Survey of Animal Kingdom Lecture Note 4 and 5 PDF

DEPARTMENT OF BIOLOGY FACULTY OF NATURAL AND APPLIED SCIENCES UMARU MUSA YAR’ADUA UNIVERSITY, KATSINA BIO 102 (GENERAL BIOLOGY 11) LECTURE NOTE 4 and 5 Survey of Animal Kingdom INTRODUCTIO...

DEPARTMENT OF BIOLOGY FACULTY OF NATURAL AND APPLIED SCIENCES UMARU MUSA YAR’ADUA UNIVERSITY, KATSINA BIO 102 (GENERAL BIOLOGY 11) LECTURE NOTE 4 and 5 Survey of Animal Kingdom INTRODUCTION There is a vast diversity in the number and types of animals in nature. They range from unicellular to multicellular. They are found in the deepest of the oceans, in snow-covered mountains, from the poles to the equator. There are differences in the structure and forms of the different animals. But there are some fundamental features in them which show resemblance such as arrangement of cells, body plan, symmetry, segmentation, coelom, germ layer, body temperature, skeleton and notochord, types of digestive, respiratory, circulatory, excretory, and reproductive systems. We need to classify organisms to make our study easier and to study the interrelationship between different groups. BASES OF CLASSIFICATION Habitat ⚫ On the basis of habitat, animals are divided into the following types: □ Aquatic-Organisms that are found in water. They can be: ⬥ Marine-Echinoderms, many sponges and coelenterates. ⬥ Fresh water-Prawns, some fishes and molluscs. □ Terrestrial-Organisms that are found on land. They can be: ⬥ Fossorial animals (found in burrows) - Earthworm, snake, rabbit. ⬥ Arboreal (found on trees) - Birds, bats, monkeys. ⬥ Scansorial (climb the walls) - House lizards, squirrels. Animal Kingdom  Levels of Organisation ⚫ Animals are divided into five types, on the basis of their level of organisation: □ Protoplasmic level of organisation: A cellular body performs all the biological activities. Example: Protozoa □ Cellular level of organisation: The cells of the body are present in loose aggregates and together perform all the functions. Example: Sponges □ Tissue level of organisation: The cells of the organism unite together to form a tissue system which helps the organism to perform different functions. Example: Coelenterata □ Organ level of organisation: The tissues combine together to form organs which perform different functions. Example: Platyhelminthes □ Organ-system level of organisation: The organs of an organism combine together to form different organ-systems which help in the functioning of the whole organism. Examples: Aschelminthes to Chordata. Symmetry It is the arrangement of the body organs on either side of the main axis of the body. It is of two types – Asymmetry and symmetry. ⚫ Asymmetry: When the body of an organism cannot be divided into two identical halves in any plane. Examples: In some sponges and snails. ⚫ Symmetry: When the body of an organism can be divided into two identical halves in one or more planes. On the basis of the plane involved, it is of two types: □ Radial: ⬥ When the body of an organism can be divided into two identical halves by any plane passing through the central axis of the body. ⬥ For sessile animals, radial symmetry was useful as it helped them in food gathering from all sides. They might have developed appendages all around to capture the prey. Examples: Coelenterates, Ctenophores, Echinoderms □ Bilateral: ⬥ When the body of an organism can be divided into two identical halves by only one plane, passing through the longitudinal axis of the body. ⬥ It arose when animals on the ocean floor became mobile. A crawling animal will encounter food with the end that moves first. ⬥ So, mouth developed at this end. Sensory organs and a coordinating brain developed at the front end. ⬥ These organs helped in sensing food. So, the head enclosing the brain became associated with the mouth end. This is cephalization. Examples: Annelids, Arthropods. s  Body Plan Animals show three different types of body plan: ⚫ Cell aggregate plan: In this case, the body is just an aggregate of cells. Example: Sponges ⚫ Blind sac plan: In this case, the multicellular organism has tissue or organ level of organisation. The organism has only one opening for intake of food as well as it is through this pore, the waste is thrown out of the body. Example: Platyhelminthes ⚫ Tube within the tube plan: In this case, the body consists of two tubes. One tube is formed by the wall of the body and the second is formed by the digestive tract. It has two openings. One at the anterior for intake of food and the other at the posterior end for egestion of undigested food. It is of two types – Protostomes and Deuterostomes. □ Protostomes: ‘Proto’ means first and ‘stoma’ means mouth. Thus, in protostome organisms, the development of the mouth in the embryo takes place first followed by the anus. Examples: Platyhelminthes, Aschelminthes, Annelida, Mollusca □ Deuterostomes: ‘Deutero’ means second, and ‘stoma’ means mouth. Thus, in deuterostome organisms, the development of the anus takes place first and development of mouth in the embryo takes place after it. Examples: Echinodermata, Hemichordata, Chordata  Germ Layers The layer of the gastrula which gives rise to the different parts of the body is called the germ layers. On the basis of the number of the layers, there are two categories: ⚫ Diploblastic: Two germ layers i.e., ectoderm and endoderm give rise to the different parts of the body. In between the two layers is present a non- cellular layer known as mesoglea. Examples: Sponges, Coelenterate, Ctenophores ⚫ Triploblastic: Three germ layers i.e., ectoderm, mesoderm and endoderm give rise to the different parts of the body. Examples: Flatworm to mammals Segmentation Segmentation is the division of a body into portions known as segments. It is of four types: ⚫ Metameric segments (True segmentation): The body is divided into segments; internally and externally. Example: Annelida  ⚫ External Segmentation- Arthropoda ⚫ Internal Segmentation- Chordata ⚫ Pseudometameric segments (False segmentation): The segments of the body are not formed from the embryo and thus are known as pseudometamerism. Example: Tape worm Coelom The space between the body wall and the gut wall is known as coelom. On the basis of the nature of coelom, organisms are of the following types: ⚫ Acoelomates: Organisms do not have any cavity or coelom and thus are called as acoelomates. Examples: Platyhelminthes, porifera, coelenterata, ctenophora ⚫ Pseudocoelomates: The mesoderm is present in form of small pouches between the ectoderm and endoderm. Example: Aschelminthes ⚫ Coelomates (Eucoelomates): It is a body cavity which arises from the mesoderm. It is of three types: □ Schizocoelom: It develops due to the split in the mesoderm sheet. Examples: Arthropods, molluscs, annelids □ Enterocoelom: The mesoderm arises from the wall of the embryonic gut as a hollow outgrowth and forms the coelom. Examples: Echinoderms, chordates □ Haemocoelomates: In Arthropods and Molluscs, the true coelom is reduced and filled with blood and known as haemocoel. Skeleton The framework of the body that gives shape and protection to the animals is known as skeleton. It is of two types on the basis of their position: ⚫ Endoskeleton: Hard structure that is present inside the body. Examples: Bones present inside the body, like humans.  ⚫ Exoskeleton: It is present outside the body. It is of different types like- □ Calcareous shells in Mollusca. □ Epidermal scales in reptiles. □ Feathers in birds. □ Hair, nails, claws, horns in mammals. Notochord It is a solid, unjointed and mesodermal rod, present on the dorsal side of the body. Depending upon its presence or absence, there are two groups of animals: ⚫ Non-Chordates: Organisms that do not have the notochord are known as non-chordates. Examples: Poriferans to Hemichordates ⚫ Chordates: Organisms that have the notochord are known as chordates. Examples: Pisces to mammals Cleavage It is of two types: ⚫ Mosaic (Determinate) Cleavage: Complete embryo is formed from the whole blastomere. If any of the blastomere gets detached accidentally then the embryo formation will cease. Example: Annelids ⚫ Non-Mosaic (Non-determinate) Cleavage: On separation of some of the blastomeres in the early stage, the leftover blastomeres will give rise to the complete embryo. Example: Chordates  Development ⚫ Indirect: The young one does not resemble the parent. It undergoes metamorphosis through a number of larval or nymphal stages to develop into an adult. Examples: Mosquito, frog, tape worm CLASSIFICATION IN ANIMALS ⚫ On basis of the above-given characteristics, animals were classified into different groups by the different scientists. ⚫ Aristotle: He divided animalia into two groups: ⚫ Anaima: It included animals without red blood cells. Examples: Sponges, Arthropoda, Mollusca. ⚫ Enaima: It included animals with red blood cells. Example: Chordates Many scientists later tried to classify organisms into different groups but the finally accepted classification is of Robert Whittaker. ⚫ Robert Whittaker’s five kingdom classification (1969): Whittaker divided the living organisms into five kingdoms: □ Monera □ Protista □ Fungi □ Plantae □ Animalia. In 1969, Robert Harding Whittaker proposed this system. He argued that fungi, which had been previously placed along with plants, had a unique method of obtaining food. So he proposed Kingdom Fungi and separated it from plants. Now, living organisms are divided into five kingdoms; Monera, Protista, fungi, Plantae and Animalia. Criteria used by Whittaker for his classification scheme were: ⚫ Cell structure ⚫ Body organisation ⚫ Mode of nutrition ⚫ Reproduction ⚫ Phylogenetic relationships This system placed all prokaryotes in Kingdom Monera and unicellular eukaryotes were placed in the kingdom Protista. Fungi were elevated to the level of kingdom. ⚫ Kingdom Animalia is divided into 31 phyla, 11 of which are considered to be major ones. ⚫ Animal kingdoms have organisms which are multicellular, eukaryotic, heterotrophic. They lack a cell wall. ⚫ They depend upon plants or plant products for their food. ⚫ They digest food inside a cavity. ⚫ They store digested food as Glycogen and fats. Animal Kingdom – Characteristics of Classification ⚫ They respond to stimuli and have a nervous system. Exception-Sponges do not have nerve cells. Summary: Classification of Animal Kingdom Broad classification of kingdom Animalia based on common fundamental characters Summary: Characteristics of Animal Kingdom  Non-Chordata Phylum Protozoa ⚫ Initially, it was placed in animal kingdom but they could not be called as animals as they showed characteristics of both plants and animals like Euglena. Thus, finally Haeckel placed them in a separate kingdom Protista and later Robert Whittaker maintained its status as a kingdom in his five-kingdom classification. But here we will keep in mind the traditional concept and study it here as a phylum of non-Chordata. ⚫ Microscopic one-celled organism performs all the metabolic activities, and thus known as ‘Acellular’ organisms. ⚫ Habitat: □ Aquatic □ Terrestrial □ Free living -Amoeba □ Parasitic -Plasmodium □ Solitary or colonial -Proterospongia □ Pathogenic -Entamoeba histolytica, Leishmania ⚫ Level of body organisation: Protoplasmic level. ⚫ Consists of protoplasm with a single or more than one nucleus. ⚫ Maybe enveloped by plasmalemma, pellicle, cyst, theca, lorica or shell. ⚫ Locomotion: By means of- □ Pseudopodia-Amoeba □ Flagella-Euglena □ Hairy cilia-Paramoecium □ No locomotory organelles-Plasmodium ⚫ Nutrition □ Holozoic-Amoeba □ Mixotrophic-Euglena □ Parasitic- Plasmodium □ Digestion is intracellular, takes place in food vacuole. ⚫ Respiration: By exchange of gases through body surface. ⚫ Excretion: Takes place by contractile vacuole. □ Nitrogenous waste is Ammonia. □ Some fresh water protozoans get rid of excess water through contractile vacuole and the phenomenon is known as osmoregulation. □ Amoeba has one vacuole and Paramoecium has two vacuoles. ⚫ Reproduction: □ Asexual ⬥ Binary fission -Amoeba ⬥ Transverse fission -Paramoecium ⬥ Longitudinal fission - Euglena ⬥ Multiple fission -Plasmodium □ Sexual : ⬥ Syngamy -Plasmodium ⬥ Conjugation -Paramoecium ⚫ Some also form cyst which helps in reproduction in unfavorable conditions. They do not have natural death because in unicellular animals, growth is always followed by binary fission. The parent cell divides and forms two daughter individuals and thus, loses its identity. ⚫ Examples: □ Amoeba □ Plasmodium □ Euglena □ Leishmania  Classification of Protozoa Phylum Protozoa is classified into the following four classes on the basis of modes of locomotion- ⚫ Mastigophora or Flagellata: Locomotion is by flagella. Examples: Trypanosoma gambiense, Giardia intestinalis ⚫ Sarcodina: Locomotion by pseudopodia. Examples: Amoeba, Entamoeba histolytica ⚫ Ciliata: Locomotion by cilia. Example: Paramoecium ⚫ Sporozoa: Locomotory organs absent. Example: Plasmodium PHYLUM PORIFERA (Sponges or pore bearing) ⚫ Robert Grant gave the term ‘Porifera’. They are commonly known as Sponges. ⚫ Shape: tubular, vase-like, cylindrical and branched. ⚫ Habitat: Aquatic, mostly marine and a few are found in fresh water (Spongilla). They are solitary or colonial. They are attached to the substratum and hence are sessile. ⚫ Level of body organisation: They are multicellular, having a cellular level of organisation. ⚫ Symmetry: Mostly asymmetrical. ⚫ Germ Layer: They are diploblastic, having two layers namely dermal layer and gastral layer. ⚫ Body layers: The body wall of sponges consists of three layers Pinacoderm, Choanoderm and Mesenchyme lining the central cavity called the spongocoel. ⚫ Coelom: Acoelomate ⚫ Canal System: A distinguishing feature of the sponges is the presence of a canal system in the body. This system helps the organism to obtain food and oxygen from the surrounding medium whereas harmful substances and reproductive bodies are carried out of the body.  PHYLUM COELENTERATA OR CNIDARIA ⚫ The term ‘Coelenterata’ was given by Leuckart while Hyman gave the term ‘Cnidaria’. ⚫ Habitat: They are aquatic and most of them are found in marine water except Hydra which is a freshwater cnidarian. ⚫ They are solitary or colonial and may be sedentary or free swimming. ⚫ Level of organisation: They are the first group of organisms that show tissue level of organisation. ⚫ Symmetry: They show radial symmetry. ⚫ Germ Layer: They are diploblastic animals. ⚫ The body wall: The outer Epidermis and inner Gastrodermis. In between these two layers, a non-cellular layer called mesoglea is present. ⚫ Epidermis: It is the outer-most layer and consists of small cuboidal cells. Its function is protective and sensory. Various cells that constitute this layer are: □ Epithelio-muscle cells: The muscle contracts and shortens the body and the tentacles. □ Gland cells: Secrete a sticky material which helps in capture and entanglement of the prey.  PHYLUM CTENOPHORA ⚫ The phylum is commonly known as comb jellies or sea walnuts. KĒene means comb-a group of cilia and phoros means bearing. Initially,they were placed as a subphylum in Cnidaria but Eschscholtz recognised it as a separate phylum Cnetophora. Nematocysts are absent so known as Acnidaria. ⚫ Habitat: Mostly marine, solitary, free swimming ⚫ Level of organisation: Tissue level of organisation. ⚫ Symmetry: Symmetry is radial. The arrangement of combs gives it a radial symmetry whereas the tentacles and the gastrovascular cavity are bilaterally symmetrical. ⚫ Germ layer: They are diploblastic, having outer epidermis and inner gastrodermis. ⚫ Coelom: Acoelomate ⚫ Body structure: Most adult, tentacle-bearing ctenophores have a high capacity to regenerate the missing body regions. □ The body wall consists of two layers – the epidermis and gastrodermis and middle jelly- like mesoglea with some cells and muscle fibres. □ Nematocysts are absent. Special adhesive cells known as Colloblasts are present in the epidermis of the tentacles which help in capture of food. ⚫ Locomotion: It is with the help of eight external vertical ciliated comb plates called as swimming plates. The combs usually propel away from the mouth and thus they usually swim in the direction in which the animal is eating. ⚫ Nutrition: The digestive tract consists of the mouth, pharynx, stomodeum or stomach, which is highly coiled, has canals and two anal pores. □ Thus, digestive tract is complete. Digestion is both extracellular and intracellular. □ They are carnivorous animals. Most of the unwanted matter is thrown out of the mouth and small unwanted particles are ejected through the anus. ⚫ Most ctenophores are capable of reproduction before they reach adulthood and this is known as paedogenesis. ⚫ Examples: □ Pleurobrachia: Sea Gooseberry □ Beroe □ Cestum: Venus’s Girdle  Distinctive Features Over Cnidaria Comb like ciliary plates Bioluminescence PHYLUM PLATYHELMINTHES (FLAT WORMS) ⚫ The term Platyhelminthes was given by Gegenbaur. Platy-flat; helminth-worms. ⚫ Habitat: They are mostly parasitic and a few are free-living like Dugesia. ⚫ Level of Organisation: They have an organ-system level of organisation. The body is dorsoventrally flat and hence known as flatworms. The body is usually unsegmented like in Liver fluke (Fasciola hepatica) except in Tapeworm (Taenia solium). ⚫ Symmetry: They have bilateral symmetry (first bilateral animal). ⚫ Germ Layer: They are first triploblastic organisms. ⚫ Body structure: The space between the body wall is filled with parenchyma. The fluid present in the parenchymal walls maintains the body shape and acts as a hydroskeleton. □ Muscles in the body wall are mesodermal. □ Below the epidermis longitudinal, circular, oblique muscles are present. □ The body consists of sucker with which they attach to the host. The suckers are present at the anterior end i.e. oral suckers. □ First animal to have cephalisation. ⚫ Coelom: Acoelomate. ⚫ Nutrition: Digestive system consists of an alimentary canal which is incomplete (without anus). □ Mouth leads into the pharynx, then oesophagus which opens into the intestine and the intestine is divided into many branches known as diverticula or caeca. This is the case in Liver fluke. In tapeworm the gut is absent.  ⚫ Excretion: Excretory system consists of flame cells or protonephridia that consist of cilia. □ The cilia move and this appears like flickering flame and is thus known as flame cell. Flame cells are also known as Solenocytes. □ Flame cells help in osmoregulation. □ Excretory pore present on the ventral surface of the body. ⚫ Nervous system: Nervous system consists of a brain around the pharynx. □ Nervous system is primitive and ladder-like having a brain ring and 1-3 paired longitudinal nerves connected at intervals by transverse commissures. □ Nerves arise from the brain towards the anterior and posterior part of the body. ⚫ Reproduction: They are hermaphrodite. □ Life cycle is digenetic i.e., completed in two hosts. □ Primary host is sheep and secondary host is snail as in Liver fluke. Primary host is man and secondary host is pig in case of Tapeworm. □ Self-fertilisation is seen in Taenia and cross- fertilisation is seen in Fasciola. □ Development is through the formation of many larval forms. In flukes miracidium, sporocyst, redia, cercaria and metacercaria larvae are present. In tapeworm, oncosphere, hexacanth and cysticercus larvae are seen. ⚫ Examples: □ Dugesia: Planaria □ Schistosoma: Blood fluke □ Fasciola: Liver fluke □ Taenia: Tapeworm  Classification of Phylum Platyhelminthes Is classified into the following three classes on the basis of body shape, mouth position and habitat: ⚫ Class Turbellaria: Body is leaf-like, free-living and mouth is present on the ventral side. Highest power of regeneration. Examples – Planaria ⚫ Class Trematoda: Body is leaf-like, either ecto or endoparasites. Mouth is present on the anterior end. Example – Fasciola ⚫ Class Cestoda: Ribbon-like, endoparasites. Mouth and alimentary canal are absent. Example: Taenia solium Distinctive Features Over Ctenophora ⚫ Organ/organ-system level of organisation ⚫ Bilateral symmetry ⚫ Triploblastic ⚫ Nervous system with brain, nerve cords ⚫ Organised excretory organs, gonads PHYLUM ASCHELMINTHES OR NEMATHELMINTHES OR NEMATODA (ROUNDWORM) ⚫ Gegenberg proposed the term – Nemathelminthes. ⚫ The word “nematode” comes from a Greek word ‘nema’ means thread ‘eidos’ means form. They are commonly known as roundworms, as they appear round in cross-section. They are found in aquatic and terrestrial habitat. Some are parasitic and are some free living. ⚫ Level of organisation: The body is unsegmented, elongated, cylindrical, tapering towards the two ends. They have organ level of organisation. ⚫ Germ layer: Triploblastic ⚫ Body Structure: Body wall consists of an outer cuticle, middle syncytial epidermis and innermost longitudinal muscles. □ Cuticle is thick, tough, transparent layer secreted by the epidermis. It consists of five distinct layers. □ First layer is made up of lipids, second layer is made up of keratin, third layer is sulphur-rich protein matricin, and fourth layer is of fibres, and the fifth layer is the inner basement membrane.  □ Epidermis is present below the cuticle, bearing fat and glycogen reserves. The innermost layer consists of longitudinal muscles. □ The pressure of the fluid and action of the surrounding muscles are used to change an organism’s shape that produces movement. ⚫ Coelom: True coelom is absent. Pseudocoelom as mesoderm is found in the form of small pouches in between the ectoderm and endoderm. □ The pseudocoelomic cavity is filled with the pseudocoelomic fluid. It maintains the shape of the body and forms the hydro skeleton of the body. ⚫ Digestion: The digestive tract is complete and straight. □ It consists of the mouth, muscular pharynx, straight intestine and anus. □ They feed on the blood and the partially or fully digested food from the host. Food is sucked by the rhythmic muscular activity of the pharynx. □ Digested food is absorbed by the intestine and the undigested food moves out of the anus. ⚫ Excretion: Excretory system is simple. □ Flame cells or protonephridia are absent. They consist of giant cells known as renette cells or H-shaped excretory system. □ It consists of two longitudinal excretory canals which are connected by a transverse network (below the pharynx). This transverse duct opens into a common canal that runs to the excretory pore. ⚫ Examples: □ Ascaris: Intestinal Roundworm □ Wuchereria: Filarial worm □ Ancylostoma: Hook worm □ PHYLUM ANNELIDA (SEGMENTED WORM) ⚫ The phylum Annelida was named by Lamarck. Habitat: They occur in fresh water, seawater or moist soil. Some are free-living and some are burrowing or parasitic. The body of the Annelids is divided into metameric segments (externally by ring like growth known as annuli and internally by transverse septa). Level of Organisation: They show organ- system level of body organisation. Symmetry: Bilateral symmetry.  Classification of Phylum Annelida ⚫ Phylum Annelida is classified into the following four classes, on the basis of the presence or absence of parapodia, setae, metamers: □ Class 1 – Polychaeta – Segmentation is internal or external. Many setae on the lateral parapodia. Examples – Nereis, Aphrodiea □ Class 2 – Oligochaeta – Segmentation is internal and external. Few Setae. Examples – Lumbricus, Nais □ Class 3 – Hirudinea-Segmentation is external without internal septa. Setae absent. Example – Leech □ Class 4 – Archiannelida-Segmentation is internal. No setae. Examples – Dinophilus, Proeodrilus. PHYLUM ARTHROPODA (ANIMALS WITH JOINTED APPENDAGES) ⚫ Habitat: They are found in air , water, lan d, burrowed in soil and in the bodies of plants and animals. The body consists of jointed legs or appendages. ⚫ Level of Organisation: They have an organ-system level of organisation ⚫ Symmetry: Show bilateral symmetry and body is segmented. ⚫ Coelom: They are coelomate. ⚫ Germ Layer: Triploblastic ⚫ Body structure: Body is divided into head thorax and abdomen. □ The head and thorax fuse together to form the cephalothorax. The body wall or exoskeleton consists of a single layer of epidermis, an internal basement membrane and cuticle. Classification of Phylum Arthropoda ⚫ Phylum Arthropoda is divided into many subphyla and classes on the basis of the body divisions and presence or absence of appendages. Few of the subphyla have been divided into classes. Some of the classes are: □ Class – Crustacea: The body is divided into cephalothorax. and abdomen. Two pairs of antennae and a pair of compound eye are present. Example – Palaemon, Cancer □ Class – Chilopoda: Body is divided into head and trunk. Each trunk bears a pair of legs. Example – Scolopendra (Centipede) □ Class – Arachnida: The body is divided into cephalothorax and abdomen. It bears six pairs of appendages. Examples – Scorpion, Spider □ Class – Diplopoda: Body is divided into head, thorax and abdomen. A single pair of antennae is present. Each thoracic segment bears a pair of legs. Example – Julus □ Class – Insecta: Body is divided into head, thorax and abdomen. Consists of a pair of antennae and a pair of compound eye. Examples – Silverfish, termites, butterfly □ Class – Merostomata: Aquatic, antennae absent, body segmented. Example – Limulus  PHYLUM MOLLUSCA (SOFT BODIED ANIMAL) It is the second-largest phylum after Arthropoda. Mollusca is derived from the word mollis or molluscs which means soft-bodied. ⚫ Habitat: It consists of all marine animals ranging from a giant squid to a small snail. ⚫ Level of Organisation: Organ-system level of organisation. ⚫ Symmetry: It is bilateral but in Pila (apple snail) due to the presence of twisting of the body during the growth (torsion) is asymmetrical. Classification of Phylum Mollusca ⚫ Phylum mollusc is divided into seven classes on the basis of the shell: □ Aplacophora: Shell a b s e n t. Example – Neomenia □ Monoplacophora: They are one plate bearing. The shell is spoon-shaped. Example – Neopilina □ Polyplacophora/Amphineura: Shell consists of 8 plates. Non-ganglionated nerve ring is present around the mouth with two interconnected nerve cords. Example – Chiton □ Scaphopoda: Shell is tubular and open at both ends. Example – Dentalium □ Gastropoda: It includes the largest number of molluscs. Shell is made up of one piece. Example – Helix □ Pelecypoda or Bivalvia: Shell is made up of two halves. Pinctada, Unio □ Cephalopoda: Shell is external, Head and foot region are modified to form a structure which has eyes and tentacles. Thus, their name is cephalopoda or ‘head –foot’. Examples – Sepia, Loligo, Octopus ⚫ Distinctive features over Arthropoda □ Distinct head □ Better sense organs □ Gills/lungs for respiration PHYLUM ECHINODERMATA (SPINY SKINNED ANIMALS) ⚫ Initially, Echinodermata was placed along with colelenterata in Radiata. Later, Leukart in 1847, identified it as a separate group. Echinodermata (echinos-spiny; derma-skin) are known as spiny- skinned animals. The term echinodermata was coined by Jacob Klein. ⚫ Habitat: They are marine animals and found at the bottom of the water body. Except-Synapta similis, some are free living or sessile. □ The shape of the body may be star-shaped, cylindrical or spherical. □ The star-shaped body consists of five radiating arms ambulacral and five interradii arms called as inter-ambulacral. ⚫ Level of organisation: They have an organ-system level of organisation of the body, Classification of Phylum Echinodermata □ Phylum Echinodermata is divided into five classes on the basis of the shape of the body: □ Class Asteroidea: Body is star-shaped. Example – Asterias □ Class Ophiuroidea: Body is star-like, sharply marked off from the central disc. Example – Ophiothrix □ Class Echinoidea: Body is globular or disc- like. Example – Echinus (sea urchin)  □ Class Holothuroidea: Body elongated and cylindrical. Example – Holothuria (sea cucumber) □ Class Crinoidea: Body has a central disc. Example – Antedon PHYLUM HEMICHORDATA ⚫ hemi-half; chorde-chord. Initially was treated as a sub-phylum of Chordata but later given the status of an independent phylum. ⚫ Habitat: They are living in burrows and are mostly marine. Shape: Body is elongated worm like consisting of proboscis, collar and trunk. ⚫ Body layer: Skin layer consists of single epidermis. ⚫ Symmetry: Bilateral ⚫ Coelom: Body cavity is enterocoelus, that is divided into protocoel, mesocoel and metacoel. ⚫ Germ Layers: Triploblastic ⚫ Nutrition: Mostly ciliary feeders. Complete alimentary canal is present in digestive system. □ This is straight or U-shaped. Digestive tract is complete. □ Narrow openings called gill slits are present on the dorsal side. They are usually present in several pairs. □ Excretion: A single proboscis gland helps in excretion. □ Reproduction: Sexes are separate. □ Gonads are one to many. □ Fertilisation is external. □ Direct or indirect development with a free- swimming tornaria larva. □ Special Feature: True notochord is absent. □ A notochord like structure is found in their buccal cavity, that is called ‘buccal diverticulum’ or ‘stomochord’ (a hollow outgrowth arises from the roof of buccal cavity). ⚫ Examples: □ Balanoglossus □ Saccoglossus  Identifying characteristics of the chordates ⚫ Presence of a notochord: A rod-like structure is present in the organisms, which in the later stages undergoes some changes to form the vertebral column. ⚫ Presence of dorsal hollow nerve cord: The nerve cord lies to the dorsal of the notochord and is always hollow. ⚫ Presence of pharyngeal gill slits: At some stage of the life cycle the chordates have a pair of gill slits on the lateral side. In Pisces,they are present throughout the life. Classification of Chordata Phylum Chordata is divided into three subphyla: □ Subphylum Urochordata □ Subphylum Cephalochordata □ Subphylum Vertebrata ⚫ Sub-phylum Urochordata Uros-tail; chordate-notochord bearing □ The organisms of this phylum are sedentary. □ They are called tunicates as they are covered by a leathery test made up of a chemical tunicin. The notochord is only present in the tail of the larva and disappears in the adult. □ Dorsal nerve cord in the larva is replaced by nerve ganglion in the adult. □ They have gill slits for respiration. □ Open circulatory system. The heart is tubular and ventral. □ Mostly hermaphrodite. Development is indirect with a swimming larval form. ⚫ Subphylum Cephalochordata cephalos-head; chordata-notochord bearing □ The organisms in this phylum are motile. □ The notochord is present from head to tail and is persistent throughout the life of an organism. □ Gills slits are better developed and adapted for respiration..  □ Tail present throughout the life cycle. □ Excretion by protonephridia. □ Nerve cord dorsal and tubular. □ Hermaphrodite. □ Fertilisation is external. Indirect development through a free-swimming larva. ⚫ Examples: Amphioxus ⚫ Subphylum Vertebrata □ The members of this subphylum are much advanced than the members of the above- mentioned two phyla. □ Notochord is replaced by a bony structure called the vertebral column in the adult. □ Brain is enclosed in a hard bony structure called cranium. □ Exoskeleton and endoskeleton both are present. □ Digestive system is well developed. □ Respiration is either by gills, skin or by the lungs. □ Circulatory system and heart are well developed; heart having two, three or four chambers. □ Sense organs are well developed like the eyes, ear, nose, and tongue. □ Pair of kidneys are present for excretion. Substances that are excreted can be Ammonia, uric acid, and urea. □ Nervous system consists of brain and the spinal cord. □ Sexes are separate. □ Fertilisation can be either external or internal. There is no asexual reproduction. □ It is divided into two divisions: ⬥ Division 1: Agnatha - Jawless Vertebrates. ⬥ Division 2: Gnathostomata-Jawed Vertebrates. Classification of Amphibia Living Amphibians are classified into three orders: ⚫ Apoda: Limbless,blind and elongated. Examples: Ichthyophis ⚫ Urodela: Tail present, two limbs are present that are weak. Examples: Necturus (Mudpuppy), Amphiuma (Congo eel) Ambystoma-Tiger Salamander, Proteus ⚫ Anura: Tail absent, two limbs are present. Examples: Rana (Frog), Bufo (Toad)  Distinctive Features of Class Amphibia ⚫ Live both on land and water ⚫ Skin with mucous glands is seen ⚫ Three-chambered heart ⚫ Poikilothermic animals ⚫ Ureotelic CLASS REPTILIA (CREEPING OR CRAWLING VERTEBRATES) ⚫ Habitat: They are found both on land and in water but mostly on land. They are creeping, burrowing and mostly carnivores. ⚫ Body Structure: Body is bilaterally symmetrical and consists of head, neck, trunk and tail. □ Two pair of limbs that are pentadactyl. Limbs are absent in snakes. □ Digits are provided with claws. □ Endoskeleton consists of bones. □ Exoskeleton consists of epidermal scales or scutes and plates. □ Skin is dry, rough without any glands. Snakes shed their skin. Classification of Reptilia ⚫ Class reptilia is divided into two subclasses consisting of living members: □ Subclass Anapsida: Solid skull roof and no temporal opening. Examples – Turtle,Tortoise □ Subclass Diapsida: Skull with two temporal openings separated by bones. Examples – Lizard, Alligator, Cobra  CLASS AVES ⚫ They are flying vertebrates. They can also be referred to as ‘glorified reptiles’. ⚫ Body Structure: Body is spindle-shaped and divided into four regions namely head, neck, trunk and tail. □ Skin is dry, except for the presence of oil gland or green gland at the root of the tail. □ Neck is long and flexible and tail is short and stumpy. □ Two pair of limbs. □ The forelimbs are modified into wings, covered with feathers and consisting of hollow (pneumatic) bones. □ Forelimbs are used for flying. □ The hindlimbs are modified for walking, running, food capturing and swimming. □ The foot consists of four clawed toes, out of which the first one is directed backward. □ Endoskeleton consists of long, pneumatic bones. □ Bone marrow is absent. ⚫ Digestive System: Jaws are modified into a beak, which lacks teeth. □ Beak is modified for crushing, tearing, nectar sipping, wood cutting. □ Mouth leads into the alimentary canal that has crop and gizzard. □ Crop stores and softens the food while gizzard helps in crushing and churning the food. □ A three-chambered cloaca is present. ⚫ Respiration: Respiration is by lungs. □ Air sacs are connected to the lungs. □ Larynx is without vocal cords. A voice box or syrinx is present at the junction of the trachea and bronchi. ⚫ Circulation: Heart is four-chambered and they are warm-blooded. ⚫ Excretory System: Kidneys are metanephric and consist of three lobes. Urinary bladder is absent and excretion is uricotelic. ⚫ Examples: □ Corvus splendens-Crow □ Passer domesticus-Sparrow □ Pavo Cristatus-Peacock □ Bubo bubo-Great-horned owl □ Psittacula eupatria-Alexandrine Parrot  CLASS MAMMALIA ⚫ Habitat: They are found in a large number on terrestrial habitats. ⚫ Body Structure: Body is divided into a head, neck, trunk and tail. □ Limbs are two with five or less than five digits. These help in walking, running, flying, swimming. □ Exoskeleton is made up of nails, hairs, scales, claws, hooves and horns. □ Endoskeleton is made up of hard bony structure. □ Oil glands (sebaceous glands) and sweat glands are present on the body. □ The coelom consists of three cavities: One is the pericardial cavity which lodges the heart, second is the two pleural cavities which lodge the lungs and the abdominal cavity with the other parts of the body. ⚫ Examples: □ Panthera leo – Lion □ Panthera tigris – Tiger □ Phoca – Seal □ Camelus – Camel □ Bos indicus – Cow □ Homo sapiens sapiens – Human Classification of Mammalia Mammalia is divided into two subclasses: ⚫ Subclass Prototheria: They are oviparous i.e. egg-laying mammals. Examples – Duck-billed Platypus, Tachyglossus (Echidna ⚫ Subclass Theria: They are viviparous i.e. give birth to young ones. Examples – Humans, Kangaroo. It has been further divided into Metatheria and Eutheria. Metatheria consists of infra-class marsupialia i.e., pouched animals. Examples: Macropus (Kangaroo), Phascolarctos (Koala), Didelphis (opossum).