What is the difference between lamarck theory and darwin theory

Appeared by spontaneous generation, organisms become more complex over time. There is no filiation between two distinct lines. Thus, since the origin of the planet, the simplest organisms would spontaneously appear from the inert matter and would repeatedly initiate series that would evolve in parallel Figure 3.

Within each of these lines, filiation exists, from the simplest to the most complex, but there can be no genealogical relationship between the lines.

Lamarck also postulates that primitive plants and animals appear in two independent ways. It also allowed two separate routes for animals. In short, in Lamarckian theory, the living world would be composed of multiple successive and independent lines. There would be no single common ancestor. Darwin, for his part, does not speak of the appearance of life in The Origin of Species , except to say that the knowledge of his time did not allow him to approach it.

It is sometimes mentioned in his correspondence, notably in a letter from to his best friend Joseph Hooker. But if and oh! Figure 4. Darwin describes very clearly here his ideas on the appearance and extinction of species. He refuses the idea of permanent spontaneous generation, which has been universally accepted since Pasteur [4]. As a result, all living beings on the planet are derived from this ancestral form of life Figure 4.

Figure 5. This vision is fully in line with modern scientific research that is trying to understand the characteristics of this primordial ancestral form, called LUCA for Last Universal Common Ancestor Figure 5.

There are at least two other important differences between these theories. As they both concern the modalities of evolution, they are very intertwined; but for the sake of clarity we will present them separately. We are entering into what is really the heart of the two theories.

In plants, Lamarck is led to propose an even more direct influence of the environment on the organism because, of course, we cannot talk about efforts and habits in plants!

In his theory, variations are therefore always induced, more or less directly, under the influence of external conditions. Since the discovery of genetic mutations at the beginning of the 20 th century, neolamarckians have had to integrate the idea that these mutations are at the root of variations.

They then imagined that they had to be directed by the environment, on specific genes, to adapt the organism to its environment. But this idea is in contradiction with all the experimental research carried out since the s.

The most recent and one of the most demonstrative was published in by an American team [6]. We will come back to this later. Based on these induced variations, the transformation of species would be driven by a trend towards increasing complexity, at least in animals.

But where would this trend come from? It would be an immanent property of living beings that irreversibly pushes them towards ever greater complexity. It is therefore a law of nature that requires no explanation. It should be noted in passing that, in the same logic, Lamarck did not believe in the extinctions of species, except those destroyed by human actions.

For him, species are transformed by becoming more complex but do not become extinct. Lamarck, however, wanted to be very materialistic and often repeats that the living obey only physical laws. It should be noted that this trend towards complexity, as well as the influence of the environment on changes, both function as an anti-hasard. On the other hand, Charles Darwin believed that all species came from a single ancestor. He believed that there were types of giraffes with longer necks and with shorter necks.

However, those giraffes with shorter necks died due to competition and the drive of the environment, and those with longer necks survived. Darwin is an Englishman while Lamarck is French. Darwin is known for his theory of evolution while Lamarck is known for his theory of inheritance of acquired characteristics. Difference Between Darwin and Lamarck. Difference Between Similar Terms and Objects. MLA 8 J, Joshua. Name required. Email required. This theory was anticipated by Charles Darwin.

Individual population has identical characteristics. Individuals can make a difference. The interbreeding population of individuals always has similar characteristics with certain variability. Individuals are eternal. The population will turn itself. Internal drive towards greater complexity, influenced by the inheritance of properties acquired. Variations are tailored to the needs of the organism. Variation does exist regardless of the condition of the organism.

Eg: The long neck of a giraffe. Eg: Keen eyesight of the hawk. During a famine year, f falls to 1. Now suppose there are a bunch of smaller individuals whose f values are 1. How long would a famine have to last for the small individuals to do better than normal ones? How many famine years before small individuals make up 90 percent of the population? Suppose there exists an initially normal mutant group of individuals called Epi2s, whose germ cells are affected by a year of famine in such a way that their progeny changes to the small type for two generations before they revert back to normal in the third generation, through epigenetic mechanisms.

Consider a year period that starts and ends with normal years but has a one-year famine, two two-year famines and a three-year famine in between. Which of the three groups normal, small, Epi2s will be most successful? Are there famine patterns in which Epi2s overwhelm the other two groups over the very long term?

As these vignettes show, it does not matter to natural selection whether characteristics are controlled by genetic or epigenetic mechanisms. If the conditions that confer a fitness advantage on a given group last long enough and select that group across multiple generations, then that group will dominate the population, and the species characteristics will change. So if there is a sizable subset of a population that exhibits advantageous epigenetic inheritance, natural selection is very likely to maintain it.

On the other hand, if epigenetic modifications in a population are deleterious, natural selection will eliminate it. There is no top-down, purposeful information passing across generations here, no matter how sensible that seems to us. Based on these considerations, can you speculate how the elegant information transfer across generations that is embodied by the CRISPR-Cas system in bacteria could have evolved?