Why cephalization is important

Fully cephalized organisms have a head and brain, whereas less cephalized animals have one or more nervous tissue regions. Cephalization is associated with bilateral symmetry and forward head movement. Bilateria: Cephalization is a distinguishing feature of the Bilateria, a large group that includes the vast majority of animal phyla. These have the capacity to move using muscles and a body plan with a front end that encounters stimuli first as the animal begins to move and has evolved to contain many of the body's sense organs, able to detect light, chemicals, and sometimes sound.

A collection of nerve fibres capable of processing information from these sense organs is often present, forming a brain in some phyla and one or more ganglia in others. Acoela: The Acoela are a type of basal bilaterian that belongs to the Xenacoelomorpha. They are small and simple animals with slightly more nerve cells at the head end than anywhere else, resulting in the absence of a unique and compact brain.

This is a very early stage of cephalization. Flatworms: Platyhelminthes flatworms have a more complex nervous system than Acoela and are lightly cephalized, with an eyespot above the brain near the front end, for example. Cephalization provides three benefits to an organism-.

For starters, it promotes brain development. The brain serves as a command and control centre for organising and controlling sensory information. Animals can evolve complex neural systems and higher intelligence over time. The second benefit of cephalization is that sense organs can be concentrated in the front of the body.

This allows a forward-facing organism to scan its environment more efficiently, allowing it to find food and shelter while avoiding predators and other dangers. As the organism moves forward, the front end of the animal senses stimuli first. Third, cephalization moves the mouth closer to the sense organs and brain. As a result, an animal can quickly analyse food sources. Predators frequently use special sense organs near the oral cavity to gather information about prey when vision and hearing are insufficient.

Cats, for example, have vibrissae whiskers that detect prey in the dark and when it is too close to see. First, an species has to develop bilateral symmetry. Organisms with bilateral symmetry have a distinct right and left side. This contrasts with asymmetry and radial symmetry. In organisms with radial symmetry, you could take cross-sections of the organism across the center from multiple angles and get identical pieces.

One way to help visualize this is to remember that a hot dog in a bun has bilateral symmetry, while a hamburger has radial symmetry. Bilateral symmetry sets a species up for cephalization, since organisms with bilateral symmetry can now have a "front" end. Since the front of an organism is the first part to enter a new area, concentration feeding and sensory structures at the front gives it an adaptive advantage.

Cephalization is widespread across the animal kingdom. You can find many examples of this trend from different phyla, including both invertebrates and vertebrates. This includes examples in the arthropods, mollusks, annelids, and all vertebrates.

Many arthropods, including crustaceans, insects and arachnids have cephalization. Some mollusks have high degrees of cephalization like the cephalopod. Cephalopods includes squid, octopuses and related mollusks.

Additionally, the annelids, better known as segmented worms, have cephalization. This is a preview of subscription content, log in to check access. Boddy, A. Comparative analysis of encephalization in mammals reveals relaxed constraints on anthropoid primate and cetacean brain scaling. Journal of Evolutionary Biology, 25 , — Cozzi, B. The brain of the horse: Weight and cephalization quotients.

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