In the evolution of animal kingdom, the first animals with true body cavity belong to the phylum

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Q: 44 (IES/2003)
In the evolution of animal kingdom, the first animals with true body cavity belong to the phylum

question_subject: 

Science

question_exam: 

IES

stats: 

0,13,56,13,30,8,18

keywords: 

{'arthropoda': [0, 0, 2, 0], 'first animals': [0, 0, 1, 0], 'true body cavity': [0, 0, 1, 0], 'platyhelminthes': [1, 0, 0, 0], 'annelida': [2, 0, 1, 1], 'phylum': [0, 0, 0, 1], 'animal kingdom': [1, 1, 1, 1], 'aschelminthes': [1, 0, 1, 0], 'evolution': [1, 0, 1, 0]}

The correct answer is option 1: Annelida.

The first animals with a true body cavity, known as a coelom, belong to the phylum Annelida. A coelom is a fluid-filled cavity that is completely lined with mesoderm, one of the three primary germ layers in animal embryos. This coelom provides space for various organs and systems to develop and function properly.

Option 2: Arthropoda is incorrect because although arthropods have a body cavity called a hemocoel, it is not a true coelom. The hemocoel is not completely lined with mesoderm but rather consists of a limited amount of fluid-filled spaces.

Option 3: Aschelminthes is also incorrect because they do not have a true coelom. Instead, they have a pseudocoelom, which is a body cavity that is only partially lined with mesoderm.

Option 4: Platyhelminthes is also incorrect as they also do not possess a true coelom. They are acoelomate, meaning they lack a body cavity altogether.

Therefore, the correct statement is that the first animals with a true body cavity belong to the phylum Annelida.