Mammals and birds are the pinnacle of vertebrate evolution. And they both appeared at about the same time. Even in the Triassic period, the very first mammals appeared, which separated from the dinosaurs. They were primitive and did not at all resemble modern animals. And at the beginning of the Jurassic period, flying individuals descended from land lizards, which gave rise to a class of birds.
Reptiles did not populate the entire territory, which allowed the first birds and mammals to settle in free territories. And the fact that they conquered new lands that were not previously used by the lizards, contributed to the fact that mammals and birds appeared adaptations for survival in a variety of conditions. Lizards are the main competitors, thanks to them the birds improved their nervous system, sensory organs and behavior. Today, we are particularly interested in the question of structure. We offer to get acquainted with such a part of the body as the keel. This device is in birds and other animals. What it is, what functions it performs, we learn from this work.
Bird structure
Many birds can fly, some during evolution have lost this ability. Now let's talk a little about the structure of these light and air creatures. Tubular bones, saturated with calcareous salt, allow birds to fly, so their skeleton becomes very strong and light. The skull is also different in birds: on the front wall there are only large eye sockets and a beak, which previously was a jaw with teeth.
The neck is distinguished by length and mobility; it numbers from ten to twenty-five vertebrae. Since the forelimbs are wings, the load on the legs has increased: the bones that form the pelvic part have grown together, so they become much stronger. There are also features in the structure of the shoulder, for example - keel. This is a very strong bone that serves as a fastener for the pectoral muscles. Let's talk about this a little more.
Keel
As we have already said, the keel is the outgrowth that birds need for fastening the pectoral muscles. This outgrowth was formed in the process of evolution, since birds can fly thanks to this device, because their pectoral muscles are very developed. It is found not only in birds, but also in some animals that are distinguished by strong forelimbs: as a rule, they dig the earth. An example is the mole. But keel nevertheless has a special development in flying birds and bats. There are even so-called keel birds: hummingbirds, swifts and so on. That is, we can say that keel is a tool for birds and burrowing animals, without which they simply can not do.
Functions
The keel is, in birds, mainly a bone outgrowth in the thoracic region, it is flat, serves to attach quite strong muscles involved in movements. We single out the main purpose and functions of this bone process.
- The keel is also needed in order to strengthen the thoracic region, that is, the skeleton in this part is quite strong. We can say that it is an additional tool for protecting vital organs.
- Since quite a lot of muscles are involved in the movement of the wings of birds, the keel is a fixture for so many muscle fibers.
- Also, this outgrowth promotes thoracic mobility. This allows you to make deep movements while breathing.
- The last function is to change the flight path; the keel is far from the last place in this process.
Which birds don't have a keel
So keel - what is it? We have answered this question. It was said that outgrowth is present in birds, but they did not talk about exceptions. It is important to clarify that there is a subclass of ratites. Earlier they were called like this:
- Running
- Ostrich.
- Smooth breasts.
This subclass includes as many as 8 units:
- Cassowary.
- Kiwiformes.
- Nanduide.
- Ostrich-shaped.
- Tinamoobraznye.
- Epiorniform.
- Literniferous.
- Moaiformes.
Many could never have heard about the last three detachments, since their representatives have already become extinct.