The breathing It is the process by which living beings exchange oxygen and carbon dioxide with the environment that surrounds them: the process occurs because organisms capture oxygen from the environment and at the same time release the dioxide produced in cells.
In the case of the most evolved living beings, this exchange it is produced before the environment by means of certain specialized organs in that function. A classification is usually made of the different ways in which this exchange occurs:
Direct breathing
The direct breathing It is one that occurs when there is an exchange of gases between the environment and the cells of the body, without the intervention of a respiratory organ. The gas enters by simple passive diffusion, the irreversible physical process from which the particles are introduced into a medium in which they were previously absent from the passage through a membrane.
The fundamental cause of this step is that the oxygen concentration is higher in the external environment than in the internal environment. It is also called skin respiration, and is produced from the epidermis as long as the outer cuticle is moist.
Examples of direct breathing
| Calcareous sponges | Corneal sponges |
| Actinias | Corals |
| Nematodes | Jellyfish |
| Hydras | Anemones |
| Flatworms | Polyps |
Indirect breathing
The indirect breathing It is the process of incorporation of cells that are not in contact with the environment, so a set of specialized organs must mediate for gas exchange.
In cases where indirect respiration occurs with the gas diffusion in the blood by means of a specialized respiratory organ they are called external respiration, while the exchanges between blood and cells are called internal respiration.
This type of breathing is usually divided into three groups:
Indirect breathing examples
The lung respiration It is the one that is carried out through the structures of the respiratory system that limit the mediastinum on two sides. In these organs the blood receives oxygen from the air, and at the same time gives off carbon dioxide that is released. Here are some species that perform this type of respiration:
| Dolphins | Crow |
| Frogs | Eagle |
| Zebras | Mice |
| Parrots | Dogs |
| Hummingbird | Horses |
Branchial breathing
The gill breathing It is the one carried out by aquatic animals that capture the oxygen dissolved in the water, which is transported to the tissues. The gills differ strongly from the lungs because they are outside the body of the fish in the head section, because they need to be in direct contact with the water.
There are animals with gills that live in salt water and animals with gills that live in fresh water. These are some animals of this type:
| Catfish | Hammerhead shark |
| Crabs | Striped blanket |
| Shark | Cod |
| Tuna | Sword shark |
| Octopus | Prawns |
Tracheal breathing
The respiration of insects and invertebrates is of the type tracheal, from the tubes that open on the outside of your body (tracheae), through which oxygen passes until it reaches the cells. These tracheae divide to form trachealas, which open to the environment through tiny seals. Here are some of these animals:
| Butterfly | Wasp |
| Cicada | Spider |
| Ants | Mites |
| Bee | Peripatoids |
| Cricket | Centipede |