The scientist who first observed the 'cell' under a microscope was: MCQ with Answer and Explanation

Explanation:
Robert Hooke, an English scientist, is credited with the discovery of cells in 1665. He observed a thin slice of dead cork tissue from an oak tree under a primitive compound microscope. He saw a honeycomb-like structure of small compartments, which he called 'cells' (from the Latin 'cella', meaning small room). He was actually observing the non-living cell walls of dead plant cells.

Explanation:
Photoperiodism is the response of plants to the relative lengths of day and night, influencing flowering. Short-day plants (e.g., poinsettia) flower when day length is less than a critical period; long-day plants (e.g., spinach) flower when days are longer. Phototropism is growth towards light, geotropism to gravity, chemotropism to chemicals.

Explanation:
Erythropoietin (EPO) is a glycoprotein hormone that is the primary regulator of red blood cell production (erythropoiesis). It is primarily produced and secreted by the interstitial fibroblasts in the kidneys (specifically in the peritubular capillary bed) in response to cellular hypoxia (low oxygen levels). A small amount is also produced by the liver. EPO travels to the bone marrow, where it stimulates the proliferation and differentiation of erythroid progenitor cells into mature red blood cells.