Mammals and birds are the pinnacle of vertebrate evolution. Both of them appeared at about the same time. Back in the Triassic period, the very first mammals appeared, which separated from the pangolins. They were primitive and did not at all resemble modern animals. And at the beginning of the Jurassic period, flying individuals originated from terrestrial lizards, which gave rise to the class of birds.
Reptiles did not inhabit 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 lizards contributed to the fact that mammals and birds developed adaptations for survival in various conditions. Lizards are the main competitors, thanks to them the nervous system, sense organs and behavior of birds improved. Today we are especially interested in the question of structure. We offer you to get acquainted with such a part of the body as the keel. Birds and other animals have this adaptation. What it is, what functions it performs, we will learn from this work.
The structure of birds
Many birds can fly, some have lost this ability in the course of evolution. NowLet's talk a little about the structure of these light and airy creatures. Tubular bones, saturated with lime s alt, 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 was previously a jaw with teeth.
The neck is distinguished by its length and mobility, it has 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 have become much stronger. There are also features in the structure of the shoulder section, for example, the keel. This is a very strong bone that serves as a mount for the pectoral muscles. Let's talk about this a little more.
Kiel
As we have already said, the keel is an outgrowth that birds need to attach the pectoral muscles. This outgrowth was formed in the process of evolution, since birds can fly thanks to this adaptation, because their pectoral muscles are very strongly developed. It is present not only in birds, but also in some animals that are distinguished by strong forelimbs: as a rule, they dig the ground. An example would be a mole. But the keel still has a special development in flying birds, bats. There are even so-called keel birds: hummingbirds, swifts, and so on. That is, we can say that the keel is a tool for birds and burrowing animals, without which they simply cannot do.
Functions
Kiel is, in birds mainly, a bone outgrowth in the thoracic region, it is flat, serves toattachment of fairly strong muscles involved in movements. Let's 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.
- Because birds use so many muscles to move their wings, the keel is the anchor for so many muscle fibers.
- Also, this outgrowth contributes to the mobility of the thoracic region. This allows deep breathing movements.
- The last function is a change in the flight path, the keel is far from the last place in this process.
Which birds have no keel
So, keel - what is it? We have answered this question. It was said that the outgrowth is present in birds, but they did not talk about exceptions. It is important to clarify that there is a subclass of ratites. Previously, they were called like this:
- Running.
- Ostrich.
- Smooth chested.
This subclass includes as many as 8 units:
- Cassuaries.
- Kiwifruit.
- Nandu-shaped.
- Ostrich-shaped.
- Teenamu-shaped.
- Epiornisoid.
- Litornites.
- Moalike.
Many might never have heard of the last three orders, as their representatives have long since died out.
