Natural selection is a key mechanism of evolution proposed by Charles Darwin in his groundbreaking 1859 book, On the Origin of Species. It explains how species adapt to their environment over time through the survival of individuals with favorable traits. This process is the primary driver of evolution and helps explain the diversity of life on Earth.
Natural selection operates through four key components. First, there must be variation within a population, with individuals possessing different traits. Second, these traits must be heritable, meaning they can be passed from parents to offspring. Third, selection occurs when individuals with advantageous traits survive and reproduce at higher rates. Finally, over many generations, these small changes accumulate, potentially leading to significant adaptations in the population.
The peppered moth provides a classic example of natural selection in action. Before the industrial revolution, light-colored moths were well-camouflaged against lichen-covered trees, giving them a survival advantage. Dark moths stood out and were easily spotted by predators. During the industrial revolution, pollution killed lichens and darkened trees with soot. This reversed the selection pressure - dark moths now had better camouflage and became the dominant form. After pollution controls were implemented, trees recovered their lighter appearance, and light moths once again became more common. This rapid evolutionary response is one of the best-documented examples of natural selection.
Natural selection can operate in several different ways, leading to various evolutionary outcomes. Directional selection favors one extreme of a trait over the other, shifting the population in a specific direction. An example would be giraffes evolving longer necks to reach higher leaves. Stabilizing selection favors the average, intermediate forms of a trait, reducing variation in the population. Birth weight in humans follows this pattern - babies that are too small or too large have lower survival rates. Disruptive selection favors both extremes of a trait over intermediate forms, which can sometimes lead to the formation of new species. An example is seed size preferences in finches, where birds with either very large or very small beaks have advantages in eating different sized seeds.
To summarize what we've learned: Natural selection is the process where traits that increase survival and reproduction become more common in populations over time. This mechanism requires four key components: variation within a population, inheritance of traits, selection pressure from the environment, and time for changes to accumulate. Examples like the peppered moth clearly demonstrate natural selection in action. Selection can operate in different ways - directional, stabilizing, or disruptive - depending on which trait variations are favored. While natural selection is a fundamental mechanism of evolution, it's important to remember that it works alongside other processes like genetic drift, gene flow, and mutation.
Natural selection operates through four key components. First, there must be variation within a population, with individuals possessing different traits. Second, these traits must be heritable, meaning they can be passed from parents to offspring. Third, selection occurs when individuals with advantageous traits survive and reproduce at higher rates. Finally, over many generations, these small changes accumulate, potentially leading to significant adaptations in the population.
The peppered moth provides a classic example of natural selection in action. Before the industrial revolution, light-colored moths were well-camouflaged against lichen-covered trees, giving them a survival advantage. Dark moths stood out and were easily spotted by predators. During the industrial revolution, pollution killed lichens and darkened trees with soot. This reversed the selection pressure - dark moths now had better camouflage and became the dominant form. After pollution controls were implemented, trees recovered their lighter appearance, and light moths once again became more common. This rapid evolutionary response is one of the best-documented examples of natural selection.
Natural selection can operate in several different ways, leading to various evolutionary outcomes. Directional selection favors one extreme of a trait over the other, shifting the population in a specific direction. An example would be giraffes evolving longer necks to reach higher leaves. Stabilizing selection favors the average, intermediate forms of a trait, reducing variation in the population. Birth weight in humans follows this pattern - babies that are too small or too large have lower survival rates. Disruptive selection favors both extremes of a trait over intermediate forms, which can sometimes lead to the formation of new species. An example is seed size preferences in finches, where birds with either very large or very small beaks have advantages in eating different sized seeds.
To summarize what we've learned: Natural selection is the process where traits that increase survival and reproduction become more common in populations over time. This mechanism requires four key components: variation within a population, inheritance of traits, selection pressure from the environment, and time for changes to accumulate. Examples like the peppered moth clearly demonstrate natural selection in action. Selection can operate in different ways - directional, stabilizing, or disruptive - depending on which trait variations are favored. While natural selection is a fundamental mechanism of evolution, it's important to remember that it works alongside other processes like genetic drift, gene flow, and mutation.