Ok about reproduction?

Question

why cant a cat get a dog pregnant? why cant a dog get a cat pregnant?

Answer 1

Well they are totally different species. In addition, the number of chromosome that a cat has is different from what a dog would have. Even though a sperm might penetrate an egg, if they are not genetically compatible the end result is automatic death of the cell.  

Answer 2

In order for anything to get anything else pregnant, they have to be able to donate exactly half of their genetic material.  That genetic material is carried on Chromosomes (composed of DNA).  

When an organism produces gametes (s*x-cells) they are essentially making cells with half of their chromosomes that would be in regular cells.  Each partner has to donate their part.  If the two parts do not match, they cannot come together to create the offspring.

Different species have different numbers and different types of chromosomes.  This is why only a cat can get another cat pregnant!

Answer 3

Chromosomes don't match.

Answer 4

Well I can't give you a well-enough answer but can you imagine all the breeds of humans... Labrador humans, terrier humans, rottweiler humans, and then cat-humans, and fish-humans, and cat-dogs, and bear-birds. Well, you get the picture.