Which one of the following is the correct chronological sequence of development stages? 1. Foetus 2. Zygote 3. Embryo 4. Ball of cells Select the correct answer using the code given below:

The correct option is (a). Explanation The development of a new individual in sexual reproduction follows a specific biological sequence starting from fertilization and leading to the formation of a fully developed organism. This process involves cell division, differentiation, and organogenesis. Chronological Sequence of Development: 1. Zygote (2): This is the first stage of development. It is a single cell formed by the fusion of a male gamete (sperm) and a female gamete (ovum) during fertilization. 2. Ball of cells (4): The zygote undergoes repeated mitotic divisions (cleavage) as it moves down the oviduct. This results in a solid ball of cells known as the morula, which eventually develops into a hollow structure called the blastocyst. 3. Embryo (3): Once the ball of cells (blastocyst) implants itself into the wall of the uterus, it is referred to as an embryo. During this stage, cells begin to differentiate into specific tissues and organs. 4. Foetus (1): This is the stage of the embryo in which all the main body parts (such as hands, legs, head, eyes, etc.) can be identified. In humans, the embryo is generally termed a foetus from the eighth week of pregnancy until birth. Therefore, the correct sequence is Zygote → Ball of cells → Embryo → Foetus (2 - 4 - 3 - 1). Key Takeaway: Development proceeds from a single-celled zygote to a multicellular cluster (ball of cells), followed by tissue differentiation (embryo), and finally the maturation of identifiable body structures (foetus).

NCERT Class 8 Science — Chapter 3: Reproduction in animals

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Which one of the following is the correct chronological sequence of development stages?

Foetus
Zygote
Embryo
Ball of cells

Select the correct answer using the code given below:

Official previous-year question

Verified 1 Aug 2026.

Options

A2 - 4 - 3 - 1
B2 - 3 - 4 - 1
C4 - 2 - 3 - 1
D2 - 4 - 1 - 3

Did you get this right?

Solution

The correct option is (a).

Explanation

The development of a new individual in sexual reproduction follows a specific biological sequence starting from fertilization and leading to the formation of a fully developed organism. This process involves cell division, differentiation, and organogenesis.

Chronological Sequence of Development:

Zygote (2): This is the first stage of development. It is a single cell formed by the fusion of a male gamete (sperm) and a female gamete (ovum) during fertilization.
Ball of cells (4): The zygote undergoes repeated mitotic divisions (cleavage) as it moves down the oviduct. This results in a solid ball of cells known as the morula, which eventually develops into a hollow structure called the blastocyst.
Embryo (3): Once the ball of cells (blastocyst) implants itself into the wall of the uterus, it is referred to as an embryo. During this stage, cells begin to differentiate into specific tissues and organs.
Foetus (1): This is the stage of the embryo in which all the main body parts (such as hands, legs, head, eyes, etc.) can be identified. In humans, the embryo is generally termed a foetus from the eighth week of pregnancy until birth.

Therefore, the correct sequence is Zygote → Ball of cells → Embryo → Foetus (2 - 4 - 3 - 1).

Key Takeaway: Development proceeds from a single-celled zygote to a multicellular cluster (ball of cells), followed by tissue differentiation (embryo), and finally the maturation of identifiable body structures (foetus).

Your note

More from Chapter 3: Reproduction in animals

With reference to the development of the embryo in humans, consider the following statements: 1. The embryo gets embedded in the wall of the uterus for further development. 2. The stage where body parts like hands and eyes can be identified is called the zygote. 3. The embryo completes its full development into a baby within the fallopian tube. Which of the statements given above is/are correct?

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In the context of human reproduction, what is the primary distinction between a zygote and a foetus?

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In the context of hen reproduction, consider the following statements: 1. Hens undergo internal fertilisation. 2. The hard shell of the egg is formed after the egg is laid. 3. The embryo takes about 3 weeks to develop into a chick. Which of the statements given above is/are correct?

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With reference to the development of a chick, which one of the following statements is correct?

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Consider the following statements distinguishing Viviparous and Oviparous animals: 1. Viviparous animals are those that lay eggs. 2. Oviparous animals lay eggs which later develop into young ones. 3. Frogs and hens are examples of oviparous animals. Which of the statements given above is/are correct?

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The correct option is (a).

Explanation

Chronological Sequence of Development:

Zygote (2): This is the first stage of development. It is a single cell formed by the fusion of a male gamete (sperm) and a female gamete (ovum) during fertilization.
Ball of cells (4): The zygote undergoes repeated mitotic divisions (cleavage) as it moves down the oviduct. This results in a solid ball of cells known as the morula, which eventually develops into a hollow structure called the blastocyst.
Embryo (3): Once the ball of cells (blastocyst) implants itself into the wall of the uterus, it is referred to as an embryo. During this stage, cells begin to differentiate into specific tissues and organs.
Foetus (1): This is the stage of the embryo in which all the main body parts (such as hands, legs, head, eyes, etc.) can be identified. In humans, the embryo is generally termed a foetus from the eighth week of pregnancy until birth.

Therefore, the correct sequence is Zygote → Ball of cells → Embryo → Foetus (2 - 4 - 3 - 1).