Darwinism — Core Principles

Core Principles

Darwinism, proposed by Charles Darwin, explains evolution through natural selection. Its core idea is that all life shares a common ancestor and has diversified over vast periods. The theory rests on several key observations: organisms produce more offspring than can survive (overproduction), leading to a 'struggle for existence' for limited resources.

Within any species, individuals show 'variation' in their traits, and these variations are heritable. Those individuals with 'favorable variations' that make them better adapted to their environment are more likely to survive, reproduce, and pass on these advantageous traits.

This process is called 'natural selection' or 'survival of the fittest' (where fitness means reproductive success). Over many generations, the accumulation of these beneficial traits leads to gradual changes in populations and eventually to the formation of new species.

Key examples like industrial melanism and antibiotic resistance demonstrate natural selection in action, providing strong evidence for Darwin's theory.

Important Differences

vs Lamarckism and Neo-Darwinism

Aspect	This Topic	Lamarckism and Neo-Darwinism
Mechanism of Evolution	Lamarckism (Inheritance of Acquired Characters)	Darwinism (Natural Selection)
Source of Variation	Organisms acquire traits during their lifetime in response to environment (use and disuse).	Pre-existing, random variations within a population (source unknown to Darwin).
Inheritance	Acquired characters are inherited by offspring.	Heritable variations are passed on; mechanism unknown (blending inheritance was a problem).
Role of Environment	Environment directly induces changes in organisms, which are then inherited.	Environment acts as a selective agent, favoring certain pre-existing variations.
Example	Giraffes got long necks by stretching them, and this stretched neck was inherited.	Giraffes with naturally longer necks survived better and reproduced more, passing on long-neck traits.
Modern Validity	Largely discredited, though epigenetics shows some limited, non-Lamarckian inheritance of acquired traits.	Core principles remain valid, but incomplete without genetics.

Darwinism, Lamarckism, and Neo-Darwinism offer distinct explanations for evolutionary change. Lamarckism proposed that traits acquired during an organism's lifetime could be inherited, a concept largely disproven. Darwinism introduced natural selection, where pre-existing, heritable variations that confer an advantage in the struggle for existence are favored, leading to differential survival and reproduction. However, Darwin lacked knowledge of the genetic basis of variation and inheritance. Neo-Darwinism, or the Modern Synthesis, integrates Darwin's natural selection with Mendelian genetics, explaining variation through mutations and recombination, and inheritance through genes, providing a more complete and robust framework for understanding evolution.