Cleavage Biology
Cleavage refers to the division of cells in the early embryo and it is a characteristic term for embryology. After cleavage, fertilization follows where the transfer is triggered with an activation of cyclin-dependent kinase complex. Many species have their zygotes undergo rapid cell cycles having no significant overall growth. It produces a cluster of cells of the same size as that of the origins zygote. Different cells which are obtained as a result of the cleavage are called Blastomeres and these form a compact mass known as Morula. The cleavage biology ends with the formation of the Blastula.
What is Cleavage in Biology?
Cleavage in biology or cleavage in zoology is the same as explained in the above paragraph. The repeated mitotic division of the zygote in order to form a solid ball of cells is known as the morula and is later changed into a hollow ball of cells known as the blastula, this process is known as the Cleavage. This process of Cleavage of the human zygote takes place within the fallopian tube. The zygote is entirely divided into the daughter cells or blastomeres.
The two categories of cleavage depend on the amount of yolk present in the egg and those are holoblastic, where total or entire cleavage takes place and the second one is meroblastic cleavage also known as partial cleavage. Meroblastic cleavage takes place in the presence of a large amount of yolk in the fertilized egg cell and its two types are discoidal and superficial cleavage. Vegetal pole is the pole of the egg where the highest concentration of yolk is present and its opposite is known as animal pole.
The three types of cleavage are determinate cleavage, indeterminate and holoblastic cleavage. Holoblastic cleavage can be further divided into bilateral, radial, rotational and spiral.
After 30 hours of fertilization, the first Cleavage takes place. In this process, the zygote is completely divided longitudinally into two blastomeres. After 40 hours of fertilization, the second Cleavage takes place which results in four blastomeres formed in the first Cleavage and to which the second Cleavage is at right angles. After 72 hours of fertilization, the third Cleavage takes place. The young embryo slowly moves towards the uterus down the fallopian tube during the early Cleavage process. The embryo reaches the uterus at the end of the fourth day which looks like mulberry and is called the morula. There are 32 cells present in the morula. The Cleavage is radial and in Determinate in the case of the human zygote.
Below are some of the samples for Cleavage Biology MCQs for NEET 2025
1. Meroblastic Cleavage is another name for which of these
(a) Equal holoblastic
(b) Unequal holoblastic
(c) Partial
(d) Superficial
Answer: (c)
2. Which type of Cleavage is found in Insects?
(a) Discoidal
(b) Holoblastic
(c) Meroblastic
(d) Superficial
Answer: (d)
3. Discoidal and Superficial Cleavages belong to which type of Cleavage?
(a) Unequal holoblastic
(b) Equal holoblastic
(c) Both (a) and (b)
(d) Meroblastic
Answer: (d)
4. When the first Cleavage furrow divides the Zygote completely into two, it is
(a) Meroblastic cleavage
(b) Radial cleavage
(c) Equatorial cleavage
(d) Holoblastic cleavage
Answer: (d)
5. The only system in Humans which is derived from all the three Germ layers is
(a) Nervous system
(b) Respiratory system
(c) Digestive system
(d) Excretory system
Answer: (c)
6. The process by which fertilized egg divides is known as
(a) Cleavage
(b) Oogenesis
(c) Regeneration
(d) Invagination
Answer: (a)
7. When an unfertilized egg is pricked with a micro needle, what happens?
(a) It will transform into a tadpole at a faster rate
(b) It starts dividing
(c) It will remain undivided
(d) It will die immediately
Answer: (b)
8. How many cells are there in a freshly unfertilized egg of hen?
(a) One cell
(b) 1,000 cells
(c) 100 cells
(d) 10,000 cells
Answer: (a)
9. A 16 celled stage of egg completes how many Cleavages?
(a) 12
(b) 4
(c) 8
(d) 3
Answer: (b)
10. The spindle in determinate Cleavage is situated
(a) Horizontal
(b) Vertical
(c) Oblique
(d) Sub-equatorial
Answer: (c)
11. How many hours after fertilization, the zygote undergoes a series of Mitotic divisions to form Blastomeres?
(a) 10 hours
(b) 5 hours
(c) 15 hours
(d) 30 hours
Answer: (d)
12. An outer envelope of cells in the Blastocyst is called
(a) Trophoblast
(b) Embryoblast
(c) Animal pole
(d) Anembryonic pole
Answer: (a)
13. Implantation occurs after how many days of Fertilization?
(a) 2 days
(b) 4 days
(c) 10 days
(d) 7 days
Answer: (d)
14. Which of the following is correct during Cleavage?
(a) Embryo size decreases
(b) Cell’s size decreases
(c) Cell’s size increases
(d) Embryo size increases
Answer: (b)
15. In mammalian egg, Cleavage is
(a) Discoidal meroblastic
(b) Unequal holoblastic
(c) Equal holoblastic
(d) Superficial meroblastic
Answer: (c)
16. In an egg, the Cleavage type can be determined by
(a) Sperm’s shape and size
(b) Location and size of the nucleus
(c) Distribution and amount of yolk
(d) Number of egg membranes
Answer: (c)
17. What’s true about the Cleavage in fertilized eggs of Humans?
(a) It starts in the fallopian tube
(b) It starts when egg reaches the uterus
(c) It is meroblastic
(d) It is identical to normal mitosis
Answer: (a)
18. How is the division of Meroblastic Cleavage?
(a) Horizontal
(b) Spiral
(c) Total
(d) Parietal/partial
Answer: (d)
FAQs on Cleavage Biology MCQs for NEET 2025
1. Is Cleavage an important topic in NEET 2025?
Yes, Cleavage is an important topic if students are aiming to go for the competitive exam NEET. Cleavage means the rapid series which occurs after the fertilization of mitotic division of the zygote which results in the formation of the blastula. Some of the important sub-topics of Cleavage include its definition, difference between Cleavage and typical mitosis, planes of Cleavage, patterns of Cleavage, Cleavage on the basis of potency, types of Cleavage, Cleavage in the human zygote, types of blastula, the significance of Cleavage, and so on. For a better understanding of the topic- Cleavage, students can visit Vedantu.
2. What are some of the importance of Cleavage?
Cleavage is important as it restores the nucleo-cytoplasmic ratio and the cell size of the species. It just increases the cell number, not the growth. Most of the cellular activities are controlled by the organelles while the process of Cleavage takes place. Cleavage also segregates the different substances into different cells that are present in the cytoplasm. These substances help in the determination of how the various cells will develop later.
3. What are some of the types of Blastula?
There are a total of 5 types of blastula which include coeloblastula, stereoblastula, discoblastula, blastocyst, and peri blastula. Coeloblastula is a hollow blastula with either single or multi-layered blastoderm. Stereoblastula does not have any blastocoel. Discoblastula lies on the top of the yolk of the animal pole. The blastocyst contains blastula in the form of cysts composed of two cells- outer epithelium and embryonal knob. The peri blastula contains the blastocoel which is filled with yolk and surrounded by a peripheral layer of cells.
4. What is meant by Bilateral Cleavage?
The Cleavage in which the blastomeres are arranged in a way that the right and left sides become distinct. In the case of bilateral Cleavage, the first four blastomeres might appear larger than the other two. This property helps in establishing a plane for the development of an embryo of bilateral symmetry. Examples of organisms where bilateral Cleavage takes place include cephalopods, nematodes, some echinoderms, mollusks, and tunicates.
5. What is meant by Spiral Cleavage?
The Cleavage which is diagonal to the polar axis is known as the spiral Cleavage. In the case of spiral Cleavage, the spindles for the third Cleavage are oriented diagonally which results in the sidewise upper tier of cells. Between the four lower cells, the upper 4 cells are placed on the junction. The lower cells are larger and are known as macromeres while the upper cells are smaller known as micromeres. During the third Cleavage, the fourth spindle is arranged in a sort of spiral which is the reason why it is known as spiral Cleavage.
