RBSE Solutions Class 12 Biology Chapter 33 Embryonic Development in Man

RBSE Class 12 Biology Chapter 33 Multiple Choice Questions

Question 1. How many cells are found in Morula?
(a) 4
(b) 8
(c) 16
(d) 32
Answer: (c) 16
In simple words: The morula is an early stage of an embryo. It usually has about 16 cells that look like a mulberry.

🎯 Exam Tip: Remember the approximate cell count for key early embryonic stages like morula, blastula, and gastrula to correctly identify them.

Question 2. Which cavity is formed during gastrulation?
(a) Animal pole
(b) Vegetal pole
(c) Blastocoel

🎯 Exam Tip: Familiarize yourself with the major cavities and structures formed during different stages of embryonic development, such as blastulation and gastrulation.

Question 3. Major parts of eyes are derived from which germinal layer?
(a) Ectoderm
(b) Mesoderm
(c) Endoderm
(d) None of the options
Answer: (a) Ectoderm
In simple words: The outer layer of cells in an embryo, called the ectoderm, gives rise to important parts of the eyes.

🎯 Exam Tip: Know which organs and body parts develop from each of the three primary germ layers (ectoderm, mesoderm, endoderm).

Question 4. Formation of Kidney takes place from which of the following germinal layer
(a) Ectoderm
(b) Mesoderm
(c) Endoderm
(d) None of the options
Answer: (b) Mesoderm
In simple words: The middle layer of cells in an embryo, known as the mesoderm, is responsible for forming the kidneys.

🎯 Exam Tip: Distinguish between the derivatives of each germ layer to correctly answer questions about organ development.

Question 5. Which activity does not takes place during the first week of embryonic development of human?
(a) Implantation
(b) Formation of blastocoel
(c) Morula formation
(d) Formation of Primitive streak
Answer: (d) Formation of Primitive streak
In simple words: The primitive streak forms later in development, not during the very first week of a human embryo.

🎯 Exam Tip: Understand the timeline of major developmental events in the first few weeks of human embryonic life to identify processes that occur early versus later.

Question 6. Development of heart completes during embryonic development of human in -
(a) First week
(b) Second week

🎯 Exam Tip: Keep track of the critical periods for the development of major organs like the heart, as these are frequently tested in embryology.

RBSE Class 12 Biology Chapter 33 Very Short Answer Type Questions

Question 1. What is Embryogenesis?
Answer: Embryogenesis is the process where a single-celled zygote develops into a multicellular embryo. It involves cell division and differentiation.
In simple words: It's the journey from one cell to a full, early-stage embryo.

🎯 Exam Tip: Define key biological terms clearly and concisely, highlighting the main stages or outcomes of the process.

Question 2. What kind of cell divisions take place during cleavage?
Answer: During cleavage, mitotic cell divisions occur. These divisions happen very quickly without any growth phase, meaning the cells divide but do not increase in size between divisions.
In simple words: Cells divide by mitosis rapidly, but the overall embryo doesn't grow bigger during this phase.

🎯 Exam Tip: Emphasize the key characteristic of cleavage, which is cell division without growth, making it distinct from typical mitosis.

Question 3. What are blastomeres?
Answer: Blastomeres are the individual cells that are formed when a zygote undergoes cleavage, which is a series of rapid mitotic cell divisions.
In simple words: They are the cells created when an egg starts dividing after fertilization.

🎯 Exam Tip: Use precise terminology. "Blastomeres" refers specifically to the cells produced during cleavage, not just any dividing cell.

Question 4. How many blastomeres are found in morula?
Answer: A morula typically contains 16 blastomeres.
In simple words: A morula stage embryo has 16 cells.

🎯 Exam Tip: Remember the specific cell count (16 cells) associated with the morula stage, as it's a defining characteristic.

Question 5. What is derived from blastopore in a man?
Answer: In humans, the blastopore develops into the anus.
In simple words: For humans, the blastopore opening becomes the anus.

🎯 Exam Tip: Understand the fate of the blastopore in different animal groups (protostomes vs. deuterostomes) and specifically for humans.

RBSE Class 12 Biology Chapter 33 Short Answer Type Questions

Question 1. How the formation of blastocyst takes place in Human?
Answer:
Blastulation is the process where a morula transforms into a blastula, or specifically a blastocyst in humans. As the human morula travels towards the uterus, its outer cells flatten. These flattened outer cells are called the trophoblast, which helps the embryo attach to the uterine lining. Inside, the cells differentiate into two groups: the trophoblast (nutritive cells surrounding a cavity) and an inner cell mass (formative cells of the embryo). A cavity called the blastocoel forms within this structure. The entire embryo at this stage, with its blastocoel cavity, is known as a blastocyst.
In simple words: The morula changes into a blastocyst. This involves the outer cells becoming a trophoblast, an inner cell group forming, and a fluid-filled space (blastocoel) appearing inside.

🎯 Exam Tip: When describing a biological process, break it down into sequential steps, clearly naming the structures involved at each stage.

Question 2. Differentiate between blastulation and gastrulation?
Answer:

🎯 Exam Tip: For differentiation questions, use a table format to clearly present contrasting features, ensuring each point corresponds to the opposite process.

RBSE Class 12 Biology Chapter 33 Essay Type Questions

Question 1. How and when the formation of blastocyst takes place?
Answer:
Blastulation is the process of forming a blastula or blastocyst from a morula. This process typically occurs about 4-5 days after fertilization, as the embryo reaches the uterus.
In a human morula, as it enters the uterus, the outer cuboidal cells flatten and become known as the trophoblast. These trophoblast cells help the embryo attach to the uterine lining. The cells continue to divide, and a cluster of cells begins to differentiate. Two distinct groups emerge: the epithelial-like trophoblast cells that surround an expanding cavity, and the inner cell mass, which consists of formative cells of the embryo.
A fluid-filled cavity, called the blastocoel, forms within this structure. At this stage, the entire embryo is called a blastocyst. The trophoblast cells aggressively invade the uterine tissue, making contact to help form the placenta. Meanwhile, the inner cell mass differentiates. A layer of very flat cells appears on its interior surface, which will form the future endoderm. The remaining dorsal inner cell mass is known as the epiblast, which will later form the ectoderm and mesoderm.
In simple words: The blastocyst forms from the morula around 4-5 days after fertilization, when it reaches the uterus. The outer cells become the trophoblast to help implantation, while inner cells form the embryo. A fluid-filled cavity also forms inside.

🎯 Exam Tip: For essay questions, provide a detailed, step-by-step explanation. Include timing, key cell types, and structures formed during the process, and clearly define any specialized terms.

Question 3. A child born after seven months gestation period can survive. Explain How?
Answer: A child born after seven months of pregnancy, which is a gestation period of about 28 weeks, can often survive because most of the vital body organs have already formed and developed by this time. While they may still require significant medical support and care, the basic structures and functions needed for life are in place, allowing for survival outside the womb.
In simple words: By seven months, a baby's important body parts are mostly formed. This means they can live outside the mother, often with special medical help.

🎯 Exam Tip: Explain the physiological reason behind the survival, focusing on organ development rather than just stating the possibility of survival.