Animal Kingdom Essay

INTRODUCTION:
The Animal Kingdom is generally believed to have originated in Archeozoic oceans long before the first fossil record. Every major phylum of animals has at least some marine representatives; some groups, such as cnidarians and echinoderms, are largely or entirely marine lives. From the ancestral marine environment, different groups of animals have invaded fresh water; some have moved onto land. There are over a million described species of animals. About 5% of this number are consists of animal with backbones or simply known as vertebrates. The rest of the 95% consist the greater part of the Animal Kingdom, which are the invertebrates. Backbone is the single characteristic which separates the entire animal kingdom into two groups. However, the most successful animal among all the animal exist are the arthropods which consist of 85% of the animals. Invertebrates do not hold a single positive characteristic in common. Some invertebrates have common phylogenetic origins and others are only remotely related.

o GROUPS OF INVERTEBRATES AND THEIR CHARACTERISTICS

1. Domain: Eukaryota
Kingdom: Animalia
Phylum: Porifera
Phylum Porifera or sponges are primarily marine animals consisting of loosely organized cells. Characteristics of the phylum Porifera include: o Asymmetrical or superficially radially symmetrical o Three cell types: pinacocytes, mesenchyme cells, and choanocytes o Central cavity or a series of branching chambers, through which water circulates during filter feeding. o No tissue or organs.
One of the classes in this phylum is Class Hexactinellida. The general characteristic of this class are the spicules composed of silica and six rayed, spicules often fused into an intricate lattice, cup or vase shaped, sycon...

... middle of paper ...

...eviana.

5. Domain: Eukaryota
Kingdom: Animalia
Phylum: Nematoda

Phylum Nematoda are the roundworms which is one of the most abundant animals on earth. Characteristics of the phylum Nematoda include: o Triploblastic, bilateral, vermiform (resembling a worm in shape, long and slender), unsegmented, pseudocoelomate o Body round in cross section and covered by a layered elastic cuticle, molting usually accompanies growth in juveniles o Complete digestive tract, mouth usually surrounded by lips bearing sense organs o Most with unique excretory system comprised of one or two renette cells or a set of collecting tubules o Body wall has only longitudinal muscles
One of the classes in this phylum is Class Adenophorea. The general characteristic of this class are the phasmids are absent, most are free-living but some parasitic species occur. Example : Trichinella spiralis.