Homologues are organs that have passed the path of divergence

In the first half of the 19th century, German scientists E. Haeckel and F. Muller carried out serious embryological and comparative-anatomical studies that led to the creation of a biogenetic law and the development of representations about analogies, homologies, atavisms and rudiments. This article will be devoted to the study of such a group of living organisms that contain homologous organs. These are widely distributed plant and animal objects in the world, in which parts of the body have a common origin and a single outline of the structure, although outwardly they can vary greatly. What has led to their appearance?

Causes

Evolutionary processes occur in populations of living beings and underlie microevolution. The appearance of new species is possible due to the accumulation in organisms of ever greater differences affecting both their structure and functions. The process leading to a divergence of morphological and anatomical features, arising as a response of the organism to changed environmental factors, is called a divergence. Homologues are parts of the body in individuals that have undergone natural selection and are formed as a result of adaptation to the conditions of their habitat. They are thoroughly studied in the course of zoology. Let us consider them in more detail.

Features of the structure of vertebrates

The forelimbs of all mammals consist of the same bones: the humerus, the elbow, the radial, the bones of the wrist, the pastern and the phalanges of the fingers. But different environmental conditions with the course of evolution imposed imprints both on the shape of the skeleton of the forelimb, and on its functions. It is enough to compare the appearance, shape and dimensions of this part of the body, for example, in a giraffe, monkey or mole. It is the divergence that underlies the emergence of such organs as homologues. This is confirmed by comparative-anatomical studies not only among different groups of animals, but also in the plant world. Let's consider them in the next paragraph.

Modifications of vegetative organs

During ontogeny, representatives of the world of flora not only acquire new signs, but also modify parts of their body. In botany, this phenomenon is called the modification of vegetative parts and is seen as an adaptation that arose during phylogenesis. You can observe it from the representatives of the department of flowering plants. At them it leads to occurrence of such structures, as homologues. This manifests itself in the form of an adaptive response of the body to environmental factors. It is known that the root system of all seed plants develops from the embryonic root by a single plan and performs functions common to all kinds: fixation in the soil, support, absorption and carrying out of water and solutions of mineral substances. However, the appearance of the roots can vary greatly if they begin to perform special functions. Thus, the stilted roots of the pandanus growing in tropical bogs are homologous.

They do not give the bottom part of the stem completely immersed in water, protecting it from decay. Orchids have air roots homologous to an underground organ - they participate in extracting additional air volumes for breathing a plant. They serve as a reservoir that accumulates starch and other organic compounds, root crops of beets and carrots, rootstocks of Jerusalem artichoke and dahlias. All these modifications are homologues. This biology claims with good reason, as they correspond to each other and the general principle of the structure of the underground organ - the root.

Homology in the human body

Representatives of the vertebrate class, which includes Homo sapiens, have a single plan for the structure of the musculoskeletal system, in particular, its axial part - the spine.

But the person has features that appeared as an adaptation to the upright, for example, the shape of the spine resembles the Latin letter S. In addition, in the skeleton of the upper limb, consisting of the same bones as in animals, the phalanx of the thumb is opposed to the other four fingers, which Is the result of the ability to work. Homologues are all the examples mentioned that arose in the process of anthropogenesis.