Lamarckism and Lamarck theory of evolution / postulate of Lamarckism / theory, example , definition and question related to Lamarckism

LAMARK AND LAMARCKISM:

the first attempt to explain the origin of species and their adaptation to the environment was done by French naturalist Jean Baptiste de Lamarck (1744-1829). he gave the first theory of evolution known as Lamarckism or the theory of inheritance to acquire characters. it states that all changes, which organisms acquire during their lifetime, are transmitted to their offspring by the process of inheritance. Lamarck believed that a nervous fluid within each species helps to progress up the change of being. the more strongly exercised organ attract more of the nervous fluid which in turn enlarge this organ and such alternation are inherited. 

Lamarck publishes this theory in 1809 (the same year of Darwin's birth )in his famous book "philosophy zoologique". he also introduces certain terms such as invertebrates, vertebrates, and Annelid. 

POSTULATE OF LAMARCKISM 

the theory of inheritance of acquired characters was explained by Lamarck using four main postulates. 

these postulate along with the classical example of the evolution of long necks is in giraffes are as follows

1 internal vital force

organism and their organ have a natural tendency to continuously increase in size, generation after generation. for example, the ancestors of parent day giraffes were bearing small neck and forelimbs. however, these had an internal vital force to increase their size and become relatively larger in due course of time.

effect of environment  and new needs 

continuous change in the environment condition directly influences the nature, habit, way of living, of an organism, and their structural organization. for example, early giraffes used to feed on the grasses and other surface plants of an area. with time the climate of these areas becomes arid. it means that the grasses and other surface vegetation dried up living only a few taller trees. thus, the leaves of these tall trees were the only food available to ancestors. it is called the doctrine of appetency | desire.

                                           

 

uses and disuses of organ 

the grown of less used part decline, while that of better-used part progresses. for example, to full fill their new need the giraffes continuously stretched their neck to reach the taller trees. as the necks were comprehensively used to reach to the tree, its permanent elongation took place and the character was acquired. 

                                                                          

inheritance of acquired characters

the growth of organ ( either better or poorer) acquired during the lifetime of an organism in hereditary. as in the case of giraffes where, the acquired characters, i.e. along the neck was transmitted in the next generation.

                                                       

other examples in Favour of Lamarckism 

snakes: the present day limbless snake with a long slender body were developed from the limbed ancestors. it is due to continued disuse of limb and stretching of their body to suit their creeping mode of locomotion and fossorial mode of living. 

aquatic bird: aquatic bird-like ducks, geese, etc. developed, from their terrestrial ancestors by the inheritance of acquired characters like a reduction of wings due to their continued discus, development of webs between their toes for wading purposes, etc. these changes were mainly induced due to the deficient of food on land and severe competition. 

flightless birds: the development of flightless birds like an ostrich from flying ancestors is considered due to continued disuse of wing as they were found in well-protected areas with plenty of food. 

flat fishes : these are deep sea fishes present at the bottom of sea where there is no sunlight . they lead an inactive life. 

whales : they lost there hind limb as the consequence of there disuse.

wading bird :  they developed long legs through the generation of sustained stretching to keep the body above the water level, example : jacana bird  

cave dwellers : eyes are reduce in cave dwellers ( mole ) since , they live underground. 

Emergent hydrophytes :  in emergent hydrophytes like a ranunculus aquatilis the submerged leaves are dissected while the emerged ones are simply lobed. when the plant is grown out of water , all the leaves are undissected. in the submerged environment, all leaves are dissected.

there are other effect also, such as vestigial organ in some living animals, strong claws and canines in carnivores, sensitive skin and tactile point on the ventral side of the body and callosities of palm in hard workers, exemplifying the Lamarckian theory.

this is all about Lamarckism above example are common example to gives the Lamarckism theory . 

to under stand more about above topic we are to gives some question are related with Lamarckism theory.

(1) the term 'evolution' was first used by? 

(a) spencer

(b) Darwin

 (c) Lamarck

(d) Mendel

solution: the term evolution was first used by spencer 

Q(2) ' Phiosophie zoologique' was written by?

(a) De varies 

(b) Lamarck 

(c) Mendel 

(d) Spencer

solution: phiolosophie of zoologoque was written by Lamarck 

(3) according to the Lamarck , acquired characters are? 

(a) inherited 

(b) artificial

(c) superficial

(d) all of the above

solution : inherited 

(4) whose theory of evolution believes  that every organism has an internal vital force?  

(a) Darwinism 

(b) Lamarckism 

(c) de varies theory 

(d) all of the above

solution : Lamarckism 

Author : scienceinfo

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