Best Mid-priced Av Receivers

Convergent and divergent evolution

Convergent evolution

convergent evolution, independent evolution of the same nature or similar characters in two or more species belonging to independent evolutionary lines (by nature is not understood in this If the personality, but any physical or behavioral attribute of an organism). These lines are based on independent evolutionary ancestral forms studied different character that gradually converge in a unique way.

Almost all examples of convergence can be interpreted in terms of adaptation to similar conditions is the environment of the organisms or their way of life, as with the adjustments to the movement. The physical demands of flight drastically limit the possible forms of the body to maintain it. The ability to fly has evolved independently in bats, birds and insects, as well as in groups now extinct and known for their fossils, like reptiles called pterosaurs. All these animals have evolved by convergent evolution wings. Also, all animals must be moved in the water face similar physical constraints imposed by the environment, and both aquatic mammals such as dolphins, and fish have developed bodies with the same and effective way hydrodynamics.

Convergent evolution is also seen in adaptations to food. Several different groups of mammals have independently evolved to feed on ants, anteaters from South America, the aardvark aardvark or Eastern and Southern Africa, the pangolin of Africa and Asia and the marsupial anteater and echidna of Australia. All of them have developed through convergent evolution powerful claws to open ant and termite mounds and a head provided with an elongated tubular snout with a long tongue to catch insects in their nests. Convergence is also observed in the physiology and anatomy digestion. As you know, cows ruminating digest plant material (see Ruminants); the fermentation capacity of the plant material in the stomach also been acquired by convergence a group of monkeys called colobinos that feed on leaves. Convergence comes to details of enzymes used in digestion. The ruminants colobinos and secreted into the stomach (unlike mammals) on the enzyme lysozyme, digests the bacteria responsible for fermentation of plant products. The amino acid sequence of the lysozymes of ruminants colobinos and unique similarities are examples of convergent evolution at the molecular level, this convergence reflects molecular probably the common role played by the enzyme in both groups of mammals. Characters

Homologues and Analogues

When two species share a character, like the eyes in humans and chimpanzees, or the wings of birds and bats, can be for one of two reasons: either the character was present in the common ancestor of both species and share it simply because they have inherited (in this case we speak of character homology, the eyes of man and chimpanzee are homologous), or the non- was in the common ancestor, but acquired by convergent evolution (in this case it is similar character.)

is important to distinguish between homologous and analogous characters in reconstructing the phylogeny or evolutionary diversification of organisms (see cladistics). It is assumed that two species have a close family if they seem much, but this hypothesis is valid only if the answers like homology, analogy or not convergence. Sometimes convergence can be detected by examining the characters in detail. The wings of birds, bats and insects are superficially similar, but their internal structures are very different: in insects, the wings are supporting structures called nerves, while in birds and bats wing structure is bone, in addition, the wings are covered by different bones of birds and bats, in fact, the bones of the wings of birds correspond by homology to the second finger of other vertebrates, in the case of the bat, correspond to fingers two to five.

Parallel Evolution

sometimes convergent evolution can be distinguished from the parallel. In both cases, the same character evolves independently along two lines. In the evolution parallel, the ancestral state of the two species was the same, in the convergent was different (see illustration). The parallel development, the two species can evolve independently to reach a new common state. Rarely can differentiate the parallel evolution of convergent real cases, because the dispute is about ancestral states of characters, which are usually unknown. However, the South American butterfly mimicry of passion flower is probably a result of parallel evolution, there are two species of butterflies that exhibit the same arrangement of colors, both of which are poisonous to birds and share the color of so that one looks to the other. The arrangement of the colors varies by region, but in each, the two species look alike. The advantage of mimicry requires the two species at each site followed a parallel evolution. Divergent Evolution

adaptive radiation and divergent evolution is a process that describes the rapid speciation of one or more species to fill many ecological niches. This is a process of evolution whose tools are mutation and natural selection.
Adaptive radiation often occurs when a species is introduced into a new ecosystem, or when there are species that survive in an environment that was previously unattainable. For example, Darwin's finches of the Galapagos Islands evolved from a single species of finch that arrived on the island. Other examples include the introduction by humans of mammalian predators in Australia, the development of the first birds that suddenly had the ability to expand its territory by air, or the development of lungfish in the Devonian, about 300 million years.

The dynamics of adaptive radiation is such that within a short period of time, many species are derived from one or more ancestral species. In this great number of genetic combinations, only a few can survive over time. Following the rapid development of many new species, many or most of them disappear as quickly as they appeared. The surviving species are almost completely adapted to the new environment. The rise and fall of the new species is currently progressing very slowly, compared with the initial outbreak species.

There are three basic types of adaptive radiation. These are:
1. General adaptation . A species that develops a radically new skill can reach new parts of their environment. The flight of birds is one of those general adaptations.
2. environmental change. A species that can, unlike others, survive in a radically changed environment will probably branch into new species to fill the ecological niches created by environmental change. An example of adaptive radiation as a result of environmental change was the rapid expansion and development of mammals after the extinction of the dinosaurs.
3. Archipelagos. isolated ecosystems such as islands and mountainous areas can be colonized by new species which are to establish a rapid process of divergent evolution. Darwin's finches are examples of radiation adaptive happened in an archipelago.

sometimes In science fiction scenarios have created human adaptive radiation leading to a range of species that evolve from the man.

To Return To Home Page Click Here Evolution:
http://evolucionbrad12.blogspot.com/