Answer: A the chromosomes from another parent cell were introduced
Explanation: A child is created when the male sex cell joins the female cell. If the male and female sex cells had the standard number of chromosomes, as is found in body cells then the zygote (baby) would have double that number of chromosomes. The number of chromosomes would keep doubling every generation. To avoid this doubling the parent's body cells split by miosis which halves the number of chromosomes and so when the sex cells join the total number of chromosomes is the same as that found in the parent's body cells.
Well there are many catastrophic scenarios that we already overcome. You should consider educating yourself about the great filter. A great filter is a hypothetical barrier that each civilization can or cannot overcome. From here on things get a little complex so I won't bore you with them. But there are experts in this theory called great filter and I'm sure they can tell you a lot about.
A pedigree or a pedigree chart is used to track which organisms are carriers of a specific trait through several generations.
C.
The correct terms to fill in the blanks are gastric cavity and extracellular. In cnidarians, the mouth of both the medusa and polyp form opens into an internal gastric cavity where extracellular digestion takes place. The polyp and medusa are body forms that can be found in the phylum Cnidaria. The polyp is a nonmotile body form while the medusa is a free swimming body form.
