Invertebrates

CHAPTER ONE

1.0              INTRODUCTION

Invertebrates are animals without a vertebral column. This has led to the conclusion that invertebrate are a group that deviates from the norm, invertebrate. This has been said to be due to the fact that researchers in the past, such as lamark’s theory of evolution, he evolution, he believed that characteristics acquired through the evolutionary process involved  not only survival, but also progression toward a “higher form”, to which humans and vertebrates were closer than invertebrate were in any event in the 2000 (Barnes etal; 2001) edition of invertebrate zoology, it is noted that “division of the animal kingdom in to vertebrates and invertebrates is artificial and reflects human bias in favor of mains own relatives. The book also point out that the group lumps a vast a vast number of species together, so that no one characteristics describe all invertebrates. In addition, some species included are only remotely related to one another, with some more related to vertebrates than other  invertebrate (Barns and Robert, 1968) for many centuries, invertebrates , invertebrates have been neglected by biologist, in favor of big vertebrates and “useful” or charismatic species (Ducarme, 2015) During the 20^th century, many discoveries made invertebrate zoology, one of the major fields of natural sciences with prominent discoveries of medicine, genetics, ecology. (Ducarme 2015).

Invertebrates are also used by scientists in the field of aquatic biomonitoring to evaluate the effect of water pollution and climate change. (Lawrence et al 2010). The trait that is common to all invertebrates is the absence of a vertebral column. This creates a distinction between invertebrates and vertebrates. The distinction is one of convenience only. It is not base on any clear biologically homologous trait any more than the common trait of having wings functionally unites insects, bats, and birds, or than not having wings unit’s tortoises, snails and sponges.  Being animals invertebrate are heterotrophs and require of sustenance in the form of the consumption of other organisms with a few exception, such as porifera, invertebrate generallyhave body composed of differentiated tissues. There is also typically a digestive chamber with one or two opening to the exterior. Most invertebrates reproduce at least partly through sexual reproduction. They produce specialized reproductive cells that undergo meiosis to produce smaller motile spermatozoa or large, non-motile ova (Schwartz et al; 2010) which fuse to form zygotes, which develop in to new individual reproduction or sometimes both methods of reproduction.

1.1       CLASSIFICATION OF INVERTEBRATE

Invertebrate can be classified in to several main categories, some of which are taxonomically obsolescent or debatable, but still used as terms of convenience. Each however appears in its own article at the following links protozoa (like the worms, an arbitrary grouping of convenience link to their article for details). The word “invertebrate” comes from the form of the latin word vertebra. Vertebra means a joint in general and sometimes specifically a joint from the spinal column of a vertebrate. In turn the jointed aspect of vertebra divided from the concept of turning, expressed in the root verto or vorto to turn. (Turker, 1931). The term invertebrates is not always precise among non-biologiests since it close not always describe a taxon in the same way that Arthropoda, Vertebrate or Manidae do. Each of these terms descrbes a valid taxon phylum, subphylum or family. “Invertebra” is a term of convenience not a taxon, it has very little circumscriptional significance except within the chordata. The vertebrate as a subphylum comprises such a small proportion of the metazoan that to speak of the kingdom animalia in terms of “vertebrata” and invertebrate” has limited practicality. In the more formal taxonomy of animalia other altributes that logically should precede the presence of a notochord. However, even the notocord would be a less fundamental criterion than aspects of embryological development and symmetry (pecheniket el; 1996) or perhaps bauphanbrusa (Brusa et al; 1990) of the million more animal species in the word more than 98% are invertebrates.

Invertebrate don’t have a skeleton of bone, either internal or external. They include hugely varied body plans. Many have fluid filled, hydrostatic skeleton, like jelly fish or worms. Others have hard exo-skeletons, outer shell like those of insect and crustaceans. The most familiar invertebrats include the protozoa, porifera, coelenterate, protyhelminthes, nematode, Annelida, Echinodermata, mollusca and Arthropoda.

Arthropoda include insect, crustaceaus and arachnids.

–          Sponges (Porifera)

–          Stinging jelly fish (Cnidaria)

–          Comb jellies (Ctenophora)

–          Flatworm (Platy helminthes)

–          Round or thread worms (Nematoda)

–          Segmented worms (Annelida)

–          Insect, spiders, crabs and their kin (Arthropoda)

–          Cuttle fish, snails, mussels and their kin (Mollusca)

–          Starfish, sea-cucumbers and their kin  (Echinodermata)

     1.2         AIM AND OBJECTIVES

–          To collect and preserve some invertebrate for further study.

–          To examine the morphological feature of the organisms.