BIO 102 animal kingdom 1

Basis for Animal Kingdom Classification

• Levels of Organisation

• Symmetry

• Diploblastic and Triploblastic Organisation

• Coelom

• Segmentation

• Notochord

Classification of Animal Kingdom

Introduction to Kingdom Animalia

• Kingdom Animalia encompasses all animals, making it the largest kingdom.

• Animals are multicellular eukaryotes lacking chlorophyll and cell walls.

• They exhibit a heterotrophic mode of nutrition.

• The animal kingdom ranges from simple to complex organisms.

• It is classified into ten subphyla based on body design and differentiation.

• With over a million described species, classification is crucial for systematic organization and assigning new species.

Basis of Classification

• Fundamental features used:

  • Arrangement of cells

  • Body symmetry

  • Nature of coelom

  • Patterns of digestive, circulatory, and reproductive systems

Different Levels of Organization

• Chemical and Molecular Level: Atoms form molecules; molecule shape determines function.

• Cellular Level: Molecules form organelles; organelles perform specific functions; cells are the smallest living units.
  *Example: Protein filaments in muscle cells.

• Tissue Level: Similar cells performing specific functions.
  *Example: Cardiac muscle cells forming heart muscle tissue.

• Organ Level: Two or more tissues performing multiple functions.
  *Example: Heart wall composed of cardiac muscle and connective tissue.

• Organ System Level: Organs interacting within systems.
  *Example: Heart, blood, and blood vessels forming the cardiovascular system.

• Organism Level: All organ systems working together to maintain life.

Levels of Organisation within Animalia

• All animals are multicellular but vary in cellular organization.

• Cellular Level: Cells arranged as loose aggregates with some division of labor.
  *Example: Sponges (phylum Porifera).

• Tissue Level: Cells performing the same function are organized into tissues.
  *Example: Coelenterates.

• Organ Level: Tissues grouped to form organs specialized for particular functions.
  *Example: Platyhelminthes and higher phyla.

• Organ System Level: Organs associated to form functional systems for specific physiological functions.
  *Example: Annelids, Arthropods, Molluscs, Echinoderms, and Chordates.

• Organ systems can exhibit varying complexities.

  • Incomplete Digestive System: Single opening for both mouth and anus.
    *Example: Platyhelminthes.

  • Complete Digestive System: Two openings – mouth and anus.

  • Circulatory System:

    • Open Type: Blood pumped out of the heart bathes cells and tissues directly.

    • Closed Type: Blood circulates through vessels of varying diameters (arteries, veins, capillaries).

• $\text{Cells } \rightarrow \text{ Tissues } \rightarrow \text{ Organs } \rightarrow \text{ Organ System } \rightarrow \text{ Organism}$

• Complex organisms, like humans, have all four levels of organization.

Symmetry in Animals

• Animals are categorized based on symmetry.

• Asymmetrical: No plane divides them into equal halves.
  *Example: Sponges.

• Radial Symmetry: Any plane through the central axis divides the organism into identical halves.
  *Example: Coelenterates, ctenophores, and echinoderms.

Characteristics of Radial Symmetry

• Oral side (containing the mouth) and aboral side (without the mouth).

• Absence of dorsal (back) and ventral (belly) surfaces.

• Commonly aquatic; many are sessile or weakly swimming.

• Differences between dorsal and ventral surfaces aid in floating upright (jellyfish) or gripping rocks (sea anemones).

• Bilateral Symmetry: Body divided into identical left and right halves in only one plane.
  *Example: Annelids, arthropods.

Characteristics of Bilateral Symmetry

• Dorsal and ventral surfaces; cephalic (head) and caudal (tail) ends.

• Well-suited for directional movement.

• Generally move head first.

Diploblastic and Triploblastic Organization

• Diploblastic Animals: Cells arranged in two embryonic layers – ectoderm and endoderm.
  *Example: Coelenterates. Mesoglea (undifferentiated layer) present between ectoderm and endoderm.

• Triploblastic Animals: Developing embryo has a third germinal layer – mesoderm – between ectoderm and endoderm.
  *Example: Platyhelminthes to chordates.

Coelom (Body Cavity)

• Presence or absence of a cavity between the body wall and gut wall is critical for classification.

• Coelom: Body cavity lined by mesoderm. Animals possessing a coelom are called coelomates.
  *Example: Annelids, molluscs, arthropods, echinoderms, hemichordates, and chordates.

• Pseudocoelom: Body cavity not lined by mesoderm; mesoderm present as scattered pouches between ectoderm and endoderm. Animals possessing a pseudocoelom are called pseudocoelomates.
  *Example: Aschelminthes.

• Acoelomates: Animals lacking a body cavity.
  *Example: Platyhelminthes.

Advantages of a Coelom

• More room for organ development.

• Increased surface area for gas, nutrient, and waste diffusion.

• Area for storage.

• Acts as a hydrostatic skeleton.

• Vehicle for waste and reproductive product elimination.

• Facilitates increased body size.

Segmentation

• Body divided into segments externally and internally with serial repetition of some organs. Each segment has organ system subdivisions.
  *Example: Earthworm exhibiting metameric segmentation.

• Metamerism: Pattern of segmentation.

• Ideal metamerically segmented animal: Each segment has reproductive, excretory organs, skin, muscles, nerves, and circulatory structures.

• Segmentation facilitates differential development for different uses in different body regions.
  Example: Annelids.

Notochord

• Mesodermally derived rod-like structure formed on the dorsal side during embryonic development.

• Chordates: Animals with a notochord.

• Non-chordates: Animals without a notochord.
  *Example: Porifera to echinoderms.

Classification of Animals

• Broad classification of Animalia based on fundamental features.

Phylum - Porifera (Sponges)

• Characteristics

  • Cellular level of organization, lacking true tissues.

  • Adults exhibit radial symmetry or asymmetry.

  • Possess totipotent cells.

  • Unique flagellated choanocytes create water flow through a canal system.

  • Outer and inner cell layers lack a basement membrane.

  • Non-cellular mesohyl layer divides outer and inner cell layers; contains cells and skeletal material.

  • Body support: Spicules of calcium carbonate or silicon.

• Mostly marine, asymmetrical animals.

• Primitive multicellular animals with cellular level organization.

• Water transport system (canal system) for food gathering, respiratory exchange, and waste removal.

  • Water enters through ostia (minute pores) into spongocoel (central cavity), exits through osculum.

  • Choanocytes (collar cells) line spongocoel and canals.

• Intracellular digestion.

• Skeleton of spicules or spongin fibers.

• Sexes not separate (hermaphrodite); eggs and sperm produced by the same individual.

• Asexual reproduction by fragmentation, sexual reproduction by gamete formation.

• Internal fertilization; indirect development with a morphologically distinct larval stage.

• Examples: Sycon (Scypha), Spongilla (freshwater sponge), Euspongia (bath sponge).

Types of Sponge Cells

• Cells loosely arranged in a gelatinous matrix (mesenchyme or mesohyl).

  • Pinacocytes: Protective and contractile.

  • Choanocytes: Create water currents and engulf food particles.

  • Archaeocytes: Phagocytize particles, receive particles for digestion from choanocytes.

  • Collencytes: Secrete collagen.

Classification of Sponges

• Demospongiae (bath sponges): 95% of living sponges; siliceous spicules (not six-rayed) bound by spongin or absent.
  *Example: Cliona, Spongilla.

• Calcarea (calcareous sponges): CaCO3 spicules.
  *Example: Sycon.

• Hexactinellida (glass sponges): Six-rayed, siliceous spicules.
  *Example: Hyalonema.

• Homoscleromorpha (marine sponges): Spicules may be absent or small and simple.
  *Example: Oscarella, Corticium.

Phylum - Coelenterata (Cnidaria)

• Characteristics

  • Includes corals, jellyfish, Hydra, sea anemones, sea fans, siphonophores, zoanthids, myxozoans (approx. 11,000 species).

  • Unique cnidae (nematocysts) for stinging or adhesion.

  • Ectoderm and endoderm separated by mesoglea (connective tissue-like layer).

  • True gut (coelenteron) with digestive and circulatory function (gastrovascular cavity).

    • Single opening (mouth/anus).

  • Musculature from myoepithelial cells.

  • No head, centralized nervous system, gas exchange, excretory, or circulatory structures. Primitive nerve net.

  • Life histories alternate between asexual polypoid and sexual medusoid generations (Metagenesis).

  • Planula larvae.

  • Mainly marine environments; some hydrozoans in fresh waters.

• Composed of 4 classes: Hydrozoans, Scyphozoans (True jellyfish), Cubozoans (sea wasps, box jellyfish), and Anthozoans.

• Aquatic, mostly marine, sessile, or free-swimming; radially symmetrical.

• Cnidaria named for cnidoblasts or cnidocytes (stinging capsules/nematocytes) on tentacles and body used for anchorage, defense, and prey capture.

• Tissue level organization; diploblastic.

• Central gastro-vascular cavity with a single opening (mouth) on hypostome.

• Extracellular and intracellular digestion.

• Some cnidarians (corals) have skeletons of calcium carbonate.

• Two basic body forms: polyp (sessile, cylindrical) and medusa (umbrella-shaped, free-swimming).

• Metagenesis: Polyps produce medusae asexually; medusae form polyps sexually.
  *Example: Obelia.

Polypoid and Medusoid Body Forms

• Medusa: Free-swimming, umbrella-like form with tentacles. Thick mesoglea makes up body mass (jellyfish).

• Some species exist only in polypoid form, others only in medusa form, some in both during the life cycle.

• Colonial aggregations are common in polyps.

Three Classes of Cnidaria

• Scyphozoa: Solitary medusoid forms; reduced polyp stage.

  • Medusa dominant, umbrella-shaped. Polyps often absent. Mesoglea cellular.

  • Marine animals.

  • Aurelia aurita (Jellyfish), Rhizostoma.

  • Medusae can injure or kill humans.

• Hydrozoa: Solitary or colonial forms.

  • Asexual polyps and sexual medusae (one type may be suppressed). Marine or freshwater.

  • Acellular mesoglea.

  • Hydra, Obelia, Tubularia, Physalia physalis.

• Anthozoa: All polyps.

  • Solitary or colonial. Gonads are gastrodermal. Marine.
    *Example: Sea anemones and corals.

Phylum - Ctenophora

• Commonly known as sea walnuts or comb jellies.

  • Free-living marine organisms.

  • Diploblastic (ectoderm and endoderm; mesoglea).

  • Acoelomates (no body cavity).

  • Radially symmetrical.

  • Tissue level organization.

  • Ciliated comb plates for locomotion (eight rows).

  • Colloblasts (adhesive cells) to capture prey.

  • Sensory cells in outer epidermis.

  • Interstitial cells can transform into other cell types.

  • Internal cavity formed by mouth, pharynx, and internal canals; lined by gastrodermis.

  • Gastrodermis contains nutritive cells, germ cells, and photocytes.

  • Digestion is extracellular and intracellular.

  • Nerve net around the mouth region, concentrated in comb rows and tentacles.

  • Statocyst in aboral region for sensory function (balancing organ).

  • Bisexual; sexes not separate.

  • Sexual reproduction; external fertilization; indirect development.

  • Some produce sperm and eggs at the same time, some at different times.

  • Platyctenids reproduce by fragmentation and show internal fertilization.

  • Regeneration of damaged tissues.

  • Bioluminescence.

Characteristics of Ctenophora

• Exclusively marine, radially symmetrical, diploblastic organisms with tissue level of organization.

• Eight external rows of ciliated comb plates aid in locomotion.

• Digestion both extracellular and intracellular.

• Bioluminescence is well-marked.

• Sexes are not separate.

• Reproduction takes place only by sexual means.

• Fertilization is external with indirect development.

• Examples: Pleurobrachia and Ctenoplana.

Phylum - Platyhelminthes (Flatworms)

• General Characteristic Features

  • Bilaterally symmetrical.

  • Dorsoventrally flattened.

  • Triploblastic.

  • Acoelomate.

  • Complete reproductive organs.

  • Digestive system absent in some; if present, has only the mouth but no anus; incomplete.

  • Ladder-like nervous system with simple sense organs.

  • No respiratory, circulatory, or skeletal system.

  • Protonephridial excretory system.

• Mostly endoparasites in animals, including humans.

• Hooks and suckers in parasitic forms.

• Nutrient absorption directly through the body surface in some.

• Flame cells for osmoregulation and excretion.

• Hermaphroditic with well-developed reproductive organs (sexes not separate).

• Internal fertilization; development through many larval stages.

• High regeneration capacity.

• Examples: Taenia (Tapeworm), Fasciola (Liver fluke).

Classification of Platyhelminthes

The phylum Platyhelminthes is classified into three main classes.

• Turbellaria: Mostly free-living and aquatic, with soft leaf-like bodies; ciliated body covering; some terrestrial in humid areas; one opening to the gut.
  *Example: Planaria.

• Trematoda: Parasitic; lacking cilia; cuticle covering leaf-like body with one or more suckers. Found in vertebrates, infecting the digestive system, liver, blood vessels, lungs, and other organ systems. May be hermaphroditic or have separate sexes.
  *Example: Fasciola hepatica (liver fluke), Schistosoma (blood fluke).

• Cestoda: Endoparasites, lacking a gut (digestive) system. Parasites in the digestive tracts of vertebrates. Ribbon-like, made up of many segments (proglottids) with an anterior scolex carrying suckers and hooks.
  *Example: Taenia solium, Taenia saginata (tapeworms).
  Monogenea (gill Flukes)

Monogenea (Gill Flukes)

• The parasitic class Monogenea includes Dactylogyrus spp., commonly called a gill fluke.

• They are ectoparasites, mostly of fish, with simple lifecycles that consist of a free-swimming larva that attaches to a fish to begin transformation to the parasitic adult form.

• The parasite has only one host and that host is usually only one species.

• The worms may produce enzymes that digest the host tissues or simply graze on surface mucus and skin particles.

• Most monogeneans are hermaphroditic, but the male gametes develop first and so cross-fertilization is quite common

Phylum – Aschelminthes (Roundworms)

• Aschelminths can be free-living or parasitic.

• The free-living organisms are extremely abundant in soils and sediments and they feed on bacteria.

• Some are plant parasites and can cause disease in crops that are economically important.

• Parasitic worms include hookworms, pinworms, Guinea worms, and intestinal roundworms.

Characteristics of Aschelminthes

• Unsegmented and triploblastic body.

• Pseudocoelom; body cavity not lined by mesoderm.

• Bilateral symmetry.

• Cylindrical or thread-like body with elongated, slender, worm-like appearance, tapering at both ends.

• Body wall with epidermis, muscle layer, and cuticle.

• Size varies from microscopic to several centimeters.

• Mostly parasitic, with few free-living forms.

• Organ system level of organization.

• Little external differentiation between anterior and posterior regions, but internal cephalization is present.

• No distinct head; mouth present in the anterior.

• Complete digestive system with mouth and anus.

• Terminal mouth surrounded by lips bearing sense organs.

• Amphids and papillae are the main sensory organs.

• Nervous system consists of a nerve-ring that encircles the oesophagus; nerves extend anteriorly and posteriorly.

• Respiratory organs are absent; respiration occurs through the general body surface (aerobic in free-living, anaerobic in parasitic forms).

• Excretory system has canals and gland-like structures.

• Sexes are separate and unisexual, exhibiting sexual dimorphism.

• Fertilization is internal.

• Ovoviviparous, oviparous, or viviparous.

• Complicated life cycle with or without an intermediate host.

• Examples: Ascaris Lumbricoides, Wuchereria sp.

• Roundworm Ascaris Lumbricoides is a parasite in the intestine of man

  • They are usually found in the intestinal cavity of man, surrounded by already digested food from which it obtains nutrients

  • It undergoes holozoic mode of nutrition; it causes lethargy, weakness, dizziness, vomiting, headache, anemia and pain in the intestine

Diseases Caused by Aschelminthes

• Ascariasis: Caused by Ascaris lumbricoides in humans; abdominal pain, diarrhea, vomiting.

• Ancylostomiasis: Hookworm infection in the small intestine; causes anaemia.

• Filariasis: Caused by roundworms; lymphatic filariasis by Wuchereria bancrofti, Brugia timori, and Brugia malayi causes thickening of the skin and tissues.

• Loa loa causes subcutaneous filariasis, infecting the eyes and skin.

• Enterobiasis: Pinworm Enterobius vermicularis; causes itching in the anal area and sleeping discomfort.

• Other diseases include trichuriasis, strongyloidiasis, trichinosis, etc.

• Nematodes cause plant diseases such as root-knot, root-lesion, cyst, burrowing, etc.

• Bacillus thuringiensis (Bt) produces insecticidal proteins (toxins) effective against nematodes.

Classification of Aschelminthes

• Include several classes such as;

  • Nematoda

  • Nematomorpha

  • Rotifera

  • Gastrotricha

  • Kinorhyncha

Order Oxyuroidea (Enterobius Vermicularis)

• Commonly known as pinworm (threadworm).

• One of the most common worm of man, particularly children.

• Thread like, whitish or cream in color.

• The pinworm infection is called enterobiasis.

• The movement of the female worm around the peri-anal region of children causes intense itching.

• The most common symptom is itching in the anal area

Order Ascarordia

• Ascaris is the most common roundworm

• They are quite large and found as intestinal parasites in vertebrates

• Sexual dimorphism is well distinct

• only sexual reproduction takes place
  Pathogenicity

• The disease caused by Ascaris is called Ascariasis

• Degree of pathogenesis depends upon the number of worms present in the intestine

• It causes more harm to the children than adult

• Pathogenesis caused by adult Ascaris

  • Abdominal discomforts like vomiting and colic pains, interferes in protein digestion

• Absorb host’s digested food resulting in malnutrition and hence shunted growth

• Irritation of mucous membrane results in involuntary muscular contractions. Acute infection can cause coma and death

• Can cause appendicitis and hepatitis. Larva: It may prove to be more harmful than the adult by causing hemorrhages.

Order Strongyloidea

Pathogenicity

• The larvae penetrations the skin and causes tiny irritating sores and inflammation of the skin

• Damage is done to the vital organs for example brain, heart, kidney, particularly lungs by the circulating larva.

• The maximum damage is done by the adult by forming wounds in the walls of the intestine from where the blood keeps on flowing, causing blood stools, severe anemia, lower immunity and the host becomes lethargic.

Order Filarioidea

• It is also called filarial worm

• The effect caused by the adult Wuchereria is called Wuchereriasis, more filariasis

• The pathologic effects are due to the adult living worm, as well as the dead worm

• The microfilariae present in the blood do not cause any pathological effect

Phylum - Annelida (Segmented Worms)

• Coelomate and triploblastic.

• Organ system level organization.

• Segmented body covered with a thin cuticle.

• Respire through body surface; true closed circulatory system.

• Nephridia for excretion.

• Well-developed circulatory and digestive systems.

• Body contains haemoglobin for red color.

• Regeneration is a common characteristic.

• Setae help them in movement.

• Most are hermaphrodite (male and female organs in the same body); reproduce sexually and asexually. Others reproduce sexually.

• Aquatic (marine and freshwater) or terrestrial; free-living, or sometimes parasitic.

• Exhibit organ-system level organization and bilateral symmetry.

• Triploblastic, metamerically segmented, and coelomate animals.

• Body surface marked into segments or metameres

• Longitudinal and circular muscles which help in locomotion

• Aquatic annelids like Nereis possess lateral appendages, parapodia which help in swimming

• Closed circulatory system is present
  Examples: Earthworms, and leeches

Classification of Phylum Annelida

• Polychaeta (many chaetae/hairs): Mostly marine; distinct head with eyes and tentacles; segmental with lateral parapodia; sexes separate; asexual reproduction via budding.
  *Example: Nereis.

• Oligochaeta (few chaetae/hairs): Live in soil or freshwater; conspicuously segmented but no distinct head; parapodia absent, setae present; hermaphroditic; clitellum present; no larva, direct development.
  *Example: Earthworm.

• Hirudinea: Mostly ectoparasitic and freshwater; elongated, flattened dorsoventrally, with reduced coelom; definite number of segments; anterior and posterior suckers; hermaphrodite, sexual reproduction.
  *Example: Leeches.
  structural adaptation of the earthworm

• the body wall forms a protective covering for all the enclosed internal parts

• the mucus in the epidermis underlying the body wall keeps the skin of the earthworm Slimy and clean and does not carry any foreign germs to settle in it

• the body wall serves as the only organ of respiration because of its thin pervious and highly vascularized nature

• the skin serves as an efficient receptor organ

• mucus acts as cement for plastering the walls of the burrow

• the setae aid in locomotion

• the earthworm feeds in decaying leaves and humus present in the soil

• the Earthworm excretes waste products with the aid of an organ known as Nephridia

Phylum - Arthropoda (Joint-Legged Animals)

• Triploblastic, coelomate, metamerically segmented.

• Jointed appendages modified for various purposes.

• Living in marine, freshwater, and terrestrial habitats; many are capable of flight.

• Exoskeleton of chitin, periodically moulted for growth.

• Body divided into head, thorax, and abdomen.

• Reduced coelom in adults; body cavity consists of haemocoel filled with blood.

• Possession of striated and non-striated muscles

• Complete digestive system with mouth-parts for different methods of feeding

• Open blood system; dorsal heart distributing blood by arteries to organs and tissues, returns through haemocoel to the heart.

• cilia and flagella are absent

• Respiration is through body surface, spiracles, trachea, gills or lung books.

• Excretory system by green or antennary gland in aquatic ones and malpighian tubules in terrestrial ones.

• Well-developed nervous system, consisting of paired dorsal ganglia over the mouth, a ring or collar round the gullet and a ventral chain of ganglia

• Pronounced cephalisation with definite anterior end where sensory organs are concentrated.

• Sexes nearly always separate

• Fertilization is internal and most arthropods undergo a more or less extensive metamorphosis
  *Examples: crayfishes, crabs, spiders, ticks, scorpions, mites, millipedes etc

• Arthropods are said to have evolved from annelids, with which they show certain similarities.

• The Phylum Arthropoda may be classified, based on their diversity of appendages, lifestyles, and other features, as shown in Table 1

Classification of Arthropods

The various classes of arthropods are:

• Insecta: e.g. Grasshopper, Cockroach, housefly, butterfly

• Arachnida: e.g. Spider, Scorpion, Mites, Ticks

• Crustacea: e.g. Crab, Crayfish, Shrimps, Prawns, Lobsters

• Myriapoda: e.g. Centipedes and Millipedes

Subphylum Trilobita (Primitive Arthropods - Trilobites)

• An extinct group of arthropods.

• Body molded longitudinally into three lobes (Trilobitomorpha).

• A pair of antennae and appendages on post-antennal somites were of a common type.

• Marine arthropods, numerous in Cambrian and Silurian periods, extinct by secondary period.

• E.g. Olenus

Subphylum Chelicerata

• Includes spiders, scorpions, and ticks.

• No antennae.

• First pair of appendages (chelicerae) used in feeding.

• Body divided into prosoma (head and thorax/cephalothorax) and opisthosoma (abdomen).

• Made up of three classes: Merostomata (horseshoe crabs); Pycnogonida (sea spiders); Arachnida (spiders, ticks, mites, scorpions)

subphylum crustacea

• Crustaceans can generally be distinguished from the other groups of Arthropods by the possession of two pairs of antennae

• By the presence of biramous limbs.

• Cephalocarida(Cephalocarid)

• Branchiopoda (brine shrimps, water fleas)

• Ostracoda ( mussel shrimps)

• Mystacocarida (mystacocarid)

• Copepoda (copepod)

• Branchiura (fish lice, Argulus nobilis)

• Cirripedia ( Barnacles)

• Malacostraca (crayfishes)

• Remipedia (remipede

Subphylum Uniramia

• Individuals with uniramous (single-branched) appendages.

• One pair of antennae and two pairs of mouthparts (mandibles and maxillae).

• Includes millipedes, centipedes, and insects.

• Most common and diverse major group of arthropods.

• Very important both economically and ecologically.

• Insecta

• Chilopoda (centipedes).

• Diplopoda (millipedes).

Myriapodous Arthopods

• Symphyla (Scutigerella)

• Pauropoda (Pauropus)

The Class Insecta

*This is the largest phylum of Animalia which includes insects.

• Over two-thirds of all named species on earth are arthropods.

• They have organ-system level of organisation.

• They are bilaterally symmetrical, triploblastic, segmented and coelomate animals.

• The body of arthropods is covered by chitinous exoskeleton.

• The body consists of head, thorax and abdomen.
  *They have jointed appendages
  Respiratory organs are gills, book gills, book lungs or tracheal system
  Classifaction of insects

Subclasses & Features

Apterygota
*These are wingless insects and their body structure suggests that they have never had wings during the course of evolution.
*Young stages resemble the adults - no metamorphosis
*Their mouthparts are partially enclosed within the head capsule/withdrawn into head.
Pterygota
*Division Exopterygota
*These are winged insects, although some have lost their wings during the course of evolution.
*When present, the wings develop externally and there is no marked change (metamorphosis) during the life cycle
Pterygota
*Division Endopterygota
*These are winged insects, although some have lost their wings during the course of evolution.
*When present, the wings develop internally (i.e. inside the body of the immature insect) and there is a marked change
*metamorphosis

Economic Importance of Insect

• The activities of insects have impacted directly and indirectly, and positively and negatively on the existence of humans on earth.
  *They are often studied on their own under the subject of entomology.
  Beneficial ways in which they are to humans

• Some are sources of food for humans e.g. honey from the honeybee; termites, grubs etc.

• They pollinate flowers and consequently aid in fruit formation, vegetation cover, etc.

• They produce important raw materials for industries e.g. silk from the silkworm.

• They constitute food for other animals in the biosphere e.g. lizards, toads and fish, all feed on insects.

• They help in the decomposition of dead organic matter by scavenging. E.g. dung beetles.
  *They form important research tools (Drosophilla)
  Harmful efffects

• Serve as vectors of bacterial and viral plant diseases.
  *Some are vectors of important parasitic diseases of humans and animals e.g. tsetse flies , mosquitoes etc.
  *They are parasites of humans and plants e.g. lice, fleas, bedbugs etc.

Phylum - Mollusca (Soft-Bodied Animals)

• This is the second largest animal phylum.

• Molluscs are terrestrial or aquatic (marine or fresh water) having an organ-system level of organization.

• They are bilaterally symmetrical, triploblastic and coelomate animals.

• Body is covered by a calcareous shell and is unsegmented with a distinct head, muscular foot and visceral hump/ mass.

• Visceral hump contains digestive and excretory organs, also the heart.

• A soft and spongy layer of skin forms a mantle over the visceral hump.

• The calcareous shell is secreted by glands in the mantle.

• The space between the hump and the mantle is called the mantle cavity in which features like gills are present.
  *They have respiratory and excretory functions.
  *Fertilization external
  example pila
  defining characteristics
  *dorsal epithelium (forming a mantle, cuticular band of teeth (radula)
  mollusca body plan
  *large muscular foot usually.
  usually small head.
  *SOFT unsegmented body

• hard NON-living cacareous
  Classsification;phylum mollusca is then divided into seven classes
  Importance of molluscs to humans
  *1.Bivalves such as clams and mussels have been an important food source for many different people around the world
  *Research at the University of Otago in New Zealand has shown that jelly produced from squid pen can be used in wound healing.
  painsful stings and fatalities in humans have been reported.

Phylum – Echinodermata (Spiny-Skinned Animals)

• Have an endoskeleton of calcareous ossicles.
  Characteristics
  *They are penta radially symmetrical coelomate animals
  with locomotion and respiratory purposes
  Body wall is made up of a ciliated epidermis underneath which is a dermis that contains calcareous ossicles, which give rise to spines. .
  with organ system level organisation
  classified into crinozoa, sterozoa and echinozoa

  classifications subhphyla
  Classification

Phylum - Hemichordata

• Earlier considered a sub-phylum under Chordata but now is placed as a separate phylum under non-chordata.

• They are marine animals that feed on fine particles in the water
  characteristics
  *Organ system level of organization, marine worm with proboscis, collar and trunk

• Bilaterally symmetrical, triploblastic and coelomate animals.
  *stomochord
  The hemichordates share some (but not all) of the typical chordate characteristics. They have bronchial openings, or "gill slits," that open into the pharynx; there is a rudimentary structure in the collar region called the stomochord,
  The enteropneuets are slow mud burrowers that have well developed gills

Phylum - Chordata (Animals with a Notochord)

• About 48,000 species, very diverse phylum and the most advanced phylum of animal kingdom.

• Included are fish, amphibians, reptiles, birds and other mammals
  Major Identifying Characteristics
  *the presence of a notochord flexible rodd like structure by a sheath
  dorsal hollow nerve cord single dorsal and the front end usually enlarged to form brain
  pharyngeal gill slits
  A post-anal tail
  have four major characteristic features namely, notochord, dorsal nerve cord, post anal tail and pharyngeal slits.
  Chordates and Non - chordates
  Phylum Chordata is divided into 3 subphyla: Urochordata, Cephalochordata and Vertebrata.
  specifically kind found only in chordates and was originally part of the feeding apparatus
  Most are sessile as adults , attached to rocks
  Haemocyanin as blood pigment

Subphylum: Cephalochordata

• The cephalochordates are the most advanced protochordates which show the five basic features of chordates throughout their life
  gill slits
  external fertilization
  subphylum vertebrata (craniata)
  separate males and females
  lack jaws

CLASS – CYCLOSTOMATA

*All living are ectoparasites on some fishes
marine by die in fresh water
Petrozimon
The super class gnathostomata
The super