ZOO501T Final Term Past Papers 2023 by Sulman Ali

ZOO501- DEVELOPMENTAL BIOLOGY · Final-Term File 2023 By · SULMAN ALI (BS-ZOOLOGY) · Composition of hyaline membrane:

The hyaline layer is actually made up of two layers, an outer lamina made primarily of hyalin protein and an inner lamina composed of fibropellin proteins.

Which type of egg present in birds or chicks.

Telolecithal egg is present in birds. It is a type of egg that has large amount of yolk that is unevenly distributed in the cytoplasm.

In which portion the hemisphere present.

The portion of egg that has large amount of yolk is known as vegetal hemisphere and it is present toward posterior side of the egg.

Write the three name of vesicle formed in brain.

1= Prosencephalon (forebrain), 2= Mesencephalon (midbrain), 3= Rhombencephalon (hindbrain).

What are the osteoclasts:

the bone marrow.

Differences between identical and fraternal twins.

Identical twins

Fraternal twins

Identical twins are monozygotic twins. Fraternal twins are dizygotic twins. They are formed from a single zygote or fertilized egg. They are formed from two eggs are fertilized by two different sperms. The zygote splits into two parts and each part develops into an individual embryo. Two eggs are fertilized by two different sperms. Their genetic origin is the same and therefore they have the same DNA. They share 50% of their genetic traits, just like any other sibling born at different times. They are of the same sex. The sexes may be the same or different. They share the same blood type. The blood types may or may not be the same.

What are the three axis of foundation of the body:

Three axes are the foundations of the body: the anterior-posterior axis (head to tail or mouth to anus), the dorsal-ventral axis (back to belly), and the right-left axis (between the two lateral Sides of the body).

Write a note on osteoclast in detail:

the bone marrow. The blood vessels also import the blood-forming cells that will reside in the marrow for the duration of the organism's life. The number and activity of osteoclasts must be tightly regulated. If there are too many active osteoclasts, too much bone will be dissolved, and osteoporosis will result. Conversely, if not enough osteoblasts are produced, the bones are not hollowed out for the marrow, and osteopetrosis results.

Differentiation of the neural tube:

The brain develops from this early tube structure and gives rise to specific regions of the adult brain. As the neural tube grows and differentiates, it enlarges into three vesicles that correspond to the forebrain, midbrain, and hindbrain regions of the adult brain. Later in development, two of these three vesicles differentiate further, resulting in five vesicles. Those five vesicles can be aligned with the four major regions of the adult brain. The cerebrum is formed directly from the telencephalon. The diencephalon is the only region that keeps its embryonic name. The mesencephalon, metencephalon, and myelencephalon become the brain stem. The cerebellum also develops from the metencephalon and is a separate region of the adult brain.

Define neural plate:

The neural plate is a key developmental structure that serves as the basis for the nervous system. Opposite the primitive streak in the embryo, ectodermal tissue thickens and flattens to become the neural plate. The region anterior to the primitive knot can be generally referred to as the neural plate.

What is meroblastic Cleavage.

Meroblastic cleavage involves an early separation between cells at the animal pole and yolk at the vegetal pole of the egg, and cell furrows encompass only the animal-most region of the embryo, leaving the yolk intact. For example: cleavages of birds, insects, fish, and reptiles.

Define sub-germinal cavity and its function:

Between the blastoderm and the yolk is a space called the subgerminal cavity. This space is created when the blastoderm cells absorb fluid from the albumin (“egg white”) and secrete it between themselves and the yolk. It gives the central part of the blastodisc a semitransparent appearance and this area is called the area pellucida.

Define diploblastic animals and their examples:

Diploblastic animals are those who have ectoderm and endoderm, but no true mesoderm. These include the cnidarians (jellyfish and hydras).

Events of primary neurulation:

The head and trunk regions both undergo variants of primary neurulation, and this process can be divided into four distinct but spatially and temporally overlapping stages: (1) formation of the neural plate; (2) shaping of the neural plate; (3) bending of the neural plate to form the neural groove; and (4) closure of the neural groove to form the neural tube.

Function of placenta:

Placenta is a disc like structure that forms a connection between the embryo and the uterine wall. The placenta acts to provide oxygen and nutrients to the fetus, whilst removing carbon dioxide and other wasteproducts. It metabolises a number of substances and can release metabolic products into maternal and/or fetal circulations.

Blastula formation in Tunicate:

These animals are characterized by bilateral holoblastic cleavage, a pattern found primarily in tunicates. Each successive division orients itself to this plane of symmetry, and the half-embryo formed on one side of the first cleavage plane is the mirror image of the half-embryo on the other side. The second cleavage is meridional, like the first, but unlike the first division, it does not pass through the centre of the egg. Rather, it creates two large anterior cells (the A and D blastomeres) and two smaller posterior cells (blastomeres B and C). Each side now has a large and a small blastomere. During the next three divisions, differences in cell size and shape highlight the bilateral symmetry of these embryos. At the 32-cell stage, a small blastocoel is formed, and gastrulation begins.

Classes of twins:

Human twins are classified into two major groups: monozygotic (one egg, or identical) twins and dizygotic (two egg, or fraternal) twins.

Factors in myogenesis:

The Myogenic Regulatory Factors (MRFs) Myf5, MyoD, myogenin and MRF4 are members of the basic helix-loop-helix family of transcription factors that control the determination and differentiation of skeletal muscle cells during embryogenesis and postnatal myogenesis.

Primary vesicles of the brain:

Initially there are three primary brain vesicles: prosencephalon, mesencephalon, and rhombencephalon.

Why ascidian are called tunicates:

Ascidiacea, commonly known as the ascidians, tunicates (in part), and sea squirts (in part), is a polyphyletic class in the subphylum Tunicata of sac-like marine invertebrate filter feeders. Ascidians are characterized by a tough outer "tunic" made of a polysaccharide.

They are known as Tunicate because the body of an adult is enclosed within a tunic made of a polysaccharide.

Tunicate gastrulation:

Tunicate gastrulation is characterized by the invagination of the endoderm, the involution of the mesoderm, and the epiboly of the ectoderm. About 4–5 hours after fertilization, the vegetal (endoderm) cells assume a wedge shape, expanding their apical margins and contracting near their vegetal margins. Pairs of blastomeres appear to lead this invagination into the centre of the embryo. This invagination forms a blastopore whose lips will become the mesodermal cells.