Caenogenesis (also variously spelled cenogenesis, kainogenesis, kenogenesis) is the introduction during
embryon
An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...
ic development of characters or structure not present in the earlier
evolution
Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, re ...
ary history of the strain or
species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
, as opposed to
palingenesis
Palingenesis (; also palingenesia) is a concept of rebirth or re-creation, used in various contexts in philosophy, theology, politics, and biology. Its meaning stems from Greek , meaning 'again', and , meaning 'birth'.
In biology, it is anothe ...
.
Notable examples include the addition of the
placenta
The placenta (: placentas or placentae) is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas, and waste exchange between ...
in
mammal
A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...
s.
Caenogenesis constitutes a violation to
Ernst Haeckel
Ernst Heinrich Philipp August Haeckel (; ; 16 February 1834 – 9 August 1919) was a German zoologist, natural history, naturalist, eugenics, eugenicist, Philosophy, philosopher, physician, professor, marine biology, marine biologist and artist ...
's
biogenetic law and was explained by Haeckel as adaptation to the peculiar conditions of the
organism
An organism is any life, living thing that functions as an individual. Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have be ...
's individual development. Other authorities, such as
Wilhelm His, Sr.
__NOTOC__
Wilhelm His Sr. (9 July 1831 – 1 May 1904) was a Swiss anatomist and professor who invented the microtome. By treating animal tissue with acids and salts to harden it and then slicing it very thinly with the microtome, scientists wer ...
, on the contrary saw embryonic differences as precursors to adult differences.
See also
*
Ontogeny
Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the ovum, egg to adult. The term can also be used to refer to t ...
*
Recapitulation theory
The theory of recapitulation, also called the biogenetic law or embryological parallelism—often expressed using Ernst Haeckel's phrase "ontogeny recapitulates phylogeny"—is a historical hypothesis that the development of the embryo of an ...
References
Bibliography
Gould, S.J. 1977. Ontogeny and Phylogeny. Cambridge: Harvard University Press.
Developmental biology
{{Developmental-biology-stub