There are three forms of evolution. Divergence is based on the similarity of homologous organs; convergence is based on similar organs. The third form of evolution is concurrency.
In biology, this is such a process in which development occurs associated with the acquisition of similar characteristics and qualities that develop independently and are based on homologous rudiments.
Parallel evolution and speciation
Parallel speciation is a type of parallel evolution in which the reproductive incompatibility of closely related populations is determined by traits that develop independently due to adaptation in different environments. These groups of animals are reproductively incompatible, and only those populations that live in similar environmental conditions are less likely to become reproductively isolated.
Evolutionary form
Concurrency in biology describes how independent species acquire similar characteristics due to their evolution in similar ecosystems, but not at the same time (for example, dorsal fins of sharks, cetaceans and ichthyosaurs). The definition of a feature is critical in determining whether a change is considered diverging, converging, or parallel.
Proceeding from this, parallelism in biology is the development of a similar trait in related, but separate species, having the same common ancestor.
Taking into account the homology of morphological structures
The homology of morphological structures is also worth considering. For example, many insects have two pairs of flying wings. But in beetles, the first pair of wings hardens into elytra, and the second is used in flight, while in flies, the second pair of wings is reduced to small nodes used for balance.
If two pairs of wings are considered interchangeable, homologous structures, this can be described as a parallel reduction in the number of wings, but otherwise two changes occur with different differences in one pair of wings.
Concurrency in Biology: Characterization and Examples
An example of parallelism is the similarity of the axial skeleton of an ichthyosaurus and a dolphin. For this form of evolution, the appearance in unrelated organisms of similar characteristics or adaptive mechanisms due to the nature of their environment is characteristic.
Or, in other words, parallelism in biology is observed under similar conditions, the result of which is the formation of such devices. Morphologies (or structural forms) of two or more lines develop together in a similar way in parallel evolution, and do not diverge (as in convergence) or do not converge (as in divergence) at a certain point in time.
One example is the plumage model complexes that developed independently in different species of birds. Other examples can be mentioned:
- In the plant kingdom, the most familiar patterns of parallel evolution are similar leaf shapes that appear again and again in individual genera and families.
- Butterflies have much in common in models of wing coloring both within the same species and among families.
- Ancient and modern porcupines share a common ancestor, both developed strikingly similar body structures. This is also an example of convergent evolution, since similar structures evolved in the hedgehog and echidna.
- Some extinct archosaurs developed a vertical pose and were probably warm-blooded. These two characteristics are also found in most mammals.
- Interestingly, modern crocodiles have a four-chambered heart and an additional, so-called left artery, which is also characteristic of Triana mammals.
- The extinct pterosaurs and birds developed both wings, as well as the beak, but not from a common ancestor.
- Inner fertilization independently developed in sharks, some amphibians and amniotes.
By the way, there are quite unusual examples of parallelism in biology. So, the octopus eye has the same complex structure as the human eye. This is quite unusual, as two species developed at a time when animals were turning into vertebrates and invertebrates.
Concurrency in biology is the appearance in the evolution of living things of similar characteristics and properties that are formed from the same rudiments and on a single genetic basis, but this happens independently of each other.
The main difference from convergence
But this form should be distinguished from convergence - when similar characters also appear independently, but the genetic basis for their appearance is different. Both there and there are common features in the structure of the body, but the types of animals are different.
Translated from Greek, parallelos means "nearby." Concurrency in biology is the evolutionary development of genetically close groups based on features that they have inherited from common ancestors. Certain similar features and properties in parallelism make it possible to indicate the unity of origin of these living organisms, as well as the presence of similar conditions and habitats.