<span>A tiger looks so much different as an adult than it did as a single fertilized egg because it developed through different stages from being a zygote (fertilized egg), to becoming an embryo (where it experiences intense cellular changes), to becoming a fetus (where it gains a great measure of cell specialization, and develops distinct tissues and organ systems). After birth, the tiger still undergoes further growth and development into adulthood. This is largely regulated by the expression of different genes at different times and also by environmental factors.</span>
This can happen because you have recessive and dominant characteristics passed down. So you can get a totally different chromosome that doesn't come from your parents because your grandparents may have had it or great grand parents, the line keeps going .
