Introduction to Animal Kingdom Diversity:
This is 6th kingdom of living things. It has highest number of phylum and individuals. They are all animals at different levels of complexity from simple multicellular ones to complex ones.
Diagnostic characteristics of Animal Kingdom Diversity:
i) They are eukaryotes and their cells don't possess cell walls and are multi-cellular.
ii) They are heterotrophs and don't possess chloroplasts.
iii) Most animals are sessile. They spend most of the lives in one place. Animals are motile, meaning that they can move the whole body from place to place not like plants.
Categorization of Animal Kingdom Diversity:
In animal kingdom there are 10 phyla and they are given below based on growing complexities and growth advancement.
a) Phylum Porifera:
Introduction: Porifera are also called as Sponges. Name signifies "pore-bearing". They are aquatic animals and approx all of them are marine. Sponges are simplest form of multi-cellular animals. They are very varied and come in a broad diversity of colors, shapes and structural complexities. Their walls are lined with several small pores known as ostia which permit water to flow into sponge's body
Diagnostic features: Body-cells are freely arranged in 2 layers that are divided by mesenchyme. Several Ostia are there throughout body and large opening osculum is discovered on upper end. Canal system is present, by which water flows throughout body supplying food and oxygen. Endoskeleton is composed of calcareous and siliceous spicules, and spongin fibres. Many Choanocyte-lined spaces are there.
Habitat: Approximately all sponges live in marine water, but some sponges composed of spongin fiber live in freshwater.
Morphology: Sponge bodies are varied in form, they may be: encrusting sheets, volcano-shaped mounds, tubes upright sheets. Sponges can be discriminated by level of difficulty shown by their bodies.
i) Ascon: This is simplest type comprises of the single tube, 2 cell layers thick. Poriferans with this kind of architecture are essentially very small because of surface area to volume constraints.
ii) Sycon: The simple folding of wall which yields the sponge body.
iii) Leucon: Huge majority of sponges are prepared in the more complex way, leucon situations, with folds upon folds, resulting in the series of flagellated chambers joined by canals.
Structure: The structure of the sponge is easy. One end is joined to the solid like as the rocks while other end, known as osculum, is open to environment. Sponges are able to get microorganisms like algae and bacteria for food by openings. Few sponges are carnivorous and utilize their spicules to capture small crustaceans. Sponges are composed of four simple and independent cells. First are collar cells that line canals in interior of sponge. Flagella are joined to ends of cells and they assist pump water through sponge's body. By pumping water, they assist carry oxygen and nutrients to sponge while as well eradicating waste and carbon dioxide. The second cells are porocytes that are cells make up pores of sponge. Epidermal cells form skin on outside of sponge. At last, amoebocytes exist between epidermal and collar cells in the area known as mesohyl. They perform functions of sponge and assist transport nutrients.
Categorization: There are 3 classes of poriferans. They are
i) Calcarea. e.g Sycon,Leucosolenia
ii) Hexatinella .e.g Euplectella, Hyalonema
iii) Demonspongia e.g Spongilla,Cliona
Adaptive Features: Skeleton permits them to live in either hard sediments or soft sediments. Pores permits them to filter water around them for food. Flagella develops currents so the collar cells may trap food. Strong Structures allow sponges to handle high volume of water which flows through them every day.
b) Phylum Cnidaria:
Introduction: These are invertebrate marine animals which have tentacles enclosing the mouth. They all have the simple structure. Their bodies can be pictured as being sac like, Phylum cnidaria comprises jellyfish, anemones, corals and hydroids.
Habitat: They are marine animals
i) Tissue grade of organization with two tissue kinds: a) gastrodermis and b) epidermis
ii) They have layer of mesoglea (the protein) between tissues and their symmetry is radial.
iii) Their nerve cells, are organized in the loose "nerve net".
iv) They have a cnidocyte(nettle cell) which contains the nematocyst
v) Their most obvious unique feature is their highly specialized stinging cells (nematocysts).
Morphology: There are 2 body forms in the phylum. The Polyp like Hydra and Medusa like Obelia polyp: this is sessile flower such as cnidarians like Hydra medusa: motile bell shaped like Obelia
Categorization: Taxonomy is based upon 2 body forms: Polyp and medusa
There are 3 major classes in phylum:
i) Hydrozoa e.g Hydra
ii) Scyphozoa e.g Jellyfish (medusa)
iii) Anthozoa e.g sea anemones, most corals (polyps)
Adaptive Features: Hydrostatic Skeleton permits Cnidarians to move rapidly and easily through water. Cnidarians utilize their nematocytes to stun, kill, or paralyze the prey and to protect them. They may utilize the tentacles to drag the prey into mouth alive.
c) Phylum Platyhelminthes (The Flat Worms):
Introduction: Most members of this phylum are parasitic (flukes and tapeworms), but some are free living (e.g planaria).They are dorsoventrally compressed (i.e., "flat").Platyhelminthes are hermaphroditic, and parasitic species regularly have complicated reproductive cycles.
The mesoderm forms a type of connective tissue called parenchyma which fills the body spaces between the ectoderm and endoderm so that there is no coelom; hence they are called as acoelomate animals. Excretory system has one or two canals with branches which end in structures known as flame cells and the canals have no internal opening, but they open to the exterior. They do not have circulatory and respiratory systems. Flatworms have a dorsoventrally compressed and bilaterally symmetrical body. They are the lowest triploblastic, acoelomate metazoans but they are advanced over coelenterates because their tissues are organized into organs.
Categorization: The phylum is separated into 3 classes as given below:
i) Turbellaria: Mainly free-living flatworms but some are ecto-commensals and endo-commensals or parasitic with simple life cycles. Like Ectoplana, Notoplana, Planaria.
ii) Trematoda: They live as ctoparasitic or endoparasitic forms, generally known as flukes. Body shape generally leaf-like, dorsoventrally flattened. They have well created suckers and cuticle on the body. Their life history may be plain or complicated. Examples Fasciola.
iii) Cestoda: Endoparasites in intestine of vertebrates. Generally known as tapeworms. Body without epidermis and cilia but covered with cuticle. Life cycle complicated generally comprising two or more hosts. Embryos have hooks. Examples: Taenia
Parasitic Adaptations: The shape of the body is flattened like the leaf or ribbon so that they can fit in any space which is available to them. They do not possess cilia. Body is enclosed with many layered cuticle to protect them from hosts enzymes. There is reduction in trophic organs. In cestodes mouth and alimentary canal have gone. They don't possess any locomotory organs. Few parasites have the extra multiplicative stage at some point in life cycle intrematodes he rediae may create daughter rediae or sporocyst may either split by transverse fission or itnmay make miracidiumlarvae; in cestodes there may be many generations of bladder worms as in the hydatid cyst.
d) Phylum Rotifera:
Introduction: The name Rotifera signifies "wheel bearing," they are so called due to corona, the feeding structure that is on the head and looks like wheel. Rotifers have pseudocoelomate animals which are microscopic and near-microscopic.
Habitat: Many of them live in fresh water, a some are marine or live in damp terrestrial habitats.
Morphology: Many rotifers are around 0.1-0.5 mm long (though their size lie from 50 μm to over 2 millimeters)., Few rotifers are free swimming and truly planktonic, others move by inchworming along the substrate, and few are sessile, living within tubes or gelatinous holdfasts which are joined to the substrate.
Structure: The body of rotifer is separated into 3 parts, head, trunk and foot. Head has the ciliary organ known as corona which, when beating, looks like wheels turning. Corona is utilized for feeding .They has the complete gut. Rotifers possess protonephridia but lack specialized circulatory or gas-exchange structures. Many structures in rotifers are syncytial ("multinucleate mass of protoplasm not separated in separate cells," or "a multinucleated cell") and
Phylum Rotifera is split into 3 classes:
ii) Bdelloidea, and
Cryptobiosis this is extraordinary skill to live drying or to survive desiccation .Rotifer eggs can also survive drying, with older embryos having the greater probability of survival. Energy conservation like Brachonius calyciflorus it decreases rate of its respiration when food is scarce to save energy. While other species illustrate no change in respiration rate. Coexistence of competing species. It is forecasted that skill of some rotifer species to adapt to resources with temporal variation in availability permits coexistence of competing species of rotifers.
e) Phylum Nematoda:
Introduction: The name Nematoda derives from Greek word for "thread". Phylum is composed of round worms. They are vermiform or wormlike and body is covered by the layered cuticle. Juveniles in the phylum develop by molting. They are significant parasites of plants, man and animals .
Habitat: They are found in soil, within plants and animals comprisin man, ice hot deserts, oceans.
Morphology: Main body axis is longitudinal. They are mainly bilaterally symmetrical and possess lateral sides a dorsal and ventral side that comprises body openings. Nematodes are not segmented and usually colorless. They don't possess the true body cavity lined with epithelial tissue.
Structure: This comprises the digestive system, body wall, reproductive system, and nervous excretory but lacks the typical circulatory respiratory and endocrine system. Body wall is composed of somatic muscles, hypodermis and cuticle. Cuticle is outermost layer and provides protection and support. Cuticle has alternating horizontal grooves and ridge at usual intervals known as striations or annulations also longitudinal markings.
Habitat: Ascaris lumbricoides is the endoparasite in small intestine of man lying freely in lumen. It is cosmopolitan in distribution. It is discovered more generally in children than in adults. At times it travels from intestine to stomach and comes out through mouth or nostrils of host.
Physical Adaptive characteristics:
They have a simple Structure. Reproduction: roundworms lay eggs that can be extremely resistant to unfavorable environments like dry, hot or cold conditions. Eutely: Each individual of roundworm species has exact, same number of cells.
f) Phylum Annelida:
Introduction: The name signifies ringed derived from Greek word annulatus. Members of phylum Annelida are segmented worms, all show bilateral symmetry, cephalization, have the open digestive system, segmentation, and body cavity. This phylum comprises of leeches, earthworms and different marine worms provided several different names (like, sand worms, tube)
Habitat: Annelids discovered in aquatic environments either marine or fresh water and on land
Diagnostic features: They are segmented worms, segments are both internal and external. Segments are divided by crosswalls or septa and every segment can function as individual
Categorization: Phylum Annelida is separated into 3 main groups
1) Class Oligochaeta: This class of segmented worms comprises earthworm and variety of aquatic species. Earthworm extracts nutrients soil. Undigested material mixed with mucus secreted into digestive tract is egested through anus.
2) Class Polychaeta: Every segment of polychaeta has the pair of paddle-like structures known as parapodia (''almost feet''), which function in locomotion.
3) (Class Hirudinea Leeches): Leeches (500 species) lack parapodia and are generally without chaetae. They are differentiated by the two suckers - one anterior surrounding mouth, other posterior. As dissection of medicinal leech, Hirudo medicinalis, illustrates the bodies are flattened with 32 segments, but every segment has many external grooves.
i) Presence of coelom
ii) Effortlessly replaceable body parts
iii) Metameric segmentation
iv) Longitudinal muscles aid movement
g) Phylum Mollusca:
Introduction: This phylum comprises animals such as bivalves, snails, slugs, octopus,chitons, ssquids. They are soft bodied animals generally with the exoskeleton which is composed of calcareous shell. They have at least 2 characters radula and mantle not discovered elsewhere in animal kingdom. Their life cycles comprise a trochophore larva found in annelids.
Habitat: The molluscs are found in the wide range of habitats terrestrial, aquatic that may be fresh or marine. Abysses of coral reefs, sea, mudflats, rivers, deserts, forests, lakes, underground and in body of other animals.
Diagnostic features: Their bodies are usually lengthen and bilaterally symmetrical. Many organs are contained by the body wall separated into muscular lower part (foot) utilized for locomotion or feeding, and upper part (mantle) that covers most of body along with free space (the mantle cavity). Sensory structures are found in the head (cephalization) (except bivalves).
Categorization: There are 3 classes in phylum mollusca which are:
Gastropoda (gastropods like Helix aspersa (land snail) patella (limpet) Buccinum (whelk) Limax slug)
Pelycopoda (bivalves) like Mytilus edulis (marine mussel) ostrea (oyster)
Structure: The muscular foot, usually used for movement. Visceral mass, comprising most of internal organs. Mantle, a fold of tissue which drapes over visceral mass and secretes shell, if present. Most have radula, or rasping organ to scrape food.
Adaptive features: Shell is for protection, Radula is for drilling, they have poisons in their teeth.
h) Phylum Arthropoda:
Introduction: Arthropoda is largest phylum of animal kingdom. This phylum possesses more individuals and greater diversity and ecological spread than all other phyla in animal. Most distinguished improvement of this phylum is rigid exoskeleton. It has main implications in the organisms' flexibility, locomotion, circulatory systems, gas exchange systems, and growth.
Diagnostic features: They have segmented bodies, have jointed appendages and possess chitinous exoskeleton.
Categorization: Classes are:
i) Class Arachnida (mites, scorpions, spiders, ticks)
ii) Class Diplopoda (Millipedes)
iii) Class Chilopoda (Centipedes)
iv) Class Insecta
v) Class Crustacea (Crabs, Crayfish, Lobsters, Shrimps)
Habitat: Arthropods are situated everywhere. Soils, water, decaying organic material. Bodies of other living things comprising humans.
Adaptive Features: They have hard outer body covering exoskeleton and possess jointed appendages.
i) Phylum Echinodermata:
Introduction: Name Echinoderm signifies "spiny skin" examples of animals in this phylum include sea stars, brittle stars, sea urchins, and sea cucumbers. They are generally sessile or slow moving animals. As adults, they are radially symmetrical, but in larval stage, they are bilaterally symmetrical. And regarded as deuterostomes.
Habitat: Echinoderms are discovered only in marine habitat.
i) They have calcite skeletons that are composed of plates of calcite. Every plate is, crystallographically, a single crystal.
ii) They have radial symmetry (generally 5-fold symmetry in most star-fish) but other degrees of radial symmetry are recognized.
Categorization: There are 2 subphyla in the phylum, they are
a) Pelmatozoa includes 1 living class Crinoidea
b) Eleuthrozoa includes 4 living classes, Ophiuroidea, Holothuroidea, Echinodea and Asteroidea.
Class Crinoidea (Gk. Krinou, sea-lily): Example: Sea lilies (Antedon)
1) External characters: Starfish lives in sandy and rocky parts of sea. Its body is flat and comprises of disc with 5 radiating arms that are broad at the bases and tapering towards outer extremities. Lower side of animal is known as oral side as mouth is in center and upper side is called as abroal or abactinal side.
2) Adaptations: Spikes and toxins are to repel predators. Sea Stars and sea cucumbers, can live in rocky areas whereas others frequently stay in sandy areas where they can hide themselves. Echinoderms can dwell inside skin of other animals like fish to cover themselves in day time. Echinoderms have adapted to match color of their environment.
j) Phylum Chordata:
Introduction: This is last phylum in animal kingdom. These are animals with the notochord at one stage or other in the life cycle, dorsal hollow nerve tube situated just dorsal to notochord; and pharynx with gill slits for respiration. Members of phylum comprise tunicates, lancelets, and vertebrates. For many observers, these are not obvious features of phylum. This is due to they may only be present in embryonic stages.
Habitat: Chordates are discovered on land and in water
Diagnostic Features: They all possess the notochord (non-bony structure which runs length of back and gives them with some inflexibility and attachment for muscles) at some stage in the lives. They possess bi-lateral symmetry. They possess distinguished 'head' and 'tail'. They are utilized in primitive chordates to filter food, are altered by addition of gills in fish and utilized for breathing, and in most land animals become visible only in embryo and are converted in other structures (like lower jaw and parts of cardiovascular system) before birth.
Categorization: Three subphyla make up the phylum Chordata:
Subphylum Urochordata (tunicates): adults are surrounded in the tunic composed of carbohydrate much like cellulose. They squirt water out of excurrent siphon. Urochordates are differentiated by errant (mobile and active) larvae and sessile adults. All are filter feeders. Only "chordate" features retained in adult life are pharyngeal slits. Subphylum Vertebrata (vertebrates) officially, phyla Urochordata and Cephalochordata are regarded as invertebrates.
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