Directions and ways of the evolutionary process

The doctrine of the directions of the evolutionary process was developed by the Russian scientist A.N.Severtsov.

Biological progress is a direction of evolution characterized by an increase in the adaptability of a systematic group of living organisms to their environment.

Criteria for biological progress:

  • an increase in the number of individuals;
  • expansion of the area;
  • an increase in the number of taxa (populations, subspecies, species, etc.).

Biological progress is the result of the success of the systematic group in the struggle for existence. It is provided by the emergence of new adaptations that are useful in this habitat. Organisms survive and multiply, which leads to an increase in numbers and the development of new habitats. New populations are emerging. They are subjected to the action of multidirectional natural selection and gradually turn into new species, species – into genera, genera – into families, and so on. There is an increase in the number of taxonomic groups and their improvement.

Many weeds (dandelion, wheatgrass, white gauze), pests of agricultural crops (Colorado potato beetle, late blight) are currently in progress. Their progress is associated with human activities.

Biological progress is achieved in three ways: by increasing the organization and mastering a new habitat; adaptation to the new environment and its settlement; by lowering the organization and adopting a simpler environment.

An evolutionary change leading to the complication of the structure and functions of organisms, increasing the general level of their organization, allowing them to master a new habitat, is aromorphosis.

Aromorphoses led to the emergence of large systematic groups: types, divisions, classes, some orders.

Examples of aromorphoses in animals:

  • bilateral body symmetry;
  • end-to-end intestine;
  • tracheal breathing in arthropods;
  • pulmonary respiration in vertebrates;
  • alveolar lungs;
  • four-chambered heart;
  • two circles of blood circulation;
  • warm-bloodedness.

Examples of aromorphoses in plants:

  • the occurrence of photosynthesis;
  • tissue formation;
  • the emergence of a leaf, stem, root;
  • the appearance of a seed;
  • flower and fruit formation.

An evolutionary change that adapts organisms to specific conditions of existence, but does not increase the general level of their organization, is idioadaptation (allomorphosis).
Idioadaptations arise on the basis of aromorphoses and allow the systematic group to more fully populate the habitat. Lead to the emergence of species, genera, families.

Examples of idio adaptations:

  • different types of leaves and stems in plants;
  • different structure of flowers in plants;
  • modification of plant shoots;
  • different beaks of birds;
  • different body shape and color of fish;
  • different types of insect mouthpieces.

Simplification of the structure of organisms during the transition to a simpler habitat – degeneration.

Examples of general degeneration:

  • simplification of the nervous system and sense organs in parasitic worms;
  • reduction of the digestive system in tapeworms;
  • head reduction in bivalve molluscs;
  • the disappearance of the wings of some parasitic insects;
  • reduction of leaves in parasitic plants.

Biological regression is a direction of evolution characterized by a decrease in the adaptability of a systematic group of living organisms to the environment and its gradual extinction.

Biological regression criteria:

  • decrease in the number of individuals in systematic groups;
  • narrowing of the area;
  • decrease in the number of taxa (populations, subspecies, species, etc.).

Species in a state of regression need protection and are listed in the Red Book. These are the Ussuri tiger, brown and Himalayan bears, black stork, lady’s slipper, ginseng and many others.

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