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Apply market research to generate audience insights. Measure content performance. Develop and improve products. List of Partners vendors. Share Flipboard Email. Anne Marie Helmenstine, Ph. Chemistry Expert.
Helmenstine holds a Ph. She has taught science courses at the high school, college, and graduate levels. Facebook Facebook Twitter Twitter. Updated January 29, Animal phyla are also traditionally defined by the fact that all members of the phylum share a number of distinct morphological features, which are known as the body plan of that phylum.
Thus, by studying the defining features of various animal phyla, you are also studying the fundamental features that define animal diversity. The fundamental features that define animal phyla are based on early events in animal development, such as gastrulation. These early events change rarely in evolution, and in many cases set the stage for later developmental events. Features that appear later in development, such as feathers or hair in vertebrates, are more likely to be defining features of clades within a phylum.
Animals come in an immense range of different styles, and animal diversity can't be described in a few short paragraphs.
The majority of introductory textbooks classify these animals as acephalic or lacking cephalization. While none of these creatures has a brain or central nervous system, their neural tissue is organised in such a way that they can experience rapid muscular excitation and sensory processing.
Nerve nets have been discovered in these creatures by modern invertebrate zoologists. Cephalization progressed in arthropods with increasing incorporation of trunk segments into the head region.
This was beneficial because it allowed for the evolution of more efficient mouth-parts for capturing and processing food. Insect brains are strongly cephalized, with three fused ganglia attached to the ventral nerve cord, which has a pair of ganglia in each segment of the thorax and abdomen.
The insect head is a complex structure composed of several segments that are rigidly fused together and equipped with both simple and compound eyes, as well as multiple appendages such as sensory antennae and complex mouthparts maxillae and mandibles. Planarians are free-living flatworms that are completely harmless. They live in water freshwater or saltwater or on moist soil.
Tapeworms and flukes are both internal parasites that live in the tissues, cavities in body organs, or blood vessels of their hosts. Animals in the Phylum Platyhelminthes have bilateral symmetry, as opposed to those in the Phylum Cnidaria, which have radial symmetry. This implies that there is only one plane of symmetry one way you can slice the animal in half and produce two pieces that are mirror images of one another.
It also means that you can tell the difference between the animal's anterior and posterior, right and left, and dorsal and ventral halves. A bilaterally symmetrical animal moves forward with its anterior and crawls on its ventral surface with its dorsal surface upward. Members of the Phylum Platyhelminthes particularly planarians, Class Turbellaria have brain and sense organs in front of the animal. List of Characteristics of Mammals. Basic Characteristics of Cnidaria. General Characteristics of Protista.
Levels of Cell Organization. The Anatomy of the Hydra. What Animals Live in Aquatic Habitats? Four Major Types of Chromosomes. Crabs That Are Related to Spiders.
Five Classes of Chordates.
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