Consider the following statements about the 'streamlined' shape: 1. It helps animals move inside water. 2. It is a feature exclusively found in fish and not in mammals like whales. 3. Squids and octopuses maintain a streamlined shape even when resting. Which of the statements given above is/are correct?

The correct option is (a). Explanation Aquatic animals often develop specific physical adaptations, such as a streamlined body shape, to overcome the resistance of water and facilitate efficient movement. This shape minimizes friction and drag. Statement-wise Analysis: - Statement 1 is Correct: A streamlined shape tapers at both ends (like a boat), allowing water to flow easily around the body. This significantly reduces resistance, enabling animals to move faster and with less energy expenditure inside water. - Statement 2 is Incorrect: This feature is not exclusive to fish. Aquatic mammals, such as whales and dolphins, also possess streamlined bodies to swim efficiently. This similarity between fish and aquatic mammals is a classic example of convergent evolution, where unrelated species evolve similar traits to adapt to the same environment. - Statement 3 is Incorrect: Squids and octopuses do not maintain a streamlined shape permanently. They typically inhabit deeper ocean waters near the seabed and do not have a streamlined body when resting or waiting for prey. However, when they move quickly through the water, they are capable of altering their body posture to make it streamlined. Key Takeaway: Streamlining is a structural adaptation to reduce fluid friction. While permanent in fish and whales, some animals like squids and octopuses only adopt this shape temporarily during fast movement.

NCERT Class 6 Science — Chapter 4: The living organisms - characteristics and habitats

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Consider the following statements about the 'streamlined' shape:

It helps animals move inside water.
It is a feature exclusively found in fish and not in mammals like whales.
Squids and octopuses maintain a streamlined shape even when resting.

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

The correct option is (a).

Explanation

Aquatic animals often develop specific physical adaptations, such as a streamlined body shape, to overcome the resistance of water and facilitate efficient movement. This shape minimizes friction and drag.

Statement-wise Analysis:

Statement 1 is Correct: A streamlined shape tapers at both ends (like a boat), allowing water to flow easily around the body. This significantly reduces resistance, enabling animals to move faster and with less energy expenditure inside water.
Statement 2 is Incorrect: This feature is not exclusive to fish. Aquatic mammals, such as whales and dolphins, also possess streamlined bodies to swim efficiently. This similarity between fish and aquatic mammals is a classic example of convergent evolution, where unrelated species evolve similar traits to adapt to the same environment.
Statement 3 is Incorrect: Squids and octopuses do not maintain a streamlined shape permanently. They typically inhabit deeper ocean waters near the seabed and do not have a streamlined body when resting or waiting for prey. However, when they move quickly through the water, they are capable of altering their body posture to make it streamlined.

Key Takeaway: Streamlining is a structural adaptation to reduce fluid friction. While permanent in fish and whales, some animals like squids and octopuses only adopt this shape temporarily during fast movement.

Your note

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The correct option is (a).

Explanation

Statement-wise Analysis:

Statement 1 is Correct: A streamlined shape tapers at both ends (like a boat), allowing water to flow easily around the body. This significantly reduces resistance, enabling animals to move faster and with less energy expenditure inside water.
Statement 2 is Incorrect: This feature is not exclusive to fish. Aquatic mammals, such as whales and dolphins, also possess streamlined bodies to swim efficiently. This similarity between fish and aquatic mammals is a classic example of convergent evolution, where unrelated species evolve similar traits to adapt to the same environment.
Statement 3 is Incorrect: Squids and octopuses do not maintain a streamlined shape permanently. They typically inhabit deeper ocean waters near the seabed and do not have a streamlined body when resting or waiting for prey. However, when they move quickly through the water, they are capable of altering their body posture to make it streamlined.