Future followers of Lamarck tried to modify Lamarckism in order to make it acceptable, based on the idea of adaptation and an intimate direct and causal relationship between structure, function and environment. Prominent Neo-Lamarckians like Mc Dougall, Giard (1846-1908), Cope (1840-1897), and T.H. Morgan believed that only those characters, which are incorporated into the germplasm, are inherited to the next generation and result in origin of new species. Under Neo-Lamarckism following assumptions were proposed:
1. Only germ cells are influenced by the environmental changes.
2. Germ cells carry the acquired characters or somatic variations to the offspring in the next generation (supported by Heslop Harrison’s experiment on…show more content… While in Lamarckism, these acquired characters result from needs, according to Neo-Lamarckism these are induced due to change in the environment, habit and habitat.
Charles Robert Darwin (1809-1882) proposed the Theory of Natural Selection in his famous book 'Origin of Species' published late in 1859. Natural selection is a slow evolutionary process by which biological traits become either more or less common in a population as a function of the effect of inherited traits on the differential reproductive success of organisms interacting with their environment. Charles Darwin compared natural selection t with artificial selection, which is now called selective breeding, a process by which animals and plants with traits considered desirable by human breeders are systematically favored for…show more content… Struggle for existence: According to Darwin, individuals multiply in geometric ratio whereas space and food remain almost constant. As a consequence of this prodigal rate of reproduction, Darwin reasoned that there must be a competition between individuals belonging to the same or other species, for sharing food, water and living space. Every individual puts efforts for fulfilling the basic needs such as space for living, food for living, mate for reproduction and also protection from enemies (Figure 1.3). This competition was termed as 'struggle for existence' by Darwin. However, this struggle does not necessarily mean a battle between and among the organisms but more simply implies that the death occurs by any means preventing all offspring of a species from surviving to reproductive age. Among individuals, struggle for existence occurs at three