Other than helping in muscle contraction, calcium ions are very important in various ways like;
Calcium ions are the key players in many biochemical and physiological processes in the cells.
They take part in the signal transduction pathways as second messengers to trigger neurotransmitter release from neurons. This activates various cellular activities like excitability, motility, exocytosis, transcription, and apoptosis.
Calcium ions take part in electrical signals and control the heart functions. It is also necessary to pump blood from the heart.
Calcium ions function as a co-factor and facilitate blood clotting
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It's likely an illustration of competition. Bob the plant and bacteria must fight for the same resources, and neither population can take full advantage of the resources available.