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Excretory system absent. Dioecious, ex...

Excretory system absent.
Dioecious, external fertilization, indirect development with free swimming larva
Water vascular system is present
Unsegmented body
Complete digestive system with ventral mouth and anus on dorsal or upper side The above characters are associated with animals of -

A

Mollusca

B

Hemichordata

C

Echinodermata

D

Annelida

Text Solution

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The correct Answer is:
To solve the question regarding the characteristics of certain animals, we will analyze each of the provided options based on the given features. ### Step-by-Step Solution: 1. **Identify the Key Features**: - Excretory system absent. - Dioecious (separate sexes). - External fertilization. - Indirect development with free-swimming larva. - Presence of a water vascular system. - Unsegmented body. - Complete digestive system with a ventral mouth and anus on the dorsal side. 2. **Evaluate Each Option**: - **Option 1: Mollusca**: - Mollusca typically have a kidney-like structure for excretion, so they do not fit the criteria of having an absent excretory system. - **Option 2: Hemichordata**: - Hemichordata possess a proboscis gland for excretion, indicating that they also do not meet the requirement of having an absent excretory system. - **Option 3: Echinodermata**: - Echinoderms have no specialized excretory system, which aligns with the requirement of an absent excretory system. They are dioecious, undergo external fertilization, and have indirect development with free-swimming larvae. They also possess a water vascular system and have an unsegmented body with a complete digestive system (mouth ventral, anus dorsal). - **Option 4: Annelida**: - Annelids have nephridia for excretion, which means they do not fit the criterion of having an absent excretory system. 3. **Conclusion**: - Based on the analysis, the only group that meets all the specified characteristics is **Echinodermata**. Therefore, the correct answer is **Option 3: Echinodermata**.
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