Autotroph: definition and meaning

Autotroph: definition and meaning


They define themselvesautotrophies all those organisms that are capable of forming organic substances starting from inorganic compounds using either light energy (photosynthesis) or chemical energy (chemosynthesis). starting from carbon dioxide and water with the energy supplied by the sun.

Many groups of bacteria and algae are also photosynthetic or chemosynthetic.

On the other hand, the organisms that are unable to carry out this process are definedheterotrophs (all animals, including man) and can therefore exist only thanks to the autotrophic organisms that provide them with the organic substances necessary for their life.

Botanical dictionary from A to Z.

Hooke's Law - Source: istock

A stationary body does not spontaneously set in motion. To move it, some external agent is needed: for example, the attraction of a piece of iron if the object is a magnet, a muscular effort if the object is a mass to be lifted. All external agents that disturb the "natural" state of rest or, as we shall see, of uniform rectilinear motion, are given the name of Strength.

What is believed today, namely that a body in uniform rectilinear motion in the absence of forces does not stop, appears counterintuitive, but let us console ourselves… since Aristotle also believed that bodies tended to stop. The problem is that in reality it is difficult to observe mechanically isolated bodies, due to the ubiquitous presence of the forces of friction, which restrain moving bodies. But that these forces exist due to the interaction of bodies with the medium in which they move is evident: the stopping time of a moving body on a sheet of ice is much longer than that on a paved road!


A method for measure the static intensity of a force consists in applying it to a spring and observing what is the elongation produced. The direction and direction of the force are those in which the object moves. The spring can be used as force measuring instrumentonce it has been properly calibrated.

The calibration of the instrument that we are going to build, said dynamometer, occurs in the following way: the spring is arranged vertically, a ruler is placed next to it in which the position of the spring “at rest” is marked (point 0). A sample weight of unit mass (1 kg) is then hung on the spring and the new position of the spring is marked (point 1). At this point we can say that if a weight is applied to the spring that makes it stretch more, it will be heavier than the sample weight and our graduated scale will allow us to establish exactly how much the body under examination weighs.

In the International System the unit of measurement of force is the Newton (N). The force with which the Earth attracts a body with a mass of 1 kg is 9.8N. Here, the order of magnitude of some forces that occur in nature.

Phenomenon: Force (N)
Sun-Earth attraction: 1022
Traction of a locomotive: 106
Weight of the atmosphere on a man's head: 103
Electron-proton attraction: 10-7

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