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Comparative Anatomy & Developmental Biology

Integumentary System

Derivatives of integument with respect to glands—

In Birds

Q.What is pterylosis?

Pterylosis refers to the arrangement of feathers and how they are implanted in the skin, while ptilosis refers to the properties of the feathers themselves. Each feather originates from the epidermal layer of the skin and are arranged in definite tracts called pterylae, which are separated from the featherless tracts, called apteria.

In Mammals

Q.Distinguish between horn and antler

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Digestive System

Q.Who are the ruminants?

Ruminants are mammals that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions. The process, which takes place in the front part of the digestive system and therefore is called foregut fermentation, typically requires the fermented ingesta (known as cud) to be regurgitated and chewed again. The process of rechewing the cud to further break down plant matter and stimulate digestion is called rumination. Ruminating mammals include cattle, all domesticated and wild bovines, goats, sheep, giraffes, deer, gazelles, and antelopes.

Respiratory System
  • Brief account –

  • Gills

  • Lungs 

  • Air sacs

  • Swim bladder

Q.What is labyrinthine organ?

A labyrinth fish is one that has a special organ, known as the labyrinth, which allows the fish to breathe air from the surface of the water. The air is forced into the labyrinth organ, to allow the oxygen to be absorbed. Within the labyrinth, cavities are many small maze-like compartments of thin boney plates called lamellae. The lamellae are covered with extremely thin membranes, so thin that oxygen can pass through. Blood within the membranes absorbs the oxygen and carries it throughout the body.

Circulatory System

Evolution of heart

Evolution of aortic arches

Q.Define aortic arch.

Paired arteries connecting the ventral aorta with dorsal aorta in vertebrates in their adult or developmental stages are known as aortic arches.

Urino-genital System

Succession of kidney

Q.What do you mean by Tripartite concept of kidney organization?

Developmental and structural differences in the nephric tubules that arise within the nephric ridge inspired a view of kidney formation known as the tripartite concept. This concept envisions formation of nephric tubules in one of the 3 locations within the nephric ridge. Subsequent loss, merger or replacement of these tubules constitutes the developmental basis for the definitive adult kidneys. Tripartite concept of kidney organization: tubules develop in one of three regions on nephric ridge, anterior – pronephros, middle – mesonephros and posterior – metanephros.

Evolution of urino-genital ducts

Early Embryonic Development


Spermatogenesis with respect to mammals

Oogenesis with respect to mammals

Q.What is informosome?

Some of these mRNA molecules become inactive by wrapping of protein and stores as mmRNA or as informosmes (Spirin, 1965). These informosomes bring about protein synthesis during early cleavage, when chromosomal DNA remains condensed and involved in nuclear division and as such is not able to synthesize mRNA.

Fertilization: Sea-Urchin

Q.What is the basic principle of slow block polysperrmy?

Slow block to polyspermy (cortical granule reaction/ sperm removal): [in sea urchins and most mammals]. The components of cortical granules bind to the vitelline envelope to form fertilization envelope. After that accumulated mucopolysachhrarides absorb water and expand the space between the cell membrane and the fertilization envelope.The fertilization envelope then stabilized by cross linking adjacent proteins through egg-specific peroxidase enzymes and a transglutaminase released from cortical granules. This crosslinking allows the egg and early embryo to resist the shear forces of the oceans intertidal waves.


Early development of frog

Structure of mature egg and its membranes

Q.What are the major function of egg membrane?

1.Prevents further sperm entry after fertilization.

2.Helps the egg to assume bilateral symmetry from a state of radial symmetry.

3.Secondary membrane provides protection and ensures processing of nutritive materials from the surroundings.

4.Tertiary membrane ensures adequate water supply and provisions for organic food.

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Patterns of cleavage

Q.State Sach’s law of cleavage.

i.Cells tend to divide into equal daughter cells.

ii.The cleavage furrow of each new division tends to bisect the plane of preceding cleavage at right angles.

iii.Blastomeres tend to assume and maintain speroidal space.

Fate map up to formation of gastrula

Q.What is a fate map?

A fate map is a diagram of an egg or blastula, indicating the fate of each cell or region, at a later stage of development. Fate maps are essential tool in most embryological experiments. They provide researchers with information on which portions of the embryo will normally become which larval or adult structure. The analysis of the fate of each blastomere after first and second cleavage is called cytogeny or cell lineage study.

Types of morphogenetic movements

Fate of germ layers

Late Embryonic Development


Types and function

Q.What do you mean by Deciduous Placenta?

In cat, dog, primates, rodents etc., the degree of intimacy between the chorionic villi and the endometrium is greatly increased. The uterine wall gets eroded. The chorionic villi fuse with the eroded uterine mucosa. Such a placenta is termed as placenta vera (true placenta).

At the time when parturition takes place the uterine wall does not remain intact. It tears away and extensive haemorrhage takes place at birth. Such a type of placenta is termed as decidu­ous placenta.

This phenomena of shedding (tearing off) and replacement of maternal tissue is termed as decidua (meaning, to shed). Here the placenta is physiologically more efficient, where the mothers are pro­tected enough to recover fully after child birth.

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Metamorphic events in frog life cycle and its hormonal regulation

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