Answering Frequent Questions on Animal Biology

In life, all animals have lived with and for some time will live without an animal body of their own. The term animal can be used in several different contexts, including in physiology and biochemistry. The word animal refers to any living thing capable of moving about on its own, consuming food, secreting waste products, reproducing, breathing air, and so on. In modern usage, animal refers only to those living things that have a nervous system capable of moving about on their own. Many animals have nervous systems, but birds, fish, amphibians, mollusks, invertebrates, and even humans are not technically considered to be animals because they lack a centralized nervous system.


All vertebrates are members of the class Arachnida, the most common vertebrate animal being the human. Humans, however, are not the only species of animal with a central nervous system. The class Cymatidae, also consisting of humans and all other cephalopods (squids, lobsters, shrimp, and crabs) have a series of nerve tissues called the nerves. The afferent nerves come from the eyes, ears, spine, and nervous system, while the sensory nerves go from the skin, teeth, and claws of animals. All other nerves are referred to as afferent nerves, while nerves in the other areas of the body are referred to as secreters.

Virtually all animals make use of at least one set of organs for the purpose of obtaining nourishment, while all other animals use several sets of organs for the same purpose. Insects, for example, need to feed on certain parts of the plant leaves, stems, roots, leaves, and other parts of the foliage, whereas mammals need to eat meat, bones, fur, feathers, and so on. Birds and mammals have even more sets of organs involved in obtaining nourishment.

Each animal has only one type of cell in its body, which is called a single cell. The animal kingdom consists of animals that have cells of various types – protoplasmic cells (cell-like tissue) and metazo cells (non-cellular). The metazo cells reproduce by means of a gene called a mitochondria. Cells of the animal kingdom can be further classified into protoplasmic, endosympathetic, and lymphoid. Metazoa are not part of the animal kingdom and make up a part of theacteria, fungi, and plants kingdom.

All living creatures belong to the animal kingdom except the unicellular algae, bacteria, protozoa, molds, yeasts, and some unicellular plants. All animals have the ability to move, though they are mostly capable of swimming. Most animals have a heart, lungs, intestine, urinary bladder, skin, muscles, digestive tract, and nervous system. Although most animals cannot swim, some can glide through water by means of their gills, while some others swim using their nerves.

A number of the animals have certain characteristics in common with all the other multicellular organisms. They possess vascular system, nervous system, respiratory system, excretory system, blood, digestive system, genitalia, nervous system, somatic organs, immunity system, reproduction system, photosynthetic apparatus, and internal organ systems. Since the animal kingdom consists of numerous different kinds of living creatures, it is quite difficult to classify each and every kind of organism in the biological kingdom.

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