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BIOLOGY 3 Marks Question

Human Reproduction · Gujarat Board (GSEB) STD 12 Science (GSEB - English Medium). 126 questions.

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Question 13 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 23 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 33 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 63 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 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
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 163 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 173 Marks
How is a primary spermatocyte different from a secondary spermatocyte?
Answer
  1. A primary spermatocyte is diploid and has 46 chromosomes; it undergoes meiosis I and forms two secondary spermatocytes.
  2. A secondary spermatocyte is haploid and has 23 chromosomes; it undergoes meiosis II and forms two spermatids.
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Question 183 Marks
Sperms have a tail whereas egg does not, why?
Answer
Sperms swim by vibrating their tail in the fluid while eggs do not require it.
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Question 203 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 213 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 223 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 233 Marks
What is trophoectoderm?
Answer
The outer layer of blastocyst is referred to as trophoectoderm or trophoblast.
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Question 253 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 263 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 273 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 283 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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Question 293 Marks
How many eggs do you think were released by the ovary of a female dog which gave birth to 6 puppies?
Answer
Six eggs were released by the ovary of a female dog which gave birth to six puppies.
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Question 313 Marks
Given below are the stages 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 323 Marks
Which type of cell division forms spermatids from the secondary spermatocytes?
Answer
Second meiotic division.

 

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Question 333 Marks
What is semen?
Answer
Seminal plasma (secreted by the male reproductive glands) along with the spermatozoa, constitute semen.
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Question 343 Marks
The diagram shows the female reproductive system. Where do fertilisation and implantation occur?

Answer
Fertilisation takes place in Fallopian tube (W) and implantation takes place in uterus (Y).
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Question 353 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 363 Marks
Luteal phase of the menstrual cycle is also called the secretory phase. Give reason.
Answer
In this phase, progesterone stimulates the endometrial glands of the uterus to secrete a nutrient fluid for the foetus hence, also called the secretory phase.
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Question 383 Marks
Males in whom testes fail to descend to the scrotum are generally infertile. Why?
Answer
If the testes fail to descend to the scrotum, gametogenesis could be inhibited. The process of spermatogenesis requires a marginally lesser ambient temperature than that in the abdominal cavity.
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Question 393 Marks
Mention the importance of LH surge during menstrual cycle.
Answer
LH surge is essential for the events leading to ovulation.
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Question 403 Marks
Mention the function of trophoblast in human embryo.
Answer
Trophoblast is the outer layer of blastocyst which helps in the attachment of blastocyst to the endometrium of the uterus.
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Question 413 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 423 Marks
What is the significance of ampullary–isthmic junction in the female reproductive tract?
Answer
First cleavage division of zygote occurs in the ampullary-isthmic junction in the female reproductive tract.
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Question 433 Marks
What do you mean by foetal ejection reflex?
Answer
These are mild uterine contraction induced by the signals for parturition originated from fully developed foetus and placenta.
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Question 443 Marks
List the changes that the primary ooctye undergoes in the tertiary follicular stage in the human ovary.
Answer
The primary oocyte within the tertiary follicle grows in size and completes its first meiotic division to form secondary oocyte and first polar body.
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Question 453 Marks
Are there any homologous organs in male and female reproductive system? If yes, give examples.
Answer
Yes. For example, the external reproductive organ penis in males and clitoris in females.
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Question 463 Marks
Name the hormones produced only during pregnancy in a human female. Mention their source organ.
Answer
During pregnancy, placenta produces hormones like human chorionic gonadotropin and human placental lactogen and ovary produces relaxin.
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Question 493 Marks
What is endometrium?
Answer
It is the innermost glandular layer of uterus which lines the uterine cavity. Here, implantation of blastocyst takes place. It undergoes cyclical changes during menstrual cycle.
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Question 503 Marks
Mention the difference between spermiogenesis and spermiation.
Answer
Spermiogenesis: It is the transformation of spermatids into spermatozoa or sperms.
Spermiation: It is the release of sperms from seminiferous tubules.
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3 Marks Question - BIOLOGY STD 12 Science Questions - Vidyadip