Small openings of glands onto the surface of the skin.

Tiny darker spots under 2500 km in size, often having fairly short lifetimes. Pores occasionally form where several granulation channels meet and can sometimes precede the development of sunspots.

The thousands of minute openings in the shell of the egg through which gases are exchanged.

small tubular cavities in wall plates of barnacles, the ends of which may be viewed from below.

1. the spaces in soil, rock and sediment that are filled by air or water. 2. Any small opening in the outer covering of an organism.

Spaces between the mineral grains of a soil. The size, shape and arrangement of soil pores determines the rates of water and air movement into and through the soil. They also control the amount of available water that a soil can store for plant use.

The part of the bulk volume of soil not occupied by soil particles.

The fraction of the soil volume not occupied by solid particles.