What is missing from this food chain

What are two ways that harvesting algae from the ocean may benefit human society? how might the harvest of algae negatively impact the ocean communities where that algae grows? how could this be prevented?

Cpr, or cardiopulmonary resuscitation, is a first-aid technique to save lives. it involves compressions of the patient's chest cavity. which description is the best description of the functions of chest compressions in cpr? chest compressions are done to pump the heart. chest compressions are done to strengthen the rib bones. chest compressions increase carbon dioxide inhalation. chest compressions allow the patient's muscles to wake up.

In general, characteristics that an organism survive and reproduce become more common in a population over time. what mechanism of evolution cause this change?