Biology Test Biology Developmental Biology & Embryology 1 — Questions and Answers
Question 1: What term describes the series of rapid mitotic cell divisions that occur immediately after fertilization, producing smaller and smaller cells?
- Gastrulation
- Cleavage (Correct answer)
- Organogenesis
- Neurulation
Correct answer: Cleavage
Cleavage refers to the rapid mitotic divisions following fertilization that divide the zygote into blastomeres without significant cell growth between divisions.
Question 2: What is the inner cell mass (embryoblast) of the blastocyst primarily responsible for forming?
- The trophoblast layer
- The embryo proper and some extraembryonic structures (Correct answer)
- The zona pellucida
- The corpus luteum
Correct answer: The embryo proper and some extraembryonic structures
The inner cell mass of the blastocyst gives rise to the embryo proper as well as some extraembryonic membranes, and is the source of embryonic stem cells.
Question 3: During gastrulation, which three primary germ layers are established?
- Ectoderm, mesoderm, and endoderm (Correct answer)
- Epidermis, dermis, and hypodermis
- Cortex, medulla, and stroma
- Periosteum, endosteum, and bone marrow
Correct answer: Ectoderm, mesoderm, and endoderm
Gastrulation establishes the three primary germ layers—ectoderm, mesoderm, and endoderm—from which all tissues and organs of the body will ultimately develop.
Question 4: Which germ layer gives rise to the central nervous system, including the brain and spinal cord?
- Endoderm
- Mesoderm
- Ectoderm (Correct answer)
- Trophoblast
Correct answer: Ectoderm
The ectoderm, specifically the neuroectoderm, gives rise to the central nervous system through the process of neurulation.
Question 5: What is neurulation?
- The formation of early blood vessels
- The process by which the neural plate folds and fuses to form the neural tube (Correct answer)
- The migration of neural crest cells to peripheral targets
- The terminal differentiation of neurons in the adult brain
Correct answer: The process by which the neural plate folds and fuses to form the neural tube
Neurulation is the embryonic process by which the flat neural plate (derived from ectoderm) folds at the neural folds and fuses to create the hollow neural tube, precursor to the brain and spinal cord.
Question 6: What is the primitive streak in early vertebrate development?
- A cluster of cells that gives rise to the heart
- A thickening of the epiblast that marks the site of gastrulation and establishes the body axis (Correct answer)
- The first blood vessel to form in the yolk sac
- A structure in the trophoblast that anchors the embryo
Correct answer: A thickening of the epiblast that marks the site of gastrulation and establishes the body axis
The primitive streak is a thickening and groove along the midline of the epiblast that marks the initiation of gastrulation and defines the anterior-posterior axis of the vertebrate embryo.
Question 7: Which extraembryonic membrane functions primarily in gas exchange and metabolic waste storage in bird and reptile embryos, and contributes to the umbilical cord in mammals?
- Amnion
- Chorion
- Yolk sac
- Allantois (Correct answer)
Correct answer: Allantois
The allantois is a sac-like outgrowth of the hindgut that stores nitrogenous waste and facilitates gas exchange in reptiles and birds; in mammals it contributes blood vessels to the umbilical cord.
Biology Test Biology Developmental Biology & Embryology 1
What term describes the series of rapid mitotic cell divisions that occur immediately after fertilization, producing smaller and smaller cells?