What do you have to do over and over again for even heat distribution of the PCR tube?

When we are talking about a traditional PCR tube moder day expirements would use a thermal cycler for even distrobution . Placing your tubes in a water bath or heat block moving your tubes from one temperature to another for thermal distrubution/ regulation. So basically moving and ajusting the temp.

where is the diagram?

if you insert the diagram ill be able to you

not necessarily. higher fitness requires the organism to be reproductive successful. for example, an organism at age 10 with 15 offspring is much more fit than an organism at age 15 with only 5 offspring.