The shoreline is one of the harshest and most changeable environments for living creatures. The changing tides shift the environment dramatically within a sub-daily cycle. Here, we can consider two typical shoreline organisms, and the changing environment they must endure. Within the rocky shore environment, an octopus would be within the shallow but open sea environment during high tide, and water temperature and salinity conditions would be fairly constant. During low tide, the octopus might become trapped in a rock pool. This environment is dramatically different. The water temperature and salinity might increase drastically with exposure to solar radiation. The octopus is also more vulnerable to predation by humans and other land animals. Within the sandy shore environment, sand clams would be actively positioned at the interface of the sand and water, and will be actively filtering sea water for detritus. During low tide, the sand would be exposed to the air, and the clams would burrow down into the sand so as to avoid dessication.
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The answer is Respiration
I cannot found the images of the microscopy anywhere. But I can explain how you can differentiate a procaryote from a eucaryote under a microscope.
The first difference between them is the size of the cell. eucaryotes are generally much bigger than procaryotes. Procaryotes are visible only at x100 objective, but eucaryotes are visible starting from the x10 zoom.
The second difference is the presence of a nucleus in eukaryotes and the absence of it in procaryotes.
The third difference is the presence of organelles in eukaryotes and the presence of a cell wall in procaryotes (only visible at electronic microscopy).