Natural Selection and Evolutionary Mechanisms

Natural Selection and Evolution

Introduction to Natural Selection

Natural selection is a fundamental mechanism of evolution, explaining how populations change over time as advantageous traits become more common. This process is driven by differences in reproductive success among individuals due to inherited traits.

• Individuals in a population vary: Each member of a population is unique, exhibiting differences in physical and genetic traits.

• Some traits are heritable: These differences can be passed from parents to offspring through genetic inheritance.

• Not all offspring survive and reproduce: Due to limited resources, only some individuals survive long enough to reproduce, and some produce more offspring than others. This process is not random.

• Individuals with certain traits are more likely to survive and reproduce: Traits that confer an advantage in survival or reproduction become more common in the population over generations.

Modern Reformulation of Natural Selection

The modern understanding of natural selection incorporates genetic principles and emphasizes the role of heritable variation in reproductive success.

• Evolution by Natural Selection (ENS) occurs when:

  • Heritable variation leads to differential reproductive success among individuals.

Result/Consequence of Natural Selection

• Selected traits increase in frequency: Traits that enhance survival and reproduction become more common in the population from one generation to the next.

Key Definitions

• Biological fitness: The ability of an individual to produce surviving, fertile offspring relative to other individuals in the population.

• Adaptation: A heritable trait that increases an individual's fitness in a particular environment.

• Selection: The differential reproduction as a result of heritable variation. Individuals with advantageous traits are more likely to survive and reproduce, passing those traits to the next generation.

Summary Table: Key Terms in Natural Selection

Term	Definition	Example
Biological Fitness	Ability to produce surviving, fertile offspring relative to others	A bird that lays more eggs that hatch and survive to adulthood
Adaptation	Heritable trait increasing fitness in a specific environment	Thicker fur in arctic foxes for cold climates
Selection	Differential reproduction due to heritable variation	Beetles with camouflage coloring surviving predation

Key Points to Remember

• Natural selection acts on existing variation within a population.

• Only heritable traits can be passed to offspring and thus be subject to selection.

• Evolution by natural selection is not a random process; it is driven by differential survival and reproduction.

• Over time, populations become better adapted to their environments as advantageous traits accumulate.