Organism (biology)
An organism, in biological terms, refers to a living individual that meets certain criteria necessary for life. Traditionally, an organism must exhibit movement, response to stimuli, growth, respiration, and the ability to take in nutrients and expel wastes, among other characteristics. However, as advances in biology, particularly in genetics and evolutionary studies, have emerged, the definition of what constitutes an organism has been challenged. For instance, the classification of complex entities like the Portuguese man-of-war raises questions about whether they are single organisms or collections of interdependent organisms.
Biologists have proposed various methods to refine the definition of organisms, such as measuring genetic variability and interdependence within a group. Some suggest viewing structures like insect colonies, which operate cooperatively, as "superorganisms." Additionally, there is ongoing debate about the necessity of the term "organism," with some scientists arguing that it is outdated and lacks a fundamental distinction between living and non-living entities. Others maintain that while the term is useful, it requires context-specific definitions to accurately describe the diverse manifestations of life. Overall, the study of organisms remains a dynamic and evolving field, reflecting the complexity of life itself.
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Organism (biology)
The word organism refers to a living biological individual. However, biologists need a more precise definition of this term. They set specific conditions that must be met for something to be considered both living and an organism. These conditions included being able to regulate body temperature, being able to move, and being able to grow. As biologists made new discoveries, they revised these conditions. Recently, with the rise of genetic evolutionary biology, many biologists have come to question the traditional qualifications for organisms. Many even think the term itself is no longer necessary.
Defining Organism
Traditionally, an individual had to meet eight criteria to be considered a living organism. The individual had to be able to move itself, perceive and respond to its surroundings, and reproduce. It also had to grow, either by creating more cells or by increasing the size of its cells. It had to breathe in some way, and it had to have systems that allowed it to take in nutrients and excrete wastes. Lastly, it had to have some way of regulating its body temperature. While this definition of an organism works well for everyday use, biologists have several problems with it.
First, under that definition of an organism, some groups of animals can be classified as a single organism. For example, many groups possess the ability to move, reproduce, respond to stimuli, and increase their collective size. Because of this, biologists disagree about whether a group of organisms should be considered alive in the same way that a single organism is alive. Individuals that have a body comprised of several separate parts, such as the Portuguese man-of-war, further complicate matters. While the man-of-war seems like a jellyfish, it is actually comprised of several interdependent but separate creatures. Although they are physically connected to each other, each has its own distinct biological systems. Experts disagree about whether to consider the man-of-war a single organism or several symbiotic organisms (or organisms that survive by symbiosis) bound together.
Biologists have discussed several potential ways to differentiate between an organism and a group of organisms. One proposed method is to measure genetic variability. This would mean that a group of extremely genetically similar individuals could be considered a single organism, but a group of more varied individuals would be considered separate organisms. Other methods include measuring interdependence and the amount of conflict between the individual members of the group. For example, while a community of humans might be interdependent enough to qualify as a single organism, the group would have too much conflict among its members to fit the definition. However, creatures like the Portuguese man-of-war would likely be counted as a single entity.
Some biologists assert that insect colonies and similar groups should be included in the "superorganism" category, which is normally reserved for structures like coral. A beehive is a good example of a superorganism. Collectively, the bees meet all the traditional qualities of an organism. Colonies are structured well, and individuals cooperate in much the same way that cells and organs do in traditional organisms. Additionally, recategorizing insect colonies as organisms would explain several abnormalities. For example, the queen ant in an ant colony can live up to twenty years. When viewing a queen ant as an individual organism, an ant living for two decades is exceptional. However, if the colony is viewed as a single organism, the queen ant is viewed as the organism's reproductive organ. A reproductive organ functioning longer than parts of less-necessary biological systems is much less exceptional.
Other traditional qualifiers, such as the abilities to move and maintain body temperature, are also problematic. Many biological individuals exhibit these qualifications to different degrees, and some exhibit them in barely measurable amounts. No known method can effectively determine how much individuals must be able to move or how well they need to be able to regulate their body temperatures to qualify as living organisms. Any attempt at doing so involves placing arbitrary limits.
Because of these problems, biologists have proposed new methods to differentiate organisms from nonorganisms. Some advocate classifying organisms as any biological individual that has some form of immune system. Other biologists propose analyzing whether an individual can be shown to act with purpose by engaging in actions such as reproducing and feeding. A number of biologists have even proposed using natural selection, which shows if a species can adapt over time, to determine whether an individual qualifies as an organism. However, the scientific community has not yet reached a consensus on any single proposition.
Necessity of the Term
Advances in genetics and evolutionary biology have led some biologists to consider the term organism obsolete. They assert that the term is impossible to define, primarily because there is no fundamental distinction between what is alive and what is not. They believe that "life" is a concept that humans have created, and living things are simply different arrangements of atoms. Because of this, they assert that attempting to divide the two is attempting to arbitrarily categorize biological individuals.
Other biologists believe that while the term organism is necessary, a single definition of the term is not. They think that life is more than a specific arrangement of atoms, and thus it is something that can be quantified and documented. These biologists assert that different definitions of organism provide useful perspectives on what life is. Regardless, they believe that biologists need to be more specific about which definition they are choosing to apply to a specific situation or individual.
Bibliography
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"Portuguese Man-of-War." National Geographic. National Geographic Society. Web. 15 Dec. 2014. http://animals.nationalgeographic.com/animals/invertebrates/portuguese-man-of-war/
Pradeu, Thomas. "What is An Organism? An Immunological Answer." History and Philosophy of the Life Sciences. 32.2–3 (2010): 247–268. Web. http://thomaspradeu.com/wp-content/uploads/2011/12/Pradeu‗Organism‗final.pdf
Rettner, Rachel. "Insect Colonies Function Like Superorganisms." LiveScience. Purch. Web. 15 Dec. 2014. http://www.livescience.com/8020-insect-colonies-function-superorganisms.html
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