[thedoc (OP)]

Kevin McElroy asked the Naked Scientists:
   Regardless of type, brain coral, staghorn coral, etc seem always to maintain their characteristic shape. In the absence of an overall designer, what's happening at level of, I presume, the individual animalcule, that prevents the development of bizarre and random formations?
 Not sure about ph# below. .
What do you think?
Edit: chorals -> corals

[RD]

The surface of brain-coral looks like a reaction-diffusion pattern ...




https://en.wikipedia.org/wiki/Pattern_formation#Computer_graphics

... The science of pattern formation deals with the visible, (statistically) orderly outcomes of self-organization and the common principles behind similar patterns in nature.
     In developmental biology, pattern formation refers to the generation of complex organizations of cell fates in space and time. Pattern formation is controlled by genes ...

https://en.wikipedia.org/wiki/Pattern_formation

[JimBob]

Chris, chorals are formed by people interested in corale music. Corals order themselves because they are made so they can, They are made by the crystals of the chemical, calcium carbonate.  They would be amorphous if not for the underlying crystals.

[alancalverd]

Basses are usually taller than sopranos, who are prettier and generally take the melody line.

[evan_au]

what's happening at level of, I presume, the individual animalcule, that prevents the development of bizarre and random formations?

The individual "animalcule"s that make up a coral all have basically the same DNA code. So if they find themselves in a similar environment, they will act in a similar way.

The environment is determined by:
- external factors such as the depth, temperature & pH of the water, the brightness of sunlight, food supply in the water, the strength of waves and types of predators
- and internal factors like the position of their neighbors, and by signaling molecules that pass between neighbors.

Given a similar environment (both internal & external), the same type of coral will form a similar set of shapes.

...and the different creatures of the reef ecosystem will make beautiful music together.

[JimBob]

"They would be amorphous if not for the underlying crystals."

As well as what I said.