Problem 134 - Objective Biology for NEET

Question

Animals having calcareous endoskeleton with organ-system level of organization, completely marine are (a) Arthropoda (b) Mollusca (c) Hemichordates (d) Echinodermates

Step-by-Step Solution

Answer

The animals that fit the problem's criteria are Echinodermates.

Step 1: Identifying the characteristic of calcareous endoskeleton

Phyla Mollusca, Hemichordates, and Echinodermates have some species with calcareous endoskeleton. However, not all species in these phyla have the calcareous endoskeleton and it is not a defining characteristic of Arthropoda.

Step 2: Recognizing the level of organization

All the mentioned phyla (Arthropoda, Mollusca, Hemichordates and Echinodermates) exhibit organ-system level of organization.

Step 3: Determining the living environment

While Arthropods, Molluscs and Hemichordates can be found in a variety of environments - terrestrial, freshwater, and marine, Echinodermates are exclusively marine.

Step 4: Final Conclusion

Considering all the provided characteristics - having a calcareous endoskeleton, exhibiting organ-system level of organization, and being exclusively marine, only Echinodermates fit all the criteria.

Key Concepts

Calcareous Endoskeleton

A calcareous endoskeleton is like an internal support system made mostly of calcium. It provides structure and protection for animals that possess it.
In the animal kingdom, Echinodermata, such as starfish and sea urchins, are well-known for their calcareous endoskeletons. These structures are not hard and inflexible like bones but have a unique ability to be both strong and light.
This type of skeleton is formed of small plates or ossicles which often have spiny or bumpy surfaces.

• The calcareous composition gives these animals distinct texture and strength.
• It allows them to maintain their shape and fend off predators.
• It contributes to movements and flexible body shapes by the arrangement of the plates.

Unlike exoskeletons found in insects, a calcareous endoskeleton grows with the animal, ensuring that no molting is necessary.

Organ-System Level of Organization

The organ-system level of organization refers to how animal bodies are arranged into different organs, each with specific functions, and how these organs interact to form systems.
In organisms with this level of complexity, systems such as the digestive, circulatory, and nervous systems work in harmony to ensure survival, growth, and reproduction.
Among Echinodermata, the division of labor is quite mature with specialized organs for various functions.

• The water vascular system is unique to echinoderms, aiding in movement and food gathering.
• The digestive system is simple yet complete, capable of breaking down and absorbing nutrients efficiently.
• Reproductive and nervous systems ensure adaptability to marine life challenges.

This level of organization represents an evolutionary advantage that allows these animals to efficiently manage essential life processes.

Marine Environments

Marine environments are ecosystems found in oceans and seas, characterized by salty water and diverse living conditions.
Echinodermata are uniquely adapted to life in these environments, which include conditions like varying salinity, temperature, and pressure.
All members of Echinodermata are exclusively marine, showcasing their ability to thrive in these habitats.

• Their calcareous endoskeleton provides buoyancy and mobility in water.
• They have developed specific physiological adaptations to manage high salt concentrations.
• Complex life cycles are often synchronized with tides or lunar cycles.

The marine habitat provides immense biodiversity, and echinoderms play roles in maintaining ecological balance, such as through predation and as part of the food chain.