Question

write an essay on lamarckism
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Answer 1

Answer:

Lamarckism

Lamarckism was proposed by Jean-Baptiste de Monet Lamarck in the year 1744-1829. This theory was based on the principle that all the physical changes occurring in an individual during its lifetime are inherited by its offspring. For eg., the development of an organ when used many times. This theory has been explained here.

Lamarck’s Theory

Lamarck’s theory includes four main propositions:

Change Through Use And Disuse

The organs which are used frequently by the organism develop and the characteristics that are used seldom are lost in the succeeding generations. For eg., a giraffe stretches its neck to eat leaves, a “nervous fluid” would flow in its neck and it enlarges. The organs which the organisms have stopped using would shrink with time.

Organisms Driven To Greater Complexity

As the organisms adapted to their surroundings, they became increasingly complex from the simpler forms. Lamarck believed in the spontaneous generation of life.

Also read: Evolution

Inheritance of Acquired Characters

An individual acquires certain characteristics during its lifetime. These characters are inherited by their offspring as well. He explained this with an example of a blacksmith. A blacksmith has strong arms due to the nature of their work. He proposed that any children a blacksmith conceives will inherit the development of strong muscles.

Effect of Environment and New Needs

The environment influences all the organisms. A slight change in the environment brings about changes in the organisms. This gives rise to new needs which in turn produces new structures and changes the habits of the organisms.

Examples of Lamarckism

Few of the examples of Lamarckism are mentioned below:

Evolution of giraffe

The ancestors of the giraffe looked like horses with small necks and forelimbs. They lived in areas where there was no surface vegetation. Therefore, they had to stretch their neck and forelimbs to eat leaves from tall plants. Consequently, these parts got elongated. This trait was transmitted in the successive generations.

Aquatic Birds with Webbed Toes

Aquatic birds such as ducks are believed to have evolved from terrestrial animals.

Extinction of Limbs in Snakes

The snakes are believed to have evolved from lizard-like ancestors that have two pairs of limbs.

Flightless Birds

It is believed that the ancestors of birds such as Ostrich were able to fly. Due to some environmental changes, they had a lot of food and were well protected. They stopped using their wings and as a result, the wings became vestigial.

Cave Dwellers

The ancestors of the animals living in caves are believed to have powerful eyesight. Due to living under continuous dark conditions, they lost their power to see.

Answer 2

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➣ ➢ Solution ➣ ➢

• Lamarckism, also known as Lamarckian inheritance or neo-Lamarckism,[1] is the notion that an organism can pa.ss on to its offspring physical characteristics that the parent organism acquired through use or disuse during its life ti।me. 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.

• Introductory textbooks contrast Lamarckism with Charles Darwin's theory of evolution by natural selection. Darwin's book On the Origin of Species however supported the Lamarckian idea of use and disuse inheritance, and his own concept of pangenesis implied a Lamarckian soft inheritance.