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The term boundary paradox refers to the conflict between traditional, rank-based classification of life and evolutionary thinking. In the hierarchy of ranked categories it is implicitly assumed that the morphological gap is growing along with increasing ranks: two species from the same genus are more similar than other two species from different genera in the same family, these latter two ...
However, it may also reflect a sudden environmental change or boundary. Examples of rapidly changing environmental boundaries like this include abrupt changes in the heavy metal content of soils, and the consequent narrow clines produced between populations of Agrostis that are either adapted to these soils with high metal content, or adapted ...
In evolutionary biology, a spandrel is a phenotypic trait that is a byproduct of the evolution of some other characteristic, rather than a direct product of adaptive selection. Stephen Jay Gould and Richard Lewontin brought the term into biology in their 1979 paper " The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the ...
Surtsey, a volcanic island off the southern coast of Iceland, is an important example of a place where primary succession has been observed. [2] [3] On the other hand, secondary succession happens after disturbance of a community, such as from a fire, severe windthrow, or logging. Succession was among the first theories advanced in ecology.
Introgression is an important source of genetic variation in natural populations and may contribute to adaptation and even adaptive radiation. [7] It can occur across hybrid zones due to chance, selection or hybrid zone movement. [8]
As there are no cell boundaries in the syncytium, these morphogens can influence nuclei in a concentration-dependent manner. It was discovered that cellularization of the blastoderm took place either during or before the specifications of body regions. [26] Also, one cell could contain more than one nucleus due to fusion of multiple uninuclear ...
In these examples, the source of selection on a trait coevolves with the trait itself, therefore causation is reciprocal and developmental processes potentially become relevant to evolutionary accounts. For instance, a peacock’s tail evolves through mating preferences in peahens, and those preferences coevolve with the male trait.
The recurrent evolution of flight is a classic example, as flying insects, birds, pterosaurs, and bats have independently evolved the useful capacity of flight. Functionally similar features that have arisen through convergent evolution are analogous , whereas homologous structures or traits have a common origin but can have dissimilar functions.