. It carries out various cellular processes in an orchestrated, systematized manner. It is responsible for maintaining the living state of the organism by performing various metabolic processes, e. g. cell growth, cell respiration, responding to stimuli, reproduction, sustenance, biomolecular syntheses, waste elimination, and other processes essential to homeostasis.
The cell is made up of protoplasm surrounded by a plasma membrane. Several cytoplasmic structures are suspended in the cytosol. One of the most prominent cytoplasmic structures is the nucleus. Based on the presence of membrane-bound organelles, such as nucleus, living things may be classified into either prokaryotes or eukaryotes. Membrane-bound organelles are lacking in prokaryotes whereas in eukaryotes they are present.
Growth by accretion
A non-living thing does not grow the same way a living thing does. Some non-living things seem to display growth, however, the growth occurs by accretion rather than by metabolic reactions.
In living things, growth at the cellular level is manifested by an increase in the number of cells or by an increase in the cell size. The cells grow in number through cell division (e.g. mitosis). As for the increase in cell size, it is attributed often to an increase in the cytoplasmic mass. Some organisms have the capacity to regrow lost parts. Plants, for instance, can grow new shoots at the site where it has been cut as long as the meristematic tissue remains intact. Salamanders can regenerate new eyes or new limbs. Humans have a rather limited regeneration capacity. They can regenerate skin and certain parts of the liver.
Non-living things are non-motile whereas most living things are motile. Non-living things may seem to move. However, the movement is due to an external influence. Many living things can move around spontaneously. Animals have locomotory organs that enable movement. They use them to move, especially in response to stimuli. For instance, animals escape by running away from their predators when they see them. Animals also move with the intent to forage, look for more suitable habitat, or seek a potential mate. While most animals can move at will, most plants cannot. Although plants are not as motile as most animals, they are still regarded as living because they manifest many other characteristics of life.
Lack of reproduction
Non-living things cannot naturally create copies of their own kind; living things can, by reproduction. A living thing can produce life. There are two ways by which a living thing can: sexual reproduction and asexual reproduction. In sexual reproduction, male and female sex cells of the two parents unite and form a zygote that will develop eventually into a being of their own kind. In asexual reproduction, sex cells are involved and the offspring comes from only one parent.
Lack of metabolism
A non-living thing does not metabolize whereas a living thing does. Metabolism refers to the various processes that enable the cell to stay alive. There are two forms of metabolism: catabolism and anabolism. In catabolism, the living thing carries out degradative chemical reactions that lead to the breaking down of complex molecules into smaller units, and obtains energy that is released from the process. In anabolism, energy-driven chemical reactions build molecules from smaller units. Thus, a living thing needs energy that they can use to fuel these reactions. Conversely, non-living things do not carry out such metabolic processes and they do not require energy to put up with their existence.
Not responding to stimuli
A non-living thing can neither detect changes in their environment nor respond to stimuli; a living thing can. Non-living things do not have the specialized receptors of living things that can detect changes in the environment. Humans and other animals have different senses that enable sight, hearing, smell, touch, and taste. Plants and other organisms may not have the elaborate sense organs of animals but they can still detect changes from their environment, and as such, can respond to stimuli. The response may either be positive or negative. A positive response is when the response is towards the source of the stimulus whereas a negative response is when it is away from the source.
Not capable of adapting
A non-living thing does not adapt; a living thing does by adjusting to new conditions. Living things set them apart from non-living things by having the capacity to adapt to environmental changes. They are capable of change to make themselves adapted or a better fit to their surroundings. In relation to this, it can also be said that a non-living thing does not mutate whereas a living thing does and, as such, diversifies.
Lack of life cycle
A non-living thing has no life and therefore does not die. A non-living thing does not die but it decays. Abiotic decomposition, in particular, refers to the degradation of a substance by chemical or physical means. Conversely, a living thing dies and decays. Death occurs where life ends. When a living thing dies, the organs, tissues, and cells cease to function. Decay in biological context refers to the decomposition process. A dead organism decomposes by biodegradation. For instance, microbes break down organic materials into simpler forms.
Non-living things are those lacking the characteristics of life. Based on that definition, non-living things include rock, water, sand, glass, and sun. None of them shows the characteristics of being alive. Others define a non-living thing as that, which used to be part of a living thing. For example, coal, wood, rubber, paper, etc. They are considered as non-living things in spite of initially being a part of a living tree.
In ecology, non-living things are one of the constituents of the abiotic components (abiotic factors) of the environment, such as soil and atmosphere. They affect the living things in terms of their growth, reproduction, and maintenance. The living things, in turn, are called the biotic components or biotic factors.
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