This post was deleted so I can't find who wrote it wrote: ↑January 4th, 2021, 3:05 pm
Evolution = Δ gene frequency / Δ generation. Slow reproducing organisms have faster evolution because they are exposed to more selection, mutation, and drift before producing the next generation.
Example:
Let's say that there is a purple allele in a population of asexual bacteria. All purple bacteria have a 60% chance of dying every day and non purple have a 30% chance of dying every day. We have two populations; one population splits every day, and the other splits every other day, doubling in number.
We'll start with a population of 100 purple (P) and 100 non-purple (p). The allele frequency is 50% purple.
Daily splitting population:
Generation 1: We start with 100 P and 100 p. At the end of day 1, we have 40 P and 70 p
Generation 2: doubles to 80 P and 140 p. Allele freq = 36% purple. At the end of day 2, we have 32 P and 98 p
Generation 3: doubles to 64 P and 196 p. Allele freq = 25% purple. At the end of day 3, we have 26 P and 137 p
Generation 4: doubles to 51 P and 274 p. Allele freq = 16% purple. At the end of day 4, we have 20 P and 192 p
Generation 5: doubles to 41 P and 384 p. Allele freq = 10% purple.
As you can see, the change in allele frequency from each generation to the next is 14%, 12%, 9%, and 6%.
Every-other day splitting population:
Generation 1: We start with 100 P and 100 p. At the end of day 1, we have 40 P and 70 p At the end of day 2, we have 16 P and 49 p
Generation 2: doubles to 32 P and 98 p. Allele freq = 25% purple. At the end of day 3, we have 13 P and 69 p At the end of day 4, we have 5 P and 48 p
Generation 3: doubles to 10 P and 96 p. Allele freq = 10% purple.
As you can see, the change from each generation to the next is 25% and 15%.
Notice that the actual allele frequency between each population is the same at the end of 4 days. However, evolution is actually happening faster in the population which reproduces every other day, because it has the same amount of change in 2 generations, rather than 4. In fact, it's evolving twice as fast! This is because this is an example of a selective pressure which occurs at a constant rate with respect to time, as opposed to one which occurs at a constant rate with respect to each generation. If the selection event only happened a set number of times per generation, rather than per day, then the faster reproducing population would evolve at the same rate (per generation) as the slower reproducing population, yet the faster one would evolve more in a shorter timespan because it would go through twice as many generations. There are many examples of this type of selection, for example, if birds have a 50% chance of hatching, then it doesn't matter how many years they live before breeding, they still had a 50% chance of dying before hatching. Or, if two populations of mice breed at 11 and 15 months, respectively, but both experience decreased immune function during their 3rd month of life. Another would be bacteria that survive 100%, but purple ones only successfully split 60% of the time. Those are just some examples to give you an idea.