Heredity
Organisms inherit genetic material from their parents in the form of homologous chromosomes, containing a unique combination of DNA sequences that code for genes.
[11] Recent findings have confirmed important examples of heritable changes that cannot be explained by direct agency of the DNA molecule.
[12] DNA methylation marking chromatin, self-sustaining metabolic loops, gene silencing by RNA interference, and the three dimensional conformation of proteins (such as prions) are areas where epigenetic inheritance systems have been discovered at the organismic level.
For example, ecological inheritance through the process of niche construction is defined by the regular and repeated activities of organisms in their environment.
[16][17][18] These examples of heritability that operate above the gene are covered broadly under the title of multilevel or hierarchical selection, which has been a subject of intense debate in the history of evolutionary science.
[17][19] When Charles Darwin proposed his theory of evolution in 1859, one of its major problems was the lack of an underlying mechanism for heredity.
[23] Galton found no evidence to support the aspects of Darwin's pangenesis model, which relied on acquired traits.
[25] Scientists in Antiquity had a variety of ideas about heredity: Theophrastus proposed that male flowers caused female flowers to ripen;[26] Hippocrates speculated that "seeds" were produced by various body parts and transmitted to offspring at the time of conception;[27] and Aristotle thought that male and female fluids mixed at conception.
In direct opposition, the Doctrine of Preformation claimed that "like generates like" where the germ would evolve to yield offspring similar to the parents.
[citation needed] During the 18th century, Dutch microscopist Antonie van Leeuwenhoek (1632–1723) discovered "animalcules" in the sperm of humans and other animals.
Ovists thought women carried eggs containing boy and girl children, and that the gender of the offspring was determined well before conception.
[32] An early research initiative emerged in 1878 when Alpheus Hyatt led an investigation to study the laws of heredity through compiling data on family phenotypes (nose size, ear shape, etc.)
[33] The idea of particulate inheritance of genes can be attributed to the Moravian[34] monk Gregor Mendel who published his work on pea plants in 1865.
The modern synthesis bridged the gap between experimental geneticists and naturalists; and between both and palaeontologists, stating that:[36][37] The idea that speciation occurs after populations are reproductively isolated has been much debated.
The traditional view is that developmental biology ('evo-devo') played little part in the synthesis, but an account of Gavin de Beer's work by Stephen Jay Gould suggests he may be an exception.
[40] It cleared up many confusions, and was directly responsible for stimulating a great deal of research in the post-World War II era.
In addition, more specifications may be added as follows: Determination and description of a mode of inheritance is also achieved primarily through statistical analysis of pedigree data.
