Concept explainers
Introduction:
Cephalization and bilateral symmetry of a body contribute to the evolutionary development of invertebrates. Cephalization is the formation of head at the frontal region of the body of organisms. The head consists of brain having ganglia and nerve cords. Ganglia is a group of nerve cells with specialized functions. The enlargement and clustering of ganglia lead to the development of brain.
Answer to Problem 1TYK
Correct answer:
Cephalopods.
Explanation of Solution
Justification/explanation for the correct answer:
Option (d) is cephalopods. Mollusks have neuron clusters and major nerves. Different mollusks have different degree of cephalization. The cephalopods groups of mollusks have cluster of ganglia, which gets fused into a complex lobe. Hence, option (d) is correct.
Explanation for the incorrect answer:
Option (a) is vertebrates. The cephalization occurs in invertebrates and the vertebrates are evolved from invertebrates. So, it is an incorrect option.
Option (b) is annelids. Annelids have a cerebral ganglion at the front of their body and a ventral nerve cord, which works as brain, whereas a true brain has a cluster of ganglia and two nerve cords. So, it is an incorrect option.
Option (c) is
Option (e) is mammals. Mammals come under vertebrate group, which have developed from invertebrates, and head formation occurred in invertebrates. So, it is an incorrect option.
Hence, options (a), (b), (c), and (e) are incorrect.
Therefore, it can be concluded that the process of cephalization (frontal head formation) was first seen in cephalopods.
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Chapter 40 Solutions
Biology: The Dynamic Science
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