On the Origins of New Forms of Life

4.12: Section Conclusion



(Continued from the previous page)

This section has listed several different types of well-documented stabilization processes:

  1. Production of a Polyploid. In this process, an offspring form is produced that has more chromosome sets than its parental form(s). For example, a hybrid derived from two forms has all the chromosomes of both its parent forms so that it has two full sets of chromosomes one derived from each of its parents. Another example would be an offspring form that had three full sets of chromosomes, whereas its parent form had only two.
  2. Production of an Aneuploid. One or more chromosomes are added to or deleted from the chromosome set of the parental form.
  3. Production of a Recombinant Derivative (Recombinational Stabilization). In this process, which depends on hybridization, the chromosome set of the offspring form is composed of chromosomes derived from two different parents. The chromosomes may be inherited intact, or some or all of them may be rearranged. Some or all may also be of mixed origin (composed of blocks derived from both parents).
  4. Production of a Permanent Translocation Heterozygote. In this process, a new permanent translocation heterozygote is produced by hybridization between two pre-existing permanent translocation heterozygotes.
  5. Production of an Agamosperm. The production of a form capable of reproduction in which the embryo develops without fertilization. Such organisms are usually the products of hybridization between two or more pre-existing forms.
  6. Production of a Vegetative Form. Production of a form capable of reproduction via budding or segmentation.
  7. Production of a Contingently Stable Form. Production on an ongoing basis of individuals that are incapable of reproduction themselves, but that continue to occur so long as their parental forms continue to exist. Such forms are often treated as species.
  8. Production of a Symbiotic Association. Two or more forms join together to exist as a single entity that ends up being treated as a taxonomic category.

These various types of stabilization processes are all well-known, well-understood ways of producing new types of organisms. This section also pointed out that many such forms have been, or are currently being, treated as species. Most, but not all, of these processes depend upon hybridization. It was also explained how such processes, through their repeated occurrence can generate entire complexes of related forms (e.g., agamic complexes, polyploid complexes). Concrete examples were given of each of these various types of stabilization processes. So stabilization processes are observed facts, not theoretical mechanisms. They provide proof of evolutionary change. NEXT PAGE >>


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