NationMaster - Encyclopedia: Divergent evolution

Divergent evolution occurs when two or more biological characteristics have a common evolutionary origin but have diverged over evolutionary time. This is also known as adaptation or adaptive evolution. These characters can be observable structures from different species or they can be molecular entities, such as genes or pathways. This is a kind of relationship observed in evolutionary biology. This article is about evolution in biology. ... A biological adaptation is an anatomical structure, physiological process or behavioral trait of an organism that has evolved over a period of time by the process of natural selection such that it increases the expected long-term reproductive success of the organism. ... In science, a molecule is a group of atoms in a definite arrangement held together by chemical bonds. ... For other meanings of this term, see gene (disambiguation). ... Evolutionary biology is a subfield of biology concerned with the origin and descent of species, as well as their change, multiplication, and diversity over time. ...

Divergent evolution can be seen in some higher-level characters of structure and function that are readily observable in organisms. For example, the vertebrate limb is one example of divergent evolution. The limb in many different species has a common origin, but has diverged somewhat in overall structure and function. Classes and Clades See below Male and female Superb Fairy-wren Vertebrates are members of the subphylum Vertebrata (within the phylum Chordata), specifically, those chordates with backbones or spinal columns. ...

Alternatively, "divergent evolution" can be applied to molecular biology characteristics. This could apply to a pathway in two or more organisms or cell types, for example. This can apply to genes and proteins, such as nucleotide sequences or protein sequences that derive from two or more homologous genes. Both orthologous genes (resulting from a speciation event) and paralogous genes (resulting from gene duplication within a population) can be said to display divergent evolution. Because of the latter, it is possible for divergent evolution to occur between two genes within a species. Molecular biology is the study of biology at a molecular level. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... A nucleotide is a chemical compound that consists of a heterocyclic base, a sugar, and one or more phosphate groups. ... In biology, homology is any similarity between structures that is due to their shared ancestry. ... Charles Darwins first sketch of an evolutionary tree from his First Notebook on Transmutation of Species (1837) Speciation is the evolutionary process by which new biological species arise. ... Schematic of a region of a chromosome before and after a duplication event Gene duplication occurs when an error in homologous recombination, a retrotransposition event, or duplication of an entire chromosome leads to the duplication of a region of DNA containing a gene [1]. The significance of this process for...

Divergent evolution and convergent evolution are distinct. In the case of divergent evolution, similarity is due to the common origin, such as divergence from a common ancestral structure or function has not yet completely obscured the underlying similarity. In contrast, convergent evolution arises when there are some sort of ecological or physical drivers toward a similar solution, even though the structure or function has arisen independently, such as the different characters converge on a common, similar solution from different points of origin. In evolutionary biology, convergent evolution is the process whereby organisms not closely related, independently evolve similar traits as a result of having to adapt to similar environments or ecological niches. ...

Usage

The usage of this term and other related terms can vary slightly from one researcher to the next. Furthermore, the actual relationships might be more complex than the simple definitions of these terms allow. "Divergent evolution" is most commonly meant when someone invokes evolutionary relationships and "convergent evolution" is applied when similarity is created by evolution independently creating similar structures and functions. The term parallel evolution is also sometimes used to describe the appearance of a similar structure in closely related species, whereas convergent evolution is used primarily to refer to similar structures in much more distantly related clades. For example, some might call the modification of the vertebrate limb to become a wing in bats and birds to be an example of parallel evolution. Vertebrate forelimbs have a common origin and thus, in general, show divergent evolution. However, the modification to the specific structure and function of a wing evolved independently and in parallel within several different vertebrate clades. Also, it has much to do with humans and the way they function from day to day. Bee hovering in flight In evolutionary biology, parallel evolution refers to the independent evolution of similar traits in closely related lineages of species, while convergent evolution refers to the appearance of striking similarities among lineages of organisms only very distantly related. ... It has been suggested that Clade be merged into this article or section. ... Suborders Megachiroptera Microchiroptera See text for families. ... â€œAvesâ€ redirects here. ...

In complex structures, there may be other cases where some aspects of the structures are due to divergence and some aspects that might be due to convergence or parallelism. In the case of the eye, it was initially thought that different clades had different origins of the eye, but this is no longer thought by some researchers. It is possible that induction of the light-sensing eye during development might be diverging from a common ancestor across many clades, but the details of how the eye is constructed--and in particular the structures that focus light in cephalapods and vertebrates, for example--might have some convergent or parallel aspects to it, as well. (See Gehring reference below and other researchers cited in that research field).

A good example of divergent evolution is the Darwin's finches, which has now over 80 varieties which all diverged from one original species of finch. (John Barnes) Darwins finches (also known as the GalÃ¡pagos Finches) are 13 or 14 different closely related species of finches Charles Darwin discovered on the GalÃ¡pagos Islands, 13 reside on the GalÃ¡pagos Islands, one on the Cocos Islands. ... Genera Many, see text Finches are passerine birds, often seed-eating, found chiefly in the northern hemisphere and Africa. ...

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