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BIOLOGY 3 Marks Question

Human Reproduction · Bihar Board (BSEB) STD 12 Science (BSEB - English Medium). 126 questions.

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Question 13 Marks
How many eggs are released by a human ovary in a month? How many eggs do you think would have been released if the mother gave birth to identical twins? Would your answer change if the twins born were fraternal?
Answer
One egg is released by human ovary in a month:

Identical twins:

Identical twins are formed when a single fertilized egg splits into two genetically identical parts. The twins share the same DNA set, thus they may share many similar attributes. However, since physical appearance is influenced by environmental factors and not just genetics, identical twins can actually look very different.

Fraternal twins:

These twins are formed when two fertilized eggs are formed. The twins share the different DNA set, thus they may share different attributes (dizygotic embryo).

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Question 53 Marks
What is parturition? Which hormones are involved in induction of parturition?
Answer
The process of delivery of the foetus (childbirth) at the end of pregnancy is called parturition.
The hormones involved in induction of parturition are:
  • Oxytocin hormone from maternal pituitary stimulates strong uterine contractions that lead to expulsion of the baby from the uterus.
  • Relaxing hormone from ovary widens the vagina to facilitate birth.
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Question 63 Marks
Describe the structure of a seminiferous tubule.
Answer
The seminiferous tubule is a structural unit in the adult testis. The seminiferous tubules are situated in testicular lobules. Seminiferous tubule consists of two types of cells – Sertoli or supporting cells & spermatogenic cellsl Sertoli cells, are elongated and pyramidal & partially envelop the spermatogenic cells. The cells provide nourishment to the developing spermatogenic cells. Spermatogenic cells are stacked in 4-8 layers. These cells divide several times & differentiate to produce spermatozoa. Between seminiferous tubules lie the interstitial cells or leydig cells which produces testosterone hormone.
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Question 73 Marks
In our society the women are often blamed for giving birth to daughters. Can you explain why this is not correct?
Answer
All human beings have 23 pairs of chromosomes. Human males have 22 pairs of autosomes and contain one or two types of sex chromosome. They are either X or Y. On the contrary, human females have 22 pairs of autosomes and contain only the X sex chromosome. The sex of an individual is determined by the type of the male gamete (X or Y), which fuses with the X chromosome of the female. If the fertilizing sperm is X, then the baby will be a girl and if it is Y, then the baby will be a boy.
Hence, it is incorrect to blame a woman for the gender of the child.
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Question 93 Marks
Where is acrosome present in humans? Write its function.
Answer
On the sperm head, has enzymes to dissolve the follicles of ovum/facilitate entry of sperm nucleus for fertilisation/help the sperm enter into the cytoplasm of the ovum.
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Question 103 Marks
Name the embryonic stage that gets implanted in the uterine wall of a human female.
Answer
Blastocyst/Blastula.
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Question 113 Marks
Where does fertilisation normally take place in a human female?
Answer
Fallopian tubes/ (ampulla of) oviduct.
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Question 123 Marks
Write the location and function of the Sertoli cells in humans.
Answer
In the seminiferous tubules/testes, nourishes sperms/germ cells.
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Question 133 Marks
Name the type of cell division that takes place in the zygote of an organism exhibiting haplontic life cycle.
Answer
Meiosis.
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Question 143 Marks
How does colostrum provide initial protection against diseases to newborn infants? Give one reason.
Answer
Colostrum has abundant antibodies/IgA to develop resistance in newborn babies.
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Question 153 Marks
How many sperms will be produced from 100 primary spermatocytes and how many eggs will be produced from 100 primary oocytes?
Answer
400 sperms and 100 ova.
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Question 163 Marks
Identify the odd one out in each of the following sets:
  1. Rete testis, vas deferens, isthmus, epididymis.
  2. Seminal vesicles, ampulla, prostate, bulbourethral glands.
Answer
  1. Isthmus.
  2. Ampulla.
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Question 183 Marks
What is the role of cervix in the human female reproductive system?
Answer
Cervix helps in regulating the passage of sperms into the uterus and forms the birth canal to facilitate parturition.
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Question 213 Marks
When and where do chorionic villi appear in humans? State their functions.
Answer
Chorionic villi appear after implantation on the trophoblast. It becomes interdigitated with uterine tissue to form the placenta and increases the surface area for exchange of materials between the mother and the embryo.
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Question 223 Marks
What is the function of bulbourethral glands?
Answer
The secretions of the bulbourethral glands help in the lubrication of the penis.
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Question 233 Marks
Name the process of the rupture of Graafian follicle and the subsequent release of the egg from the ovary.
Answer
Ovulation.
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Question 243 Marks
How many primary follicles are left in each ovary in a human female at puberty?
Answer
60,000-80,000 primary follicles are left in each ovary.
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Question 253 Marks
Mark the odd one the following groups.
Fimbriae, Labia minora, Infundibulum, Isthmus.
Answer
Labia minora.
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Question 273 Marks
Mark the odd one the following groups.
Luteinizing hormone, Progesterone, Chorionic gonadotropin, Estrogen.
Answer
Luteinizing hormone.
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Question 283 Marks
The corona radiata of an ovum acts as a barrier for the penetration of sperms. How do sperms overcome this barrier?
Answer
The acrosome of the sperm contains sperm lysin (hyaluronidase) which dissolve the mucopolysaccharide, hyaluronic acid by which the cells of corona radiata glued together.
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Question 293 Marks
Mark the odd one the following groups.
Rete testis, Vasa efferentia, Epididymis, Ampulla.
Answer
Ampulla.
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Question 333 Marks
Name the cells that nourish the germ cells in the testes. Where are these cells located in the testes?
Answer
Sertoli cells. They are found on the inner lining of seminiferous tubule.
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Question 343 Marks
Sperms have a tail, whereas eggs do not. Why?
Answer
Because eggs are non-motile (stationary) and sperms have to travel up to eggs.
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Question 353 Marks
State where the signals for parturition arise from, in humans.
Answer
The signals for parturition arise from the fully-developed foetus and the placenta.
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Question 363 Marks
Name the important mammary gland secretions that help in resistance of the new born baby.
Answer
Colostrum.
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Question 383 Marks
How is the first sign of growing foetus noticed?
Answer
The first sign of growing foetus is noticed by listening to the heart sounds through a stethoscope.
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Question 393 Marks
Define spermiogenesis. Where does it occur?
Answer
Spermiogenesis is the formation of haploid, microscopic and functional spermatozoa (male gametes) from the spermatids. It takes place in the testes (male reproductive organ).
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Question 403 Marks
Observe the relationship between first two words and suggest suitable word for the fourth one:
  1. Ovary : Mesovarium :: Uterus: A.
  2. Male : Penis :: Female : B.
  3. Male gametes: Sperms:: Female gametes: C.
Answer
  1. A - Pelvic wall.
  2. B - Clitoris.
  3. C - Ova.
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Question 413 Marks
Match Column I with Column II.
S. No.
Column I
S. No.
Column II
A.
Cleavage
1.
Outer layer of the blastocyst that attaches to the endometrium during implantation.
B.
Implantation
2.
Mitotic divisions of the zygote in quick succession.
C.
Inner cell mass
3.
Embedding of the blastocyst in the endometrium of uterus.
D.
Trophoblast
4.
Release of secondary oocyte from the ovary.
E.
 
5.
Group of cells attached to one end of trophoblast that differentiate into embryo proper.
Answer
S. No.
Column I
S. No.
Column II
A.
Cleavage
2.
Mitotic divisions of the zygote in quick succession.
B.
Implantation
3.
Embedding of the blastocyst in the endometrium of uterus.
C.
Inner cell mass
5.
Group of cells attached to one end of trophoblast that differentiate into embryo proper.
D.
Trophoblast
1.
 
Outer layer of the blastocyst that attaches to the endometrium during implantation.
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Question 423 Marks
From which germ layers do the following organs differentiate?
  1. Kidney.
  2. Urinary bladder.
Answer
  1. Mesoderm.
  2. Endoderm.
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Question 433 Marks
Given below are the events in human reproduction. Write them in correct sequential order.
Insemination, gametogenesis, fertilisation, parturition, gestation, implantation.
Answer
Gametogenesis → Insemination → Fertilisation → Implantation → Gestation → Parturition.
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Question 443 Marks
During reproduction, the chromosome number (2n) reduces to half (n) in the gametes and again resume the original number (2n) in the offspring, what are the processes through which these events take place?
Answer
Halving of chromosomal number takes place during gametogenesis by meosis and regaining the 2n number occur as a result of fertilisation by fusion of male and female gametes.
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Question 453 Marks
Female reproductive organs and associated functions are given below in column A and B. Fill in the blank boxes.
Column A
Column B
Ovaries
Ovulation
Oviduct
A
B
Pregnancy
Vagina
Birth
Answer
A-Fertilisation.
B-Uterus.
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Question 463 Marks
What is trophoectoderm?
Answer
The outer layer of blastocyst is referred to as trophoectoderm or trophoblast.
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Question 473 Marks
Spermatids possess haploid chromosome number. Explain.
Answer
Spermatids are produced by meiosis during spermatogenesis. Thus, they possess haploid number of chromosomes.
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Question 483 Marks
How is the entry of only one sperm and not many ensured into an ovum during fertilisation in humans?
Answer
During fertilisation a sperm head comes in contact with zona pellucida layer of ovum and induces changes in the membrane that block the entry of additional sperms.
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Question 493 Marks
State the stage at which oogonia reach their maximum number.
Answer
Before birth at five months of foetal life, oogonia reach their maximum number.
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Question 503 Marks
Explain the function of umbilical cord.
Answer
Umbilical cord transports nutrients and respiratory gases and metabolic wastes to and from mother and foetus.
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