Systematic Zoology PDF

# Systematic Zoology ## Subkingdom Protozoa ### Phylum Protozoa The phylum includes more than 50,000 species which are found in almost all habitats, wherever moisture is present. #### General characters - The great majority are very small in size (unicellular animals) and can only be seen by th...

# Systematic Zoology ## Subkingdom Protozoa ### Phylum Protozoa The phylum includes more than 50,000 species which are found in almost all habitats, wherever moisture is present. #### General characters - The great majority are very small in size (unicellular animals) and can only be seen by the aid of the light microscope. Some of them are only 2 or 3 µm in length. - Many species live as solitary individuals, while a few live in colonies. - Some Protozoa live as free living inhabiting fresh, salt water and damp places, others are parasitic as endoparasites. - In the majority of cases, there is only one nucleus in the cytoplasm with distinct nucleoli often referred to as the endosomes. The cytoplasm is usually differentiated into outer clear ectoplasm and inner granular endoplasm. The cell is covered by a delicate plasma membrane or by a firm living pellicle. Some forms have non-living external envelopes of gelatinos, cellulose or calcareous substances. - They move either by temporary protrusions of their cytoplasm known as pseudopodia. (sing, pseudopodium) by long whip-like filaments known as flagella (sing, flagellum) or by short hair-like filaments known as cilia (sing, cilium) and some have no locomotory organelles. - Holozoic nutrition (animal-like) is the most common type of nutrition with in this phylum. In this type, the animal feeds actively on other organisms (bacteria, algae, smaller protozoa, etc.) or on decaying organic matter. Some protozoa having chlorophyll-bearing organelles. Exhibit a plant-like mode of nutrition known as holophytic nutrition. In this type, the organism synthesizes its own complex organic food material in the presence of carbon dioxide, water and presence of sunlight, as plants generally do. Some protozoa were thought to adopt saprozoic nutrition feeding by diffusion through their body surfaces on the simple organic and inorganic substances found in the surrounding medium. - Osmoregulatory organelles, in the form of contractile vacuoles are characteristic of the great majority of the protozoa which live in fresh water. - Aerobic respiration is the rule in many protozoa. Exchange of respiratory gases occurs by simple diffusion through the body surface. - Excretion of catabolic nitrogenous watses (mostly in the form of ammonia) takes place also by diffusion through the body surface. There are no specialized excretory organelles for excretion. - All protozoa can reproduce asexually, either by binary fission or by multiple fission. But, in addition, some protozoa can reproduce sexually by forming male and female gametes. - Encystment is a common feature of the life cycle of many protozoa where the animal secretes a resistant protective cyst around itself to enable it to survive unfavorable environmental condition; and for dispersal. ### Classification Phylum Protozoa is divided into four classes on the basis of the locomotory organelles found in the various species: #### Class Mastigophora Includes protozoa which characterized by: - They move by one or more flagella. - Many species live in fresh or marine waters, and some live as parasites. This class is of particular interest because its members combine the characters of plants and animals, and is therefore considered as the most primitive of the protozoan classes. It is divided into 2 classes - Sub-Class Phytomastigophorea: includes plant-like free living flagellates which have chromatophores, e.g. Euglena. - Sub- Class Zoomastigophorea: these are animal-like flagellates The great majority of this group live as parasites in larg animals, e.g. Trypanosoma, and Leishmania. Trypanosomes live as parasites in the blood and some tissues of many warm and cold blooded vertebrates (primary or final host). Several species are found in fishes, amphibians (e.g. frogs and toads), reptiles (e.g. snakes), birds and mammals, including man. But the life cycle usually involves another blood-sucking invertebrate host (secondary or intermediate host) which is frequently an insect (e.g. flies, fleas or bugs). In their natural and wild primary hosts, these parasitic flagellates usually produce very little harm, i.e. they are non-pathogenic. However, in man and some of his domesticated animals, they produce a dangerous disease which is frequently fatal. Trypanosomes produce in man a disease known as sleeping sickness which in many parts of Africa ranks as the first problem in economic and social progress. #### Common species of trypanosomes are: - Trypanosoma gambiense and Trypanosotna rhodesiense which infect man in some parts of Africa. - Trypanosoma lewisi which is cosmopolitan and infects rats. #### Class Sarcodina Which are characterized by: - They have bodies of a less organized shape than most protozoa. - They have pseudopodia for movement and trap of food. - Sarcodines include the genus Amoeba (Free living) and pathogenic species, e.g., Entamoeba histolytica which causes the amoeboid-dysentery. - They have marine forms which have (foraminiferans and radiolarians) have shell or skeleton. #### Entamoeba Entamoeba is similar to Amoeba in many of its characteristics, but lives as an endoparasite in the large intestine of certain mammalian hosts. Three species of Entamoeba infect man: E. histolytica, E. coli and E. gingivalis. Several other species occur in other mammals, e.g. E. muris which is a parasite of rats and mice. #### Class Sporozoa The Sporozoa are characterized by: - All parasites which have no distinct locomotory organelles and reproduce by spores. - Their life cycle is complex and usually involves asexual and sexual generations, and sometimes also two hosts (intermediate and final hosts). e.g Plasmodium sp. which is interacellular parasite in the blood and liver cells of the human (final) and the gut of the fly intermediate). #### Class Ciliophora This group includes: - Protozoa which have cilia as locomotory organelles. - There are two types of nuclei, a large nucleus known as the macronucleus and a small nucleus referred to as the micronucleus. - Nutrition is holozoic. - There are free-living as well as Paramecium and parasitic as Balantidium sp. ## Subkingdom Parazoa ### Phylum Porifera Sponges are sessile and mostly marine animals which show little or no detectable movement. They are regarded as the most primitive multicellular animals and are placed in a separate subkingdom called the Parazoa, including one phylum, the Porifera. ## Subkingdom Metazoa Multicellular animals, other than the Porifera, constitute the true Metazoa. This separation between multicellular groups is largely based on the differentiation or specialization of cells to perform different functions. Cell specialization has led to the development of tissues, each tissue being formed of structurally similar cells performing similar functions. In lower phyla, tissue formation is primitive, while in higher groups, the tissues are more developed and organized into organs and organs into systems. ### General characters of Metazoa - The Metazoa differ from the Protozoa in attaining much larger sizes. As they became larger, their food requirements increased and therefore a specialized digestive cavity and digestive system have developed in them for collecting and digesting food. Their food is usually of such a large size that it cannot be taken inside food vacuoles as in Protozoa. Also with increasing size, the distance between the digestive organs and many parts of the body became too great to allow for the travel of digested material and respiratory gases by simple diffusion. Thus, a special transport system, called the blood vascular systems, has been developed in most Metazoa for internal transport of nourishment and respiratory gases. - Some of the smallest Metazoa are aquatic and respire and excrete by simple diffusion. But the large majority of the Metazoa are of such a size that their surface area is proportionally small compared to their volume, and thereby insufficient for gas exchange and for the excretion of nitrogenous wastes. Therefore, various branching respiratory and excretory organs have developed in them. - The Metazoa have developed a nervous system made up of specialized nerve cells that synapse with each other. Besides coordinating between the performance of the different cells and tissues of the body, this system serves the conduction of nerve impulses from the receptor cells, found on the outer surface, to the effector cells found in the deeper tissues. - The Metazoa have developed various kinds of external and internal supporting structures to their bodies, or skeletal system, which enabled them to attain much larger sizes and to live in a wider variety of habitats. - The Metazoa have also developed certain reproductive organs or gonads specialized for the production of sexual gametes, which are never produced within the cells as in the Protozoa. - All Metazoa pass through similar steps during their early stages of embryonic development. Any metazoan animal passes onto 3 steps from the fertilized egg until it reaches the adult stage. These are cleavage, germ-layer formation and organ formation. ### Classification of Metazoa According to the above description, the true metazoan phyla fall under two main divisions; - **Diploblastica,** where the body is built up of two layers, an outer ectoderm and inner endoderm. This division includes the phylum Coelenterata. - **Triploblastica,** where a middle layer, or mesoderm is formed in between the ectoderm and endoderm of the embryo. This division includes: - **Acoelomata,** with no internal body cavity, or coelom, in the mesoderm and filled with parenchyma cells and includes the following phylum: - Phylum: Platyhelminthes. - **Pesudocoelomata,** with internal body cavity, or coelom, in the mesoderm but filled with fluid and includes the following phylum - Phylum: Aschelminthes/Nematoda. ## Systematic Zoology (Turbellaria), and two other groups of very important parasites, the flukes (Trematoda) and the tapeworms (Cestoda). ### General Characters - They are free-living or parasitic, triploblasiic acoelomate animals, i.e. they possess no coelom; the spaces between the internal organs are filled by loose parenchyma cells of mesodermal origin. - They have soft dorsoventrally flattened and bilaterally symmetrical bodies, i.e. only one median or sagittal section can divide the body into two symmetrical halves. - The body muscles are fairly well developed, and share in the formation of the body wall. - The digestive system, when present, is simple with only a mouth opening, but no anus. - The excretory system is essentially formed of basic units, known as flame cells, connected together by minute excretory ducts, leading to exterior by one or more excretory pores. - They have no respiratory or circulatory systems but through body surface via simple diffusion. - In addition to a diffuse nerve-net, they have a centralized nervous system with a pair of cerebral ganglia lying in the anterior region of the body, and connected to one to three pairs of longitudinal nerve cords with occasional transverse commissures. - The majority are hermaphrodite, with complicated reproductive systems including internal mesodermal gonads, genital ducts, occasionally, accessory genital glands, and copulatory organs. ### Classification Phylum Platyhelminthes is divided into three classes: - **Class Turbellaria,** includes free living platyhelminthic worms and lives in the fresh and marine waters (aquatic). - **Class Trematoda** with two Order Monogenea (Monogcnetic trematodes) and Order Digenea and Class Cestoda. The trematodes Fasciola hepatica (also known as the common liver fluke or the sheep liver fluke) and Fasciola gigantica are large liver flukes (F. hepatica: up to 30 mm by 15 mm; F. gigantica: up to 75 mm by 15 mm), which are primarily found in domestic and wild ruminants (their main definitive hosts) but also are causal agents of fascioliasis in humans. - **Class Cestoda** (Cestodes or Tapeworms) Adult cestodes or tapeworms commonly occur in a wide range of vertebrate hosts including fishes, amphibians, reptiles, birds and mammals. Unlike trematodes. Their presence in the body of the final host is restricted to the alimentary canal. T. saginala, which is commonly named the beef, tapeworm, is a cosmopolitan parasite among beef-eating people. The pork tapeworm, Taenia solium, occurs wherever raw or inadequately cooked pork is consumed. Cattle and pigs are the intermediate hosts of T. saginata and T. solium respectively. These tapeworms are generally found in the middle third of the intestine. In the majority of human cases, only one worm is present in the intestine of the host; very rarely more than one worm may be present. ## Psuedocoelomata ### Phylum Nematoda/Aschelminthes This phylum is one of the largest phyla of the Kingdom. The majority of nematodes are free-living forms universally present in enormous numbers in all types of environments or habitats, including the sea bottom, bottoms of all kinds of freshwater bodies, and the surface layer of all kinds of soils. There are also many parasitic forms which attack all kinds of plants and animals. As parasites of animals, many of them are found in the alimentary canal, liver, kidneys, lungs, blood, lymph, etc. The numerous species which infect crop plants, domestic animals and man make of this phylum one of man's worst enemies. ### General Characters - This phylum includes elongate, cylindrical, non-segmented animals, exhibit bilateral symmetry; - The body is covered with a thick layer of finely or smooth cuticle. - The musculature is well developed, but entirely consisting of longitudinal fibers. - There is no true coelomic cavity, but there is a cavity often referred to as the pseudocoel which is formed by the junction of the large vacuoles of special cells that occupy the space between the intestine and the body wall. - They have a complete digestive tract with a mouth and an anus. - The excretory system consists fundamentally of few (usually two) cells or renettes which are drawn into two longitudinal tubules, that end blindly at their posterior ends, while anteriorly they have a transverse ventral connection with a single mid-ventral opening close behind the mouth. - The nervous system is composed of a circum-oesophageal nerve ring contain 4 ganglia from which four nerve cords (2 lateral, 1 dorsal and 1 ventral) - They are mostly sex separated, their genital organs are usually filamentous (thread-like) and they produce eggs with tough resistant coverings. - The life cycle is direct and rarely indirect with larval stage. This phylum is divided into 2 main classes; Ascaridata, ex. Ascaris lumbricoids and Strongylata, ex. Ancylostoma dudenale. ### Class: Ascaridata #### General characters: - These are oviparous, large stout nematodes living as parasites in the intestine of the large vertebrates as caws. - Mouth possesses 3 prominent lips; lone dorsal and two laterals. - There is no buccal capsule. - The male hind end is curved to the ventral surface and ends with two copulatory spicules ### Class: Strongylata #### General characters: - They are vertebrate parasites devoid of lips. - They have a well-developed buccal capsule with three pairs of teeth. - Males possess a true copulatory bursa with supporting rays.