In a population of bacteria reproducing asexually, adaptive traits like heat resistance can emerge through mutations and natural selection, even without direct sexual reproduction. Here’s how the process works:

1. Mutation: When bacteria reproduce, random mutations occasionally occur in their DNA. Some mutations may provide beneficial traits, such as heat resistance. While rare, if a mutation for heat resistance arises, it can offer an advantage in hot environments.

2. Selection: If the bacteria are exposed to heat over generations, those with the heat-resistant mutation will have a survival advantage, allowing them to thrive while others perish.

3. Proliferation of Advantageous Traits: Since bacteria reproduce quickly and can create numerous generations in a short time, beneficial mutations (like heat resistance) spread rapidly through the population. By the seventh generation, many bacteria may carry the heat-resistant trait.

In this way, through mutation and selection, an initially absent trait like heat resistance can become common in later generations.