Here is the order:
Gene,
DNA,
Chromosome,
Nucleus,
Cell,
Organism.
[Hey if this is wrong, don't post a rude reply! Message me and I will try to correct the answer!]
The countercurrent heat exchanger that prevents arterial blood from overheating the testes is the pampiniform plexus of veins. The pampiniform plexus helps to regulate testicular temperature, allowing sperm maturation. It surrounds the testicular arteries and works as a countercurrent heat-exchanger system to cool the arterial blood before entering the testes. This is because the sperms can not develop if the testis is at body temperature.
sea creatures and fish may lose their homes because one, they live their, and two, animals they may eat live there, so if their food leaves, they will die out or they might leave.