Natural Selection—Survival of the Fittest

 

What is Natural Selection?

Natural selection is nature's way of ensuring that only the best-suited organisms survive and reproduce. Over time, populations change as these “winners” pass on their advantageous traits to the next generation.

 

Key Steps of Natural Selection

1. Genetic Variation

   • Within any population, individuals are different due to genetic variation.
   • Example: Some giraffes have longer necks than others.

2. Overproduction of Offspring

   • Organisms produce more offspring than can survive.
   • Example: A fish lays hundreds of eggs, but only a few grow into adults.

3. Struggle for Survival

   • There’s competition for resources like food, water, and shelter.
   • Example: Giraffes with longer necks reach higher leaves, giving them a survival advantage.

4. Survival of the Fittest

   • Individuals with traits that are better adapted to the environment are more likely to survive and reproduce.
   • Example: Long-necked giraffes have more babies, while short-necked ones struggle.

5. Passing on Advantageous Traits

   • The “winners” pass on their favorable alleles to their offspring.
   • Over generations, the population becomes better adapted to its environment.

 

Natural Selection in Action

Example	Description
Antibiotic Resistance	Some bacteria develop resistance to antibiotics and survive, passing this trait to offspring.
Peppered Moths	During the Industrial Revolution, darker moths survived better on soot-covered trees.

 

 

Adaptation

Over many generations, populations become better suited to their environment.

• Example: Polar bears in the Arctic evolved thick fur and white coats to blend in and stay warm.

 

Differences Between Natural and Artificial Selection

Feature	Natural Selection	Artificial Selection
Cause	Happens naturally due to the environment.	Controlled by humans for desirable traits.
Goal	No specific goal—organisms just survive better.	Humans aim to produce organisms with specific traits.
Example	Antibiotic-resistant bacteria.	Breeding dogs for friendliness or speed.