Question

Which of the following are correct?
(i) Sponges: Cellular level of organization
(ii) Cnidaria: Tissue level of organization
(iii) Platyhelminthes: Organ level of organization
(iv) Annelids, Arthropods, Molluscs, Echinoderms, and Chordates: Organ system level of organization.

A. (i) and (ii) only
B. (ii) and (iv) only
C. (ii) and (iii) only
D. (i), (ii), (iii) and (iv)

Answer 1

Living things are highly organized and structured, following a hierarchy that can be examined on a scale from small to large starting with the basic unit constituting their bodies, Iie cells, and their arrangement. With evolution, the level of the organization becomes more complex with each phylum.

Complete answer: In larger organisms i.e. in the animals belonging to animal Kingdom, organisms are classified according to the arrangement of cells at various levels:
1. These are cellular level, tissue level, organ level, and lastly organ system level of organization.
2. Phylum Porifera which includes sponges has the basic cellular level of organization.
3. The subsequent phylum i.e. phylum Cnidaria exhibits the tissue level of the organization.
3. In these animals, cells combine and arrange to form tissues, which are groups of similar cells carrying out specific related functions.
4. The next level of organization i.e. the Organ level is the collections of tissues grouped together performing a common function, and it is found in the phylum Platyhelminthes.
5. The last level which is the organ system level consists of functionally related organs.
6. It can be found in the remaining phyla namely, Annelids, Arthropods, Molluscs, Echinoderms, and Chordates.

So, the correct answer is option D. (i), (ii), (iii) and (iv).

Note: It is important to note that cells are the smallest units of life and are responsible for regulating their own environment. The most complex level of organization is the organismal level, where all eleven organ systems function in the human organism, the whole living person.