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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Aristotle's biology | 2/6 | https://en.wikipedia.org/wiki/Aristotle's_biology | reference | science, encyclopedia | 2026-05-05T16:11:59.770600+00:00 | kb-cron |
a metabolic process, whereby animals take in matter, change its qualities, and distribute these to use to grow, live, and reproduce a cycle of temperature regulation, whereby animals maintain a steady state, but which progressively fails in old age an information processing model whereby animals receive sensory information, alter it in the seat of sensation, and use it to drive movements of the limbs. He thus separated sensation from thought, unlike all previous philosophers except Alcmaeon. the process of inheritance. the processes of embryonic development and of spontaneous generation The five processes formed what Aristotle called the soul: it was not something extra, but the system consisting exactly of these mechanisms. The Aristotelian soul died with the animal and was thus purely biological. Different types of organism possessed different types of soul. Plants had a vegetative soul, responsible for reproduction and growth. Animals had both a vegetative and a sensitive soul, responsible for mobility and sensation. Humans, uniquely, had a vegetative, a sensitive, and a rational soul, capable of thought and reflection.
=== Processes ===
==== Metabolism ====
Aristotle's account of metabolism sought to explain how food was processed by the body to provide both heat and the materials for the body's construction and maintenance. The metabolic system for live-bearing tetrapods described in the Parts of Animals can be modelled as an open system, a branching tree of flows of material through the body. The system worked as follows. The incoming material, food, enters the body and is concocted into blood; waste is excreted as urine, bile, and faeces, and the element fire is released as heat. Blood is made into flesh, the rest forming other earthy tissues such as bones, teeth, cartilages and sinews. Leftover blood is made into fat, whether soft suet or hard lard. Some fat from all around the body is made into semen. All the tissues are in Aristotle's view completely uniform parts with no internal structure of any kind; a cartilage for example was the same all the way through, not subdivided into atoms as Democritus (c. 460–c. 370 BC) had argued. The uniform parts can be arranged on a scale of Aristotelian qualities, from the coldest and driest, such as hair, to the hottest and wettest, such as milk. At each stage of metabolism, residual materials are excreted as faeces, urine, and bile.
==== Temperature regulation ====
Aristotle's account of temperature regulation sought to explain how an animal maintained a steady temperature and the continued oscillation of the thorax needed for breathing. The system of regulation of temperature and breathing described in Youth and Old Age, Life and Death 26 is sufficiently detailed to permit modelling as a negative feedback control system (one that maintains a desired property by opposing disturbances to it), with a few assumptions such as a desired temperature to compare the actual temperature against. The system worked as follows. Heat is constantly lost from the body. Food products reach the heart and are processed into new blood, releasing fire during metabolism, which raises the blood temperature too high. That raises the heart temperature, causing lung volume to increase, in turn raising the airflow at the mouth. The cool air brought in through the mouth reduces the heart temperature, so the lung volume accordingly decreases, restoring the temperature to normal.
The mechanism only works if the air is cooler than the reference temperature. If the air is hotter than that, the system becomes a positive feedback cycle, the body's fire is put out, and death follows. The system as described damps out fluctuations in temperature. Aristotle however predicted that his system would cause lung oscillation (breathing), which is possible given extra assumptions such as of delays or non-linear responses.
==== Information processing ====
Aristotle's information processing model has been named the "centralized incoming and outgoing motions model". It sought to explain how changes in the world led to appropriate behaviour in the animal. The system worked as follows. The animal's sense organ is altered when it detects an object. This causes a perceptual change in the animal's seat of sensation, which Aristotle believed was the heart (cardiocentrism) rather than the brain. This in turn causes a change in the heart's heat, which causes a quantitative change sufficient to make the heart transmit a mechanical impulse to a limb, which moves, moving the animal's body. The alteration in the heat of the heart also causes a change in the consistency of the joints, which helps the limb to move. There is thus a causal chain which transmits information from a sense organ to an organ capable of making decisions, and onwards to a motor organ. In this respect, the model is analogous to a modern understanding of information processing such as in sensory-motor coupling.
==== Inheritance ====
Aristotle's inheritance model sought to explain how the parents' characteristics are transmitted to the child, subject to influence from the environment. The system worked as follows. The father's semen and the mother's menses have movements that encode their parental characteristics. The model is partly asymmetric, as only the father's movements define the form or eidos of the species, while the movements of both the father's and the mother's uniform parts define features other than the form, such as the father's eye colour or the mother's nose shape. Aristotle's theory has some symmetry, as semen movements carry maleness while the menses carry femaleness. If the semen is hot enough to overpower the cold menses, the child will be a boy; but if it is too cold to do this, the child will be a girl. Inheritance is thus particulate (definitely one trait or another), as in Mendelian genetics, unlike the Hippocratic model which was continuous and blending.