Overview of Phylum or Phyla: 11 Important phylum’s of Animal Kingdom

The animal kingdom will treat only the 11 most important Phylum or Phyla out of the 20 or more which compose it. These 11 Phylums include about 98 per cent of all species of animals. The estimates of numbers of living species are from authorities, but new forms are being named all the time.

11 Important phylum’s of Animal Kingdom

1. Phylum Protozoa:

 These animals (30,000 species) are mostly microscopic in size, and each consists of a single cell or of simple colonies of cells. They live in fresh water, in the sea, in the soil, and in other moist places, and as parasites on or within the bodies of other animals. Some of them, such as the malarial organisms and the dysentery amoeba, are important in our study because they produce disease in man.

2. Phylum Porifera:

The sponges or pore bearers (5000 species) live only in water-most of them in salt water. The body wall is perforated with many pores and is usually supported by a skeleton of spicules of calcium carbonate, silica, or spongin. The commercial bath sponge consists of spongin.

3. Phylum Coelenterata:

Most of the coelenterates (10,000 species) also live in salt water. They are the hydro ids, polyps, jellyfishes, sea anemones, and corals. A common fresh-water type is the hydra. Coelenterates are radially symmetrical, possess single gasfrovascular cavities, and are provided with peculiar stinging capsules called nematocysts.

4. Phylum Ctenophora:

The ctenophores (100 spedes) are mostly free-swimming marine animals that resemble the coelenterate jellyfishes and are commonly called sea walnuts or comb jellies. They are biradially symmetrical.

5. Phylum Platyhelminthes:

These are wormlike, unsegmented, bilaterally symmetrical animals (10,000 species) known as flatworms. Certain tapeworms and flukes are serious parasites of man and lower animals. Other flatworms live on land, in the sea, and a few live in fresh water, including planaria, the type usually studied in general zoology.

 6. Phylum Nemathelminthes:

Nematodes The threadworms or roundworms (12,- 000 species) are likewise unsegmented and bilaterally symmetrical. They possess both a mouth and an anus. Many of them are free living, that is, they live in salt water, fresh water, or in the soil; but others are parasites in plants and animals, such as the hookworm, roundworm, and trichinella of man.

7. Phylum Annelida:

The body of an annelid consists of a row of little rings or segments; hence the members of this phylum (13,500 species) are known as segmented worms. The earthworm and leech are common representatives. Salt water, fresh water, and the soil serve as habitats.

8. Phylum Arthropoda:

The joint-footed animals belong to this phylum (875,000 species); they are about three times as numerous in species as all other animals. The principal groups of arthropods are the crustaceans, including the lobsters, crayfishes, crabs, and barnacles; the centipedes and millipedes with their many pairs of legs; the insects, such as butterflies, bees, beetles, bugs; and the arachnoids, represented by spiders, scorpions, mites, and ticks.

9. Phylum Mollusca:

Snails, slugs, clams, and oysters are common mollusks, others are known as squitis, nautili, cuttlefish, and octopi, the phylum includes at least 90,000 species. An organ characteristic of most of them is a muscular foot that usually serves as an organ of locomotion. An enclosing envelope, the mantle, is also present. The soft body of many mollusks, such as the oyster and snail, is protected by a shell of calcium carbonate which is secreted by the mantle.

10. Phylum Echinodermata:

A characteristic of most members of this group (5000 species) is a spiny skin. It includes the starfishes, brittle stars, sea urchins, sea cucumbers, and sea lilies. All are marine in habit and radially symmetrical; a skeleton of calcium carbonate is often present. Locomotion is usually accomplished by means of tube feet.

11. Phylum Chordata

Except for a few primitive species, the chordates (65,700 species) are vertebrates; that is, their axial support is made up of small bones or vertebrae and is known as the vertebral column, or backbone. Vertebrates are the most highly developed of all animals. They may be divided into 7 classes as follows:

 (1) the cyclostomes or lamprey eels and hagfishes,

(2) the cartilaginous fishes, or sharks and rays,

(3) the common bony fishes,

(4) the amphibians or frogs, toads, and salamanders,

(5) the reptiles or alligators, lizards, snakes, and turtles,

(6) the birds, and

(7) the mammals or four-footed animals.

The birds and mammals differ from the others in that they are warm-blooded; that is, their body temperature is constant and about 100° F, regardless of the temperature of the surrounding medium; whereas reptiles, amphibians, fish, and other animals are called “cold-blooded” because their body temperature varies with that of their environment. Actual1y, cold-blooded is a poor name to apply to these animals, for in summer the blood of a grasshopper may be warmer than that of a man. These so-called cold-blooded forms are really animals without a temperature-controlling mechanism. The headpiece at the beginning of this chapter helps us to realize how varied animal life is, but only a study which we are going to make of each of the 11 phyla just described can furnish a true idea of the remarkable diversities exhibited by the hundreds of thousands of different kinds of animals.