PHYLUM PORIFERA
Etymology:- From the Latin porus for pore and Ferre to bear,
hence an animal with with pores.
Characteristics of Porifera:-
1)No definite symmetry.
2)Body multicellular, few tissues, no organs.
3)Cells and tissues surround a water filled space but there is no true body cavity.
4)All are sessile, (live attached to something as an adult).
5)Reproduce sexually or asexually, sexual reproduction can be either gonochoristic or hermaphroditic.
6)Has no nervous system.
7)Has a distinct larval stage which is planktonic.
8)Lives in aquatic environments, mostly marine.
9)All are filter feeders.
10)Often have a skeleton of spicules.
Sponges are one of the better known groups of invertebrates, due to their usefulness in the bath many people who care nothing for invertebrates at least know name and may even have seen a sponges skeleton on sale in a shop. One of the more amazing things about sponges is there ability to suffer damage. Because the cells are not linked in a tissue it is possible for them to be separated an then come together again. Some species such as the freshwater sponge Ephydatia fluviatilis can be pushed through a sieve, then if given time the individual cells will come together again and make a new sponge.
A sponge is a simple organism that is easy to describe. A sponge is a sedentary, filter-feeding metazoan which has a single layer of flagellated cells that drive a unidirectional current of water through its body. such a brief description though does not do them justice. Sponges are an ancient and highly successful group of animals. In the Palaeozoic they are believed to have comprised more than half the biomass in marine reefs. They have been living in the waters of the world for more than 600 million years, and can now be found in all marine and many freshwater habitats. Sponges occur in rivers and streams, from rock pools to the deep ocean depths, from frozen arctic seas to the warm tropical seas. They are perhaps at their most beautiful in tropical marine seas. There are about 10,000 known species and though their basic organisation is pretty simple and remains fairly constant throughout the all species they do manage to show a great variety of forms.
CLASS
The Calcarea sponges have spicules of calcium carbonate that have 1,3 or 4 rays, a a skeleton that involves a single large lump of calcium carbonate rather than spicules.
The Demospongiae have their spicules made from silica and they have 1,2, or 4 rays.
The Sclerospongiae have a compound skeleton of spicules of silica that is restricted to thin layer of living sponge supported on a large basal layer of calcium carbonate.
The Hexactinellida or 'Glass sponges' have spicules made from silica that are 6 rayed.
PHYLUM CNIDARIA
The Phylum Cnidaria includes such diverse forms as jellyfish, hydra, sea anemones, and corals. Cnidarians are radially or biradially symmetric, a general type of symmetry believed primitive for eumetazoans. They have achieved the tissue level of organization, in which some similar cells are associated into groups or aggregations called tissues, but true organs do not occur. Cnidarian bodies have two or sometimes three layers. A gastrovascular cavity (coelenteron) has a single exterior opening that serves as both mouth and anus. Often tentacles surround the opening. Some cells are organized into two simple nerve nets, one epidermal and the other gastrodermal, that help coordinate muscular and sensory functions.
Cnidarians have two basic body forms, medusa and polyp. Medusae, such as adult jellyfish, are free-swimming or floating. They usually have umbrella-shaped bodies and tetramerous (four-part) symmetry. The mouth is usually on the concave side, and the tentacles originate on the rim of the umbrella.
Polyps, in contrast, are usually sessile. They have tubular bodies; one end is attached to the substrate, and a mouth (usually surrounded by tentacles) is found at the other end. Polyps may occur alone or in groups of individuals; in the latter case, different individuals sometimes specialize for different functions, such as reproduction, feeding or defense.
Reproduction in polyps is by asexual budding (polyps) or sexual formation of gametes (medusae, some polyps). Cnidarian individuals may be monoecious or dioecious. The result of sexual reproduction is a planula larva, which is ciliated and free-swimming.
If collar cells and spicules are defining characteristics of the Phylum Porifera, then nematocysts define cnidarians. These tiny organelles, likened by Hickman to cocked guns, are both highly efficient devices for capturing prey and extremely effective deterrents to predators. Each contains a coiled, tubular thread, which may bear barbs and which is often poisoned. A nematocyst discharges when a prey species or predator comes into contact with it, driving its threads with barb and poison into the flesh of the victim by means of a rapid increase in hydrostatic pressure. Hundreds or thousands of nematocysts may line the tentacles or surface of the cnidarian. They are capable even of penetrating human skin, sometimes producing a painful wound or in extreme cases, death.
The Classes of Phylum Cnidaria
Hydrozoa = Typical hydroids pass through both polyp and medusa phases in their life cycle, but some species only live as polyps. Hydroids are small, inconspicuous creatures, measuring only a fraction of an inch, and much of the marine growth on rocks and shells is produced by hydroid polyps. (ex hydra)
Scyphozoa = The medusa phase is the dominant part of the life cycle of jellyfish, although there is also a smaller, stationary polyp stage. Most jellyfish are found in coastal waters.
Cubozoa = Cubozoans, or box jellyfish, appear similar to scyphozoans and are sometimes classified with them, but differ from them in having a more square-shaped bell, four bunches of tentacles, and well-developed eyes.
Anthozoa = Anthozoans are either solitary or colonial animals in which there is no medusa phase. The digestive cavity of the polyp is divided by sheets of tissue bearing stinging cells on their edges. Corals are polyps protected by a hard external skeleton composed of calcium carbonate, which forms the material normally thought of as coral. Accumulations of coral in warm shallow seas form coral reefs.
PHYLUM PLATYHELMINTHES
Flatworms are unsegmented, bilaterally symmetrical worms that lack a coelom (acoelomate) but that do have three germ layers. Some forms are free living but many are parasitic. Flatworms have a cephalized nervous system that consists of head ganglion, usually attached to longitudinal nerve cords that are interconnected across the body by transverse branches. Excretion and osmoregulation by flatworms is controlled by "flame cells" located in protonephridia (these are absent in some forms). Flatworms lack a respiratory or circulatory system; these functions take place by absorption through the body wall. Nonparasitic forms have a simple, incomplete gut; even this is lacking in many parasitic species.
Movement in some flatworms is controlled by longitudinal, circular, and oblique layers of muscle. Others move along slime trails by the beating of epidermal cilia. The development of directional movement is correlated with cephalization. In some flatworms, the process of cephalization has included the development in the head region of light-sensitive organs called ocelli. Other sense organs found in at least some members of this group (not necessarily on the head) include chemoreceptors, balance receptors (statocysts), and receptors that sense water movement (rheoreceptors).
Most flatworms can reproduce sexually or asexually. Most are monoecious. Most of these have developed ways of avoiding self-fertilization. Development may be direct (eggs hatch into tiny worms that resemble the adults) or indirect (with a ciliated larval form).
Flatworms include a large number of parasitic forms, some of which are extremely damaging to human populations.
CLASSES
Tubellaria = Most of these flatworms are aquatic and live at the bottom of the sea or fresh waters in sand or mud, under stones and shells or on seaweed. They are usually less than 2.5cm long. (ex. Dugesia)
Trematoda = These parasitic worms are oval to elongated in shape and vary in length from 0.1cm to 7m. Fish are their main hosts. They reproduce sexually. (flukes)
Cestoda = Tapeworms are parasites living in the gut of vertebrates, They are usually long, some reaching12m.
PHYLUM NEMATODA
Roundworms (nematodes) are bilaterally symmetrical, worm-like organisms that are surrounded by a strong, flexible noncellular layer called a cuticle. Their body plan is simple. The cuticle is secreted by and covers a layer of epidermal cells. Near the body wall but under the epidermal cells are muscle cells; they run in the longitudinal direction only. A true coelom is lacking, instead, nematodes have a "pseudocoel" formed directly from the cavity of the blastula (rather than as a result of the division or folding of mesoderm). The cavity of the pseudocoel is small, being mostly filled with an intestine and oviducts or testes. A simple nervous system consists of a ring of nervous tissue around the pharynx that gives rise to dorsal and ventral nerve cords running the length of the body.
Nematodes move by contraction of the longitudinal muscles. Because their internal pressure is high, this causes the body to flex rather than flatten, and the animal moves by thrashing back and forth. No cilia or flagellae are present.
Many nematodes are free living and play critical ecological roles as decomposers and predators on microorganisms. But nematodes also include parasitic species, a number of which affect humans directly or indirectly through their domestic animals. These include the common roundworms, which probably infest more than half the world's humans; hookworms; trichina, the worms that cause trichinosis; pinworms, another extremely common parasite, even in the United States, which can be transmitted from human to human by eggs floating in household dust; and filarial worms, primarily tropical parasites that cause diseases such as filariasis (elephantiasis) and onchocerciasis (river blindness).
PHYLUM ANNELIDA
The annelids include earthworms, polychaete worms, and leeches. All members of the group are to some extent segmented, in other words, made up of segments that are formed by subdivisions that partially transect the body cavity. Segmentation is also called metamerism. Segments each contain elements of such body systems as circulatory, nervous, and excretory tracts. Metamerism increases the efficiency of body movement by allowing the effect of muscle contraction to be extremely localized, and it makes possible the development of greater complexity in general body organization.
Besides being segmented, the body wall of annelids is characterized by being made up of both circular and longitudinal muscle fibers surrounded by a moist, acellular cuticle that is secreted by an epidermal epithelium. All annelids except leeches also have chitonous hair-like structures, called setae, projecting from their cuticle. Sometimes the setae are located on paddle-like appendages called parapodia.
Annelids are schizocoelous and with a large and well-developed true coelom (i.e., one that is lined with mesoderm). Except in leeches, the coelom is partially subdivided by septa. Hydrostatic pressure is maintained across segments and helps maintain body rigidity, allowing muscle contractions to bend the body without collapsing it.
CLASSES
Polychaeta = These marine annelid worms have numerous bristles growing from muscular, fleshy, paddle-lile appendages called parapodia. They are either free-moving or sedentary, and vary greatly in structure and way of life. (ex. Bristleworms)
Oligochaeta = These worms have fewer bristles than the bristle worms and they lack parapodia. All are hermaphrodites, but they usually have a complex reproductive system which eliminates the possibility of self-fertilisation. They range in length from a few centimetres to more than 3m. (ex. Earth worms)
Hirudinea = These parasitic annelids have relatively few segments, a greatly reduced body cavity, and niether bristles or parapodia. They have suckers at both ends of the body with which to cling to their hosts, plants or animals, feeding on sap or blood. They breed in a similar complex way to earthworms and most species are found in water. (leeches)
PHYLUM ARTHROPODA
Characteristics
1. EXOSKELETON In most arthropods the body is covered with chitonous cuticle that is hardened into an exoskeleton. In crustacea and millipedes, the cuticle is hardened by the addition of calcium; in insects, the cuticle is tanned, chemically bonded with protein. Once the cuticle is hardened it can not increase in size. Some regions of the cuticle remain unhardened to allow flexibility and movement.
2. METAMERISM Body composed of numerous segments (somites), segmented condition may be concealed. In the primitive Arthropod, the body was thought to be a series of metameres, each, except for the first and last, with a pair of appendages. Metamerism is an example of an important biological trait, that of replication and modification to develop new traits and capabilities.
3. JOINTED APPENDAGES Jointed appendages give arthropods numerous, generalized appendages which were modified into numerous specialized organs for walking, grasping, and eating.
4. DOUBLE VENTRAL NERVE COR Ventral nerve cord with ganglia(swellings) at each segment. Only the brain (most anterior) ganglia is above the digestive system.
5. OPEN CIRCULATORY SYSTEM A dorsal (upper) vessel directs blood forward toward the brain, an open system allows the blood to circulate back through the body.
6. BILATERAL SYMMETRY Body can be divided into two equal halves through one plane. Most animal groups that are very active are bilaterally symmetrical. But not all animals have bilateral symmetry, some have radial symmetry, e.g.. jellyfish.
7. SEXUAL REPRODUCTION Sexual reproduction or the uniting of female and male gametes is the usual case in arthropods. However, some insects are parthenogenic, females produce female offspring without mating. In the Hymenoptera (bees and wasps) haplodiploidy is common. An example is the honey bee where the queen bee stores sperm and selectively fertilizes her eggs, unfertilized eggs develop into males and fertilized eggs develop into females.
Phylum Arthropoda - Extant Groups
CLASS INSECTA Insects (derivation: in=into, sect=cut; 750,000 known species). Link to Tree of Life - Insecta
• Single pair of antenna
• Three body regions (head, thorax, and abdomen)
• Three pairs of legs (adult insect), one on each segment of thorax
• Most adult insects with wings
CLASS CRUSTACEA Shrimp, lobsters, and crabs (derivation: crust=hard, shell-like; 26,000 known species). Link to Tree of Life - Crustacea.
• Two pairs of antennae
• Two body regions (head and thorax combined into the cephalothorax)
• One pair of appendages per body segment. Appendages terminate in pinchers.
• Primarily an aquatic group, respiration is by gills even in terrestrial species.
• Some very unusual groups, for example, barnacles and water fleas
CLASS DIPLOPODA. Millipedes (derivation: diplo=two, poda=feet; 8,000 known species).
• Single pair of antennae
• Two body regions, head and body
• Body segments fused in pairs, each apparent segment composed of two embryonic segments
• Two pairs of appendages per apparent body segment, extending out from sides of body
• Detritivore
CLASS CHILOPODA. Centipedes (derivation: chilo=lip, poda=feet; 3,000 known species).
• Single pair of antennae
• Two body regions, head and body
• One pair of legs per body segment
• Appendages of first body segment modified into poisonous claws
• Predacious
CLASS ARACHNIDA. Spiders, ticks, mites, scorpions, horseshoe crabs (derivation: arachne=spider; 57,000 known species). Link to Tree of Life - Arachnida.
• No antennae
• Most with a cephalothorax and abdomen. Some with a single body region.
• Most are terrestrial
• Most are predacious.
PHYLUM MOLLUSCA
The molluscs rival the arthropods in their diversity of body forms and sizes, as well as their ecological success. The phylum also provides some of the most familiar animals, such as snails , clams , mussels , squids , and octopus (which, like the arthropods , are well known because they're good to eat). The phylum Mollusca also includes lesser known forms such as the chitons , tusk shells, solenogasters , among others. Approximately 50,000 species of Molluscs have been described, and because of the shelled forms they have left a rich fossil record. However, the earliest molluscs probably arose in the Precambrian , and nothing is known about what they were like.
Systematic summary for the phylum Mollusca :
• Class Gastropoda ( snails, sea slugs)
• Class Pelecypoda (=Bivalvia: clams, mussels, oysters, scallops)
• Class Cephalopoda (squids, octopus, nautilus, cuttlefish)
CLASSES OF MOLLUSCS
Class Gastropoda
Hermissenda crassicornis , Nudibranch (sea slug),class Gastropoda , Order Nudibranchia , from McFarland, 1966.
Most of the approximately 40,000 living species of gastropods have shells, however there are quite a few groups that have either reduced or internal shells, or no shell at all. Shelled forms are generally called "snails " and forms without shells are called "slugs", however the terrestrial slugs are not closely related to the various marine forms that are without shells. Although most Gastropods are marine, there are numerous forms in both freshwater and terrestrial environments.
Class Pelecypoda (=Bivalvia )
Scallop , Pecten sp., class Pelecypoda , Pratt, 1923.
The bivalves include forms such as clams , mussels , scallops , oysters , as well as many less familiar forms. Bivalves are laterally compressed animals, with two shell "valves " that are hinged on the animal's dorsal surface. The approximately 8,000 living species of bivalves are mostly marine, but there are many freshwater species as well (however, no terrestrial ones). Bivalves are found in just about every marine environment, from the intertidal zone to the deepest marine habitats. Most bivalves are suspension feeders, filtering small organisms and organic particles from the water (such as bacteria , phytoplankton , zooplankton , and nonliving organic detritus ).
Class Cephalopoda
Squid , Ommastrephes sp., class Cephalopoda , from Halstead , 1965.
Cephalopods , which include the familiar squids and octopus , include species which are the largest known invertebrates (giant squid , up to 20 meters long, including tentacles), the most intelligent, and the fastest swimming aquatic invertebrates (squid ). There are also forms with external shells (nautilus ), and internal hard shells (cuttlefish ). Most of the approximately 650 living species of Cephalopods are active swimmers, however most species of octopus have secondarily assumed a benthic existence.
Cephalopods have a closed circulatory system, an adaptation to their active lifestyle, as opposed to the open circulatory system found in other molluscs . Squid in particular are often very abundant in pelagic marine environments, where they are voracious predators of many organisms, especially fish. In return, they are also the major prey item of many fish and some marine mammal species.
PHYLUM ECHINODERMATA
Echinoderms form a well-defined and highly-derived clade of metazoans. They have attracted much attention due to their extensive fossil record, ecological importance in the marine realm, intriguing adult morphology, unusual biomechanical properties, and experimentally manipulable embryos. The approximately 7,000 species of extant echinoderms fall into five well-defined clades: Crinoidea (sea lilies and feather stars), Ophiuroidea (basket stars and brittle stars), Asteroidea (starfishes), Echinoidea (sea urchins, sand dollars, and sea biscuits), and Holothuroidea (sea cucumbers). The phylogenetic position of the Concentricycloidea (sea daisies; 2 species), remains controversial (Baker et al. 1986; Smith 1988b; Pearse and Pearse 1994; Mooi et al. 1997).
Characteristics
Echinoderms are among the most distinctive of all animal phyla. Inclusion in the phylum is readily diagnosable on basis of the four synapomorphies below. Most of these features are present, or can be inferred, even in the earliest fossils. Together, these synapomorphies define much of what makes the functional biology of echinoderms distinctive from that of other metazoans.
*Calcitic skeleton composed of many ossicles.
*Water vascular system.
*Mutable collagenous tissue.
*Pentaradial body organization in adults.
PHYLUM CHORDATA
Chordates are defined as organisms that possess a structure called a notochord, at least during some part of their development. The notochord is a rod that extends most of the length of the body when it is fully developed. Lying dorsal to the gut but ventral to the central nervous system, it stiffens the body and acts as support during locomotion. Other characteristics shared by chordates include the following (from Hickman and Roberts, 1994):
• bilateral symmetry
• segmented body, including segmented muscles
• three germ layers and a well-developed coelom.
• single, dorsal, hollow nerve cord, usually with an enlarged anterior end (brain)
• tail projecting beyond (posterior to) the anus at some stage of development
• pharyngeal pouches present at some stage of development
• ventral heart, with dorsal and ventral blood vessels and a closed blood system
• complete digestive system
• bony or cartilaginous endoskeleton usually present.
CLASS AGNATHA (ORDER CYLOSTOMATA)
Lampreys and hagfish are parasites and scavengers.They lack scales and jaws.
Hagfish remain buried in mud, sand or gravel during the day and emerge at night to scavenge on dead animals and organic waste, or to act as parasites on live prey. Their eyes are vistigial and sightless. They hunt by touch and smell; the tip of the snout bears fleshy, sensitive tentacles called barbels
Lampreys attach themselves by suckers to the flanks of fish, then rasp through their prey's flesh and drain it of blood. Adult lampreys die after egg-laying and fertilisation; the eggs are laid in the gravel of stream beds and, although some species return to the sea as they mature, others remain in fresh water
CLASS CHONDRICHTHYES (bone-less fish)
ORDER SELACHII
All sharks are good swimmers, with cigar shaped bodies and gill slits at the side of the head. Most are predarors and some are dangerous to man. There are a few freshwater species. Dogfish are merely small sharks, 1-2 ft long.
ORDER BATOIDEA
Rays have flat bodies with wing-like pectoral fins attached to the sides of the head.
CLASS OSTEICHTHYES
Boned fish
CLASS AMPHIBIA
Amphibia refers to "double life", or life in water and on land
Includes the salamanders, frogs, toads, and caecilians with approximately 3,900 spp.
Characterized by:
• Being tetrapods (4 limbs) that facilitate moving about on land - these limbs evolved from the pectoral and pelvic fins
• Skin is thin, soft, glandular and magid (lack scales except in the caecilians) - skin of caecilians with scales similar to those of fish
• Ectothermic
• Both gill and lung breathers - usually gills in the larval stage, replaced by lungs in the adult; cutaneous respiration in many
• Three-chambered heart with two atria and one ventricle
Amphibian reproduction variable
• fertilization may be internal or external
• egg-layers (oviparous) but may have modifications associated with development
• egg anamniotic - doesn’t have a shell but covered with a series of gelatinous layers
• hatchling in aquatic larval form which breath by gills
• most larvae herbivorous, some omnivorous to carnivorous
• larval stage may last from 10 days to 20+ years
The Orders of Class Amphibia
Apoda
legless amphibians
Urodela
newts and salamanders
Anura
frogs and toads
CLASS REPTILIA
Reptiles are a highly successful group of 6,547 different species. Since reptiles are cold blooded, they do not need to consume as much food to maintain a body temperature. This gives them a great advantage over warm-blooded mammals, especially in desert areas where vegetation can be sparse. Reptiles can be distinguished from amphibians by their scaly skin. In addition, reptiles either lay eggs or give birth to live babies. They do not have the larval stage like amphibians (the frog has the tadpole stage).
The Orders of Class Reptilia
Chelonia
turtles and tortoises
Squamata
lizards and snakes
Crocodilia
crocodiles
CLASS AVES
Birds are vertebrates with feathers, modified for flight and for active metabolism. Birds are a monophyletic lineage, evolved once from a common ancestor, and all birds are related through that common origin. There are a few kinds of birds that don't fly, but their ancestors did, and these birds have secondarily lost the ability to fly. Modern birds have traits related to hot metabolism, and to flight:
• horny beak, no teeth
• large muscular stomach
• feathers
• large yolked, hard-shelled eggs. The parent bird provides extensive care of the young until it is grown, or gets some other bird to look after the young.
• strong skeleton
The Orders of Class Aves
Apterygiformes
kiwis
Struthioniformes
ostrich
Sphenisciformes
penguins
Anseriformes
screamers and ducks
Falconiformes
eagles, hawks and vultures
Columbiformes
pigeons
Psittaciformes
parrots
Cuculiformes
cuckoos and turacos
Strigiformes
owls
Coraciiformes
kingfishers, hornbills and allies
Piciformes
woodpeckers, barbets and toucans
CLASS MAMMALIA
Hair is a defining characteristic of mammals: no other organisms possess true hair and all mammals have hair covering at least part of their body at some time during their life. Hair grows from skin cells known as follicles. The hair shaft is made of a protein called keratin. Hair serves numerous functions.
When present as a thick covering over the animal's body (known as pelage), it provides insulation. The pelage of most mammals is a mosaic of different kinds of individual hairs (such as guard hairs, barbs, bristles, awns, underfur, wool, fur, and velli; each of these has a different structure and serves a slightly different purpose).
Another characteristic unique to mammals is the presence of mammary glands. Mammary glands, like hair, are a uniquely mammalian trait. Though present in both males and females, mammary glands only fully develop in females. Mammary glands consist of ducts and glandular tissues that secrete milk through nipples. Young mammals obtain milk from their mother by feeding from her nipples. The milk provides the young with much needed protein, sugars, fat, vitamins, and salts.
Mammals are also characterized by having a diaphram, a four-chambered heart, and a large cereberal cortex. Additionally, some mammals hibernate during time periods when resources are scarce, such as during the winter season.
The Orders of Class Mammalia
Monotremata
egg-laying mammals
Marsupialia
pouched mammals
Insectivora
insect-eating mammals
Chiroptera
bats
Primates
mostly tree-dwelling mammals
Cetacea
whales
Lagomorpha
pikas, hares and rabbits
Rodentia
rodents
Carnivora
flesh-eating mammals
Pinnipedia
seals, sea lions and walrus
Proboscidea
elephants
Sirenia
sea-cows
Perissodactyla
odd-toed hoofed mammals (rhino, horse, zebras)
Artiodactyla
even-toed hoofed mammals (pigs, hippos, camels, giraffes, deers, cattle)
