This set of Class 12 Biology Chapter 3 Multiple Choice Questions & Answers (MCQs) focuses on “Human Reproduction – Implantation”.
1. What are the mitotic divisions that a zygote undergoes called?
a) Meiosis
b) Cleavage
c) Fertilization
d) Fetal development
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Explanation: As the zygote is formed, it passes through isthmus towards the uterus. Through the passage, it undergoes rapid mitotic divisions. This is called cleavage.
2. The daughter cells formed as a result of cleavage of a zygote are called ________
a) Blastocysts
b) Blastula
c) Blastomeres
d) Blastocoel
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Explanation: Zygote undergoes cleavage producing an exponential increase in cell mass. These new daughter cells formed are called blastomeres. They form a blastula with a blastocoel cavity enclosed in between.
3. What is the correct lineage of a zygote?
a) Zygote -> Blastomere -> Morula -> Blastocyst
b) Zygote -> Blastula -> Morula -> Blastocyst
c) Zygote -> Morula -> Blastomere -> Blastula
d) Zygote -> Blastocyst -> Blastula -> Blastomere
View Answer
Explanation: Zygote undergoes rapid cleavage to form 2, 4, 6, and then 8 blastomeres. They undergo few more rounds of division to form morula. Cells divide further to form a hollow ball called a blastula. This is followed by minor differentiation of cells to produce a blastocyst.
4. What is the outer layer of blastocyst called?
a) Blastomere
b) Trophoblast
c) Blastocoel
d) Inner cell mass
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Explanation: Blastocyst is formed from blastomeres. It is organized into an outer layer of cells called trophoblast and an inner layer of cells called inner cell mass.
5. Which layer of blastomere gets attached to the endometrium of the uterus?
a) Blastomere
b) Trophoblast
c) Blastocoel
d) Inner cell mass
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Explanation: The blastomere is composed of an internal inner mass of cells and an external layer of cells called the trophoblast. The trophoblast attaches to the endometrium and forms the fetal part of the placenta.
6. What does inner cell mass give rise to?
a) Trophoblast
b) Endometrium
c) Placenta
d) Embryo
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Explanation: Inner cell mass is the internal layer of blastomere. Upon attachment of blastomere, the inner cell mass undergoes differentiation to form the embryo.
7. The embryo is derived from _________
a) uterine wall
b) trophoblast
c) inner cell mass
d) blastocoel
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Explanation: The trophoblast, along with the uterine cell wall, gives rise to the placenta. The inner cell mass, on the other hand, differentiates to form the embryo.
8. What is implantation?
a) Attachment of umbilical cord to the developing fetus
b) The fusion of male and female gametes
c) Covering of the blastomere by the uterine wall
d) Rapid division of the zygote
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Explanation: Fertilization is the fusion of male and female gametes. Cleavage is the rapid divisions that lead to the formation of a zygote. Implantation is the process that leads to the covering of the blastomere by the uterine endometrium.
9. The last process that leads to pregnancy is called _________
a) fertilization
b) cleavage
c) lactation
d) implantation
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Explanation: Fertilization is one of the first processes that may result in pregnancy. Cleavage is the division of zygote that give rise to blastomeres. Lactation occurs to post-pregnancy. Implantation is the attachment of the developing embryo to the uterine wall. This is the last step that leads to pregnancy.
10. Eight to sixteen cell stage embryo is called ______
a) Blastomere
b) Zygote
c) Blastula
d) Morula
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Explanation: Zygote divides rapidly via the process of cleavage. Each division doubles the number of cells. The 8 to 16 cell stage embryo starts attaining a bolus shape and is hence called a morula. The morula later transforms into a blastula and then a blastocyst.
11. The cavity present in the blastula is called _______
a) Coelom
b) Fluid
c) Blastocoel
d) Blastopore
View Answer
Explanation: The cell divisions after the morula stage are slightly asymmetric. This leads to the formation of a cavity in the blastula. This cavity is called blastocoel and is critical for the migration of cells that occurs during gastrulation.
Sanfoundry Global Education & Learning Series – Biology – Class 12.
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- Practice Class 12 - Mathematics MCQs
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- Practice Class 12 - Chemistry MCQs
