Question

Question 15 (2 points) The process of cephalization seen in the evolution of many animal phyla is: The development of limbs The development of multiple tissue layers The development of a segmented body The development of a distinct head at one end of the body Question 16 (2 points) The common parasites Ascaris, canine heartworm and Guineaworm are all examples of: . Nematodes Cestodes Annelids Arthropods

Answer 1

ANSWER 15 :-

1. The process of limb development is basically associated with the formation of the limb buds which act as the progenitor organ structures which are further converted into the hindlimbs and the forelimbs depending upon the developmental axis (anterior-posterior axis). Cephalization is derived from a Greek word called as 'kephale' which means the head region and thus the process is associated with the development of the anterior head structures due to which option 'A' cannot be considered as an appropriate answer.
2. Multiple tissue layers may indicate Gastrulation process during which the cells near the dorsal lip undergoes invagination and lead to the formation of three germinal layers which in turn leads to the formation of various structures of the body with the ectoderm forming the neural crest cells although there is no association with the head associated structures and hence the option 'B' is not correct.
3. Segmentation is a process by which the body of an organism lets take the example of the earthworm which belongs to the phylum Annelida is being divided into many segments and this is not at all associated with development of the head associated structures and hence option 'C' is not the appropriate answer.
4. The most appropriate answer is option 'D' which indicates the formation of head and its parts such as the eyes, the optic nerves,etc. This zone at the anterior end of the body is specialized at one end and hence cannot be seen at the opposite end as can be seen in humans.

The most appropriate answer is option 'D'.

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