* Evolution is the gradual change in the genetic makeup of a *population* over many generations. It's about the overall shift in gene frequencies within a species.
* Changes within a lifespan are generally called mutations. These are changes in the DNA sequence of an individual. While they can sometimes be beneficial or even lead to new traits, they don't automatically mean evolution is happening.
Here's the difference:
* Evolution: A species adapting to its environment over time due to changes in gene frequencies across the population.
* Mutation: A change in the DNA sequence within a single organism.
Think of it this way:
* Evolution is like a river slowly changing its course. It takes many small changes over a long period to see the big difference.
* A mutation is like a single pebble being dropped in the river. It might cause a small ripple, but it won't change the course of the river on its own.
Exceptions to the rule:
There are a few instances where mutations *within* a lifetime can be significant for evolution. For example:
* Rapidly changing environments: If a sudden environmental change happens (like a new disease), a mutation that makes an individual resistant could be crucial for the survival of that individual and its offspring, driving evolution faster.
* Organisms with short lifespans: In bacteria, for instance, mutations happen very quickly, and the effects of these mutations can be seen within a few generations. This means mutations can be a significant driver of evolution in these organisms.
In summary:
While mutations are the source of new genetic variations, they alone do not constitute evolution. Evolution requires these mutations to spread throughout a population over generations.
