ICSE 2018
Q. Given below are diagrams showing the different stages in the process of fertilization of an egg in the human female reproductive tract. [5 marks]
Study the diagrams and answer the questions:
(i) Arrange the letters given below each diagram in logical sequences to show the correct order in the process of fertilization.
(ii) Where does fertilization normally take place? What is ‘Implantation’ that follows fertilisation
(iii) Mention the chromosome number of the egg and zygote in humans.
(iv) Explain the term ‘Gestation’. How long does Gestation last in humans?
(v) Draw neat, labelled diagram of a mature human sperm.
Solution:
This 5 marks question based on Fertilization process in Humans and was asked by ICSE board in the year 2018 in SECTION-II.
The question tested the knowledge of students on the:
- Stages in the fertilization of an egg,
- Fertilization, Implantation
- Gestation
- Diagram of Human Sperm
Let's begin with solving the above mentioned questions:
(i) The logical sequence of fertilization will be in the order: D, C, B, A
A : Egg with nucleus
B: Millions of sperms approach egg
C: One sperm is able to enter the egg and others are prevented (Impregnation)
D: Nucleus of the sperm approaches nucleus of the egg and other sperms die and disintegrate
(ii) Fertilization normally takes place in Oviducts.
After an egg is fertilized by the sperm in oviducts, the cells of fertilized egg (zygote) starts to divide and multiply in number such as 2, 4, 16, 256 and so on. By the time zygote reaches uterus, it becomes a small hollow ball of numerous cells called Blastocysts. This blastocyst gets attached to the wall of uterus (endometrium) after 5-7 days of ovulation by the process called IMPLANTATION.
(iii) The number of chromosomes in egg = 23
The number of chromosomes in zygote = 46
(iv) The full term of development of an embryo in the uterus is called GESTATION.
The period of gestation in humans is of 280 days.
(v) Below is the diagram of Human Sperm:
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