Evolution goes in different ways. This showed the study of phylogenesis of the animal world. One of the directions of evolution is biological progress. How to distinguish progress from regression? And does regression always lead to a reduction in the number of species?
Biological progress in evolution
Signs of biological progress of the species are:
- An increase in the number of individuals.
- The emergence of new subspecies, which can then be modified so that they form new species of living organisms.
- Adaptive radiation. Organisms occupy new ecological niches due to the emergence of useful devices for living in previously unusual environmental conditions.
- Extension of the habitat of the species.
If at least one of the above items is implemented, then we can talk about the presence of biological progress.
What is catagenesis?
One of the areas of biological progress is catagenesis. This concept is also called morphophysiological regression. Catagenesis is a simplification of the structure. This evolutionary path is quite common in nature. It leads from a complex structure to a simpler one, but does not lead to the extinction of forms if they are sufficiently adapted to the habitat. Catagenesis is accompanied by the acquisition of new traits that allow organisms to feel great in new conditions.
Plant catagenesis examples
Morphophysiological regression is not very common among producers. Plant catagenesis is almost always associated with a parasitic lifestyle. And the very main feature of the plant, the pigment that performs photosynthesis, is chlorophyll, which often disappears, because the plant is adapted to receive ready-made organic substances.
In orchards, along roadsides, a dodger parasite plant is common. The dodger has no leaves and roots. Only the stem, and on it are suckers. They parasite is introduced into another plant and eats ready-made substances, that is, the juice of the host.
An infection is a parasite that grows together with the host at the base of the stem. Instead of real leaves - small scales arranged in a spiral. Leaf reduction is catagenesis. This species does not have suction cups, since it is fused with the vessels of the stem. There are no roots. Very little chlorophyll, so the color is not green, but red, yellow or bluish. Parasitizes on legumes, sunflower, thyme, wormwood.
Examples of catagenesis in animals
In the animal world, morphophysiological regression is a common occurrence. Not only parasites are reduced organs and tissues, but also in sedentary forms, as well as in animals living in extreme environmental conditions.
Catagenesis of sedentary forms
Ascidia is the most famous example of catagenesis among sedentary animals. Ascidia larvae have all the features of chordates. This proves that the ancestors of this species are vertebrates. However, adult ascidia lost their chord. They do not have a neural tube, only a ganglion without a cavity, innervating a huge pharynx, which serves to filter water.
Hypogenesis of animals
Hypogenesis is catagenesis too. It occurs when the organism dwells in simplified conditions all its life. For example, sirens are amphibians that never leave the aquatic environment. They do not need lungs, therefore, they were reduced. All their lives they breathe with gills, their eyes are underdeveloped, they have fewer fingers on their limbs. This example demonstrates the simplification of the structure throughout ontogenesis.
Catagenesis of parasitic forms
Tapeworms are another striking example of catagenesis. The parasitic lifestyle led to the complete disappearance of the digestive tract. Worms absorb food through the entire surface of the body, because they live in a nutrient medium. They have developed this nutritional ability: the tegument has a multilayer structure in order to implement the absorption function. Tapeworms do not have organs of vision, hearing, or smell. There are only chemoreceptors and sensitive cells, which are mostly located on the scolex. The nervous system is poorly developed. But the reproductive system has unusually developed. It is present in each segment and, moreover, occupies almost its entire area. Moreover, tapeworms are hermaphrodites. So the worms supported the biological progress of the species by producing millions of eggs per year (bovine tapeworm produces about 600 million eggs per year).
Catagenesis in extreme biotopes
Species that have migrated to extreme conditions also undergo a simplification of organization. For example, living in caves, in complete darkness, leads to the loss of organs of vision, as well as skin pigments. Often organisms become less mobile.
Those species that could not win the struggle for existence in the former conditions go into an unusual habitat. Competition grew, organisms found a freer ecological niche, were able to take root in difficult living conditions.
Recently discovered an eyeless spider in the caves of Laos. This is the only spider that does not have organs of vision. Apparently, he moved to a dark environment for a very long time, so that there were no reduced eyes.
The well-known representative of the animal world - the common mole - also has reduced organs of vision. The eyes of a mole do not distinguish the outlines of objects. There are types of moles whose eyes are hidden under the skin. Such representatives distinguish only light and shadow, which, apparently, is quite enough for them, otherwise reduction would not have occurred.
Thus, morphophysiological regression helps organisms not to go into the phase of biological regression leading to the extinction of a species. Plants and animals occupy more free ecological niches, as a rule, not comfortable for living, but suitable. They thrive in new conditions, developing the necessary signs, but gradually significantly reducing entire organs, tissues and organ systems.