Homological organs: examples and evidences of evolution

Modern biological science has enough facts that prove the existence of a process of evolutionary changes in living organisms. One of them is homologous organs, examples of which will be considered in our article.

Evidence of Evolution

The organic world of our planet is simply amazing with its diversity. All living organisms are so different that it is difficult to foresee the fact of the unity of their origin. However, there is a whole series of proofs. First of all, this is the similarity of chemical composition, namely the presence of molecules of proteins, lipids, carbohydrates and nucleic acids. All representatives of the realms of living nature, except for viruses, have a cellular structure.

Embryonic development of vertebrates

Embryology is the science of embryonic development. Researches of scientists have shown, that at early stages of development vertebrates practically do not differ from each other. Chorda, a nervous tube, gill slits in the pharynx - all these signs are present in birds, fish, and man. In the course of further development, organisms of different classes undergo metamorphosis.

Morphological Evidence of Evolution

One of the leading evidences of the evolutionary process is the similarity in the structure of various parts of the body. This attribute is called morphological. A striking example of the relationship between individual classes of vertebrates is the platypus. This animal occupies an intermediate position between reptiles, birds and mammals for a number of reasons. Accordingly, the platypus has the characteristics of representatives of all the classes listed. For example, this animal multiplies by laying eggs. At the same time he feeds his cubs with milk, like a mammal. Swimming eardrums, a way of straining the water through the beak and flattened nose make it look like birds. And he also produces poison, like many reptiles.

Homologous and similar organs

Some organs of animals and plants, in spite of various functions, have a common origin. For example, the mustache of the pea is attached to the plant support, and the cactus spikes reduce the intensity of water evaporation. But in both cases, these structures are a modification of the leaves. This phenomenon has its name - homology of organs.

But the barberry needle and the raspberry spike have a different origin. In the first case, these are the side leaves, and in the second case the derivatives of the plant cover cloth. Such organs are called similar. The wide wings of the eagle and butterflies also have different origins. Although at first glance it is difficult to determine, since all these structures provide flight. But the birds are modified front legs, covered with feathers. And in insects, the wings represent the outgrowths of the covers. The limbs are located under the body and do not participate in the flight.

Homologous and similar organs are direct evidence of the common origin of various animals. And differences in the features of their structure are due to adaptation to different habitats and lifestyle.

Which organs are called homologous: examples

The most typical example of homology is the forelimbs of vertebrates. Whale and dolphin fins, bird and bat wings, human hands, mole feet and crocodile perform different functions. But their structure is similar. All these are the forelimbs of the chordate vertebrates, consisting of three sections: the shoulder, forearm, and hand.

To homologous organs are also variations of shoots of different plants. They have significant differences in the external structure and functions. The rhizome of the lily-of-the-valley has elongated interstices, the potato tuber accumulates a supply of water with nutrients, and the onion of the onion is the basis for attaching fleshy leaves. However, all the homologous organs, examples of which we have considered, have a typical structure for escaping. But that's not all! To consider what organs are called homologous, one can also use the example of root modifications. The subterranean organ of plants can also vary considerably under different growth conditions. So, in rutabaga and carrots the main root thickens, storing nutrients. Such crops in the first year do not give seeds. In the autumn, their aerial organs die off, and due to the underground root crop, the plant experiences a cold season. Such modifications are the answer to the question of what homologous organs are. Examples of them are also air, respiratory and clinging roots.

Rudiments and Atavisms

Morphological evidences of evolution are also rudimentary organs. These are parts of plants and animals that are underdeveloped. In humans, this is the third eyelid, the second row of teeth, and also the muscles that move the auricle.

The signs opposite to the rudiments are atavisms. This is a manifestation of features of ancestors that are not characteristic of individuals of this species. As an example, the development of the coccygeal spine, multifacidity, solid hair in humans. If we consider animals, they have atavism the development of hind limbs in whales and snakes.

So, homologous organs, examples of which were considered in our article, along with analogies, rudiments and atavisms are morphological proofs of the evolution process. These symptoms are manifested in both animals and plants. Homological organs are called structures that have a common structure plan, but differ in the functions performed. The presence of the listed characteristics in humans proves its origin from animals as a result of evolutionary transformations.