The elodea cells...................................................................
These preparations are called Vaccines. <span>A </span>vaccine<span> is a biological preparation that
provides active acquired immunity to a particular disease. A </span>vaccine<span> typically contains an agent that
resembles a disease-causing micro-organism and is often made from weakened or
killed forms of the microbe, its toxins or one of its surface proteins</span>. I
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Answer:
Cardiac muscle tissue
Explanation:
Myocardium or heart muscle is a special type of muscle (differ than striated and smooth) and it is the main tissue of the walls of the heart.
Heart muscle consists of individual heart muscle cells (cardiomyocytes) which are joined together by intercalated discs. It also contains collagen fibres and other substances that form the extracellular matrix.
Heart muscle has a "special" mode of contraction: action potential triggers the release of calcium ions from the cell's internal store, the sarcoplasmic reticulum.
Oxygen.
Oxygen was fatal when organisms started using photosynthesis, this event was known as the Great Oxidation Event.
