Question

Name the ten most diverse animal phyla and either diagram their relationships or arrange them in a table according to their relationships, including identifying which clade (Parazoa, Eumetazoa, Bilateria, Deuterstomes, Protostomes, Lophotrochozoa, and Ecdysozoa) they belong to.

Answer 1

Classification of animals is termed as Kingdom Animalia. It is further divided into different phyla. These are nothing but divisions in which animals/organisms with the same characteristics are included under them. Apart from the primary distinguishing features of the Animal Kingdom (Eukaryotic, Multicellular, without a cell wall and heterotrophic); each phylum has organisms that have common characteristics. In the classification of animals chart, they move from the simplest to the most complex. The different phyla in the classification of animals are as follows: • Phylum Porifera • Phylum Coelenterata • Phylum Platyhelminthes Phylum Nematoda • Phylum Annelida Phylum Arthropoda • Phylum Mollusca • Phylum Echinodermata Phylum Protochordata • Phylum Vertebrata

Let us now look at some important features of each Phylum:- 1. Phylum Porifera:- These are the simplest multicellular animals, found mainly in marine habitats. These organisms have pores all over the body. They have a canal system that helps in circulating water and food particles and oxygen. The body design shows minimal differentiation and division of tissues. Commonly called as Sponges, some of the examples are Spongilla, Sycon etc. 2. Phylum Coelenterata:- These organisms show more body differentiation. They live in water. The body has a sac-like cavity, with a single opening for ingestion an egestion. These animals have two germ layers and hence are called diploblastic. You can see these animals living solitarily or n colonies. Examples include Jellyfish, Sea Anemone, and Hydra.

3. Phylum Platyhelminthes:- These are commonly called flatworms. Their bodies are flattened dorsoventrally. They are the first triploblastic animals, with three germ layers. The body is also bilaterally symmetrical, with both the left and right halves of the body having the same design. Flatworms can be either parasitic or free living. A few examples are Planaria, Liver Fluke, and Tapeworm. 4. Phylum Nematoda:- The bilateral symmetry and triploblastic nature continue in these animals. The body, however, is more cylindrical and not flattened. The body cavity is not a true coelom. And hence it is called a pseudo coelom. Tissues are present, but organs are absent. These organisms show a complete alimentary canal which is straight. Most of these organisms belonging to this phylum are parasitic worms, which cause diseases. Examples are Ascaris, Wucheria.

5. Phylum Annelida:- Annelids are found in different habitats, such as land, fresh water, and even marine mater. They have a bilaterally symmetrical body with three germ layers (Triploblastic). A distinguishing feature here is that they have a true body cavity. The body is also segmented with some organ differentiation seen. Examples are Earthworms, Leeches. 6. Phylum Arthropoda:- They make up the largest group in the animal kingdom. Most of the insects are included in this phylum. "Arthropoda" means jointed legs. The bodies of these animals are divided into head, thorax, and abdomen. Apart from the jointed legs, they also have a pair of compound eyes. Another distinguishing feature of these animals is the presence of an open circulatory system. Examples are butterfly housefly, spiders, mosquitoes, crabs etc.

7. Phylum Mollusca:- The bilateral symmetry and the triploblastic nature of the body layers are seen here too. Molluscans form a very diverse group and form an important part of the ecosystem. These animals can be seen aquatic habitats. They can be either marine or freshwater species. The body does not show much segmentation and the coelomic cavity is also reduced. The body is typically divided into anterior head, ventral muscular foot, and a dorsal visceral mass. The foot helps in the locomotion of the animals. Examples are Snails, Mussels, and Octopus.

8. Phylum Echinodermata:- Moving on with the classification of animals we come to Phylum Echinodermata. Echinoderms are animals with spiny skin. They live exclusively in a marine habitat. They are free-living animals. The larvae show bilateral symmetry whereas the adults show radial symmetry. These animals are triploblastic and have a coelomic cavity. They have a peculiar water driven tube system that helps them in moving around. They also have a hard exoskeleton that is made up of calcium carbonate. Examples are Starfish, Sea cucumber, Sea Urchin.

9. Phylum Protochordata:-The protochordate animals are bilaterally symmetrical and triploblastic. They have a coelom. A new body feature that is seen in these animals is the presence of notochord at some stage in their life cycle. Due to this very presence of a notochord, they are called as chordates. However, it is sometimes rudimentary. They are exclusively marine animals. Examples include Herdmania, Balanoglossus.

10. Phylum Vertebrata:- These are the advanced group of animals, showing some really advanced features of a proper digestive system, circulatory system etc. There is a complex differentiation of body tissues and organs. These animals have a true vertebral column with an internal skeleton. All chordates have the following features: • Notochord • Dorsal Nerve Cord • Post-anal tail • Pharyngeal slits Phylum Vertebrata is classified into five classes. They are: 1. Pisces 2. Amphibia 3. Reptilia 4. Aves 5. Mammalia