One of the main properties of a living organism is movement or response to an irritating factor. In developed organisms, movement is a muscular act, the implementation of which is achieved due to the influence of a nerve impulse on a muscle. However, in elementary organisms, movement and response to stimulation take on a somewhat different form. In general, these phenomena are united in the concept of "taxis". This is a motor reaction of the body, its part or a separate organelle in the direction of the stimulus or away from it. In plants, the term "tropism" has a similar interpretation. Taxis and tropisms can be positive or negative.
Sources of irritation
Sources of irritation that can provoke taxis are factors of living and inanimate nature. Any physical phenomena, biological factors or chemical substances are capable of causing the movement of an organism if its vital activity depends on them. For example, chemotaxisdirected movement towards the location of the chemical. If the cell moves towards the molecule that has value as a metabolic substrate, then such chemotaxis is positive. Negative chemotaxis is the intentional increase in the distance between a chemical and a cell. An example of positive chemotaxis is the movement of a leukocyte to the site of inflammation.
Negative chemical taxis is an active flight of cells or an attempt to delimit from them, if substances are capable of leading to their death. Also, the source of irritation is electromagnetic radiation with different wavelengths, liquid, soil and other factors. In each case, taxis can be positive, that is, the organism, its part or its separate organoid, approaches the stimulus, or negative. Negative taxis are a deliberate increase in the distance between the organism and the irritating factor.
Tropism and taxis
Tropism is a particular example of taxis in plants. They have many landmarks in relation to which they move during life or daily cycles. For example, the tops of almost all photosynthetic plants have negative geotropism and positive heliotropism. This means that they seek to reach the sun in order to increase the efficiency of photosynthesis. Plants also have positive hydrotropism, negative thermotropism.
Specific tropisms and taxises
Having figured out what taxis is in biology, the definition of specificstimuli for some organisms allows us to understand the peculiarities of their metabolism. In particular, organisms whose metabolism must proceed at high temperatures have positive thermotropism. There is also magnetotaxis, anemotaxis (movement in the direction of air), barotaxis, cytotaxis, rheotaxis (depending on the flow in water bodies), galvanotaxis (in relation to electric current). At the same time, taxis is a fundamental type of behavior of unicellular or multicellular organisms. Only in relation to the reference point, which is any of the above factors, organisms are able to move in wildlife.
