Body Symmetry Coelomate Symmetrical Acoelomate no mesoderm Pseudocoelomate

Body Symmetry & Coelomate

Symmetrical

Acoelomate no mesoderm

Pseudocoelomate mesoderm attach to one side but no cleavage

Coelomate mesoderm cleavage with coelom inbetween

Segmented Body

Porifera (spongy) • Asymmetric body • Lack of body organizaiton

Structure • Spicules as structural component • Choanocyte for water flow and feeding

Adaptive features Gaseous exchange diffusion Nutrition Choanocyte filtering Support water Fertilization external Embryo develop no Movement no Special features Asymmetical no mouth no anus

Introduction to coelenterata +Radially symmetrical +Diploblastic +With nematocysts for food capture and protection

+No blood, respiratory, or excretory organs +A network of nerve cells and fibres exists in body wall +Single internal cavity with only opening to the exterior, the ‘mouth’ which is surrounded by tentacles +Reproduction by assexual budding in polyp stage, sexual reproduction by eggs and sperm in medusa stage

Polyp and Medusa • Polyp • body is tubular or cylindrical • oral end, bering the mouth and tentacles, is directed upwards, and the opposite, or aboral end is attached • layer of mesoglea is thin

Polyp

+ Medusa + body resembles a bell or umbrella, with the convex side upward and the mouth located in the cneter of the concave under-surface + tentacles hang downwards from the margin of the ‘bell’ + layer of mesoglea is extremely thick

Medusa

Adaptive features Gaseous exchange diffusion Nutrition Holozoic by nematocyst Support water Fertilization external Embryo develop external Movement Only in larva and medusa Special features Nematocyst, polyp, medusa Radial symmetrical, acoelomate

Nematoblasts + Nematoblasts 1. they are in the ectoderm 2. each consists of highly complex organelle, nematocyst, which is a minute capsule filled with fluid and containing a coiled, barbed thread tube

+ when the triggering device, cnidocil, on the outer surface of the nematoblast is stimulated, the thread tube everts to aid in capture of prey, protection or locomotion

Morphology of Obelia 1. Classification – Class Hydrozoa (hydroids) 2. Habitat – lives in shallow coastal water attached to substratum + Morphology – – – exists in 2 distinctly different forms in its life colonial form (polyps) free living form (medusa)

The colonial form

Medusa

Sea Anemone

Introduction to Platyhelminthes +Triploblastic, bilaterally symmetrical, acoelomate and unsegmented +Body is flattened dorsoventrally +Digestive system incomplete –a mouth but no anus +No skeletal, circulatory, or respiratory systems; excretory system of many flame cells joined to excretory ducts

+Nervous system primitively a simple nerve net, but advanced forms have a pair of anterior ganglia or a nerve ring and 1 to 3 pairs of longitudinal nerve cords with transverse connectives +Complex hermaphroditic reproductive system; internal fertilization; development either direct or with 1 or more larval stages

Adaptive features Gaseous exchange Flattened, diffusion Nutrition Holozoic in planaria or parasitic Support no Fertilization Hermaphrodite Embryo develop Egg external Movement muscle Special features Bilateral symmetrical, acoelomate

Planaria 1. Habitat – the common planaria inhabit cool , clear permanent lakes and streams, where they avoid light by clinging to the under surface of stones or logs in the water

Structure

Cross section of body

Tapeworm 1. Habitat – – The adult stage lives in the small of its primary host (e. g. man) i. e. it is an endoparasite The immature stage lives inside the body of the secondary host (e. g. pig)

Structure

Life Cycle

Nematoda

Adaptive features Gaseous exchange diffusion Nutrition Parasite, holozoic Support no Fertilization hermaphrodite Embryo develop egg Movement muscle Special features Bilateral symmetrical, no segment

External view of an earthworm

Introduction to annelids Annelids…for example as earthworm F belong to the Phylum Annelida F are segmented worms showing metameric segmentation F are coleomate animals F have a fluid-filled body in which the gut and other organs are suspended F are further classified into three classes: polychaeta, oligochaeta, hirudinea

Body structure of annelids F enlarged coelom to accommodate more complex internal organs. F well-developed, fluid-filled coelom and the tough integument act as a hydrostatic skeleton. F Closed circulatory system with blood vessels running the length of the body and branching into every segment

F nervous system consists of a brain connected to a ventral solid nerve cord, with a ganglion in each segment F complete digestive system including a pharynx, stomach, intestine, and accessory glands F excretory nephridia in each segment to collect waste material from coelom and excrete it through the body wall

Anatomy of a typical annelid, earthworm

Cross section of through the earthworm body

Adaptive features Gaseous exchange Diffusion through skin Nutrition Holozoic, debris feeder Support hydroskeleton Fertilization Internal, hermaphrodite but mate Embryo develop External, cocoon Movement Muscle, chaetae Special features Coelomate, segmented,

Morphology of an earth worm Earthworms belong to the oligochaeta class. F They are hermaphroditic with both male and female gonads. F The mesoderm of an earthworm splits into outer and inner layer with coelom in between which allows: - space for development of organs - development of hydrostatic skeleton for support and movement - for independent movement of body wall and gut

FMetameric segmentation of earthworms allows for: - specialization of different body parts - division of labour - muscular body wall divides into blocks to provide independent movement of different parts of the body FEarthworms have hydroskeletons to maintain the body shape FMuscles of body wall acts on coelomic fluid to bring about locomotion, support and protection

Ecological significance of earthworms Soils may barbor 50 to 500 earthworms per square meter; they contribute to soil formation and improvement in the following ways: F tunnels improve aeration and drainage F dead vegetation is pulled into the soil where decay by saprobionts take place F mixing of soil layers F castings fertilizes the soil

F addition of organic matter by excretion and death Fsecretions of gut neutralize acid soils Fimproving tilth by passing soil through gut It may be doubted whethere are many other creatures which have played so important a part in the history of the world Charles Darwin, 1881

Classification of the Annelida

Arthropoda segmented appendices

Introduction to arthropods Arthropods… F have exoskeleton F have jointed limbs F have segmented body F have dorsal heart and open blood system Fgrow in stages after moulting (ecdysis)

F because of the size and importance of this phylum, it is mainly divided into four further classes: - crustacea: with very hard exoskeleton - insecta : body with three parts and three pairs of legs - arachnida: body divided into two parts with four pairs of legs - myriapoda: with many segments and legs

Adaptive features Gaseous exchange Trachea, gill Nutrition Holozoic, parasitic Support exoskeleton Fertilization internal Embryo develop egg Movement Leg, fly by wing, swim by tail Special features Segmented, coelomate

The subphylum crustacea Crustacea contains 30, 000 mostly marine species. A few species live in freshwater. For example: lobsters, crabs, crayfish, shrimp, etc. They process. . . F two pairs of antennae F a pair of mandibles F a pair of compound eyes (usually on stalks) F two pairs of maxillae on their heads

F a pair of appendages on each body segment F a head, thorax, and abdomen F gills for gaseous exchange F a hard exoskeleton for support and protection

Anatomy of crustacean (a prawn)

Marine Copepod (Crustacean), Pleuromamma sp. Marine Copepod (Crustacean), Actitius sp.

The subphylum insecta Insects are the largest group, with probably over one million identified and named species. Insects live in almost all terrestrial and freshwater habitats, with a few species living in the oceans. These contribute to insects that they are the most successful group of animal, and are the least likely to become extinct.

General characteristics of the insects External characteristics F body comprises head, thorax and abdomen F three pairs of thoracic walking legs F two pairs of thoracic wings derived from the outgrowths of the body wall F one pair of antennae on the head F one pair of relatively large compound eyes

Other characteristics F respiration by a tracheae system with external openings called spiracles dividing into finely branched tubules that carry gases directly to metabolizing tissues F nervous system include a number of ganglia and a ventral, double nerve cord F have a complete and complex digestive system Fvery sensitive to sound and have excellent chemoreceptive abilities. F have to moult in order to increase in size

Anatomy of the insect body

Fruit fly. Fruit Fly. The insect body is divided into head, thorax (with wings), and a segmented abdomen. The compound eye of insects is also quite prominent.

Significance of insects to the ecosystem Insects are very valuable to us although it sometimes eat our food, sting us and transmit diseases. They play a vital role in the ecosystem by functioning in: F pollination of many flowering plants F decomposition of organic materials F recycling of carbon, nitrogen, and other essential nutrients

F control of populations of harmful invertebrate species (including other insects) F direct production of certain foods like honey F manufacture of useful products such as silk and shellac F become prey of other predators to balance the food chain FInsecta is most successful animal because it divided to 70% of all animal species.

Some more examples of insects Cockroach - can transmit dieseas

Dragonfly Bee - a born pollinator of flowers

Moth - can also pollinate like the bees Cicada Ant - sometimes bite the wooden furniture