Sea urchins minimize the distance materials must be transported from a central point due to their radiating shape.
"If you let a drop of ink fall on a piece of paper, the splash pattern that results looks rather like a sea urchin. If you drop water into a bowl of liquid and photograph the moment of impact with high-speed equipment, the coronet shape formed at the surface resembles a sea anemone. Yet another of the basic shapes of life - the explosion, or radiating shape - repeats the forms taken by falling drops of water. Radiating shapes occur wherever numerous lines fan outwards from a single central point - whether in a flat plane, as with a starfish, or in three dimensions, as with a sea urchin. The plant kingdom is full of radiating shapes: the majority of flowers have this form, and many plants grow leaves that radiate directly from a stem base; but there are many examples in the animal kingdom as well. Radiating lines, as a construction design, have two useful attributes: they minimize the distance between the centre and the outlying points, and they provide great scope for increasing the surface area of an organism…The first of these qualities is most convenient in cases where materials must be transported rapidly from the centre to outer points or vice versa. There is a disadvantage, however. If there are a lot of outlying points, the lines tend to become overcrowded around the centre (diagram a). One way to overcome this problem is to develop branching patterns, to reduce the total length of travel and the congestion of lines at the centre (diagram b). If each artery and vein in the body led directly to the heart, for example, the heart would be swamped in a vast tangle of blood vessels. Instead, a few large central vessels divide and redivide into smaller branches. Physically, the resistance to flow or skeletal strength are reduced when the vessels coalesce or the skeletal rays are fused. Biologically, the smaller branching vessels help animals survive damage and aid their development and growth." (Foy and Oxford Scientific Films 1982:24)
Learn more about this functional adaptation.
- Foy, Sally; Oxford Scientific Films. 1982. The Grand Design: Form and Colour in Animals. Lingfield, Surrey, U.K.: BLA Publishing Limited for J.M.Dent & Sons Ltd, Aldine House, London. 238 p.