Macroevolution usually means the evolution of large-scale structures and traits that go significantly beyond the intraspecific variation found in microevolution (including speciation). In other words, macroevolution is the evolution of taxa above the species level (genera, families, orders, etc.).
Macroevolution is often thought to require the evolution of completely new structures such as entirely new organs. However, fundamentally novel structures are not necessary for dramatic evolutionary change. For instance, the evolution of mammal diversity in the past 100 million years has not required any major innovation. All of this diversity can be explained by modification of existing organs, such as the evolution of elephant tusks from canine teeth.
Philiptschenko distinguished between microevolution and macroevolution because he rejected natural selection in the sense of Darwin as an explanation for larger evolutionary transitions that give rise to taxa above the species level in the Linnean taxonomy. Accordingly, he restricted Darwinian "microevolution" to evolutionary changes within the boundary of given species that may lead to different races or subspecies at the most. By contrast, he referred "macroevolution" to major evolutionary changes that correspond to taxonomic differences above the species level, which in his opinion would require evolutionary processes different from natural selection. An explanatory model for macroevolution in this sense was the "hopeful monster" concept of geneticist Richard Goldschmidt, who suggested saltational evolutionary changes either due to mutations that affect the rates of developmental processes or due to alterations in the chromosomal pattern. Particularly the latter idea was widely rejected by the modern synthesis, but the hopeful monster concept based on evo-devo explanations found a moderate revival in recent times. Occasionally such dramatic changes can lead to novel features that survive.
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vignette|Selon les principes de la sélection naturelle de Darwin, les pinsons des Galápagos sont issus d'une espèce souche venue du continent. La sélection s'est traduite par une spécialisation de la taille de leur bec en liaison avec leur régime alimentaire (seconde édition de son la publiée en 1845). En biologie, la est l'un des mécanismes moteurs de l'évolution des espèces qui explique le succès reproductif différentiel entre des individus d'une même espèce et le succès différentiel des gènes présents dans une population.
vignette|Gradualisme phylétique et théorie des équilibres ponctués.|alt= La théorie des , aussi appelée ponctualisme ou ponctuationnisme, est un développement de la théorie de l'évolution proposée par deux paléontologues américains, Stephen Jay Gould et Niles Eldredge. Elle postule que l'évolution comprend de longues périodes d'équilibre, ou quasi-équilibre, ponctuées de brèves périodes de changements importants comme la spéciation ou les extinctions.
Evolutionary biology is the subfield of biology that studies the evolutionary processes (natural selection, common descent, speciation) that produced the diversity of life on Earth. It is also defined as the study of the history of life forms on Earth. Evolution holds that all species are related and gradually change over generations. In a population, the genetic variations affect the phenotypes (physical characteristics) of an organism. These changes in the phenotypes will be an advantage to some organisms, which will then be passed onto their offspring.