Lamarckism and Theory: Definition and Examples

What Is Lamarckism?

Lamarckism refers to an early evolutionary theory named after a French biologist named Jean-Baptiste Lamarck. It concentrates on the role of use and traits disuse and the inheritance of characteristics that have been acquired. While it was mainly succeeded by Darwinian evolution, Lamarck's ideas were of considerable importance in the history of thought about evolution.

Lamarck's Theory

Lamarck's theory of evolution proposed that organisms change over time by using or not using certain body parts. These acquired traits are then passed on to the next generation. It was one of the earliest ideas explaining how species evolve. Lamarck's theory was that organisms evolve by the adaptation of their traits to the environment in which they live and to their needs.

Change Through Use And Disuse

Lamarck proposed that an organism could modify its physical characteristics by use or misuse of body parts. The more frequently an animal used a particular limb or organ, that part would gain strength and develop over time. Also, traits unused would gradually decrease and weaken.

Organisms Driven To Greater Complexity

Lamarck believed that life necessarily moved toward greater complexity and perfection. They asserted that this drive vested in simple organisms makes them evolve continuously into higher and more complex forms. This idea founded itself on the principle of evolution as a progressive process leading to increasing complexity and sophistication in organisms.

Inheritance Of Acquired Characters

The central doctrine of Lamarck was that of the inheritance of acquired characteristics. He argued that any characteristic that was modified or developed during an organism's lifetime, by use and disuse, could be passed on to its offspring. In this way, the changes an organism undergoes owing to the environment and behaviours it resorts to can directly influence the characteristics of its subsequent descendants.

Effect Of Environment And New Needs

Lamarck emphasised the role played by the ecosystem in shaping organisms. He viewed that any change in the environment creates new needs and difficulties for an organism, which the organism tries to adjust to. These, through continued environmental pressure, are transmitted into changes in the succeeding generations until transformation in that species occurs.

Example Of Lamarckism

Examples related to Lamarckism often involve animals adapting their physical features due to environmental needs. These are used to illustrate how traits developed during an organism’s life could be inherited by offspring, according to his theory.

Several examples may be cited in which acquired traits were supposedly passed on to offspring according to Lamarck's theory.

Lengthening of Giraffe's Neck:

Lamarck elaborated that ancestors of these giraffes stretched their necks to reach high leaves on trees. This stretch had areas where the length of the neck was increasing generation after generation and was passed on to the offspring of that generation.

Webbed Feet in Aquatic Birds:

He thought that webbed feet in aquatic birds such as ducks evolved because they stretched their toes while swimming, which was an acquired trait passed on to subsequent generations.

Blindness in Cave Fish:

Since the fish in a cave did not use their eyes in the dark, supposedly, over generations their eyes had become non-functional. Lamarck held that this acquired blindness is then passed on to subsequent generations.

Lamarckism Vs Darwinism

Both theories aim to explain evolution but differ in mechanisms. Lamarckism is based on the inheritance of acquired traits, while Darwin’s contribution is based on natural selection. Comparing them helps understand how evolutionary thought has progressed.

Lamarckism and Darwinism differ essentially in the mechanisms of evolutionary changes they present.

Mechanism Of Evolution

• Lamarckism: Evolution through the use and disuse of traits and inheritance of acquired characteristics

• Darwinism: Evolution through natural selection on heritable variations within populations

Role Of Environment

• Lamarckism: Environmental change leads to the adaptation of organisms, which then leads to the passing of these adaptations to offspring.

• Darwinism: Differential survival or increased reproduction rate is brought about as a result of environmental selection for particular advantageous characteristics in individuals.

Inheritance

• Lamarckism: Acquired characteristics in the lifetime of an organism are passed onto its offspring.

• Darwinism: Genetic characteristics are the only inherited ones transmitted to offspring, and such characteristics occur by random mutation and recombination.

Progression

• Lamarckism: The evolutionary process is progressive, leading toward complexity and perfection.

• Darwinism: Nothing in evolution shows any progress; the causative elements are adaptation to changing conditions in the environment and struggle for existence.

Conclusion

Lamarckism was one important stepping stone toward the development of evolutionary biology, as it maintained that organisms could change because of their environment. While it is replaced by Darwin's theory of natural selection, Lamarck's ideas embedded several concepts that go on to influence evolutionary thought. The future work that can be done in evolutionary biology is going to integrate further the parts of epigenetics and environmental interactions.

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MCQs on Lamarckism and Theory

Q1. Which of the following is not explained by Lamarckism?

1. Weak progenies of a Nobel laureate

2. Elongation of neck and giraffe

3. Loss of tail in humans

4. None of the above

Correct answer: 1) Weak progenies of a Nobel laureate

Explanation:

Lamarckism is also called the ‘Theory of Inheritance’.According to him, the constant use of organs makes them more efficient, and less or no use of organs brings about degeneration. Such acquired characteristics are inherited through generations. According to this theory, a Nobel laureate has a sharp brain due to greater use of it but this character must be inherited to his progeny. Thus, it cannot explain the occurrence of the weak progeny of a Nobel Laureate.

Hence, the correct answer is option 1) Weak progenies of a Nobel laureate.

Q2. Lamarckism proposes that an organism's use or disuse of a particular body part can influence its heritable traits. Which of the following scenarios aligns with this concept?

1. A weightlifter develops larger muscles through rigorous training and passing on the increased muscle mass to offspring.

2. A cheetah evolves to have a slender body shape through natural selection favoring faster individuals.

3. A plant species adapts to different soil conditions through random genetic mutations.

4. Genetic drift causes variations in the size of a bird's beak in a population.

Correct answer: 1) A weightlifter develops larger muscles through rigorous training and passing on the increased muscle mass to offspring

Explanation:

Lamarckism proposes that an organism's use or disuse of a particular body part can influence its heritable traits. In this scenario, the weightlifter's rigorous training leads to the development of larger muscles. The increased muscle mass is acquired during the lifetime of the weightlifter through the use of the muscles. According to Lamarckism, these acquired characteristics can be passed on to offspring, resulting in the potential for their offspring to also have larger muscles.

Hence, the correct answer is option 1) A weightlifter develops larger muscles through rigorous training and passing on the increased muscle mass to offspring.

Q3. Lamarckism suggests that changes in the environment can directly influence the characteristics of an organism. Which of the following examples would support this idea?

1. A mouse develops sharper teeth over generations due to a diet primarily consisting of hard nuts.

2. A bird population adapts to its environment through random genetic mutations.

3. Polar bears evolve white fur to blend in with the snow and ice in their habitat.

4. Genetic variations in a fish population result in different color patterns.

Correct answer: 3) Polar bears evolving white fur to blend in with the snow and ice in their habitat

Explanation:

Lamarckism proposes that organisms can acquire new traits or characteristics during their lifetime in response to environmental changes and pass them on to their offspring. In this example, the polar bears' evolving white fur is a direct response to their environment. The bears with lighter fur that better blended with the snow and ice would have had an advantage in hunting and survival, increasing their chances of reproducing and passing on the trait of white fur to the next generation. This aligns with the Lamarckian concept of acquired characteristics being inherited.

Hence, the correct answer is option 3) Polar bears evolving white fur to blend in with the snow and ice in their habitat.

Also Read:

• MCQs on Lamarck’s Theory of Evolution

• Miller Urey Experiment

• Theories of Evolution