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 in its diversity. All living organisms are so different that to assume the fact of the unity of their origin is quite difficult. However, there is a whole series of evidence. First of all, it is the similarity of the chemical composition, namely the presence of molecules of proteins, lipids, carbohydrates and nucleic acids. All representatives of the kingdoms of wildlife, except viruses, have a cellular structure.
Vertebrate embryonic development
Embryology is called the science of embryonic development. Researches by scientists have shown that in the early stages of development, vertebrates practically do not differ from each other. Chorda, neural tube, gill slits in the throat - all these signs are in birds, and in fish, and in humans. In the course of further development, organisms of different classes undergo metamorphoses.
Morphological evidence of evolution
One of the leading evidence of the evolutionary process is the similarity in the structure of various parts of the body. This feature is called morphological. A striking example of the relationship between individual classes of vertebrates is the platypus. This animal, according to a number of signs, occupies an intermediate position between reptiles, birds and mammals. Accordingly, the platypus has signs of representatives of all these classes.
For example, this animal reproduces by laying eggs. At the same time, he feeds his young with milk, like mammals. Swimming membranes on the legs, a method of filtering water through the beak and a flattened nose make it look like birds. He also produces poison, like many reptiles.
Homologous and similar organs
Some organs of animals and plants, despite various functions, have a common origin. For example, pea tendrils attach a plant to a support, and cactus spikes reduce the rate of water evaporation. But in both cases, these structures are a modification of the leaves. This phenomenon has its name - organ homology.
But the barberry needles and raspberry spikes are of different origin. In the first case, these are lateral leaves, and in the second, derivatives of the integumentary tissue of the plant. Such organs are called similar. The wide wings of an eagle and butterflies also have a different origin. Although at first glance it is quite difficult to determine, since all these structures provide flight. But in birds, these are modified forelimbs covered with feathers. And in insects, wings represent outgrowths of integument. Their limbs are located under the body and do not participate in flight.
Homologous and similar organs are direct evidence of the common origin of various animals. And the 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 the vertebrates. Whale and dolphin fins, bird and bat wings, human hands, mole and crocodile paws perform different functions. But their structure is similar. All these are the forelimbs of the chordate vertebrates, consisting of three departments: the shoulder, forearm and hand.
Modifications of shoots of various plants also belong to homologous organs. They have significant differences in the external structure and functions. Lily of the valley rhizome has elongated internodes, the potato tuber accumulates a supply of water with nutrients, and the bottom of onions is the basis for attaching fleshy leaves. However, all homologous organs, the examples of which we have examined, have a typical shoot structure. But that's not all!
You can also consider which organs are called homologous, using the example of
root modifications. The underground organ of plants can also significantly change under different growing conditions. So, in rutabaga and carrots, the main root thickens, storing nutrients. Such crops do not produce seeds in the first year. In the fall, their aboveground organs die off, and due to the underground root crop, the plant experiences the cold season. Such modifications are the answer to the question of what are homologous organs. Examples of them are also airy, respiratory and clinging roots.
Rudiments and atavisms
Rudimentary organs are also morphological evidence of evolution . These are those parts of plants and animals that are underdeveloped. In humans, this is the third eyelid, the second row of teeth, as well as the muscles that move the auricle.
Signs opposite to rudiments are atavisms. This is a manifestation of the features of ancestors that are not characteristic of individuals of this species. As an example, we can cite the development of the coccygeal region of the spine, multisuckling, and continuous human hair. If we consider animals, their atavism is the development of the 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 evidence of the evolutionary process. These signs are manifested both in animals and in plants. Homologous organs are called structures that have a common structural plan, but differ in their functions. The presence of the listed features in a person proves his descent from animals as a result of evolutionary transformations.