The head is the part of most animals, located at one end of the body, that contains the highest density of neurons and often other sense organs. In humans, the head contains the brainwhich is enclosed in a protective skull, and the eyesears, ears, nose and mouth.
The following picture shows the llama’s head. The eyes, ears, nose and mouth are clear. The brain is inside the skull, which is located between the ears of the llama.
The head is believed to have evolved through a process called “cephalisation”. This term derives from “kephalo” for “head”. The clustering of nerves together is thought to allow for faster and more complex information processing.
This gives organisms an advantage by allowing them to respond more quickly and intelligently to their environments. As a result, over time, neurons tend to cluster together near one end of a organism.
Having sense organs close to the animal’s nerve centre also improves reaction time by allowing impulses from these sense organs to reach the brain almost instantaneously after perception.
Vertebrates such as humans, the invertebrates such as insects and the complex members of the group of animals known as ” chordates invertebrates ” which have no spinal cord or exoskeletons, tend to have heads where a large cluster of neurons is bordered by sense organs.
Head function
The head normally serves as the animal’s information processing centre. Information from the sense organs and the body is transmitted to the brain, which is the nerve centre found in the heads of complex life forms.
Even very simple organisms often have a point where their nerves are concentrated, along with any cells they may have, such as photoreceptors.
The brain can process information about the environment to make decisions, store memories and skills, and make changes to the animal’s behaviour and emotional states.
The head also often contains the primary organs for vision, hearing, hearing, and speech. earsmell, taste and, in some organisms, antennae.
Examples of heads
Humans
The human head contains the brain, eyes, ears, nose and mouth. The front part of the head, which is hairless and contains the eyes, nose and mouth, is known as the face.
The human brain is tuned to recognise small differences in the bone structure of the human head, which allows humans to recognise other individuals based on their facial features.
Bees
Like humans, a bee’s head contains two eyes and a mouth that is used for tasting and ingesting food. However, the bee also has antennae, which are sensory organs that humans do not possess.
The antennae are very sensitive to vibrations and also to pheromones, which are chemical signals emitted by other insects.
This is an example showing that even when organisms do not have the same sensory organs, they tend to cluster their sensory organs close to the brain for efficient processing.
Hydras
Hydras are very simple aquatic organisms that have no skeletons or exoskeletons. Hydras are believed to be a species a very ancient species, which first appeared long before the evolution of the body structure observed in most animals.
But even hydras have something that could be called a head; at one end of their bodies, a cluster of light-sensitive nerves and cells serve as primitive “eyes” and an information-processing centre.