The first line of defence (or outside defence system) includes physical and chemical barriers that are always ready and prepared to defend the body from infection. These include your skin, tears, mucus, cilia, stomach acid, urine flow, 'friendly' bacteria and white blood cells called neutrophils.
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Meristem cells are totipotent meaning they can differentiate to any type of plant cells. Therefore they can produce a variety of plant type depending on epigenetic. However, tissue culture is derived from already differentiated cells. Therefore these cells are already determined and can only produce cell type of that plant from which they were derived.
Advantages of using solar energy are pollution-free, noise-free, on installation it produces free energy, clean and renewable. Disadvantages include high cost, energy dependent on sunlight exposure, power stations are expensive to build and devices powered by solar energy cannot be used at night
