Organ music: cells self-organise into organs

Biology involves many different scales. At each scale, one considers what are the essential components and how they interact with one another. 

All living beings are composed of organs which in turn are composed of biological cells. The functionality of an organ emerges from the interaction between cells. 

Part 3 of The Economist's excellent series on biology is How organisms are organised. Here are a few highlights.

The twin processes of differentiation (many different types of cell) and integration (a highly functional structure) [are] at the heart of what makes organs tick.

How are the structures of plants and animals different? Why?

... animals and plants have different relationships with time and space. These different ways of life require different sorts of flexibility. Animals move through space but, once adult, change shape comparatively little over time. Plants stay still in space but change shape a lot as they grow. 

Most animals seek the energy they need by hunting or foraging. Plants’ energy-seeking behaviour is a matter of growing roots to take in water and minerals, and flat, green surfaces to absorb the sunshine and carbon dioxide that make up the preponderance of their food.

Muscles, nerves, and bones need to grow to a pre-arranged design much more than branches, twigs, and leaves do.

A human has about 80 distinct organs. The brain is the most complicated organ. It has about 86 billion nerve cells (neurons). There are 133 types of these in the cortex of the brain. 

Neurons are the essential components. Then one needs to consider how these components interact with one another.

A single neuron may be connected to as many as 10,000 other neurons. There are more than one hundred different types of chemical neurotransmitters with which to send and/or receive messages at the points of connection between.

The figure below shows how neurons are connected to one another via axons. Electric signals travel along the axon by action potentials.

The brain is a highly complex system. There are a large number of components, of many different types, and the large connectivity between them, and a large number of ways they can interact with one another. Given this complexity is it really that surprising that brains can "think" and process complex information. Parenthetically, I think this is another simple reason why I think proposals of quantum consciousness are so fanciful. Before, invoking such speculative ideas I think proponents should first rule out a simpler hypothesis: 

Consciousness (defined in some simple computational sense, putting aside profound philosophical nuance) can emerge from purely classical processes in such a complex system.

Hopfield showed how associative memory could emerge from a model that is much simpler than an actual brain. To me, this gives confidence that it is reasonable to work with the classical hypothesis.