Question

Some salient features and phyla of organisms are given below. Select the option which shows the correct combination of organism, its phylum and salient features.
(A) Hydra - Coelenterata - bilateral symmetry - cnidoblasts present
(B) Planaria - Platyhelminthes - bilateral symmetry - high regeneration capacity.
(C) Ancylostoma - Annelida - bilateral symmetry - elongated and worm shape
(D) Octopus - Mollusca - radial symmetry - external skeleton of shell present.

Answer 1

Hint: In Spite of differences in structure and form of different animals , there are fundamental features common to various individuals in relation to the arrangement of cells, body symmetry, nature of coelom, pattern of digestive , circulatory or reproductive systems.

Complete answer:
The common characters of different kingdom are shown here:-
> Porifera :- they are organisms which have pores in their body. For example sycon.
> Coelenterates :- they are organisms that contain cnidoblast . For example hydra.
> Ctenophores :- they are commonly known as comb jellies. For example ctenoplana
> Platyhelminthes :- they are flatworms. For example – tapeworm
> Aschelminthes:- they are roundworms. For example – ascaris
> Annelida:- the segmentation of the body is the first time seen here . For example – earthworm
> Arthropods:- it is the largest phylum . The body consists of the head, thorax and abdomen.
> Mollusca :- this is the second largest phylum . For example octopus.
> Echinodermata :- they are spiny skinned organisms. For example starfish.
Now let us match this with given options:-
> Hydra - Coelenterata - bilateral symmetry - cnidoblasts present :- hydra belongs to kingdom Coelenterates. These organisms possess radial symmetry and not bilateral symmetry.
> Planaria - Platyhelminthes - bilateral symmetry - high regeneration capacity. :- Platyhelminthes are flatworms. When any part of planaria is cut it gets regenerated into full organisms. They can be divided into two halves by only one plane so have bilateral symmetry .
> Ancylostoma - Annelida - bilateral symmetry - elongated and worm shape :- ancylostoma belongs to kingdom aschelminthes and not to Annelida. They are roundworms. It is also known as hookworm
> Octopus - Mollusca - radial symmetry - external skeleton of shell present. :- octopus belongs to Mollusks but possess bilateral symmetry and not radial symmetry They can be divided into two halves by only one plane so have bilateral symmetry.

Our required option is B that is Planaria - Platyhelminthes - bilateral symmetry.

Note:
To make the study easier the organisms are classified on different basis , one such way is to characterise organisms on the basis of their body plan. Basic body plan includes whether the organisms have a single opening for ingestion and egestion or separate opening for both the processes that is ingestion and egestion. This also includes classification:
Coelomates :- organisms that have true coelom in Annelida.
Pseudocoelomates :- they are animals that possess mesoderm in the form of scattered pouches eg platyhelminthes.
Radial symmetry :- Any plane passing through body divides the body into two halves
Bilateral symmetry :- Only one plane can divide the body into two equal halves e.g. ctenophora.