What Are the 3 Condition in the Theory of Evolution?


Jane Flores

The theory of evolution is a widely accepted scientific concept that explains how species have changed and evolved over time. The theory is based on three main conditions – variation, natural selection, and inheritance. In this article, we will explore each of these conditions in detail.


Variation refers to the differences that exist between individuals within a species. These variations can be seen in physical traits such as height, weight, and eye color, as well as behavioral traits such as hunting techniques and social behavior. Variation occurs due to genetic mutation and recombination during reproduction.

For example, consider a population of birds with varying beak sizes. Some birds may have larger beaks that are better suited for cracking open tough seeds while others may have smaller beaks that are better suited for eating insects. This variation allows the birds to adapt to their environment and survive.

Natural Selection

Natural selection is the process by which certain traits become more or less common in a population based on their impact on survival and reproduction. Individuals with advantageous traits are more likely to survive and pass on their genes to their offspring.

Continuing with our bird example, imagine that there is a drought in the area where the birds live, causing seeds to become scarce. The birds with larger beaks are better able to crack open tougher seeds and therefore have an advantage over birds with smaller beaks. Over time, the population will shift towards having more individuals with larger beaks as they are more likely to survive and reproduce.

  • Directional Selection: This occurs when one extreme trait is favored over others leading to a shift in the population towards that trait.
  • Stabilizing Selection: This occurs when intermediate traits are favored over extreme ones leading to a reduction in variation within the population.
  • Disruptive Selection: This occurs when extreme traits on both ends of the spectrum are favored over intermediate ones leading to an increase in variation within the population.


Inheritance refers to the passing on of traits from parents to offspring. Offspring inherit a combination of genes from both parents, which can result in new variations within a population.

For example, imagine that two birds with different beak sizes mate and produce offspring. The offspring may inherit genes for a larger beak from one parent and genes for a smaller beak from the other parent resulting in intermediate beak sizes in their offspring.


In conclusion, the theory of evolution is based on three main conditions – variation, natural selection, and inheritance. These conditions work together to explain how species change and adapt over time. By understanding these conditions, we can gain insight into how life on Earth has evolved and continues to evolve today.