Class 9 Science Chapter 7 Diversity in Living Organisms
Huge diversity is seen in living organisms hence, living organisms are classified into kingdom plantae and kingdom animalia. In this article we will specifically speak about kingdom animalia. Kingdom animalia is again classified into different phylums, Porifera, Coelenterata, Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca, Echinodermata, Protochordata and Vertebrata.
Animals falling under porifera have spongy body, are attached to solid support, and posses holes all over the body. These holes are called ostia. Main function of ostia is to circulate water inside the body of poriferans. However, Poriferans show less differentiation and division into tissues . Moreover, these animals are found in marine habitat and are commonly called as sponges. For example, Euplectella, Sycon, Spongilla, etc.
Animals in this category are present in various body designs. The animal body is made up of two layer. Outer layer have cells which makes outer body, whereas, inner layer consist of inner lining of body. These animals show cavity inside the body. Differentiation is seen more in these animals. Some of these species live in groups, whereas, while others live independently. For example, Hydra, Jellyfish, Sea anemone, etc.
These animals show bilaterally symmetrical body, i.e. left and right half of body are mirror images. Body is made of three layers of cells called triploblasts. These also show differentiation. Body of these organism do not contain cavity, to place developed organs. Body appears to be flattened, therefore, these are called flatworms. These animals live free or can be parasitic. Parasitic organisms are those which get attached to another organism and extract nutrition from their body. Extracted nutrition acts as a food for parasitic organisms. For example, Planaria, Liver flukes, etc.
Body of these organisms are bilaterally symmetrical, triploblastic and is cylindrical in shape. No specific organs are present in the body, also the body contains small cavity called pseudocoelom. However, these are well known as worms and are famous for causing disease. For example : Tapeworms causes diarrhoea. For example, hookworms, tapeworms, pinworms, ascarides, etc.
Annelids are bilaterally symmetrical, triploblastic and possess body cavity. These organisms contain organs which are place in body cavity. Body of annelids show segmentation from head to tail of body. These segmentation is helpful in recognising the location of organs in the body cavity. They are found in habitat such as freshwater, land, etc. For example, Earthworm, Leeches, Redworm, etc.
Arthropods are bilaterally symmetrical and have open circulatory system i.e. blood flows partially through vessels and partially through body cavity. Coelomic cavity is filled with blood. In arthropodes, blood is made up of haemolymph. Moreover, Arthropods have jointed legs. The name arthropod itself means “jointed legs”. Arthropods are the most interesting creatures which can crawl, fly, swim and they can survive on lands as well as water. For example, prawns, butterfly, housefly, spiders, cockroach, bee, etc.
Animal in phylum Mollusca show bilateral symmetry, less coelomic cavity and few segments. They have open circulatory system. Waste material are removed from body through kidney like organ called Nephridia. There is presence of foot which allows them to move. Many of these animals have shell on their body which protects their soft body. They are habituated to water as well as land. For example of mollusks are pila, octopus, unio, etc.
Echinoderms have thorny skin, are triploblastic and contains a coelomic cavity. They have special water driven tube system which helps in free movement. Thorny structures are made up of calcium carbonate and acts as a skeleton. These are marine animals. For example, starfish, sea urchin, sea cucumbers, etc.
Protochordates have special characteristic present in them called notochord. A notochord is beginning of backbone. In protochordates, notochord show a rod like structure. It separates stomach [gut] from nerve cord. Protochordates may not have notochord in all stages of life or as per length of an animal. Moreover, protochordates are bilaterally symmetrical, triploblastic and have coelom. For example, Balanoglossus, Amphioxus, Lancelet, etc.
Vertebrata Check blog on Vertebrata here
Keywords: Porifera, Coelenterata, Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca, Echinodermata, Protochordata, Vertebrata