Test: Classification of Non-Chordates - NEET MCQ

Scorpion, spider and cockroach are invertebrates and belong to the phylum Arthropoda, therefore they have ventral solid central nervous system. In cockroach and locust the body is segmented extemally. In Taenia, the body is without true segments. Liver fluke has bilateral symmetry sea anemone has radial symmetry and sea cucumber has bilateral symmetry in larval form and radial symmetry in adult form. Centipede and prawn have hointed appendages while sea urchin does not have jointed appendages.

Phylurm Mollusca includes those animals which have a soft body, usually furnished with a shell. The body is divided into a head, muscular foot and visceral mass. Loligo (squid), Teredo (shipworm) and Octopus are some of its examples.

Nereis belongs to phylum Annelida and scorpion, cockroach and silver fish belong to phylum Arthopoda. They all possess dorsal heart.

Arthropods show various body shapes with bilateral symmetry. They show incomplete metameric segmentation. They have true coelom containing haemocoel. In arthropods, blood vascular/circulatory system is of open type where blood flows in haemocoel instead of blood vessels.

A body cavity can mean any Interna space, or a series of spaces present inside body, whereas coelom or true body cavity generally refers to a large fluid-filled space (cavity) lying between the outer body wall and the inner digestive tube. In acoelomates no body cavity or coelom is present. Embryonic mesoderm remains as a solid layer, space between endoderm (gut wall) and ectoderm (body wall) is filled with mesenchyme and muscle fibres. In pseudocoelomates body space is a pseudocoelom or false coelom. In coelomates or eucoelomates body space is a true coelom enclosed by mesoderm on both sides. Aschelminthes are pseudocioelomates Molluscs and insects are coelomates while flatworms are acoelomates.

In sponges, sexes are not separate (hermaphrodite) i.e., eggs and sperms are produced by the same individuals. Sperms leave one sponge and enter another with water current to fertilize the ova (eggs) in situ. Thus, fertilization is internal.

Leucosolenia and Spongilla belong to the phylun Porifera and thus have porous body (body is provided with
Pores) and are diploblaStic (i.e. derived from two germ layers - ectoderm and endoderm).

Members of phylum Mollusca have non-segmented body with a distinct head, muscular foot and visceral hump. A soft and spongy layer of skin forms a mentle over the visceral hump. The other characteristics  mentioned in  other options are shared with other phyla e.g. bilateral symmetry is exhibited by phylums Platyhelminthes, Aschelminthes,
Annelida And Arthropoda.

In sponges, body is not supported by chitin. Their body is supported by calcareous or siliceous spicules or protein spongin fibres.

Figure 'C' is of Octopus (mollusc) and figure 'D' is of scorpion (arthropod). Both have true coeloms. Figure A is of tapeworm (platyhelminth) and Figure B is of Aurelia (cnidarian). Both arp acoelomates.

Parapodia are present in some annelid worms. These are a pair of flattened flesh lobes bearing numerous bristles Radula (rasping organ) in molluscs is a structure involved in feeding.

Molluscans are soft bodied animals. Their body is unsegmented with a distinct head, muscular foot and visceral hump. In Pila, the buccal cavity contains a resping organ, the radula with transverse rows of teeth.

Option: B is correct 
In statement 
(i) The circulatory system in arthropods is of a closed type.- Incorrect as Arthropods have an open circulatory system, not a closed one: 
(ii) Parapodia in annelids helps in swimming. - This statement is correct, Parapodia help annelids swim 
(iii) Phylum Mollusca is the second largest animal phylum after arthropods - This  statement is correct as Mollusca composes the 2nd largest phylum of animal kingdom after arthropods
(iv) Aschelminthes are dioecious.- Correct statement, as Aschelminthes are dioecious, meaning they have separate sexes
therefore the only incorrect statement is (i) 

Earthworms and Periplaneta both have segmented bodies.

Earthworms and Periplaneta are both invertebrates that have segmented bodies. This means that their bodies are divided into a series of repeating segments or rings, which are called somites. Each somite contains a pair of legs, and the number of somites in an earthworm or Periplaneta can vary depending on the species.

Both earthworms and Periplaneta also possess anal styles, which are small appendages located near the anus. These structures are thought to be involved in the excretion of waste products and may also play a role in mating.

Earthworms and Periplaneta do not have red-colored blood or Malpighian tubules. Earthworms and Periplaneta both belong to the phylum Annelida, but they belong to different classes. Earthworms belong to the class Oligochaeta, while Periplaneta belongs to the class Blattodea.

Segmentation is division or differentiation of the body into distinct portions called segments. It is first observed phylum Annelida.

Silver fish, scorpion, dragonfly and prawn belong to the phylum Arthropoda and thus jointed appendages and chitinous exoskeleton.

In animals like Hydra, jelly fish, star fish, the body can be divided into equal halves by any plane passing through the centre from top to bottom, thus exhibiting radial symmetry. In many vertebrates body can be divided into two equal halves by a single plane only thus exhibiting bilateral symmetry.
In the blind sac body plan the body has a single cavity with one opening to the outside. The single opening functions as both mouth for ingestion and anus for egestion. It is found in coelenterates and flatworms (Platyhelminthes).

Blood is colourless in insects as it has no respiratory pigment. Therefore, it has no role in O₂ transport. O₂ is transported through tracheae.

Figure 'A' is of Hydra which has radial symmetry and figure 'B' is of Cancer (crab) which has bilateral symmetry.

Stinging capsules (nematocysts) are the organs of offence and defence, present in the phylum Coelenterata. Sea pen and sea fan are members of this phylum.

All sponges have high regenerative power. Their skeleton may consist of calcareous or siliceous spicules. Some sponges live in fresh water e.g. Spongilla. Most of the sponges are asymmetrical, some are radially symmetrical.

Silver fish, scorpion, crab and honey bee, all belong to the phylum Arthropoda. The members of this phylum have characteristic feature of jointed appendages.

Sea anemone is not parasitic. It shows mutualism with hermit crab. Tapeworm is an endoparasite while leech and mosquito are exoparasites.