What is the main difference between Darwinism and Lamarckism?

The fundamental difference lies in the mechanism of evolution. Lamarckism proposed the 'inheritance of acquired characters,' meaning traits an organism develops during its lifetime (like a giraffe stretching its neck to reach leaves) could be passed to its offspring. Darwinism, conversely, states that evolution occurs through 'natural selection' acting on pre-existing, heritable variations. Giraffes with naturally longer necks had an advantage, survived, and passed on their genes, not that their necks stretched and then those stretched necks were inherited.

What did Darwin mean by 'fitness' in 'survival of the fittest'?

In the context of Darwinian evolution, 'fitness' does not primarily refer to physical strength or health, but rather to an organism's reproductive success. A 'fit' individual is one that is well-adapted to its environment, allowing it to survive long enough to reproduce and pass on its genes to the next generation more successfully than others. The more viable offspring an individual produces, the higher its evolutionary fitness.

Did Darwin know about genes and DNA?

No, Charles Darwin published 'On the Origin of Species' in 1859, well before the discovery of genes, DNA, or the principles of Mendelian inheritance. Gregor Mendel's work on heredity was published in 1866 but remained largely unrecognized until the early 20th century. Darwin understood that variations existed and were inherited, but he lacked the mechanism to explain how these traits were passed from one generation to the next. This gap was later filled by the Modern Synthesis (Neo-Darwinism).

Can an individual organism evolve according to Darwinism?

No, according to Darwinism, individuals do not evolve. Evolution is a change in the heritable characteristics of biological populations over successive generations. An individual's genetic makeup is fixed at birth. While an individual can adapt or change its behavior during its lifetime, these acquired characteristics are generally not passed on to offspring. It is the population, as a whole, that evolves over many generations through changes in the frequency of genes.

What are some common criticisms or limitations of Darwin's original theory?

While revolutionary, Darwin's original theory had some limitations. He couldn't explain the source of variation among individuals, nor the precise mechanism of inheritance (how traits were passed on without blending). He also struggled with the apparent lack of transitional fossils in some lineages. These gaps were largely addressed by later discoveries in genetics, paleontology, and molecular biology, leading to the Modern Evolutionary Synthesis (Neo-Darwinism).

Darwinism

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Darwinism, fundamentally, is the theory of evolution by natural selection, as proposed by Charles Darwin. It posits that all species of organisms arise and develop through the natural selection of small, inherited variations that increase the individual's ability to compete, survive, and reproduce. This process leads to the gradual divergence of populations and the formation of new species over ge…

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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.

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Key Concepts

Natural Selection (Mechanism)

Natural selection is the driving force behind Darwinian evolution. It's not a conscious choice but a passive…

Variation and Inheritance

Darwin observed that individuals within a species are not identical; they exhibit variations. He also noted…

Struggle for Existence and Overproduction

The concept of 'struggle for existence' arises directly from 'overproduction.' Organisms typically produce…

Darwinism: — Evolution by natural selection.

Postulates:

1. Overproduction: More offspring than can survive. 2. Variation: Differences among individuals. 3. Struggle for Existence: Competition for resources. 4. Natural Selection (Survival of the Fittest): Favorable variations lead to differential survival/reproduction. 5. Inheritance: Favorable traits passed on, leading to adaptation/speciation.

Fitness: — Reproductive success.

Key Examples: — Industrial melanism, antibiotic resistance.

Limitations: — Didn't know source of variation or mechanism of inheritance (genetics).

Contrast: — Lamarckism (acquired characters) vs. Darwinism (heritable variation + selection).

To remember Darwin's postulates: Overproduction, Variation, Struggle, Natural Selection, Inheritance.

Think: Outstanding Variations Survive Naturally & Inherit.