Problem 173 - Objective Biology for NEET

Question

Select the total number of organism which posses two chambered heart and are poikilothermal. Scoliodon, Pristis, Clarias, Betta, Pterophyllum, Echinus, Devil Fish, Cuttle fish, Sea lily, Hyla, Labeo, catla, Torpedo, Trygon (a) 7 (b) 9 (c) 11 (d) 13

Step-by-Step Solution

Answer

The total number of organisms with a two-chambered heart and are poikilothermal from the provided list is 8. Therefore, none of the options (a) 7, (b) 9, (c) 11, (d) 13 are correct.

Step 1: Understand the Characteristics

First, it's necessary to understand the characteristics that the problem is asking for. A two-chambered heart means that the heart consists of one ventricle and one atrium. Poikilotherm organisms, often referred as 'cold-blooded', are those whose body temperatures vary significantly, often matching the temperature of their environments.

Step 2: Identify Organisms with those Characteristics

Next, find out which organisms on this list have a two-chambered heart and are poikilothermal. It is typically fish and some amphibians that have two-chambered hearts and are poikilothermal. From the given list, the organisms with these characteristics are: Scoliodon, Pristis, Clarias, Betta, Pterophyllum, Cuttle fish, Torpedo, Trygon.

Step 3: Count the Total Number of Organisms

Lastly, count the total number of these identified organisms. When counted, the total number is 8.

Key Concepts

Two-Chambered Heart

In the fascinating world of biology, different organisms have hearts that vary in complexity and number of chambers. A two-chambered heart is a prominent feature of some fish. These hearts consist of:

• One atrium: This chamber receives oxygen-poor blood from the body.
• One ventricle: This chamber pumps the blood to the gills for oxygenation.

This simple cardiac structure is sufficient for the aquatic environments these organisms inhabit. Blood flows in a single circulatory loop: from the body to the heart, then to the gills, and back to the body. This efficient system supports the metabolic needs of these organisms efficiently.
Understanding this heart structure can help explain why some organisms are restricted to aquatic habitats.

Cold-blooded organisms

Poikilothermy, also known as being cold-blooded, is a physiological trait where an organism's body temperature aligns with the environmental temperature. This means:

• These organisms rely on the external environment to regulate their body temperature.
• They usually have a lower metabolic rate compared to warm-blooded organisms.

Fish, reptiles, and amphibians often display these traits. It offers advantages such as being energetically less demanding, but it also makes these organisms vulnerable to external temperature changes.
Cold-blooded organisms can become sluggish or dormant if temperatures drop too low, impacting their activity levels.

Fish physiology

Fish have unique physiological traits perfectly suited for life in water. Some notable characteristics include:

• Gills: Specialized organs that facilitate the exchange of gases, allowing fish to breathe underwater.
• Swim bladder: A gas-filled organ that helps maintain buoyancy.
• Scales: Protective layers that shield against injury and infection.

Additionally, many fish are characterized by a two-chambered heart and a cold-blooded nature, both of which enhance their survival in aquatic environments.
Fish physiology allows them to efficiently extract oxygen from water and their streamlined bodies enable swift movement, ensuring they thrive in diverse habitats.