Heredity, also called inheritance or biological inheritance, is the passing on of traits from parents to their offspring; either through asexual reproduction or sexual reproduction, the offspring cells or organisms acquire the genetic information of their parents. Through heredity, variations between individuals can accumulate and cause species to evolve by natural selection. The study of heredity in biology is genetics.
Pangenesis was Charles Darwin's hypothetical mechanism for heredity, in which he proposed that each part of the body continually emitted its own type of small organic particles called gemmules that aggregated in the gonads, contributing heritable information to the gametes. He presented this 'provisional hypothesis' in his 1868 work The Variation of Animals and Plants Under Domestication, intending it to fill what he perceived as a major gap in evolutionary theory at the time. The etymology of the word comes from the Greek words pan and genesis ("birth") or genos ("origin"). Pangenesis mirrored ideas originally formulated by Hippocrates and other pre-Darwinian scientists, but using new concepts such as cell theory, explaining cell development as beginning with gemmules which were specified to be necessary for the occurrence of new growths in an organism, both in initial development and regeneration. It also accounted for regeneration and the Lamarckian concept of the inheritance of acquired characteristics, as a body part altered by the environment would produce altered gemmules. This made Pangenesis popular among the neo-Lamarckian school of evolutionary thought. This hypothesis was made effectively obsolete after the 1900 rediscovery among biologists of Gregor Mendel's theory of the particulate nature of inheritance.
Neo-Darwinism is generally used to describe any integration of Charles Darwin's theory of evolution by natural selection with Gregor Mendel's theory of genetics. It mostly refers to evolutionary theory from either 1895 or 1942, but it can mean any new Darwinian- and Mendelian-based theory, such as the current evolutionary theory.
August Friedrich Leopold Weismann FRS (For), HonFRSE, LLD was a German evolutionary biologist. Fellow German Ernst Mayr ranked him as the second most notable evolutionary theorist of the 19th century, after Charles Darwin. Weismann became the Director of the Zoological Institute and the first Professor of Zoology at Freiburg.
The modern synthesis was the early 20th-century synthesis of Charles Darwin's theory of evolution and Gregor Mendel's ideas on heredity into a joint mathematical framework. Julian Huxley coined the term in his 1942 book, Evolution: The Modern Synthesis.
Jean-Baptiste Pierre Antoine de Monet, chevalier de Lamarck, often known simply as Lamarck, was a French naturalist, biologist, academic, and soldier. He was an early proponent of the idea that biological evolution occurred and proceeded in accordance with natural laws.
Lamarckism, also known as Lamarckian inheritance or neo-Lamarckism, is the notion that an organism can pass on to its offspring physical characteristics that the parent organism acquired through use or disuse during its lifetime. It is also called the inheritance of acquired characteristics or more recently soft inheritance. The idea is named after the French zoologist Jean-Baptiste Lamarck (1744–1829), who incorporated the classical era theory of soft inheritance into his theory of evolution as a supplement to his concept of orthogenesis, a drive towards complexity.
Genetic variation is the difference in DNA among individuals or the differences between populations among the same species. The multiple sources of genetic variation include mutation and genetic recombination. Mutations are the ultimate sources of genetic variation, but other mechanisms, such as genetic drift, contribute to it, as well.
The Weismann barrier, proposed by August Weismann, is the strict distinction between the "immortal" germ cell lineages producing gametes and "disposable" somatic cells in animals, in contrast to Charles Darwin's proposed pangenesis mechanism for inheritance. In more precise terminology, hereditary information moves only from germline cells to somatic cells. This does not refer to the central dogma of molecular biology, which states that no sequential information can travel from protein to DNA or RNA, but both hypotheses relate to a gene-centric view of life.
In evolutionary biology, the Baldwin effect, a phenotype-first theory of evolution, describes the effect of learned behaviour on evolution. James Mark Baldwin and others suggested during the eclipse of Darwinism in the late 19th century that an organism's ability to learn new behaviours will affect its reproductive success and will therefore have an effect on the genetic makeup of its species through natural selection. Though this process appears similar to Lamarckism, that view proposes that living things inherited their parents' acquired characteristics. The Baldwin effect has been independently proposed several times, and today it is generally recognized as part of the modern synthesis.
Germ plasm is a biological concept developed in the 19th century by the German biologist August Weismann. It states that heritable information is transmitted only by germ cells in the gonads, not by somatic cells. The related idea that information cannot pass from somatic cells to the germ line, contrary to Lamarckism, is called the Weismann barrier. To some extent this theory anticipated the development of modern genetics.
Blending inheritance is an obsolete theory in biology from the 19th century. The theory is that the progeny inherits any characteristic as the average of the parents' values of that characteristic. As an example of this, a crossing of a red flower variety with a white variety of the same species would yield pink-flowered offspring.
Ivan Ivanovich Schmalhausen was a Ukrainian, Russian and later Soviet zoologist and evolutionary biologist of German descent. He developed the theory of stabilizing selection, and took part in the development of the modern evolutionary synthesis.
Julian Huxley used the phrase "the eclipse of Darwinism" to describe the state of affairs prior to what he called the "modern synthesis". During the "eclipse", evolution was widely accepted in scientific circles but relatively few biologists believed that natural selection was its primary mechanism. Historians of science such as Peter J. Bowler have used the same phrase as a label for the period within the history of evolutionary thought from the 1880s to around 1920, when alternatives to natural selection were developed and explored—as many biologists considered natural selection to have been a wrong guess on Charles Darwin's part, or at least to be of relatively minor importance.
Ludwig Hermann Plate was a German zoologist and student of Ernst Haeckel. He wrote a "thorough and extensive defence" of Darwinism, but before Mendel's work had been assimilated in the modern synthesis.
This article considers the history of zoology since the theory of evolution by natural selection proposed by Charles Darwin in 1859.
Transgenerational epigenetic inheritance is the transmission of epigenetic markers and modifications from one generation to multiple subsequent generations without altering the primary structure of DNA. Thus, the regulation of genes via epigenetic mechanisms can be heritable; the amount of transcripts and proteins produced can be altered by inherited epigenetic changes. In order for epigenetic marks to be heritable, however, they must occur in the gametes in animals, but since plants lack a definitive germline and can propagate, epigenetic marks in any tissue can be heritable.
Joseph Thomas Cunningham (1859–1935) was a British marine biologist and zoologist known for his experiments on flatfish and his writings on neo-Lamarckism.
Alternatives to Darwinian evolution have been proposed by scholars investigating biology to explain signs of evolution and the relatedness of different groups of living things. The alternatives in question do not deny that evolutionary changes over time are the origin of the diversity of life, nor that the organisms alive today share a common ancestor from the distant past ; rather, they propose alternative mechanisms of evolutionary change over time, arguing against mutations acted on by natural selection as the most important driver of evolutionary change.
Evolution has been an important theme in fiction, including speculative evolution in science fiction, since the late 19th century, though it began before Charles Darwin's time, and reflects progressionist and Lamarckist views as well as Darwin's. Darwinian evolution is pervasive in literature, whether taken optimistically in terms of how humanity may evolve towards perfection, or pessimistically in terms of the dire consequences of the interaction of human nature and the struggle for survival. Other themes include the replacement of humanity, either by other species or by intelligent machines.
