Driving along a highway, you start noticing a few columbine…

Driving along a highway, you start noticing a few columbine plants with intense blue flowers. Several miles later, these flowers are super abundant. Then further along, the columbine flowers become less abundant and eventually disappear. The regions with just a few of these plants probably represented the columbine’s ___.

Your professor shows you a sealed glass sphere that contains…

Your professor shows you a sealed glass sphere that contains seawater, algae, brine shrimp, and bacteria and tells you that this small ecosystem is precisely designed to be able to live and function for up to 8 years. Being curious, you wonder what would happen if you changed the design and you start to tinker with it.  Which of the following is the only change that you found that did NOT kill the “ecosphere”?