Darwin's Big Idea
Natural selection is a key idea that helps us understand how living things change over time, a process known as evolution. For natural selection to happen, there are four important conditions that need to be met. First, there must be variation within a population. This means that not all individuals are the same; they have different traits, like color, size, or abilities. Second, some of these traits can be passed down from parents to their young, which is what we call heritable traits. This is important because it allows certain characteristics to continue in future generations. Third, more young are born than can survive to grow up. This creates competition for food, shelter, and other resources. Finally, individuals that have traits that help them survive better in their environment are more likely to live longer and have babies. Over many generations, these helpful traits become more common in the population, leading to changes in the species. This process is how evolution occurs, shaping the diversity of life we see today.