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Invertebrate Essay Question

There are different types of animals around us. The large number of animals in the world can be broadly classified into two groups on the presence and absence of the backbone.

  • Phylum: Protoza

    Protoza are unicellular organisms, having no physiological division of labour. Amoeba, Paramecium, Euglena, Stentor, stylonchia, etc. are some free living protozoa.

    Characteristics of protozoa

    1. They may be solitary, colonial or free living, aquatic parasitic.
    2. Most of them live in water (aquatic) but some live in damp soil or inside other animal (parasitic).
    3. Locomotion take place by pseudopodia, flagella or cilia.
    4. Reproduction takes place mostly by means.
    5. These constantly change the body shape.

      Examples: Amoeba, Paramecium, Euglena, Entamoeba, Plasmodium, etc.


  • Phylum : Porifera

    They live mainly in salty water. About 5,000 species are known today, commonly called sponges. These animals are referred as.


    1. These are found in salty water.
    2. These are multicellular animals.
    3. They have cylindrical shape body.
    4. Germinal layers are ill developed.
    5. Inner surface has flagellate collar cells or choancocytes.
    6. Reproduction is both sexual and asexual.

      Examples: Sycon, Bath sponge, Euplectella, Glass- rope sponge, etc.


  • Phylum : Coelenterates

    About 10,000 species are known.


    1. These are marine animals which may be solitary or colonical.
    2. They have a hollow body like a bag.
    3. The body is two layered (diplomatic).
    4. The body possesses a radii symmetry.
    5. The mouth is surrounded by tentacles which are usually thread like out growths.
    6. Stinging cells or Nematocytes are present.

      Examples: Hydra, Jelly fish, Sea anemone, Coral, pennataula, etc.

      Jelly Fish

  • Phylum : Platyhelminthes

    About 6500 species are known. Common forms are Flukes, and Tapeworms.


    1. They are commonly known as Flat worms.
    2. They are accommodate forms.
    3. They are bisexual.
    4. The body is bilaterally symmetrical.
    5. Nervous system is simple.

      Examples: Liver fluke, planaria, Tapeworm, blood fluke, etc.


  • Phylum : Nemathelminthes

    About 10000 species are known. Examples: Ascaris (Roundworm), Oxyuris (pinworm), Ancylostoma (hookworm).


    1. They are commonly known as roundworms.
    2. Body is bilaterally symmetrical.
    3. Sexes are separate. Reproductive system is simple.
    4. Usually parasites, some free living forms are also met with.
    5. The nervous system is in the form of ring.
    6. Respiratory organs and blood vascular system are absent.

      Examples: Ascaris, Anylostoma, Oxyuris, etc.


  • Phylum : Annelida

    About 13500 species are known.


    1. The body is metamerically segmented.
    2. The body shows bilateral symmetry.
    3. Excretory organs are Nephiridia.
    4. Sexes are either separate or the organism are hermaphrodite.
    5. The body has longitudinal and circular muscles.

      Examples: Earthworm, Leech, Polygordius, etc.

  • Phylum : Arthropoda

    The word arthropoda means jointed foot. It is the largest group of animals comprising of about 700000 species. The animals of this phylum are found all over the world in all climates and conditions.


    1. Body is metamerically segmented.
    2. Body is jointed outwardly and bilaterally symmetrical.
    3. A hard, non- living, exoskeleton is present.
    4. Sexes are usually separated.

      Examples: Spider, Crab, Grasshopper, Butterfly, Centipede, Millipede, etc.


  • Phylum : Mollusca

    About 90000 species are known.


    1. The animals are aquatic, some terrestrial forms are also known.
    2. Body is soft unsegmented.
    3. Coelomate animals. True coelom is present.
    4. Body consists of a head, a foot and a dorsal visceral mass.
    5. Respiration is done by a part of gills.

      Example: Snail, octopus, cuttlefish, Squid, etc.


  • Phylum : Echinodermata

    These are marine animals. About 5000 species are known.


    1. The skin forms a hard spiny protective skeletal covering.
    2. The alimentary canal is simple and usually complete.
    3. They have a coelom and water vascular system.
    4. Sexes are separated.
    5. Nervous system is well developed consisting of a circumolar ring and radical nerves.

      Example: Starfish, Sea urchin, Sea cucumber, sea lily, etc.

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    Invertebrate Questions and Answers

    • Animals with an internal skeleton made of bone are called 

    • A Hydrostatic Skeleton is

    • Vertebrates include:

    • A sponge belongs to this phylum.

    • A jellyfish belongs to this phylum.

    • Which of the following is not a Cniderian?

    • The age of the Burgess shale fauna is mainly __________.

    • This type of coral replaced the principle Silurian reef-forming coral as the main reef-forming coral during Devonian and Carboniferous.

    • Why did the innovation of the seed liberate land plants from their dependence on moist conditions and allow them to invade drier habitats in the Devonian?

    • Vertebrates have a backbone.

    • Invertebrates lack a backbone.

    • Humans are invertebrates.