Question

Describe how natural selection might cause a species to change through time.

Short answer

Natural selection causes species to evolve by favoring advantageous traits in a given environment, leading to gradual changes over generations.

Step-by-step solution

Understand Natural Selection

Natural selection is a process where organisms with traits that are better suited to their environment tend to survive and reproduce, passing on these advantageous traits to their offspring. This process leads to a gradual change in the species over time.

Identify a Trait with Variation

Within a species, there must be a trait that shows variation among individuals. This variation is often due to genetic differences. An example could be the length of a giraffe's neck.

Evaluate Environmental Pressure

Environmental pressures are those factors that make certain traits more advantageous. In the case of giraffes, a longer neck may be advantageous for reaching leaves in tall trees in areas where food is scarce.

Select Trait for Survival and Reproduction

Individuals with the advantageous trait (e.g., longer necks) survive longer and have more opportunities to reproduce, thereby passing on the trait to the next generation.

Observe Changes Over Generations

Over many generations, the frequency of the advantageous trait increases within the population. This gradual change can lead to the species evolving over time, often referred to as "descent with modification."

Key concepts

Species Evolution

Species evolution refers to the gradual change in the genetic makeup and characteristics of a species over time. This process is driven by various factors, primarily natural selection. When certain traits become more common in a population because they enhance survival or reproduction, the species as a whole starts to evolve. For example, an animal species living in a colder climate might evolve to have thicker fur, which would better protect it from the cold. Over thousands of years, these changes accumulate, resulting in significant adaptations that define the species as we recognize it. Species evolution is a continuous process that has shaped the diversity of life on Earth.

Genetic Variation

Genetic variation is the presence of differences in the genetic material of individuals within a population. This variation arises from mutations, gene shuffling during reproduction, and other processes. It's essential for natural selection to take place because it provides a pool of traits that selection can act upon. Without genetic variation, a population may struggle to survive if environmental conditions change, as there would be no individual with traits that might confer a survival advantage. Think of it as nature's way of ensuring there's a diverse toolbox to work with, allowing species to dynamically adapt and evolve.

Environmental Pressure

Environmental pressure includes any factors in an environment that influence survival. These pressures can include climate conditions, available resources, predators, and diseases. For example, in a drought-prone area, plants with deeper roots that can access underground water might be more successful.

• Competing for food
• Finding shelter
• Avoiding predators

These pressures determine which traits are advantageous, contributing to the natural selection process. As environments change, the pressures exerted can also change, leading to new evolutionary pathways for species.

Adaptation

Adaptation is the process where a species becomes better suited to its environment over time. Traits that offer a reproductive advantage in a particular environment increase in frequency through natural selection. For instance, polar bears have evolved thick fur and a layer of fat to survive in frigid climates.
Through countless small changes accumulated over generations, organisms become finely tuned to the challenges of their environment. Whether it’s a change in physical traits, behaviors, or physiological processes, these adaptations are crucial for survival. It’s a dynamic process that allows life forms to meet the demands of constantly changing conditions.

Descent with Modification

Descent with modification is a fundamental concept in understanding evolution. It refers to the transfer of genetic material from parents to offspring, where modifications might occur. These modifications can lead to changes in traits over generations, shaping the evolutionary trajectory of the species.
This concept highlights how each generation inherits a combination of traits from its forebears but with potential changes, due to new mutations or recombination of genes. Over time, this can lead to significant evolutionary changes, observed as the appearance of new species adapted to their environment. Descent with modification elegantly showcases the continuity of life and the ever-present potential for change.