Reproduction and Embryo Development

1. Asexual reproduction takes place through budding in

Asexual reproduction takes place through budding in

[amp_mcq option1=”E. coli” option2=”Amoeba” option3=”Plasmodium” option4=”Yeast” correct=”option4″]

This question was previously asked in
UPSC CISF-AC-EXE – 2021
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Budding is a form of asexual reproduction in which a new organism develops from an outgrowth or bud due to cell division at one particular site. Yeast, a type of fungus, commonly reproduces asexually by budding. A small bud emerges from the parent cell, grows, and eventually separates to form a new individual.
Other examples of organisms that reproduce by budding include Hydra (an animal) and sponges. E. coli and Amoeba reproduce by binary fission, where the parent cell divides into two equal daughter cells. Plasmodium, the parasite causing malaria, reproduces asexually by multiple fission (schizogony) within host cells.
Asexual reproduction does not involve the fusion of gametes and results in offspring that are genetically identical to the single parent. Besides budding and binary fission, other modes of asexual reproduction include fragmentation, regeneration, spore formation, and vegetative propagation in plants.

2. In a sexually reproducing organism, which one of the following stateme

In a sexually reproducing organism, which one of the following statements is appropriate both for the parent and offspring ?

[amp_mcq option1=”Chromosome number increases but DNA content remains constant” option2=”Both chromosome number and DNA content remains constant” option3=”Chromosome number decreases but DNA content remains constant” option4=”Both chromosome number and DNA content decreases” correct=”option2″]

This question was previously asked in
UPSC NDA-2 – 2023
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In a sexually reproducing species, the characteristic chromosome number remains constant from one generation to the next. Meiosis in the parent produces haploid gametes (n chromosomes, half the DNA content per set of chromosomes compared to somatic cells). Fertilization of two haploid gametes restores the diploid chromosome number (2n) in the offspring zygote. The amount of DNA per set of chromosomes is also maintained across generations through the DNA replication and segregation processes during cell division. Therefore, comparing the somatic cells of a parent and its offspring, both the chromosome number (2n) and the DNA content per somatic cell remain constant for the species.
Sexual reproduction involves the halving of chromosome number during gamete formation (meiosis) and the restoration of the diploid number during fertilization, thereby maintaining the species-specific chromosome number and genetic content across generations.
While the DNA content fluctuates within a single cell cycle (doubling before division and halving during division), the fundamental amount of DNA associated with the diploid chromosome set characteristic of the species remains constant across parent and offspring generations in terms of somatic cells.

3. The two important features of sexual reproduction in higher organisms

The two important features of sexual reproduction in higher organisms that create genetic diversity in offspring are

[amp_mcq option1=”Mitosis and fertilization” option2=”Meiosis and fertilization” option3=”Mitosis and binary fission” option4=”Meiosis and conjugation” correct=”option2″]

This question was previously asked in
UPSC NDA-2 – 2023
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Meiosis and fertilization are the two key processes in sexual reproduction that generate genetic diversity. Meiosis involves crossing over and independent assortment of chromosomes, creating unique combinations of alleles in the haploid gametes. Fertilization is the fusion of two distinct gametes (usually from different individuals), combining their unique genetic material to form a diploid zygote with a novel genetic makeup.
Genetic diversity is primarily generated through recombination (crossing over) and segregation of homologous chromosomes during meiosis, and the random combination of gametes during fertilization.
Mitosis is involved in growth and repair but produces genetically identical cells. Binary fission is a form of asexual reproduction producing clones. Conjugation is a method of genetic transfer in some prokaryotes and protists but is not the fundamental process for generating diversity in sexual reproduction of higher organisms like the combination of meiosis and fertilization.

4. Which one of the following is NOT a component of human male reproducti

Which one of the following is NOT a component of human male reproductive system ?

[amp_mcq option1=”Cervix” option2=”Urethra” option3=”Seminal vesicle” option4=”Vas deferens” correct=”option1″]

This question was previously asked in
UPSC NDA-2 – 2020
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The human male reproductive system includes organs responsible for producing sperm and male hormones, as well as transporting sperm out of the body. The Urethra is part of both the urinary and reproductive systems, carrying urine and semen. The Seminal vesicle produces fluid that contributes to semen. The Vas deferens is a tube that carries sperm from the epididymis towards the ejaculatory duct. The Cervix is the lower, narrow part of the uterus in the female reproductive system, connecting the uterus to the vagina. Therefore, the cervix is NOT a component of the human male reproductive system.
The cervix is a distinct anatomical structure found in the female reproductive system, not the male.
Key organs of the male reproductive system include the testes, epididymis, vas deferens, seminal vesicles, prostate gland, bulbourethral glands, urethra, and penis. The female reproductive system includes ovaries, fallopian tubes, uterus, cervix, vagina, and external genitalia.

5. Which one of the following is the mechanism of action of oral contrace

Which one of the following is the mechanism of action of oral contraceptive pills?

[amp_mcq option1=”They kill the egg.” option2=”They kill the sperm.” option3=”They kill the zygote.” option4=”They inhibit the release of egg.” correct=”option4″]

This question was previously asked in
UPSC NDA-1 – 2022
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The correct option is D.
Oral contraceptive pills primarily work by inhibiting ovulation, which is the release of the egg from the ovary.
Combined oral contraceptive pills (containing estrogen and progestogen) and progestogen-only pills have multiple mechanisms of action, but the inhibition of ovulation is the most significant. They also cause changes in cervical mucus (making it thicker and less penetrable by sperm) and the uterine lining (making it less receptive to implantation), but preventing the release of the egg is the primary way they prevent pregnancy. They do not kill the egg, sperm, or a formed zygote.

6. Which of the following statements are correct ? In honey bees 1. Ma

Which of the following statements are correct ?
In honey bees

  • 1. Males are haploid.
  • 2. Workers are sterile and diploid.
  • 3. Queen develops from diploid larvae that fed on royal jelly.
  • 4. Honey is collected/made by males.

Select the correct answer using the code given below :

[amp_mcq option1=”1, 2, 3 and 4″ option2=”2 and 3 only” option3=”1, 2 and 3 only” option4=”1 and 4 only” correct=”option3″]

This question was previously asked in
UPSC NDA-1 – 2016
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The correct option is C.
Let’s evaluate each statement:
1. Males (drones) develop from unfertilized eggs and are haploid (have half the number of chromosomes). This statement is correct.
2. Workers are sterile female bees that develop from fertilized eggs and are diploid (have the full set of chromosomes). This statement is correct.
3. The queen bee is a fertile female that also develops from a fertilized egg (a diploid larva). Her development into a queen is determined by being fed royal jelly exclusively throughout her larval stage. This statement is correct.
4. Honey is made by female worker bees from nectar collected from flowers. Male drones do not participate in foraging or honey production. This statement is incorrect.
Based on the evaluation, statements 1, 2, and 3 are correct.
The sex determination system in honey bees is haplodiploidy. Males are haploid, and females (workers and queens) are diploid. The destiny of a diploid larva to become a worker or a queen is determined by diet; larvae fed royal jelly exclusively become queens, while those fed a mix of pollen and nectar become workers.

7. Which one of the following animals lays eggs to reproduce?

Which one of the following animals lays eggs to reproduce?

[amp_mcq option1=”Dolphin” option2=”Seal” option3=”Platypus” option4=”Whale” correct=”option3″]

This question was previously asked in
UPSC Geoscientist – 2023
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The correct answer is Platypus.
The Platypus (Ornithorhynchus anatinus) is a monotreme, a group of mammals that lay eggs instead of giving birth to live young. Dolphins, seals, and whales are placental mammals and are viviparous, meaning they give birth to live offspring.
Monotremes are the most primitive group of mammals, and the only living examples are the platypus and four species of echidnas. They share characteristics of both mammals (like possessing mammary glands and fur) and reptiles (like laying eggs).

8. Which of the following roles is/are played by epididymis, vas deferens

Which of the following roles is/are played by epididymis, vas deferens, seminal vesicles and prostate in male reproductive system of human?

[amp_mcq option1=”Spermatogenesis and maturation of sperms” option2=”Maturation and motility of sperms” option3=”Spermatogenesis and motility of sperms” option4=”Motility of sperms only” correct=”option2″]

This question was previously asked in
UPSC CDS-2 – 2018
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The roles played by epididymis, vas deferens, seminal vesicles and prostate in the male reproductive system primarily include maturation and motility of sperms.
Spermatogenesis, the production of sperm, occurs in the seminiferous tubules within the testes. The structures listed play subsequent roles:
– Epididymis: Sperm produced in the testes are immature and non-motile. They mature and gain motility (the ability to swim) in the epididymis during their passage through this coiled tube. It also stores sperm.
– Vas deferens: This duct transports mature sperm from the epididymis to the ejaculatory duct during ejaculation. It does not play a significant role in maturation or production.
– Seminal vesicles and Prostate: These are accessory glands that produce the seminal fluid, which mixes with sperm to form semen. This fluid contains substances (like fructose from seminal vesicles and enzymes from the prostate) that provide nutrients and support for sperm motility, survival, and function within the female reproductive tract.
Therefore, maturation (epididymis) and facilitating motility (epididymis and the fluid contributions from seminal vesicles/prostate) are key roles of these structures.
The complete path of sperm from production to ejaculation involves testes (spermatogenesis) -> epididymis (maturation, storage) -> vas deferens (transport) -> ejaculatory duct (formed by vas deferens and seminal vesicle duct) -> urethra. Bulbourethral glands (Cowper’s glands) also contribute fluid to the semen.

9. An irregular mode of reproduction resulting in the development of an e

An irregular mode of reproduction resulting in the development of an embryo without fertilization is called
1. Parthenogenesis
2. Apogamy
3. Sporophytic budding
Select the correct answer using the code given below.

[amp_mcq option1=”1 only” option2=”2 only” option3=”2 and 3 only” option4=”1, 2 and 3″ correct=”option4″]

This question was previously asked in
UPSC CDS-2 – 2016
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The question describes apomixis, which is a form of asexual reproduction that mimics sexual reproduction by resulting in the formation of an embryo without fertilization. Parthenogenesis, Apogamy, and Adventitious embryony are all types of apomixis. While “Sporophytic budding” is not the most standard term, it is sometimes used to describe the development of embryos or embryo-like structures directly from sporophytic tissue, which falls under the umbrella of adventitious embryony, a form of apomixis. Given the options, it is likely intended to include different origins of apomictic embryos.
1. Parthenogenesis: Development of an embryo directly from an unfertilized egg cell.
2. Apogamy: Development of a sporophyte (embryo) from any gametophytic cell other than the egg (e.g., synergids, antipodal cells) without fertilization.
3. Sporophytic budding (or Adventitious embryony): Development of an embryo directly from diploid sporophytic cells (like nucellus or integument) without the formation of gametes or fertilization. If “sporophytic budding” refers to this, then all three processes result in an embryo without fertilization.
Apomixis is common in many plant species, including some important crop plants and wild relatives. It can lead to the production of clonal offspring.

10. Syngamy results in formation of

Syngamy results in formation of

[amp_mcq option1=”haploid zygote” option2=”diploid zygote” option3=”non-motile male gametes” option4=”motile male gametes” correct=”option2″]

This question was previously asked in
UPSC CDS-1 – 2017
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Syngamy is the fusion of two gametes (usually a male and a female gamete) to form a single cell called a zygote. In most organisms, gametes are haploid (containing half the number of chromosomes, denoted as n). The fusion of two haploid gametes results in a diploid zygote, which contains the full number of chromosomes (denoted as 2n).
Syngamy is the core event of sexual reproduction, leading to the formation of the first diploid cell of the new organism.
The zygote undergoes mitotic divisions and differentiation to develop into an embryo and eventually a complete organism. Motility of gametes is a characteristic of the gametes themselves, not an outcome of syngamy.
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