What are the reactants of photosynthesis

During the process of meiosis, special cells called gametes are formed. gametes only have half the number of chromosomes that the other cells in the body have. what form of reproduction do organisms that produce gametes use?

Glucose is a form of sugar found in the blood cells use glucose as a source of energy, but too much or too little can cause serious health issues so, the body uses the hormone insulin to regulate glucose n the blood insulin maintain glucose levels in the blood if blood glucose lovels got very high, what would you expect to see happen to insulin levels?

Is there any species that went extinct in recent years due to natural causes (not caused by human interaction). if so, what caused it?