The organisms attached to the substratum, generally, possess [1995]a)radial symmetryb)one single opening of digestive canalc)asymmetrical bodyd)cilia on surface to create water currentCorrect answer is option 'A'. Can you explain this answer?

Question

Answer

Radial symmetry is seen in sedentary animals where the environment is same along all the radius, consequently, the body is also the same along all the radius. It allows the animal to detect food on danger approaching from any side. Radial symmetry is found in cniderians , ctenophores and echinoderms. So, the correct answer is ' Radial symmetry' .

Answer

The organisms attached to the substratum, generally possess radial symmetry.
Radial symmetry is seen in sedentary animals where the environment is same along all the radius, consequently, the body is also the same along all the radius. It allows the animal to detect food or danger approaching from any side. Radial symmetry is found in cnidarians, ctenophores and echinoderms.

So, the correct answer is 'Radial symmetry'

Answer

Explanation:

When organisms are attached to a substratum, they have certain adaptations to facilitate their survival and functioning in this environment. In the case of the organisms mentioned in the question, they possess radial symmetry. Let's understand why radial symmetry is the correct answer.

Radial Symmetry:
- Radial symmetry is a type of symmetry where the body parts are arranged around a central axis, similar to the spokes of a wheel.
- This type of symmetry allows for equal distribution of sensory organs and appendages around the body, enabling the organism to detect and respond to stimuli from all directions.
- Organisms with radial symmetry are usually sessile or slow-moving, and they rely on water currents to bring food and oxygen to them.

Other Options:
a) One single opening of the digestive canal: This is a characteristic feature of organisms with radial symmetry. They have a single opening that serves as both the mouth and the anus. This opening allows food to enter the body and waste to be expelled.
c) Asymmetrical body: Asymmetrical organisms do not have a definite body shape or pattern. They lack any form of symmetry and are usually found in lower organisms like sponges.
d) Cilia on the surface to create water current: While cilia can be found in some organisms, it is not a defining characteristic of organisms attached to the substratum. Cilia are hair-like structures that beat in coordinated waves to create a water current, aiding in locomotion and feeding.

Conclusion:
Based on the given options, the correct answer is A) Radial symmetry. Organisms attached to the substratum usually possess radial symmetry because it allows for equal distribution of sensory organs and appendages around the body, enabling them to detect and respond to stimuli from all directions. This adaptation is crucial for their survival in their sessile or slow-moving lifestyle.

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