CUET UG Biology Booster Test 3 Development and Parturition -

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CUET UG Biology Booster Test 3 Development and Parturition

⏱️ 30 Minutes

❓ 20 Questions

📌 Answers are locked once submitted — results and explanations appear at the end.

CUET UG Biology Booster Test 3 Development and Parturition

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QUESTION 1 OF 20

Statement I: The meiotic division of the secondary oocyte is completed only after the sperm enters the cytoplasm.
Statement II: The sex of the baby is determined by the chromosomal contribution of the sperm at the time of fertilization.

Answer Review

1 Statement I: The meiotic division of the secondary oocyte is completed only after the sperm enters the cytoplasm.
Statement II: The sex of the baby is determined by the chromosomal contribution of the sperm at the time of fertilization.

A Only Statement I is correct.

B Only Statement II is correct.

C Both Statement I and Statement II are correct.

D Both Statement I and Statement II are incorrect.

💡 Short Explanation

The secondary oocyte completes meiosis II only after fertilization. The ovum always contributes an X chromosome. The X or Y chromosome carried by the sperm determines the sex of the offspring.

✅ Correct Answer Explanation

Statement I is correct because the secondary oocyte remains arrested at metaphase II of meiosis and completes meiosis II only after the entry of the sperm into its cytoplasm during fertilization. Statement II is also correct because the ovum always contributes an X chromosome, whereas the sperm contributes either an X or a Y chromosome. Fertilization by an X-bearing sperm produces an XX (female) offspring, while fertilization by a Y-bearing sperm produces an XY (male) offspring. Thus, the sex of the baby is determined by the sperm. Therefore, both statements are correct.

❓ Why Other Options Are Incorrect

Option A → Incorrect because Statement II is also correct.
Option B → Incorrect because Statement I is also correct.
Option D → Incorrect because both statements are scientifically correct.

🎯 Strategy

Used: Statement Verification

Application: Evaluate each statement independently using NCERT concepts of fertilization and sex determination.

Final Logic: Since both statements are individually correct, the correct answer is Option C.

🧠 Memory Trick

"Sperm Starts Meiosis II and Sets the Sex."

📚 Class XII – Biology – Chapter: Human Reproduction – Topic: Fertilization and Sex Determination

2 Which factor is NOT a biological reality in human sex determination?

A There is a 50% statistical probability of having a male or female child.

B The mother is heterogametic, producing two types of eggs.

C The genetic makeup of the sperm is the deciding factor.

D Sex is determined at the zygote stage. Correct Answer: B) The mother is heterogametic, producing two types of eggs.

💡 Short Explanation

Mothers are homogametic (XX). They produce only one type of gamete (X). Heterogametic refers to males (XY).

✅ Correct Answer Explanation

In humans, females are homogametic (producing only X-bearing ov A), whereas males are heterogametic (producing X-bearing and Y-bearing sperm). Thus, stating the mother is heterogametic is biologically false.

❓ Why Other Options Are Incorrect

Option A: Statistically, there is a 50% chance for either sex.
Option C: True; the sperm's chromosomal content determines sex.
Option D: True; sex is fixed at the moment of zygote formation.

🎯 Strategy

Used: Extreme Word Filter Application: Identify the false statement regarding human genetics (heterogamety). Final Logic: Females are XX (homogametic C), not heterogametic.

🧠 Memory Trick

"Mother-Homogametic, Father-Heterogametic."

📚 Human Reproduction – Topic: Sex Determination

3 Arrange the following cellular events from fertilization to implantation in the correct order:
1. Completion of the second meiotic division of the oocyte.
2. Formation of 2-, 4-, 8-, and 16-blastomere stages.
3. Fusion of the haploid nuclei to form a diploid zygote.
4. Formation of the morula.

A 1 → 3 → 2 → 4

B 3 → 1 → 4 → 2

C 1 → 2 → 3 → 4

D 4 → 3 → 2 → 1

💡 Short Explanation

Sperm entry completes meiosis II of the secondary oocyte. Male and female pronuclei fuse to form the diploid zygote. The zygote undergoes cleavage to produce blastomeres, which later form the morula.

✅ Correct Answer Explanation

The correct chronological sequence begins when the entry of the sperm triggers the completion of the second meiotic division of the secondary oocyte (1). This produces the mature ovum and the second polar body. The male and female pronuclei then fuse (syngamy) to form the diploid zygote (3). The zygote undergoes successive mitotic cleavage divisions, producing 2-, 4-, 8-, and 16-blastomere stages (2). When the embryo reaches the 8–16 blastomere stage, it forms a morula (4), which later develops into a blastocyst before implantation. Therefore, the correct sequence is 1 → 3 → 2 → 4.

❓ Why Other Options Are Incorrect

Option B → Incorrect because syngamy cannot occur before the completion of meiosis II, and the morula forms only after cleavage.
Option C → Incorrect because cleavage begins only after the diploid zygote is formed through syngamy.
Option D → Incorrect because the morula is formed much later, after fertilization and several cleavage divisions.

🎯 Strategy

Used: Chronological Sequence Analysis

Application: Arrange the developmental events from fertilization through the early stages of embryonic development.

Final Logic: Meiosis II completion → Syngamy → Cleavage → Morula is the correct biological sequence.

🧠 Memory Trick

"Meiosis → Merge → Multiply → Morula."

📚 Class XII – Biology – Chapter: Human Reproduction – Topic: Fertilization, Cleavage and Morula Formation

4 The transition from morula to blastocyst involves:

A Moving from the ampulla to the isthmus.

B The arrangement of blastomeres into a trophoblast and inner cell mass.

C The formation of the heart.

D The secretion of colostrum.

💡 Short Explanation

Morula (solid ball) to Blastocyst (hollow ball). Differentiation into Trophoblast and ICM occurs.

✅ Correct Answer Explanation

As the morula continues to divide and moves towards the uterus, it transforms into a blastocyst. This stage is characterized by the rearrangement of blastomeres into an outer layer (trophoblast) and an inner group of cells (inner cell mass) surrounding a cavity (blastocoel).

❓ Why Other Options Are Incorrect

Option A: This is a movement, not a transition of structure.
Option C: Heart formation occurs much later (Organogenesis).
Option D: Colostrum secretion occurs postpartum.

🎯 Strategy

Used: Contextual Matching Application: Match the structural change (morula to blastocyst) with its defining anatomical feature. Final Logic: Blastocyst = Trophoblast + Inner Cell Mass.

🧠 Memory Trick

"Blastocyst = Outer layer + Inner mass."

📚 Class XII – Biology – Chapter: Human Reproduction – Topic: Blastocyst Structure

5 Match the Following

Column I (Component)	Column II (Developmental Fate)
1. Trophoblast	i. Attaches to endometrium
2. Inner Cell Mass	ii. Differentiates into the embryo
3. Stem Cells	iii. Potency to form all tissues
4. Blastocyst	iv. Embeds in the uterine wall

A 1-i, 2-ii, 3-iii, 4-iv

B 1-ii, 2-iii, 3-iv, 4-i

C 1-iii, 2-iv, 3-i, 4-ii

D 1-iv, 2-i, 3-ii, 4-iii

💡 Short Explanation

Matches structure to its biological function.

✅ Correct Answer Explanation

Trophoblast (1) interacts with the endometrium (i). Inner Cell Mass (2) becomes the embryo (ii). Stem cells (3) in the ICM have pluripotency (iii). The blastocyst (4) is the structure that embeds into the uterine wall (iv).

❓ Why Other Options Are Incorrect

All other options misalign these well-defined developmental roles.

🎯 Strategy

Used: Option Grouping Application: Align the term with its corresponding, well-established definition in NCERT. Final Logic: A is the only logically consistent mapping.

🧠 Memory Trick

D).

📚 Human Reproduction – Topic: Blastocyst/Implantation

6 Which of the following is NOT a characteristic of the blastocyst stage?

A Presence of a trophoblast layer.

B Presence of an inner cell mass.

C Having exactly 8 cells (morula stage).

D Moving further into the uterus for attachment.

💡 Short Explanation

Blastocyst > Morula (8-16 cells). 8 cells is a developmental stage before blastocyst formation.

✅ Correct Answer Explanation

A blastocyst consists of a trophoblast and an inner cell mass; it has significantly more than 8 cells. The 8-celled stage is specifically associated with the early morula, not the blastocyst.

❓ Why Other Options Are Incorrect

Option A, B, and D are all characteristic features of the blastocyst/implantation phase.

🎯 Strategy

Used: Elimination Application: Eliminate features characteristic of the blastocyst to find the one belonging to an earlier stage. Final Logic: Blastocyst structure is more complex than a simple 8-cell morula.

🧠 Memory Trick

"8 is a Morula, Blastocyst is more."

📚 Class XII – Biology – Chapter: Human Reproduction – Topic: Blastocyst Structure

7 Multiple Statement Type
Statement I: Implantation occurs before the trophoblast layer appears.
Statement II: Implantation is the embedding of the blastocyst in the endometrium.

A Statement I is true, Statement II is false.

B Statement II is true, Statement I is false.

C Both Statement I and Statement II are true.

D Both Statement I and Statement II are false.

💡 Short Explanation

The trophoblast develops during the blastocyst stage. Implantation occurs only after the blastocyst is formed. Implantation is the embedding of the blastocyst into the uterine endometrium.

✅ Correct Answer Explanation

Statement I is incorrect because the trophoblast develops as the outer cell layer of the blastocyst before implantation begins. It plays a crucial role in attaching the blastocyst to the uterine endometrium and initiating implantation. Statement II is correct because implantation is the process by which the blastocyst becomes embedded in the endometrium of the uterus. Following implantation, the trophoblast proliferates and contributes to the formation of the placenta. Therefore, Statement I is false and Statement II is true, making Option B the correct answer.

❓ Why Other Options Are Incorrect

Option A → Incorrect because Statement I is false, whereas Statement II is true.
Option C → Incorrect because implantation cannot occur before the trophoblast is formed.
Option D → Incorrect because Statement II correctly defines implantation.

🎯 Strategy

Used: Prerequisite Identification

Application: Determine whether implantation can occur without prior blastocyst and trophoblast formation.

Final Logic: Blastocyst (with trophoblast) forms first, followed by implantation into the endometrium.

🧠 Memory Trick

(The blastocyst, containing the trophoblast, forms before it burrows into the endometrium.)

📚 Class XII – Biology – Chapter: Human Reproduction – Topic: Blastocyst Formation and Implantation

8 The rapid division of uterine cells during implantation serves to:

A Nourish the sperm.

B Cover and secure the blastocyst within the endometrium.

C Trigger the second meiotic division.

D Expel the placenta. Correct Answer: B) Cover and secure the blastocyst within the endometrium.

💡 Short Explanation

Uterine wall reaction to blastocyst. Uterine cells divide to envelop/embed the embryo.

✅ Correct Answer Explanation

As the blastocyst embeds in the endometrium, the surrounding uterine cells divide rapidly and cover it. This process effectively buries the embryo within the uterine wall, securing it for further development.

❓ Why Other Options Are Incorrect

Option A: Sperm are nourished in the fallopian tube/vagina.
Option C: Triggered by fertilization, not implantation.
Option D: Occurs at birth (parturition).

🎯 Strategy

Used: Substitution Application: Replace "rapid division of uterine cells" with the action of embedding. Final Logic: The uterine wall adapts to secure the implanting blastocyst.

🧠 Memory Trick

"Covering = Securing the blastocyst."

📚 Human Reproduction – Topic: Implantation

📄 Passage

"The placenta facilitate the supply of oxygen and nutrients to the embryo and also removal of carbon dioxide and excretory/waste materials produced by the embryo. The placenta is connected to the embryo through an umbilical cord which helps in the transport of substances to and from the embryo."

Which of the following is NOT a role of the placenta according to the passage?

A Supply of oxygen

B Removal of carbon dioxide

C Direct formation of germ layers

D Endocrine function (hormone production)

💡 Short Explanation

Passage lists: O2 supply, CO2 removal, waste removal, umbilical transport. Formation of germ layers is an embryonic process, not a placental one.

✅ Correct Answer Explanation

The placenta facilitates substance exchange (nutrients/waste) and acts as an endocrine tissue. The formation of the three germ layers (ectoderm, mesoderm, endoderm) is an activity of the inner cell mass (embryo), not the placenta.

❓ Why Other Options Are Incorrect

Options A, B, and D are all explicitly or implicitly described as functions of the placenta in the passage and NCERT.

🎯 Strategy

Used: Extreme Word Filter Application: Scan the provided passage text for the listed functions and identify the outlier. Final Logic: Placenta = Exchange/Endocrine; Embryo = Germ layers.

🧠 Memory Trick

"Placenta = Exchange, Embryo = Germ layers."

📚 Human Reproduction – Topic: Placenta

📄 Passage

The placenta and umbilical cord work together to:

A Ensure the fetus remains in the ampulla.

B Maintain a physiological connection between mother and fetus.

C Determine the sex of the child.

D Induce the first meiotic division. Correct Answer: B) Maintain a physiological connection between mother and fetus.

💡 Short Explanation

Connection bridge. Nutrient/Waste transport.

✅ Correct Answer Explanation

The placenta and the umbilical cord together serve as the vital physiological bridge between the maternal blood supply and the developing fetus, enabling the transfer of oxygen, nutrients, and waste materials.

❓ Why Other Options Are Incorrect

Option A: The fetus must be in the uterus, not the ampulla.
Option C: Determined by sperm at fertilization.
Option D: First meiotic division occurs during oogenesis.

🎯 Strategy

Used: Contextual Matching Application: Match the combined unit (placenta + cor

D) to its essential life-support role. Final Logic: They act as the transport link between mother and fetus.

🧠 Memory Trick

"Placenta + Cord = Maternal-Fetal Link."

📚 Human Reproduction – Topic: Placenta and Umbilical Cord

11 Match the Following:

Column I (Hormone)	Column II (Function/Source)
1. hCG	i. Produced only during pregnancy
2. Relaxin	ii. Secreted by ovary in later pregnancy
3. Oxytocin	iii. Released from maternal pituitary for birth
4. Progestogens	iv. Produced by placenta for maintenance

A 1-i, 2-ii, 3-iii, 4-iv

B 1-ii, 2-iii, 3-iv, 4-i

C 1-iii, 2-iv, 3-i, 4-ii

D 1-iv, 2-i, 3-ii, 4-iii

💡 Short Explanation

hCG is pregnancy-specific. Relaxin is ovarian/late-pregnancy. Oxytocin is maternal pituitary (parturition). Progestogens are placental.

✅ Correct Answer Explanation

Each hormone is correctly matched: hCG (Human Chorionic Gonadotropin) is exclusive to pregnancy (i); Relaxin is ovarian and late-stage (ii); Oxytocin acts during birth from the pituitary (iii); Progestogens are essential for uterine maintenance (iv).

❓ Why Other Options Are Incorrect

Other options mismatch the specific physiological sources and timing of these crucial pregnancy hormones.

🎯 Strategy

Used: Option Grouping

Application: Match the hormone name with its primary NCERT-defined source and timing.

Final Logic: Option A correctly maps each hormone to its corresponding biological role.

🧠 Memory Trick

"hCG-Only, Relaxin-Later, Oxytocin-Birth, Progest-Maintain."

📚 Class XII – Biology – Chapter: Human Reproduction – Topic: Pregnancy Hormones –

12 Which of the following is NOT a reason for the increased levels of maternal hormones (cortisol, prolactin, etc.)?

A Supporting fetal growth.

B Managing maternal metabolic changes.

C Maintaining the pregnancy.

D Initiating the first cleavage division.

💡 Short Explanation

Cleavage occurs due to zygote's own cycle. Maternal hormones support the gestation period, not the initial cleavage.

✅ Correct Answer Explanation

Increased maternal hormones like cortisol, prolactin, and thyroxine are essential for supporting the mother's metabolic state and fetal growth during gestation. The first cleavage division is a purely cellular event occurring shortly after fertilization, independent of maternal systemic hormones.

❓ Why Other Options Are Incorrect

Options A, B, and C are the core biological reasons for the surge in pregnancy-related hormones.

🎯 Strategy

Used: Elimination

Application: Eliminate fetal growth and metabolic support roles to find the developmental mismatch.

Final Logic: Cleavage is an intrinsic embryonic event, not regulated by late-gestation maternal hormones.

🧠 Memory Trick

"Hormones = Growth, Cleavage = Division."

📚 Class XII – Biology – Chapter: Human Reproduction – Topic: Pregnancy –

13 The presence of stem cells in the inner cell mass is significant because:

A They form the trophoblast.

B They have the potency to give rise to all tissues and organs.

C They secrete oxytocin.

D They prevent the entry of additional sperms.

💡 Short Explanation

ICM contains stem cells. These are pluripotent. They form the body (all organs).

✅ Correct Answer Explanation

The inner cell mass (ICM) is known to contain stem cells. These cells exhibit potency (pluripotency), meaning they can differentiate into all the different tissues and organs that make up the human body.

❓ Why Other Options Are Incorrect

Option A: Trophoblast forms from outer cells.
Option C: Oxytocin is pituitary-derived.
Option D: Prevention of polyspermy is a zona pellucida function.

🎯 Strategy

Used: Contextual Matching

Application: Define the role of stem cells in embryogenesis.

Final Logic: Stem cells = Tissue/Organ differentiation.

🧠 Memory Trick

"Stem Cells = Building Blocks of Body."

📚 Class XII – Biology – Chapter: Human Reproduction – Topic: Blastocyst Structure –

14 The appearance of structures from the inner cell mass: 1. Mesoderm 2. Ectoderm and Endoderm 3. All tissues/organs

A 2 → 1 → 3

B 1 → 2 → 3

C 3 → 2 → 1

D 2 → 3 → 1

💡 Short Explanation

Ectoderm and endoderm form first. Mesoderm appears subsequently. The three layers form all organs.

✅ Correct Answer Explanation

After implantation, the inner cell mass differentiates into the ectoderm and endoderm (2). Shortly after, the mesoderm appears between them (1). These three germ layers then give rise to all tissues and organs in the adult (3).

❓ Why Other Options Are Incorrect

Other sequences fail to reflect the chronological order of germ layer differentiation (Gastrulation).

🎯 Strategy

Used: Elimination

Application: Identify the primary layer formation followed by secondary formation.

Final Logic: Germ layers sequence (Ecto/Endo > Meso > Tissues).

🧠 Memory Trick

"2 Layers (E & E), then Middle (M), then Organs."

📚 Class XII – Biology – Chapter: Human Reproduction – Topic: Germ Layers –

15 By the end of the first trimester, which is NOT typically fully developed?

A Limbs

B External genital organs

C Eyelashes

D Major organ systems

💡 Short Explanation

Eyelashes appear in the 2nd trimester (5th month). 12 weeks includes limbs and genitals.

✅ Correct Answer Explanation

By the end of 12 weeks (first trimester), the fetus has well-developed limbs, digits, and external genital organs. Major organ systems are also formed. Eyelashes and eyelids are features that develop during the second trimester.

❓ Why Other Options Are Incorrect

Options A, B, and D are all classic developmental milestones reached by the end of the first trimester.

🎯 Strategy

Used: Extreme Word Filter

Application: Scan for the feature appearing latest in the gestation timeline.

Final Logic: Eyelashes are a second-trimester development.

🧠 Memory Trick

"1st Trimester = Organs/Limbs; 2nd = Hair/Eyelashes."

📚 Class XII – Biology – Chapter: Human Reproduction – Topic: Organogenesis Timeline –

16 At which stage can a doctor first listen to the fetal heart sound?

A 1 month

B 2 months

C 3 months

D 5 months

💡 Short Explanation

Heart is the first organ formed. Visible/audible early.

✅ Correct Answer Explanation

The first sign of a growing fetus, observed through a stethoscope, is the heart sound. This occurs by the end of the first month of pregnancy.

❓ Why Other Options Are Incorrect

Options B, C, and D occur after the heart has already formed and started beating.

🎯 Strategy

Used: Contextual Matching

Application: Recall the very first organogenesis milestone.

Final Logic: Heart formation = 1 month.

🧠 Memory Trick

"Heart at Month One."

📚 Class XII – Biology – Chapter: Human Reproduction – Topic: Organogenesis –

17 Statement I: Appearance of hair on the head is observed during the fifth month. Statement II: By the end of nine months, the fetus is ready for parturition.

A Only I is correct

B Only II is correct

C Both are correct

D Both are incorrect

💡 Short Explanation

Month 5 = Hair and movement. Month 9 = Full term/delivery.

✅ Correct Answer Explanation

Both statements accurately summarize key gestational milestones. The fifth month marks the emergence of hair on the head and fetal movement. By the ninth month, the development is complete, and the fetus is prepared for delivery.

❓ Why Other Options Are Incorrect

The statements accurately reflect the NCERT timeline.

🎯 Strategy

Used: Substitution

Application: Confirm both facts against standard developmental charts in NCERT.

Final Logic: Both developmental timeline facts are accurate.

🧠 Memory Trick

"Five-Hair, Nine-Done."

📚 Class XII – Biology – Chapter: Human Reproduction – Topic: Gestation –

18 The separation of eyelids and formation of eyelashes occurs at:

A 12 weeks

B 24 weeks

C 36 weeks

D 40 weeks

💡 Short Explanation

Occurs in 2nd trimester. Roughly 5-6 months.

✅ Correct Answer Explanation

By the end of the second trimester (approx. 24 weeks), the fetus shows development of the body, including the separation of eyelids and the formation of eyelashes.

❓ Why Other Options Are Incorrect

Option A (12 weeks) is too early; C and D are near the end of gestation.

🎯 Strategy

Used: Elimination

Application: Eliminate the end of the first trimester (12 weeks) to identify the second-trimester timing.

Final Logic: Eyelash development is a mid-gestation milestone.

🧠 Memory Trick

"Six Months = Eyelashes/Lids."

📚 Class XII – Biology – Chapter: Human Reproduction – Topic: Gestation –

19 Which of the following is NOT part of the neuroendocrine mechanism of parturition?

A Fetal ejection reflex.

B Release of oxytocin from maternal pituitary.

C Stronger uterine contractions.

D Regeneration of the endometrium.

💡 Short Explanation

Parturition is the birth process. Regeneration of the endometrium is part of the menstrual/recovery cycle.

✅ Correct Answer Explanation

Parturition is triggered by a neuroendocrine reflex involving the fetal ejection reflex (A), which stimulates the maternal pituitary to release oxytocin (B), causing stronger uterine contractions (C). Endometrial regeneration occurs during the menstrual cycle, not during birth.

❓ Why Other Options Are Incorrect

Options A, B, and C are the core components of the birth process.

🎯 Strategy

Used: Elimination

Application: Eliminate the components of the birth reflex to identify the process related to the menstrual cycle.

Final Logic: Parturition is an expulsive, not regenerative, event.

🧠 Memory Trick

"Birth = Expulsion, Not Regeneration."

📚 Class XII – Biology – Chapter: Human Reproduction – Topic: Parturition –

20 Why is breast-feeding recommended during the initial period of infant growth?

A It induces the fetal ejection reflex.

B Colostrum provides essential antibodies for resistance.

C It helps the placenta be expelled.

D It triggers the formation of digits.

💡 Short Explanation

Colostrum = First milk. Rich in IgA (antibodies). Provides infant immunity.

✅ Correct Answer Explanation

Colostrum, the yellowish fluid secreted by the mammary glands during the first few days of lactation, is highly recommended because it contains essential antibodies (Ig A) that provide the newborn with resistance against diseases.

❓ Why Other Options Are Incorrect

Options A, C, and D are physiologically incorrect or unrelated to breastfeeding.

🎯 Strategy

Used: Contextual Matching

Application: Match the term "Colostrum" with "Immunity/Antibodies."

Final Logic: Colostrum is immunologically protective.

🧠 Memory Trick

"Colostrum = Antibodies = Protection."

📚 Class XII – Biology – Chapter: Human Reproduction – Topic: Lactation/Colostrum –

CUET UG Biology Booster Test 3 Development and Parturition

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