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Organism The characteristics of life Since there is no unequivocal definition of life, most current definitions in biology are descriptive. Life is considered a characteristic of something that preserves, furthers or reinforces its existence in the given environment.
This characteristic exhibits all or most of the following traits: Living things require energy to maintain internal organization homeostasis and to produce the other phenomena associated with life. A growing organism increases in size in all of its parts, rather than simply accumulating matter.
A response is often expressed by motion; for example, the leaves of a plant turning toward the sun phototropismand chemotaxis. These complex processes, called physiological functionshave underlying physical and chemical bases, as well as signaling and control mechanisms that are essential to maintaining life.
Alternative definitions See also: Entropy and life From a physics perspective, living beings are thermodynamic systems with an organized molecular structure that can reproduce itself and evolve as survival dictates. One systemic definition of life is that living things are self-organizing and autopoietic self-producing.
Virus Adenovirus as seen under an electron microscope Whether or not viruses should be considered as alive is controversial. They are most often considered as just replicators rather than forms of life. However, viruses do not metabolize and they require a host cell to make new products.
Virus self-assembly within host cells has implications for the study of the origin of lifeas it may support the hypothesis that life could have started as self-assembling organic molecules. Biophysicists have commented that living things function on negative entropy. These systems are maintained by flows of information, energyand matter.
Some scientists have proposed in the last few decades that a general living systems theory is required to explain the nature of life. Instead of examining phenomena by attempting to break things down into components, a general living systems theory explores phenomena in terms of dynamic patterns of the relationships of organisms with their environment.
Gaia hypothesis The idea that the Earth is alive is found in philosophy and religion, but the first scientific discussion of it was by the Scottish scientist James Hutton. Inhe stated that the Earth was a superorganism and that its proper study should be physiology.
Hutton is considered the father of geology, but his idea of a living Earth was forgotten in the intense reductionism of the 19th century. Nonfractionability The first attempt at a general living systems theory for explaining the nature of life was inby American biologist James Grier Miller.
Specifically, he identified the "nonfractionability of components in an organism" as the fundamental difference between living systems and "biological machines. Morowitz explains it, life is a property of an ecological system rather than a single organism or species.
Robert Ulanowicz highlights mutualism as the key to understand the systemic, order-generating behavior of life and ecosystems.DNA and RNA are long linear polymers, called nucleic acids, that carry information in a form that can be passed from one generation to the next.
These macromolecules consist of a large number of linked nucleotides, each composed of a sugar, a phosphate, and a base. Zerulla K, Chimileski S, Näther D, Gophna U, Papke RT, et al., "DNA as a Phosphate Storage Polymer and the Alternative Advantages of Polyploidy At some point in the pathway to the first cellular life, such a system must have arisen spontaneously." We question this assumption.
The RNA World at IMB Jena Scientists Debate RNA's . One theory is that RNA, a close relative of DNA, was the first genetic molecule to arise around 4 Asteroid 'time capsules' may help explain how life .
Start studying Ch. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Search. a 'primitive soup' from which life arouse. Why do scientists believe that RNA, rather than DNA, was the first genetic material? RNA has both information storage and catalytic properties.
Eoc Review Biology. STUDY. Scientists continue to debate whether or not viruses are alive. If we consider the image of the flu virus seen here, we could say that a virus is NOT alive because A). It is a pathogen. That is the function of the nucleic acid, DNA or RNA, within the capsid.
C). Antibiotics could cure chicken pox sooner than 7. RNA – or ribonucleic acid – carries out the instructions coded in DNA, but is also thought to have developed before DNA.
Many scientists believe nucleic acids – the ‘NA’ of ‘ RNA ’ .