The element calcium has the atomic number of 20 and the mass number of 40, how many neutrons dose it have

The mass number is the sum of the number of protons and number of neutrons the atom has.

So, we can write the equation as:

x + 20 = 40

x = 20 neutrons.

Hey :)

Polyploidy is less common in animals, but some fish, reptiles, and one mammal, the red vizcacha rat, are polyploidy. Polyploidy changes the genome of the new organism so much that it might no longer be able to mate with the original species, resulting in speciation, or the creation of two species from one

Hope this helps! :)