Viruses can multiply very quickly, and so they can go through natural selection at a much quicker rate, allowing certain vaccine resistant mutations to take over a population.
In his experiment mendel first crossed tall and short peas plant and noticed that the F1 plants were all tall. in the second experiment he crossed the the F1 plants and noticed that short plants reappeared in the rate of 25% in F2 generation. in his third experiment he crossed he crossed F2 plants and noticed that when he crossed some tall plants with the shot plants the F3 generation contained short plant in frequency of 50%. after this observations mendel concluded that there were genes that could be only expressed in homozygous state but not in heterozygous state. these genes were later referred to as recessive alleles wheres the genes that prevented the expression of recessive genes were later referred to as dominant genes.
1. Testosterone
2. Penis
3. Testes
4. Semen
5. Scrotum
6. Vas Defrens
7. Seminal Vesicle
The most likely explanation for the variation is the offspring were produced from different combination of genes. A single pair of gold fish mentioned in the question means a male and a female gold fish. The two of them mated and contributed different genes to the fertilized fish eggs, this results in production of various body shape and colouration which is known as variation.
I may be wrong but i think that they are
1. turbines are added under the water and when the movement of water effects that is uses power to gather electricity
2. there are big barries in the water that spin the water around and then that in turn creates energy
