Free Growth and Development MCQs with Answers

221. The genetic potential for one type of cell from a multicellular organism to generate a whole new organism is called

• A. unipotent
• B. multipotent
• C. totipotent
• D. pluripotent

Explanation: Totipotent is an immature cell that is capable of giving rise to any cell type or even a complete embryo.

222. Muscles develop from:

• A. ectoderm
• B. mesoderm
• C. endoderm
• D. all of the above

Explanation: Muscles develop from the mesoderm, which is one of the three primary germ layers in the early embryo. The mesoderm also gives rise to the skeletal and reproductive systems. The ectoderm forms the skin and nervous system, while the endoderm develops into the lining of the digestive and respiratory systems. Thus, the correct answer is B: mesoderm.

223. Lungs are _ in srcin.

• A. Ectodermal
• B. Endodermal
• C. Mesodermal
• D. Preformed

Explanation: The correct answer is Endodermal. The endoderm, one of the three primary germ layers formed during embryonic development, is responsible for the formation of the respiratory tract lining, including the lungs. This layer also forms other vital internal organs such as the liver, pancreas, and parts of the digestive system. The ectoderm and mesoderm, while important for forming other bodily structures, do not contribute to the primary functional tissue of the lungs. 'Preformed' is unrelated to germ layer origins and lung development.

224. Implantation of zygote takes place in the:

• A. 2nd week
• B. 3rd week
• C. 7th week
• D. 5th week

Explanation: Implantation is the process of the blastocyst embedding into the endometrial lining of the uterus, which typically occurs in Week 2 of development. For implantation to occur, the blastocyst must completely hatch from the zona pellucida once the conceptus enters the uterine cavity

225. Embryonic mass can generate all of the following except:

• A. Amnion
• B. Chorion
• C. Yolk sac
• D. Allantois

Explanation: The embryonic mass is the mass of cells inside the embryo that will eventually give rise to the definitive structures of the fetus. It cannot generate the chorion, which forms the placenta.

226. Trophoblast cells begin to display _ selection adhesion molecules on their surface soon after the blastocyst hatching.

• A. X selection
• B. D selection
• C. L selection
• D. C selection

Explanation: Trophoblast cells begin to display adhesion molecules on their surface soon after the blastocyst hatching.

227. The foertal sex becomes apparant during the:

• A. First trimester
• B. Second trimester
• C. Third trimester
• D. Both A and B

Explanation: During pregnancy, the fetal sex becomes apparent during the second trimester, which is around the 13th to 16th week of pregnancy. This is when ultrasound scans can often reveal whether the baby is a boy or a girl.

228. The primitive streak first appears in which labeled stage of embryonic diagram?

• A. A
• B. B
• C. C
• D. D

Explanation: The primitive streak is a key structure that forms during early embryonic development and marks the beginning of gastrulation. Stage C in the diagram represents the point where the inner cell mass begins to differentiate and form the bilaminar disc, which is when the primitive streak first appears as a groove in the epiblast layer.

229. Which of the following structures is formed from ectodermal tissue:

• A. Brain
• B. Muscles
• C. Skeleton
• D. Bones

Explanation: The brain is formed from ectodermal tissue. During embryonic development, the ectoderm is one of the primary germ layers that gives rise to various structures including the nervous system, skin, hair, and nails. The brain and nervous system originate from specialized ectodermal tissue. Therefore, option a is correct.

230. All animals begin life as a _.

• A. Multicellular fertilised egg
• B. Single fertilised egg
• C. Hollow blastula
• D. Gastrula

Explanation: All animals, from simple sponges to complex humans, begin their lives as a single fertilized egg cell, also known as a zygote. This zygote is formed when a sperm fertilizes an egg cell, resulting in a single cell with a unique combination of genetic material from both parents.From this single cell, the embryo develops through various stages, including:1. Cleavage: The zygote divides into multiple cells.2. Blastula: A hollow ball of cells forms.3. Gastrula: The blastula undergoes invagination, forming a multilayered embryo.So, while all animals do pass through the blastula and gastrula stages, they all begin life as a single fertilized egg.