CBSE Questions for Class 12 Medical Biology Human Reproduction Quiz 14 - MCQExams.com

• Germ layer specification in the blastula results in formation of the three germ layers: mesoderm, endoderm, and ectoderm.
• Ectoderm develops into parts of the skin, the brain and the nervous system.
• Mesoderm gives rise to bones, muscles, the heart and circulatory system, and internal sex organs. 
• Endoderm turns into the inner lining of some systems, and some organs such as the liver and pancreas.
• So, the correct option is 'Mesoderm: pancreas'.

• Diploid primary spermatocytes undergo meiosis I and produce two secondary spermatocytes with chromosome numbers reduced to half. 
• Each haploid secondary spermatocytes will have 8 chromosomes. However, chromatids, as produced by DNA replication during S phase, are still attached to the parental chromosome at the centromere. 
• So, each secondary spermatocyte will have 16 chromatids.
  Thus, the correct answer is option C.

1. Ectoderm gives rise to hair, epithelial layer of various tissues and organs (including epidermis of skin), nails or hooves, retina of eyes, etc.
   
2. Endoderm gives rise to gut tube including stomach, intestines, cecum, pancreas and liver along with other organs like lungs, thymus, prostate, etc.

• The blastula is usually a spherical solid layer of cells surrounding a fluid-filled or yolk-filled cavity (the blastocoel).
• Cells migrate to the interior of the blastula, subsequently forming two (in diploblastic animals) or three (triploblastic) germ layers. The embryo during this process is called a gastrula.
• The zygote undergoes many cleavages (divisions) to develop into a ball of cells called a morula and when the fluid-filled cavity (blastocoele) is formed, the early embryo becomes a blastula.
• So, the correct option is 'It is a less advanced stage than morula'.

• During pregnancy, the layer of the endometrium in the uterine cavity of the mother gets transformed to form the maternal placenta, which helps in the implantation and providing nourishment to the fetus.
• The stratum basalis is the lowermost layer of the endometrium. The decidua basalis is the part between the stratum basalis and embryo.
• The decidua capsularis is the part of endometrium which covers the embryo. This part is located between the maternal endometrium and the embryo. 
  

• Embryonic induction refers to the process in which one group of cells, the inducing tissue, directs the development of another group of cells, the responding tissue.
  
• This is an important process for formation of gastrula from blalstula i.e. gastrulation.
• So, the correct option is 'Embryonic induction'.

• During formation of gastrula, cells migrate to the interior of the blastula, subsequently forming two (in diploblastic animals) or three (triploblastic) germ layers.
• Morphogenesis is the process that causes an organism to develop its shape. 
• Development of germ layers in gastrula is an example of morphogenesis as here germ layers later determines various tissue differentiation, their relative arrangements and shape of organs.
  
• So, the correct option is 'Morphogenesis'.

• The germinal epithelial cells undergo mitosis and form multiple cells.
• Some of the cells grow in size and form the primary spermatocyte which is diploid in nature.
• These primary spermatocyte undergoes a meiotic division and forms two secondary spermatocytes which are haploid in nature.
• These secondary spermatocytes again undergo the second meiosis and form four haploid spermatids.
• 
  

The first two weeks of development, which is a period of cell division and initial differentiation is called Early embryonic developmental stage. It also called prefunctional stages.