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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.

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Body Symmetry & Coelomate

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porifera spongy

Porifera (spongy)

Asymmetric body

Lack of body organizaiton



Spicules as structural component

Choanocyte for water flow and feeding





introduction to coelenterata
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 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
    • 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
  • Nematoblasts
    • they are in the ectoderm
    • 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
Morphology of Obelia
  • Classification
    • Class Hydrozoa (hydroids)
  • Habitat
    • lives in shallow coastal water attached to substratum
  • Morphology
    • exists in 2distinctly different forms in its life
    • colonial form (polyps)
    • free living form (medusa)
introduction to platyhelminthes
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 to3 pairs of longitudinal nerve cords with transverse connectives
  • Complex hermaphroditic reproductive system; internal fertilization; development either direct or with 1 or more larval stages
  • 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
  • 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)

In Human Intestine

In Human Intestine

To Soil

In Pig Muscle





introduction to annelids
Introduction to annelids
  • Annelids…for example as earthworm
  • belong to the Phylum Annelida
  • are segmented worms showing metameric segmentation
  • are coleomate animals
  • have a fluid-filled body in which the gut and other organs are suspended
  • are further classified into three classes: polychaeta, oligochaeta, hirudinea
body structure of annelids
Body structure ofannelids
  • enlarged coelom to accommodate more complex internal organs.
  • well-developed, fluid-filled coelom and the tough integument act as a hydrostatic skeleton.
  • Closed circulatory system with blood vessels running the length of the body and branching into every segment

nervous system consists of a brain connected to a ventral solid nerve cord, with a ganglion in each segment

  • complete digestive system including a pharynx, stomach, intestine, and accessory glands
  • excretory nephridia in each segment to collect waste material from coelom and excrete it through the body wall
morphology of an earth worm
Morphology of an earth worm
  • Earthworms belong to the oligochaeta class.
  • They are hermaphroditic with both male and female gonads.
  • 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

Metameric 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
  • Earthworms have hydroskeletons to maintain the body shape
  • Muscles of body wall acts on coelomic fluid to bring about locomotion, support and protection
ecological significance of earthworms
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:
  • tunnels improve aeration and drainage
  • dead vegetation is pulled into the soil where decay by saprobionts take place
  • mixing of soil layers
  • castings fertilizes the soil

addition of organic matter by excretion and death

  • secretions of gut neutralize acid soils
  • improving tilth by passing soil through gut

It may be doubted whether there are many other creatures which have played so important a part in the history of the world

Charles Darwin, 1881

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

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

the subphylum crustacea
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...

  • two pairs of antennae
  • a pair of mandibles
  • a pair of compound eyes (usually on stalks)
  • two pairs of maxillae on their heads

a pair of appendages on each body segment

  • a head, thorax, and abdomen
  • gills for gaseous exchange
  • a hard exoskeleton for support and protection

Marine Copepod (Crustacean), Pleuromamma sp.

Marine Copepod (Crustacean), Actitius sp.

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

Other characteristics

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

Fruit flyFruit 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
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:
  • pollination of many flowering plants
  • decomposition of organic materials
  • recycling of carbon, nitrogen, and other essential nutrients

control of populations of harmful invertebrate species (including other insects)

  • direct production of certain foods like honey
  • manufacture of useful products such as silk and shellac
  • become prey of other predators to balance the food chain
  • Insecta is most successful animal because it divided to 70% of all animal species.
some more examples of insects
Some more examples of insects

Cockroach - can transmit dieseas



Bee - a born pollinator of flowers


Moth - can also pollinate like the bees


Ant - sometimes bite the wooden furniture