Countercurrent exchange is evident in the flow of countercurrent exchange is evident in the flow of blood in the dorsal vessel of an insect and that of air within its tracheae water across the gills of a fish and the blood within those gills air within the primary bronchi of a human and the blood within the pulmonary veins water across the skin of a frog and the blood flow within the ventricle of its heart

transformative rocks are the stones that emerge from the transformation of existing rock composes in a procedure called changeability, implies changing of structures. transformative rocks are shaped from alternate shakes that are changing a result of warmth or weight connected. one of this model is the earth developments that making rocks profoundly cover or crushed which will make the stones warmed and put under awesome weight. they are not softening but rather the minerals they are containing are changed synthetically that will shape transformative rocks. now and again different rocks are shaped when the others are near some liquid magma and getting warmed.

condenser is used to focus in the light microscope.