How Did Darwin’s and Lamarck’s Theories of Evolution Differ?
Also known as Darwinian Theory or Theory of Natural Selection, Darwinism is defined as a theory of biological evolution founded by the English naturalist Charles Darwin (1809-1882), This describes a philosophy in which all species of organisms evolve and develop through natural selection of small and hereditary variations which enhance the ability of an individual to compete, survive and reproduce. It is, more precisely, a distinctive form of evolutionary reasoning for the origin and nature of earthly life.
About Darwinism and Lamarckism
The theory's major concepts include overproduction, the fight for life, differences, the survival of the fittest species and the origin of organisms. Those can be explained further as follows:
Species are created by individuals who differ slightly with respect to their various characteristics.
Species have a tendency to grow their numbers at a geometric rate over centuries.
This propensity is assessed by the concepts of population, limited resources, disease and predation that will ultimately determine the struggle for survival among members of a species.
Some individuals will have variations, giving them a slight advantage in this battle, where individual variations will allow more effective or better access to resources, greater disease resistance and greater success in preventing predation. These people also survive better than others, yielding more offspring. Offspring will inherit many variations on the part of their parents.
As a result, favourable variations are more frequently passed than others and thus preserved over time, and this significant trend is called ‘Natural’.
This method, however, will result in a fundamental change in the character of a given species.
How does Natural Selection Work?
The whole process of natural selection tends to carry on from generation to generation. The basis of this concept is that those genetic mutations that might result in an individual’s benefits and help him/her to survive are passed onto them through reproduction. This in turn paves the way for more organisms whose chances of survival increase.
The declining populations of an ancestor species will vary enough over a long period of time, and will be categorised as a different species with a capacity process along with an infinite iteration. The elimination of intermediate varieties will be the responsibility of forces which promote divergence among descendant populations.
Limitations to Darwinism
Charles Darwin’s theory of evolution isn’t completely unblemished as it has a few drawbacks of its own.
Here are a couple of limitations to Darwinism:
Darwin didn’t explain the concept of variation in-depth at all and still used it in his theory. He was not able to explain where exactly the variations that tend to generate during the process of evolution originate from or even how these are really inherited.
Although he put great emphasis on the idea of how evolution is basically “survival of the fittest”, that particular perspective isn’t really true. This is mainly because studies found out later that both the fit, as well as the fitter organisms can co-exist in the environment.
What is Lamarckism?
Being the first Theory of Evolution, proposed by Jean Baptiste de Lamarck, a French biologist (1744-1829), Lamarckism is defined as a combination of theories consisting of the inheritance of characters acquired and the use and disuse of organs.
In a simpler way, this concept suggests that in all species there is an inner vital force with special consideration of basic needs and desires to produce new structures and alter the behaviour of whole organisms.
Major Concepts Explained by this Theory
Internal Vital Force: As a result of a pre - existing inner vital force, all living things and their component parts are steadily increasing in number and size.
Effect of Environment and New Needs: Environment acts as an influential factor in all types of organisms, and a simple environmental change tends to bring about significant changes in organisms. It also gives rise to new needs that can over time create new systems and alter the organism's habits.
Use and Disuse of Organs: If an organ is used constantly, it will progressively develop over time where the disuse of an organ results in its degeneration.
Inheritance of Acquired Characters: As a result of the internal vital force listed above, individuals acquire characters and features during lifetime. These will eventually pass to generations to come. This whole process will continue, and these variations will accumulate to a certain degree after several generations, creating new species.
Example: Evolution of Giraffe
Originally the giraffe's ancestors had a small neck and forelimbs and looked like horses. But since they lived in places without any vegetation on the surface, they had to stretch out their neck and forelimbs to pick leaves to eat, resulting in a slight elongation of these parts. Those beneficial characteristics, however, passed over time from generation to generation and ultimately resulted in a species with long necks and forelimbs.
Limitations to Lamarckism
Lamarck’s theory also had certain limitations as follows:
According to Lamarckism, the coming/future generations tend to inherit the acquired characteristics. However, there’s a loophole here in this concept because he was unable to explain the association between those acquired characteristics and reproductive cells.
In fact, he ended up misinterpreting it all because it is not possible for said acquired characteristics to be inherited by an organism, thereby rendering his notion incorrect.
Difference Between Darwinism and Lamarckism:
Concept -
Darwinism: Darwinism suggests that all species of organisms arise and develop by natural selection of small and hereditary variations which enhance an individual's ability to compete, survive and reproduce.
Lamarckism: Lamarckism is based on new desires that generate new structures and change organismal habits over time.
Exceptions
Darwinism: Darwinism does not believe in the concept of the internal vital force explained in Lamarckism.
Lamarckism: Lamarckism refuses to accept Darwin 's natural theory of selection.
Struggle for Existence & Survival of the Fittest
Darwinism: Two major factors mentioned in Darwinism are the battle for life and survival of the fittest.
Lamarckism: Lamarckism does not recognize struggle for life and survival of the fittest.
Darwinism: Only useful variations will be translated over successive generations, according to Darwinism.
Lamarckism: Lamarckism proposes that the next generation inherit all of the acquired characters.
FAQs on Darwinism vs Lamarckism: Explained for Students
1. What is the main difference between Darwinism and Lamarckism?
The main difference lies in how they explain the inheritance of traits. Darwinism proposes that evolution happens through natural selection, where organisms with favourable random variations survive and pass those traits to their offspring. In contrast, Lamarckism suggests that organisms can pass on traits they acquired during their lifetime, like developing stronger muscles from use.
2. How would Darwinism and Lamarckism explain a giraffe's long neck differently?
Both theories use the giraffe's neck as a classic example, but their explanations are very different:
- Lamarckism: This theory suggests that ancestral giraffes stretched their necks to reach higher leaves. This effort made their necks slightly longer, and this 'acquired' longer neck was passed directly to the next generation.
- Darwinism: This theory proposes that there was natural variation in neck length in the giraffe population. Giraffes born with slightly longer necks had a survival advantage because they could access more food. They were more likely to live, reproduce, and pass the long-neck gene to their offspring.
3. What does 'natural selection' mean in Darwin's theory?
Natural selection is the core mechanism of Darwin's theory. It is the process where organisms with traits that are best suited to their environment are more likely to survive, reproduce, and pass those advantageous traits on. It is often summarized as "survival of the fittest", where 'fittest' means most well-adapted to the current conditions.
4. What are the key principles of Lamarck's theory?
Lamarck's theory is based on two main principles:
- Use and Disuse: Organs that are used frequently become stronger and more developed, while those that are not used become weak and may disappear over time.
- Inheritance of Acquired Characteristics: The changes that an organism acquires during its lifetime (like a developed muscle) are passed on to its offspring.
5. Why is Darwin's theory of evolution more accepted by scientists today?
Darwin's theory is more widely accepted because it is strongly supported by evidence from modern genetics. We now understand that traits are passed down through genes (DNA), and changes that happen to an organism's body during its life do not alter its genetic code. For instance, if a person builds large muscles through exercise, their children will not be born with large muscles.
6. What was a major weakness in Darwin's original theory?
The biggest weakness in Darwin's original theory was that he could not explain the source of variation. He observed that individuals within a population were different, which was crucial for natural selection to work, but he did not know about the mechanisms of genetics, mutation, and recombination that cause these variations.
7. How does Neo-Darwinism differ from Darwin's original theory?
Neo-Darwinism, or the Modern Synthesis, is an updated version of Darwin's theory. It combines Darwin's natural selection with the principles of Mendelian genetics. It explains that variations arise from random genetic events like mutation and recombination, providing the missing piece that Darwin could not explain.
8. Are any of Lamarck's ideas considered relevant in modern biology?
While Lamarck's primary idea of inheriting acquired physical structures is incorrect, some modern fields show a faint echo of his thinking. The field of epigenetics studies how environmental factors can cause heritable changes in how genes are expressed without changing the DNA sequence itself. This is a far more complex process than what Lamarck proposed, but it shows that the environment can influence inherited traits in subtle ways.
