Darwinism vs Lamarckism theory of evolution: definition and differences

darwinism vs lamarckism

Introduction

Evolution is an important part of Earth’s history. There are various theories of evolution like Lamarck’s and Darwin’s theory of evolution. Evolution sheds considerable light on the explanation of the distribution and characteristics of the flora and fauna of the world today. The term evolution means to evolve from an initial simple state to a more organized and complex form through natural processes. Darwinism vs Lamarckism is thus as follows.

Therefore, evolution is the change of something in a natural way, such as the origin and evolution of the earth, the evolution of the earth’s surface, the evolution of the oceans, the description of the mountains, the evolution of animals, etc.

In ancient periods, people believed that all modern animals and plants existed from the beginning of the creation of the earth. As long as the earth exists, their existence will remain unchanged. But in the fifth century, BC Xenophane discovered some fossils and showed that there is a difference between the past and present organisms. The idea of evolution begins with this theory. Since then, scientists have gradually developed various theories about evolution.

The main proponents of the theory of evolution are Democritus, Aristotle, and other Greek philosophers. And later Linnaeus, Buffon, Lamarck, St. Hilarie, Charles Darwin, Weismann, Hugo de Vries, and many other scientists published the theory of biological evolution subject to experimentation. Among these, Lamarck and Darwin’s theory of evolution has become more popular (1).

Lamarck’s theory of evolution

In 1802, the French biologist Lamarck (1744-1829) published the first modern theory of evolution in his book Philosophie Zoologique. Lamarck states in his theory that all the traits that an organism acquires by responding to changes in the environment are passed on from one generation to the next. He notes that there are considerable differences between two plants of the same species as they grow in two different environments. Environmental change brings about changes in the needs of an organism. Organisms adapt new methods to meet changing needs. As a result, the use of some organs increases, and the use of some organs decreases. In this way, a new organ can be created from the part or organ of the organism that increases its circulation and use. But the unused organs gradually become extinct. All the traits that each generation thus acquires are passed on to the next generation. Lamarck’s doctrine is based on the following theories (1).

1. Influence of the environment

According to Lamarck, changes in the environment lead to changes in the nature and physique of the organism. When a particular species of organism lives in different environments, there is a difference in their natural or physical changes.

2. Conscious effort

Lamarck stated that organ transformation is possible on its own. If the need for a particular organ increases due to changes in the environment, it can change the course of evolution by trying to nourish that organ and weakening the organ necessary for the environment.

3. Law of use and disuse of organs

In order to adapt to the environment, some organs of the organism are used more and some organs of the organism are used less. Specific organs are strong and well-organized for continuous use. On the other hand, the organs become weak and eroded due to continuous misuse and become extinct over time.

4. Law of inheritance of acquired characters

The traits acquired during the life of an organism under the influence of the environment are transmitted to the next generation of organisms. Thus a small change in each generation is seen as a major change over time as it is passed on to the next generation. This is how the organism evolved.

5. Origin of new species

According to Lamarck’s theory, the inheritance of acquired traits and the acquisition of new traits in each generation gradually led to the creation of new species from one species to another (1)(2).

Examples in favor of Lamarck’s theory

1. Birds that live on land go into the water in search of food. And as they swim constantly in the water, thin skin is attached to the space between their toes.

2. According to Lamarck’s, giraffes originated from deer. Giraffes with long necks and legs have emerged in recent generations to eat the leaves of tall trees. The deer’s neck and forelegs have grown a little longer in each generation to eat the leaves of tall trees. And now there are giraffes with long necks and legs.

3. The ancestor of the ostrich had active wings and could fly in the sky. But as a result of not using the wings for generations, now it has become an endangered organ.

4. The ancestor of the snake had four legs like a chameleon. But the snake’s legs are now completely extinct as a result of continued misuse for underground adaptation (3).

Criticism of Lamarck’s theory

Through experiments, various scientists have proved that Lamarck’s theory is scientifically baseless. Although any part of the organism is well-formed or extinct as a result of use and misuse, those altered traits are never inherited. Some information related to this is discussed below.

1. Drosophila, a type of fly, has not been able to give birth to a blind fly after conducting breeding in a completely dark room for 60 generations.

2. Scientist Weismann cut off the tail of a pair of rats. Weismann also cut off the tails of their children after they were born. Thus, despite cutting the tail of rats for 22 generations, no tailless rats have been born. Based on this experiment, Weismann said that Lamarck’s theory has no scientific basis (2).

Darwin’s theory of evolution

Charles Darwin was born in England in 1831-1835 he traveled to various islands in the Atlantic Ocean. He later developed a groundbreaking theory about the expression of living things by observing his travel experiences and samples. His theory is called Darwinism or natural selection theory. In 1859, Darwin published his theory in his book “On the origin of species by means of natural selection”. Darwin’s theory is explained below (3).

1. Prodigality of production

According to Darwin, reproduction at an excessive rate is an innate feature of an organism. As a result, the number of organisms increases at a geometric and mathematical rate. For example, an oyster produces about 120 million eggs. According to Darwin, if all the elephants produced from a pair of elephants survived, the number of elephants in 750 years would be 19 million.

2. The constancy of food and shelter

Habitat and food are also limited due to the limited surface area.

3. Struggle for existence

As the organism multiplies at a geometric and mathematical rate and the food and habitat is limited, the organism has to face tough competition to survive. Darwin called it the ‘struggle for existence’. The struggle for existence is mainly in two ways, (i) intraspecific struggle (the struggle between similar species) and (ii) interspecific struggle (the struggle between different species). Living things also have to struggle with droughts, floods, etc. It is called struggle with an adverse environment.

4. Variation

According to Darwin, two creatures on earth cannot be exactly the same. That is, there must be some difference between the two creatures.  Even between two children of the same parents, there are also some differences.

Darwin believed that continuous triple struggles resulted in variations in the organism, which are transmitted to the offspring during reproduction and are ultimately established as characteristics of the organism. According to Darwin’s theory, a small series of changes are responsible for the emergence of different species.

5. Survival of the fittest

According to Darwin, of all the organisms involved in the struggle for life, those who have small adaptive traits in their bodies win the struggle for life. Others become extinct from the earth. This passage in the struggle of life is called the survival of the fittest.

6. Natural selection

This is the most important aspect of Darwin’s theory. Through various struggles on the surface of the earth, Darwin called the survival of the fittest is natural selection. Nature selects the most suitable organism. Those who are chosen by natural selection, survive in greater numbers. They breed and their offspring inherit favorable varieties.

7. Origin of new species

As those species accumulate within a particular group of species, the differences between the generation and the offspring are much greater. And in time a new species emerges. As a result of evolution, new species of organisms are born (2)(3).

Criticism of Darwin’s theory

Although natural selection is a recognized process for explaining the causes of evolution, Darwinism has the following weakness.

  • Darwin discusses the survival of the fittest but does not discuss the most qualified organism.
  • It is true that by natural selection an organism emerges and other organisms become extinct. Although the consequences of natural selection have been discussed in evolution, the theory of extinction has not been properly explained.
  • Darwin’s evolution theory only discussed the mutual struggle between new offspring. But there has been no discussion of the impact of this struggle on previous organisms.
  • There are many organs in the body of some animals or plants which do not play any role in maintaining their existence. Darwin could not give any explanation.
  • Variations are created irregularly. So it is not possible to explain the evolution of the well-organized and body with the help of these (3).

Darwinism vs Lamarckism

Both Lamarck and Darwin expressed their theories about biological evolution. Although their theories have been criticized, Lamarck and Darwin’s theories on evolution are notable among them. These two theories differ from each other. Their differences are described below.

Content

Lamarckism

Darwinism

1. Environmental impactThe adaptation of the organism varies according to the variation of the environment. And the organism survives in harmony with nature.In order for an organism to survive, it has to struggle with the environment. And the creatures that win the struggle survive in harmony with nature.
2. Increase in the organismLamarck gave the idea of increasing the size of an organism.Darwin explained the increase in the number of organisms in his theory.
3. Cause of evolutionOrgan transformation, growth, and extinction occur for use or abuse. And acquired changes are transmitted from generation to generation. As a result, biological evolution occurs.In order to survive in the struggle of life, different variations are seen in the organism. This is the main reason for evolution.
4. Struggle of lifeLamarck did not mention the struggle of life. According to Lamarck, internal demand is the cause of an increase or decrease of any organ.Three types of life struggle explained by Darwin such as intraspecific struggle, interspecific struggle, and struggle with the environment.
5. Concept  of inactive organsInactive organs were used in the past, but are now extinct due to abuse.Darwin’s theory does not give any explanation about inactive organs.
6. Transmission of propertiesTraits acquired in life are transmitted to the next generation.The characteristics of the most naturally selected organisms are transmitted to the next generation.
7. Use and abuse of organOrgans are well-organized due to continuous use. And as a result of abuse, the organs become weak and inactive.Darwin did not explain the use and abuse of organs.
8. Natural selection theoryLamarck does not support the theory of natural selection.The theory of natural selection is most important in Darwinism.
9. Origin of the giraffe’s neckThe necks of giraffe ancestors were small. Gradually there was a shortage of grasses and short trees. So they were forced to stretch their necks to eat the leaves of tall trees.As per Darwin, giraffe ancestors had different neck lengths. This is the result of mutation. These mutations are passed down through generations (2) & (3).

 

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