Femina Nazer

CHAPTER – 4 ANIMAL KINGDOM General Account & Non chordates including Protozoa – 01 INTRODUCTION Animals are the most diverse group of organisms. A million species of animals have been described and classificstion helps in assigning a systematic position to newly described species. All animals are metazoans.Metazoans are multicellular eukaryotes and heterotrophic animals. TYPES OF CLASSIFICATION Features such as arrangement of cells, body symmetry, nature of coelom, patterns of digestive, circulatory or reproductive systems are the basis of animal classification. Levels of Organisation Cellular level of organization - cells are arranged as loose cell aggregates. Example- Sponges Tissue level of organization - cells performing the same function are arranged into tissues. Example- coelenterates. Organ level of organization - tissues are grouped together to form organs, each specialized for a particular function. Example- Platyhelminthes Organ system level of organization - organs have associated to form functional systems, each system concerned with a specific physiological function. Example- Annelids, Arthropods, Molluscs, Echinoderms and Chordates. Complexities can be seen in animals with organ system level of organization. For example- DIGESTIVE SYSTEM i. Incomplete digestive system : It has only a single opening to the outside of the body.Eg;Platyhelminthes and Coelenterates ii. Complete digestive system : It has two openings at each end ,the mouth and the anus.Eg; Man CIRCULATORY SYSTEM  i. open type circulatory system: is the one in which the blood is pumped out of the heart and the cells and tissues are directly bathed in it Eg;, Arthropods ii.Closed type circulatory system: is the one in which the blood is circulated through arteries, veins and capillaries.Eg; in humans SYMMETRY Asymmetrical - when any plane that passes through the center does not divide them into equal halves. Example- Sponges. Radial symmetry- When any plane passing through the central axis of the body divides the organism into two identical halves. Example- Coelenterates, Ctenophores etc. Bilateral symmetry- When the body can be divided into identical left and right halves in only one plane. Example- Annelids, Arthropods, etc. CLASSIFICATION ON BASIS OF GERMINAL LAYERS : Diploblastic organisation : Cells arranged in two embryonic layers i.e. external ectoderm and internal endoderm. (Mesoglea may be present in between ectoderm and endoderm) e.g., Coelentrates. Triploblastic organisation : Three layers present in developing embryo i.e., ectoderm, endoderm and mesoderm. e.g., Chordates. COELOM The fluid filled body cavity in between the body wall and digestive tract of animals is called Coelom in which the body cavity is lined by mesoderm Presence or absence of a cavity between the body wall and the gut wall is very important in classification. - COELOMATES: Animals possessing coelom.Eg;Annelids,Molluscs,Arthropods -ACOELOMATES: Animals in which the body cavity is absent.Eg;Platyhelminthes -PSEUDOCOELOMATES: In some animals ,the body cavirty is not lined by mesoderm instead the mesoderm is present scattered pouches in between the ectoderm and endoderm.Such a body cavity is called Pseudocoelomates. Eg;Aschelminthes. SEGMENTATION In some animals the body is externally and internally divide into segments with a serial repetition of at least some organs.For example;in earthworm,the body shows this pattern called metameric segmentation and the phenomenon is known as metamerism. a)TRUE METAMERISM: Found in arthropods,annelids and chordates Segment is internal as well as external in annelids Segment is external in arthropods Segment is internal in chordates. b)PSEUDOMETAMERISM Pseudometamerism occurs in cestodes in which every segment is independent of the other and contains complete set of organs that have no connection with organs in other segments Eg; in tapeworm. NOTOCHORD Rod-like structure formed during embryonic development on the dorsal side. It is mesodermally derived. i. CHORDATES:Animals with notochord are called chordates Eg;Man ii. NON-CHORDATES;Animals which do not having notochord are called non-chordates Eg;Porifera,Coelenterata,Platyhelminthes. ANIMAL KINGDOM General Account & Non chordates including Protozoa – 02 CLASSIFICATION OF KINGDOM ANIMALIA BASED ON FUNDAMENTAL FEATURES The important characteristic features of the different phyla; 1) PHYLUM PORIFERA Members of this phylum are commonly known as sponges. Mostly marine, asymmetrical and have cellular level of organization. They have water transport or canal system. Water enters through minute pores, Ostia into central cavity Spongocoel, from where it goes out through Osculum. Choanocytes or collar cells line the spongocoel and the canals Nutrition, respiration and excretion is performed by pathway of water transport system. Digestion is intracellular. Skeleton made up of spicules or spongin fibres. Egg and sperms are produced by same organism ,that is hermaphrodite. Asexual reproduction by fragmentation and sexual reproduction by gametes formation. Fertilisation internal and development is indirect having a larval stage which is morphologically distinct from the adult. Example-Sycon, Spongilla(fresh water sponge) and Euspongia(Bath sponge) 2) PHYLUM – COELENTERATA (CNIDARIA) Also called Cnidarians,they contain the stinging capsules called cnidoblasts or cnidocytes,present on the tentacles and the body. Cnidoblasts are used for anchorage,defense and for the capture of prey. Are usually marine and radially symmetrical. They have tissue level of organisation They are diploblastic Digestion extracellular and intracellular. They have gastro-vascular cavity and an opening, hypostome. Body wall composed of calcium carbonate. Cnidarians exhibit two body forms : polyp and medusa e.g., Hydra, Aurelia. Alternation of generation between body forms called Metagenesis occurs in Obelia where polyps produce medusa asexually and medusa form the polyps sexually. Examples are Physalia(Portuguese man- of- war) ,Adamsia(Sea Anemone) 3) PHYLUM CTENOPHORA Also called as sea walnuts or combjellies. Are exclusively marine, radially symmetrical. They have tissue level of organization and they are diploblastic. Digestion both extra and intracellular. Body has eight external rows of ciliated comb plates for locomotion. They shows Bioluminescence (living organism emit light). Only sexual reproduction occurs. External fertilization and Indirect development. E.g., Ctenoplana,Pleurobrachia. 4) PHYLUM PLATYHELMINTHES They have dorso-ventrally flattened body, hence are called flatworms They are endoparasites in animals. Flat worms are bilaterally symmetrical, triploblastic, acoelomate animals They have organ level of organization. Some of them absorb nutrients through body surface. Parasite forms have hooks and suckers. Specialised cells called ‘Flame cells’ help in osmoregulation and excretion. Fertilisation is internal and development through many larval stages. Planaria has high regeneration capacity. Examples are Taenia (Tapeworm) , Fasciola(Liver fluke) 5) PHYLUM ASCHELMINTHES The body of the aschelminthes is circular in cross-section, hence, the name roundworms May be free living, parasitic, aquatic or terrestrial. They are bilaterally symmetrical, triploblastic, pseudocoelomate. Alimentary canal is complete wih a well developed muscular pharynx An excretory tube removes body wastes from the body cavity through the excretory pore Sexes are separate,that is dioecious, means males and female are separate Shows dimorphism that is variation between male and female members of the same species.  Females longer than males. Fertilisation is internal and Development is direct or indirect. Examples are Ascaris(Round Worm), Wuchereria(Filaria worm), Ancylostoma (Hookworm). 6)PHYLUM ANNELIDA Their body surface is distinctly marked out into segments or metameres (Latin word, annulus means little ring) and hence, the phylum name Annelida They are aquatic or terrestrial, free-living or parasitic. They are bilaterally symmetrical , triploblastic and coelomate animals. They have organ-system level of organisation and metamerically segmented body. They have longitudinal and circular muscles for locomotion. Nereis (dioecious and aquatic annelid) has lateral appendages called parapodia for swimming. They have nephridia for osmoregulation and excretion. A closed circulatory system is present Reproduction is sexual. Neural system consists of paired ganglia (sing. ganglion) connected by lateral nerves to a double ventral nerve cord. Examples are Earthworm (Pheretima) and Leech (Hirudinaria) which are hermaphrodites (i.e., monoecious, male and female reproductive organs in the same individual; hermaphrodite) 7) PHYLUM ARTHROPODA Largest phylum of Animalia which includes insects They bilaterally symmetrical,triploblastic,segmented and coelomate animals They have organ system level of organization • Body divisible into head, thorax, abdomen and has a chitinous exoskeleton. Jointed appendages are present. Respiration by gills, book gills, lungs or tracheal system. Circulatory system is of open type Excretion through malpighian tubules. Sensory organs like Antennae, eyes, Organs of balance called Statocysts are present. They are mostly dioecious Fertilisation is internal and development is indirect or direct. They are mostly oviparous. Examples are Apis (Honey bee), Bombyx (Silkworm), Laccifer (Lac insect) Anopheles,Culex and Aedes (Mosquitoes),Living fossil – Limulus(King crab). 8) PHYLUM MOLLUSCA Phylum Mollusca is the second largest phylum of Animalia. They are bilaterally symmetrical, triploblastic and organ system level of organisation, coelomate. Body divisible into head, muscular foot and visceral hump Body is covered by calcareous shell. Body is unsegmented over visceral hump. Mantle is the soft and spongy layer of skin over the visceral hump Mantle cavity is the space between visceral hump and mantle. Respiration and excretion by feather like gills in mantle cavity. Head has sensory tentacles. The mouth contains a file like rasping organ for feeding called radula. They are oviparous, dioecious and have indirect development. Examples are Pila (Apple snail), Pinctada (Pearl oyster), Sepia (Cuttlefish), Loligo (Squid), Octopus (Devil fish), Aplysia (Seahare), Dentalium (Tusk shell) and Chaetopleura (Chiton). 9) PHYLUM ECHINODERMATA These animals have an endoskeleton of calcareous ossicles and, hence, the name Echinodermata They are spiny bodied organisms and are exclusively marine, They are radially symmetrical in adult but bilaterally symmetrical in larval stage. They are triploblastic and coelomate animals Thay have Organ system level of organisation. Digestive system is complete.Mouth on ventral side and Anus on dorsal side. The most distinctive feature of echinoderms is the presence of water vascular system which helps in locomotion, capture and transport of food and respiration. Excretory system is absent. Sexes are separate. Reproduction is sexual. Fertilisation is external and development is indirect with free swimming larva Examples are Asterias (Star fish), Echinus (Sea urchin), Antedon (Sea lily), Cucumaria (Sea cucumber) and Ophiura (Brittle star). 10) PHYLUM HEMICHORDATA Hemichordata was earlier considered as a sub-phylum under phylum Chordata. But now it is placed as a separate phylum under non-chordata. This phylum consists of a small group of worm-like marine animals They have organ-system level of organisation. They are bilaterally symmetrical, triploblastic and coelomate animals. The body is cylindrical and is composed of an anterior proboscis, a collar and a long trunk Circulatory system is of open type. Respiration takes place through gills. Excretory organ is proboscis gland. Sexes are separate. Fertilisation is external and Development is indirect. Examples: Balanoglossus and Saccoglossus ANIMAL KINGDOM CHORDATES - 01 PHYLUM CHORDATA Animals belonging to phylum Chordata are fundamentally characterised by the presence of a notochord A dorsal hollow nerve cord and paired pharyngeal gill slits These are bilaterally symmetrical, triploblastic, coelomate animals They have organ-system level of organisation. They possess a post anal tail A closed circulatory system. COMPARISON OF CHORDATES AND NON – CHORDATES CLASSIFICATION OF PHYLUM CHORDATA Phylum Chordata is divided into three subphyla: Urochordata or Tunicata Cephalochordata Vertebrata (i) SUB-PHYLA UROCHORDATA Notochord present only in larval tail. e.g., Ascidia, Salpa, Doliolum (ii) SUB-PHYLA CEPHALOCHORDATA Notochord extends from head to tail.eg.Branchiostoma (Amphioxus or Lancelet). Subphyla Urochordata and Cephalochordata are often referred to as Protochordates (iii) SUB-PHYLA VERTEBRATA They have notochord only during embryonic period. Notochord gets replaced by bony or cartilaginous vertebral column. They have ventral muscular heart, paired appendages and kidneys for excretion and osmoregulation. (a) AGNATHA (Lacks Jaw) - Class : Cyclostomata • Have sucking and circular mouth without jaws. • Live as ectoparasites on some fishes. • No scales, no paired fins. They have an elongated body bearing 6-15 pairs of gill slits for respiration. • Cranium and vertebral column is cartilaginous. Closed type of circulation • Cyclostomes are marine but migrate to fresh water for spawning (release or deposit eggs) and die after spawning. • Larva returns to ocean after metamorphosis. Examples are Petromyzon (Lamprey) and Myxine (Hagfish). GNATHOSTOMATA (Bear Jaws) SUPER-CLASS : PISCES (bears fins) Class 1 - Chondrichthyes (Cartilaginous Fishes) Mostly marine and predaceous. Body fusiform or spindle shaped. Mouth is located ventrally Teeth are modified placoid scales which are backwardly directed. Fins both median and paired, all supported by fin rays. Skin tough containing minute placoid scales and mucous glands. Endoskeleton entirely cartilaginous, without true bones Notochord persistent. Respiration by 5 to 7 pairs of gills. Heart 2–chambered (1 auricle and 1 ventricle). Due to the absence of air bladder, they have to swim constantly to avoid sinking. Some of them have electric organs (e.g., Torpedo) and some possess poison sting (e.g., Trygon). They are cold-blooded (poikilothermous) animals, i.e., they lack the capacity to regulate their body temperature. Sexes are separate. In males pelvic fins bear claspers. They have internal fertilisation and many of them are viviparous. Examples: Scoliodon (Dog fish), Pristis (Saw fish), Carcharodon (Great white shark), Trygon (Sting ray). Class 2 - Osteichthyes (Bony fishes) General Characters:- It includes both marine and fresh water fishes with bony endoskeleton.  Body spindle-shaped and streamlined. Mouth is mostly terminal They have four pairs of gills which are covered by an operculum on each side. Fins both median and paired, supported by fin rays of cartilage or bone. Skin with many mucous glands, usually with embedded dermal scales Skin is covered with cycloid/ctenoid scales. Air bladder is present which regulates buoyancy. Respiration by 4 pairs of gills on body gill arches Ventral heart 2-chambered (1 auricle + 1 ventricle). They are cold-blooded animals. Sexes are separate. Fertilisation is usually external. They are mostly oviparous and development is direct. Examples: Marine – Exocoetus (Flying fish), Hippocampus (Sea horse); Freshwater – Labeo (Rohu), Catla (Katla), Clarias (Magur); Aquarium – Betta (Fighting fish), Pterophyllum (Angel fish) GNATHOSTOMATA (Bear Jaws) SUPER-CLASS : Tetrapoda (bear limbs) CLASS : AMPHIBIA As the name indicates (Greek word Amphi means dual; bios means life) Amphibians can live in aquatic as well as terrestrial habitats Most of them have two pairs of limbs. Body is divisible into head and trunk. Tail may be present in some organisms The amphibian skin is moist (without scales). The eyes have eyelids. A tympanum represents the ear. Alimentary canal, urinary and reproductive tracts open into a common chamber called cloaca which opens to the exterior. Respiration is by gills, lungs and through skin. The heart is three chambered (two auricles and one ventricle). These are cold-blooded animals. Sexes are separate. Fertilisation is external. They are oviparous and development is indirect. Examples: Bufo (Toad), Rana (Frog), Hyla (Tree frog), Salamandra (Salamander), Ichthyophis (Limbless amphibia). CLASS REPTILIA GENERAL CHARACTERS:- Predominantly terrestrial, creeping mode of locomotion Body bilaterally symmetrical and divisible into 4 regions-head, neck, trunk and tail. Exoskeleton of horny epidermal scales, shields, plates and scutes. Endoskeleton bony Skin dry, cornified and devoid of glands. Alimentary canal terminates into a cloacal aperture. Heart usually 3–chambered, 4–chambered in crocodiles. Respiration by lungs throughout life. They do not have external ear openings.Tympanum represents ear. Limbs, when present, are two pairs. Reptiles are poikilotherms. Snakes and lizards shed their scales as skin cast. Sexes are separate. Fertilisation is internal. They are oviparous and development is direct. Examples: Chelone (Turtle), Testudo (Tortoise), Chameleon (Tree lizard), Calotes (Garden lizard), Crocodilus (Crocodile), Alligator (Alligator). Hemidactylus (Wall lizard), Poisonous snakes – Naja (Cobra), Bangarus (Krait), Vipera (Viper) CLASS AVES GENERAL CHARACTERS:- The characteristic features of Aves (birds) are the presence of feathers and most of them can fly except flightless birds (e.g., Ostrich). They possess beak. Limbs are two pairs. The forelimbs are modified into wings. The hind limbs generally have scales and are modified for walking, swimming or clasping the tree branches. Exoskeleton is epidermal and horny. Endoskeleton is fully ossified (bony) and the long bones are hollow with air cavities (pneumatic). Skin is dry without glands except the oil gland at the base of the tail. Pectoral muscles of flight are well developed. Vertebral column short. Heart completely 4–chambered. Blood corpuscles are nucleated. Birds are the first vertebrates to have blood. Larynx without vocal cords. A sound box or syrinx, producing voice, lies at or near the junction of trachea and bronchi. The digestive tract of birds has additional chambers, the crop and gizzard. Respiration is by lungs. Air sacs connected to lungs supplement respiration. Sexes are separate.Fertilisation is internal.They are oviparous and development is direct. Examples : Corvus (Crow), Columba (Pigeon), Psittacula (Parrot), Struthio (Ostrich), Pavo (Peacock), Aptenodytes (Penguin), Neophron (Vulture). CLASS MAMMALIA GENERAL CHARACTERS:- The most unique mammalian characteristic is the presence of milk producing glands (mammary glands) by which the young ones are nourished. They are mostly terrestrial, air-breathing, warm blooded, viviparous, tetrapod vertebrates Some of them have adapted to fly or live in water. Limbs 2 pairs, pentadactyle, each with 5 digits .Limbs are adapted for walking, running, climbing, burrowing, swimming or flying Exoskeleton includes epidermal hairs, spines, scales, claws, nails, hoofs, horns, bony dermal plates, etc Endoskeleton thoroughly ossified. The skin of mammals is unique in possessing hair. Skin richly glandular containing sweat, sebaceous glands Females also have mammary glands producing milk for suckling the young. External ears or pinnae are present. Different types of teeth are present in the jaw Respiration always by lungs . Larynx contains vocal cords. Heart 4-chambered with double circulation. Brain highly evolved.Senses well developed. Sexes separate.Fertilization is internal preceded by copulation. mammals are viviparous, giving birth to living young ones. They are homoiothermous; Maintaining an almost constant body temperature Sexes are separate,fertilisation is internal and development is direct. Examples: Oviparous-Ornithorhynchus (Platypus); Viviparous - Macropus (Kangaroo), Pteropus (Flying fox), Camelus (Camel), Macaca (Monkey), Rattus (Rat), Canis (Dog), Felis (Cat), Elephas (Elephant), Equus (Horse), Delphinus (Common dolphin), Balaenoptera (Blue whale), Panthera tigris (Tiger), Panthera leo (Lion).