The idea of "survival of the fittest," which was introduced by Charles Darwin, helps us understand how evolution works. This phrase mainly talks about natural selection. This is when animals or plants that have helpful features are more likely to survive and have babies. Let's break down the main parts of this idea:

1. Natural Selection:

   • Many living things have babies, but not all of them can live to grow up. In fact, about half of the young from many species don’t make it to adulthood.
   • There are different traits in populations. For example, in some species, up to 80% of their features can be different because of changes in their genes.
   • Those who have helpful traits, like being able to blend in with their surroundings or running fast, are more likely to survive and have babies. This means they can pass these good traits to their children.

2. Genetic Variation:

   • Having a mix of different genes in a group can help them adapt better. Populations that have up to 90% genetic differences tend to handle changes in their environment more easily.

3. Mutation:

   • Mutations are changes in genes that can create new traits. About 1 in every million parts of DNA might change, and this can sometimes help a living thing survive better.

4. Sexual Selection:

   • Some traits help animals attract mates. For example, peacocks with big, colorful tails can attract 70% more mates than peacocks with smaller tails.

5. Environmental Factors:

   • Changes in the environment can change what traits are favored. For example, if the temperature rises by 5°C, it can cause certain animals or plants to move to new areas, which can affect how many survive.

These mechanisms help species adapt over time. This way, the strongest and best-equipped individuals survive and pass their helpful traits on to the next generations.