31 Years NEET Previous Year Questions: Reproduction in Organisms (Old NCERT) - NEET MCQ

Option (A)

Vegetative propagules in angiosperms: (a) Eyes of potato; (b) Rhizome of ginger; (c) Bulbil of Agave; (d) Leaf buds of Bryophyllum; (e) Offset of water hyacinth

• Parthenogenesis is the spontaneous development of an embryo from an unfertilised egg cell, It naturally occurs in variety of plants, where parthenogenesis usually is found in combination with apomeiosis (the omission of meiosis) and pseudogamous (with or without central cell fertilisation) endosperm formation, together known as apomixis (clonal seed production). 
• Parthenocarpy is development of fruit without fertilisation.

Certain bamboo species are monocarpic, i.e., flower generally only once in their lifetime (after 50-100 years). Other plants (jackfruit, mango and papaya) are polycarpic, i.e., produce flowers and its many times during their lifetime.

Potato, banana and ginger Propagate Vegetatively by their modified stems. Potato propagates by tuber which has buds over its eyes or nodes. These buds produce new plantlets. Banana and ginger propagate with the help of rhizomes which also have buds on nodes for the formation of new plantlets.

In most aquatic organisms, such as a majority of algae and fishes as well as amphibians, syngamy occurs in the external medium (water) i.e., outside the body of the organism. This type of gametic fusion is called external fertilisation.

In diploid organisms, specialised cells called meiocytes(gamete mother cell) undergo meiosis. Conidia and gemmules are asexual reproductive structures found in penicillium and sponge respectively. Megaspores are female gametes in plants, which undergo sexual reproduction.

• Monoecious or homothallic condition in Chara (green algae) is used to denote upper oogonium and lower antheridium on the same plant.
• The organisms, which possess both the reproductive organs are called bisexual.
• Unisexual condition represents both male or female organs in same organism.

In oomycetes female gamete is large and non motile while male gamete is small & motile.

• Onion - Bulb - Underground stem
• Ginger - Rhizome
• Chlamydomonas - Zoospore
• Yeast - ascospores 

Vegetative reproduction and apomixis both are asexual methods of reproduction, which gives the progeny genetically similar to parent.

The axillary buds of the potato tuber are called “eyes” in common language. They are found at the nodes of the stem tuber.

Sucker is a mode of vegetative propagation. It is a non-green slender stem branch that arises from the underground base of the erect shoot or crown. It grows horizontally in the soil and ultimately comes out to form a new aerial shoot or crown. Each sucker has nodes with scale leaf and axillary bud.
Example: Mint has the sucker. It has an adventitious root and scale leaf.

Cleavage involves repeated cell division without increase in size. But cell size decrease. 

Epimorphosis is the replacement of a lost organ of the body by proliferating new cells from the surface of the wound or injured part.

Blastopore is the transitory opening on the surface of gastrula through which the internal cavity archenteron communicates with the exterior. It is formed by invagination of superficial cells during gastrulation.

• Cells in culture usually follow a standard growth pattern.
• The first phase of growth after the culture is seeded is the lag phase, which is a period of slow growth when the cells are adapting to the culture environment.
• The lag phase is followed by the log phase (logarithmic phase), a period where the cells divide exponentially and consume the nutrients in the growth medium.
• When all the growth medium is spent (one or more of the nutrients is depleted) or when the cells occupy all of the available substrates, the cells enter the stationary phase.

Therefore, the correct answer is option D.

Cytokinesis involves the division of the cytoplasm of the parent cell into its daughter cells.

Fertilization involves the fusion of two haploid gametes. Blastulation refers to the process of cleavage in the zygote to form a blastula.

In humans, the egg cleavage is homoblastic. Cleavage results in the production of cluster of cells, which is of the same size as that of zygote.
Cleavage is not identical to mitosis. The cleavage starts when the egg is in fallopian tube and not in uterus.

• A change in the amount of yolk and its distribution in the egg will affect pattern of cleavage.
• The pattern of cleavage is influenced by the amount of yolk in the egg. In eggs with less yolk, cleavages are equal, and the resulting blastomeres are of similar size.
• If the yolk is localized, such as in frog eggs, then cleavages are unequal, the cells derived from the yolky region (the vegetal pole) are larger than those derived from the region without yolk (the animal pole).

• Fusion of male and female gamete produces a zygote.
• Repeated division of the zygote is called cleavage forming a solid morula.
• After further division and rearrangement, a fluid-filled cavity surrounded by blastomeres - blastula is formed.
• The appearance of germ layers marks the gastrula.

• Eggs with abundant yolk concentrated in one hemisphere of the egg are termed telolecithal.
• This occurs in many invertebrates and in all vertebrates lower than marsupial mammals.

• The process by which the blastula becomes a three-layered embryo, or gastrula, is called as gastrulation.
• During gastrulation, the embryo begins to approximate its body plan as cells arrange themselves into three distinct germ layers, or embryonic tissue layers (the outermost layer, the ectoderm; the innermost, the endoderm; and the mesoderm) that develops between them. 
• Additional cell divisions take place during gastrulation, and the germ layers become established through a combination of processes.
• Many cells lose their old cell-to-cell contacts and establish new ones through cell recognition and adhesion processes involving interactions among the integrins and other plasma membrane proteins and the extracellular matrix. 
• The simple type of gastrulation occurs in echinoderms and in amphioxus. Gastrulation begins when a group of cells at the vegetal pole undergoes a series of changes in shape that cause that part of the blastula wall to first flatten and then bend inward (invaginate).
• The invaginated wall eventually meets the opposite wall, obliterating the blastocoel.
• The embryo is converted into a double-walled, cup-shaped structure. The new internal wall lines the archenteron, the newly formed cavity of the developing gut.
• The opening of the archenteron to the exterior, the blastopore, is the site of the future anus in deuterostomes. At first, the archenteron is a narrow slit, but it gradually expands at the anterior end of the embryo.
• As a result, the blastocoel progressively shrinks and eventually disappears, which marks the end of gastrulation.

• Blastopore is the opening by which the cavity of the gastrula (gastrocoel), communicates with the exterior. It is formed as a result of invagination of endoderm during embryonic development.
• During maturation of some animals it evolves into the anus or the mouth; in others it is covered over and contributes to the canal joining the primitive gut with the cavity of the neural tube.

• Meroblastic cleavage is a type of cleavage that occurs in very yolky eggs like birds in which the egg cytoplasm and not the yolk divides (incomplete division).
• There are two types of meroblastic cleavage: Discoidal and Superficial.
• Discoidal usually occurs in birds, reptiles, fishes, etc. which have telolecithal eggs whereas Superficial cleavage occurs in insects that have centrolecithal eggs. 

• Eye is an organ which is derived from both ectoderm and mesoderm because lens, cornea, conjunctiva muscles of iris are ectoderm in origin.
• Whereas sclera, choroid, ciliary body, iris are mesoderm in origin.

The amount of yolk and how it is distributed determines the type of cleavage.
On this basis cleavage is of two types:
(a) Holoblastic: where the segmentation line passes through the entire egg. It occurs in alecithal (without yolk), microlecithal (with a very little amount of yolk), and mesolecithal (little amount of yolk) eggs.
(b) Meroblastic: where segmentation line does not pass through the egg and remained confined to a part of the egg. It occurs in megalecithal (a large amount of yolk) egg.

After formation of three primary germ layers (i. e., ectoderm, mesoderm and endoderm), cells of these three layers become variable in morphology, shape, size and more specified to form organs so as to meet out the future functional needs of the foetus, this process is called differentiation.

No growth of the embryo occurs during cleavage because there is an increase in the number of cells and progressively they decrease in size.

The platypus is an oviparous mammal, which means that it lays eggs as its method of reproduction. Viviparous animals are those that give birth to live young, such as all placental mammals (like humans).