How Does Lamarckism Differ from Darwinism?
Biology could be called one of the most liked subjects among science students. There is always a great potential to score well in this subject. The examiners are testing students' understanding of the subject through some specific topics which often includes Lamarckism. This topic is important from the examination point of view. Examiners tend to ask questions about this topic on a recurrent basis. In this light having a good command of Lamarckism would give immense returns to the students. They must read this topic in a comprehensive way and try to grasp all the important details on Lamarckism. Making revision notes which are imperative should not be missed since they enhance our preparation for the same. Students must be cautioned again referring to unreliable sources that could hamper their score in the exams.
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Introduction to Lamarck's Theory of Evolution
Lamarckism has covered a broad spectrum of theoretical positions on the nature of evolution. Jean Baptiste Lamarck presented theories on Lamarckism. There were numerous explanations given from the 18th century until the early 20th century. Lamarckism is about the succession of life forms, their history, their transformations. Darwin believed that individuals were simply born with different traits and these differences were mostly random. This theory was contrary to Lamarck who said that traits could develop change during an animal's life. The theory is. based on evolution stated that physical changes in organisms during their life-like, in a part through increased use or greater development of organs could be transmitted to their offspring.
Inheritance of Acquired Characteristics
Characteristics that have been developed by an individual in the course of their life in the body or somatic cells are usually through the use or disuse of part or an immediate reaction to some external modification in the environment. The reappearance of variations from an individual in the next or succeeding generations is known as the inheritance of acquired characteristics. Inheritance of a change can be explained through an example of Blacksmith's arm.
When the arm is used continuously against an external resistance like the weight of the hammer then the blacksmith's arm enlarges. At birth, the smith’s children would have unusually large arms, if the effect were inherited.
Theory of Use and Disuse
Lamarck tried to explain the evolutionary process in his book Philosophic Zoologique. The use and disuse of an organ lead to acquiring changes in the feature of the organ. These changes are also inherited by offspring. ButLamarckismm was very strongly criticized by August Weismann.
Lamarck's Theory of Inheritance of Acquired Characteristics
The first theory of evolution is Lamarckism which was proposed by a French biologist. It states that modifications acquired by an organism during its lifetime are automatically handed down to its descendants, and so it becomes part of heredity. His evolution ideas are briefed as follows:
The Size of the Organism Tends to Increase with Internal Forces
The internal forces of life tend to increase continuously the size of an organism and its components.
The Direct Environmental Effect Over Living Organisms
The organs of an animal show modifications in a way that they respond directly to a changing environment.
Use of Disuse
More use of organs greatly improves them and misuse reduces the organs.
Inheritance of Acquired Characteristics
It is the direct transmission of those superficial bodily changes that arose within the lifetime of an individual.
Examples of Lamarckism
Lamarckism explained his theory by giving the following examples
Giraffe- The giraffe’s ancestors were born with a small neck and forelimbs to eat the leaves for food, which resulted in the slight elongation of these parts. The acquired characters were transmitted to the next generation.
Aquatic Birds – The evolution of Ducks occurred from terrestrial ancestors. Due to the lack of food on land, these aquatic animals need to go to water. Hence, some web-like structures are developed between the toes in them making their lives easy in the water.
Flat Fish- Deep-sea fishes are found at the sea bottom where no sunlight is present. So, they had to lead an inactive life. The eye of one side which lies on the bottom then migrates towards the upper side. Thus, both eyes are on the single side of the body.
Whales- as an outcome of the inherited effect of disuse, lost their hind limbs.
The Wading Birds- like Jacana keep their body above the water level by developing long legs through the sustained stretching generation.
Drawbacks in Lamarckism
Lamarckism is not proved experimentally.
New organs are not formed in organisms as per their wish.
It is not necessary that the acquired characters transmit into the new generation.
Exam Time Tips
The student must keep a couple of tips in mind before going for the exams. These tips will keep them ahead of others.
A student must have gone through the previous year question before going for the previous year question papers and practice them thoroughly. One should ensure that the syllabus is complete, however, it doesn't hurt if the students leave out the unimportant part from the syllabus. Have a time management plan to tackle the question paper and remember to sleep well before the exam.
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FAQs on What is Lamarckism? Theory & Key Examples
1. What is the main idea behind the theory of Lamarckism?
Lamarckism is an early theory of evolution that suggests organisms can pass on to their offspring the physical characteristics they acquire during their lifetime. The central concept is that traits developed through an organism's behaviour, such as frequent use or disuse of a body part, are heritable.
2. What are the two key principles of Lamarck's theory?
Lamarck's theory is built on two main principles:
- The Law of Use and Disuse: This states that body parts used often become larger and stronger, while those that are not used deteriorate and shrink over time.
- The Law of Inheritance of Acquired Characteristics: This principle claims that any changes an organism acquires in its lifetime through use or disuse can be passed directly to its offspring.
3. What is the classic example used to explain Lamarckism?
The most famous example is the long neck of the giraffe. Lamarck proposed that ancestral giraffes had short necks and stretched them to reach leaves on taller trees. He believed this repeated stretching made their necks longer, and this acquired trait was then inherited by the next generation, leading to progressively longer necks over time.
4. How does Lamarck's theory differ from Darwin's theory of natural selection?
The main difference is the origin of the traits. Lamarck believed that traits change based on an organism's needs or efforts, and these acquired traits are then inherited. In contrast, Darwin's theory states that variation already exists randomly within a population. Individuals with traits that happen to be advantageous for survival are more likely to reproduce and pass those existing traits on, a process called natural selection.
5. Why was Lamarck's theory of evolution disproved?
Lamarck's theory was largely rejected because there was no scientific evidence that characteristics acquired during an organism's life could be passed on genetically. Experiments, such as August Weismann's famous study involving cutting the tails off mice for many generations, showed that the offspring were always born with tails. This demonstrated that physical changes to an organism's body do not alter the genetic information in its reproductive cells.
6. Are any modern biological concepts similar to Lamarck's ideas?
While Lamarck's core theory is incorrect, the modern field of epigenetics shows some interesting parallels. Epigenetics is the study of heritable changes in gene function that do not involve changes to the DNA sequence itself. Certain environmental factors can cause epigenetic marks that can be passed down for a few generations. This concept of inheriting environmentally-influenced traits faintly echoes Lamarck's ideas, but through a much more complex and different mechanism.
7. What was Jean-Baptiste Lamarck's most important contribution to the study of evolution?
Although the mechanism he proposed was wrong, Lamarck's greatest contribution was being one of the first scientists to argue that species are not fixed and change over time. He correctly recognised that organisms adapt to their environments and proposed a naturalistic theory for evolution, which was a significant step forward in biological thought.
