Consider the following statements regarding the "Susu" dolphin found in the Ganga and Brahmaputra rivers: 1. It is locally known as the blind dolphin. 2. Its presence indicates high levels of pollution in the river. 3. It thrives in waters with high amounts of untreated industrial chemicals. Which of the statements given above is/are correct?

Correct Option The correct option is (a). Explanation The Gangetic River Dolphin (Platanista gangetica), designated as the National Aquatic Animal of India, is a freshwater cetacean found in the Ganga and Brahmaputra river systems. It is an endangered species protected under Schedule I of the Wildlife Protection Act, 1972. Statement-wise Analysis - Statement 1 is Correct: The Gangetic River Dolphin is locally known as 'Susu' due to the sound it produces when breathing. It is also referred to as the "blind dolphin" because its eyes lack a lens, rendering it effectively blind. It relies entirely on echolocation to navigate and hunt in the turbid waters of the river. - Statement 2 is Incorrect: The presence of the Gangetic River Dolphin is an indicator of the health of the river ecosystem. Since these dolphins require specific ecological conditions to survive, their presence suggests that the river water is relatively clean and the ecosystem is functional, rather than indicating high pollution. - Statement 3 is Incorrect: The species is highly sensitive to habitat degradation. Untreated industrial chemicals, agricultural runoff, and pollution are major threats to its survival. It does not thrive in polluted waters; conversely, high pollution levels lead to a decline in its population. Key Takeaway: The Gangetic River Dolphin is a blind freshwater mammal that uses echolocation. It acts as an indicator species for the health of the river; its presence signifies a healthy ecosystem, whereas pollution poses a severe threat to its existence.

NCERT Class 7 Geography — Chapter 1: The Tropical and the Subtropical Region

mcqmedium

Consider the following statements regarding the "Susu" dolphin found in the Ganga and Brahmaputra rivers:

It is locally known as the blind dolphin.
Its presence indicates high levels of pollution in the river.
It thrives in waters with high amounts of untreated industrial chemicals.

Which of the statements given above is/are correct?

Official previous-year question

Verified 1 Aug 2026.

Options

A1 only
B2 only
C1 and 3 only
D1, 2 and 3

Did you get this right?

Solution

Correct Option

The correct option is (a).

Explanation

The Gangetic River Dolphin (Platanista gangetica), designated as the National Aquatic Animal of India, is a freshwater cetacean found in the Ganga and Brahmaputra river systems. It is an endangered species protected under Schedule I of the Wildlife Protection Act, 1972.

Statement-wise Analysis

Statement 1 is Correct: The Gangetic River Dolphin is locally known as 'Susu' due to the sound it produces when breathing. It is also referred to as the "blind dolphin" because its eyes lack a lens, rendering it effectively blind. It relies entirely on echolocation to navigate and hunt in the turbid waters of the river.
Statement 2 is Incorrect: The presence of the Gangetic River Dolphin is an indicator of the health of the river ecosystem. Since these dolphins require specific ecological conditions to survive, their presence suggests that the river water is relatively clean and the ecosystem is functional, rather than indicating high pollution.
Statement 3 is Incorrect: The species is highly sensitive to habitat degradation. Untreated industrial chemicals, agricultural runoff, and pollution are major threats to its survival. It does not thrive in polluted waters; conversely, high pollution levels lead to a decline in its population.

Key Takeaway: The Gangetic River Dolphin is a blind freshwater mammal that uses echolocation. It acts as an indicator species for the health of the river; its presence signifies a healthy ecosystem, whereas pollution poses a severe threat to its existence.

Your note

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With reference to the agricultural practices in the Amazon Basin, consider the following statements: 1. Women are primarily responsible for taking care of the crops while men hunt. 2. The staple food is wheat, which grows above ground. 3. Cash crops like coffee, maize, and cocoa are also grown. Which of the statements given above is/are correct?

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Correct Option

The correct option is (a).

Explanation

Statement-wise Analysis

Statement 1 is Correct: The Gangetic River Dolphin is locally known as 'Susu' due to the sound it produces when breathing. It is also referred to as the "blind dolphin" because its eyes lack a lens, rendering it effectively blind. It relies entirely on echolocation to navigate and hunt in the turbid waters of the river.
Statement 2 is Incorrect: The presence of the Gangetic River Dolphin is an indicator of the health of the river ecosystem. Since these dolphins require specific ecological conditions to survive, their presence suggests that the river water is relatively clean and the ecosystem is functional, rather than indicating high pollution.
Statement 3 is Incorrect: The species is highly sensitive to habitat degradation. Untreated industrial chemicals, agricultural runoff, and pollution are major threats to its survival. It does not thrive in polluted waters; conversely, high pollution levels lead to a decline in its population.