Reproduction in Organisms Test - 10

Gametes are a mature sperm (from a male) and a mature egg, or oocyte (from female). Each gamete is haploid (n), that is half the number of DNA required for the growth and development of an organism. Fusion of these two gametes results in a diploid cell (2n) with the right amount of DNA required. A fertilized egg is known as zygote which can develop to form an embryo.

Vallisneria  is a submerged hydrophyte. It is a dioecious plant with the flowers borne under water. The male flowers detach on maturity and float on the surface of the water while the female flowers grow under water and they come up to the surface with the help of their thin long stalk. As the stalk grows further, the flowers which were vertical become horizontal and thus, a cup like depression is formed around the female flower. The male flowers which are floating on the surface of the water, fall into the cup and due to jerk, the anthers dehisce and pollen is transferred to the stigma and thus, pollination occurs on the surface of the water. This kind of pollination found in  Vallisneria  is called ephydrophily. 

Amphibious are the animals that can live on water as well as on land. Oviparous are the animals that lay eggs. Triploblastic describes the animal having a body composed of three embryonic cell layers as the ectoderm, mesoderm, and endoderm. Viviparous are animals that give birth to live young one that has developed inside the body of the parent.

Tissue culture involves the culture of totipotent cells in nutrient media under sterile conditions. The mass of the totipotent cell is known as a callus. It is unorganized actively dividing the mass of cells maintained in culture. It has the meristematic cell which has an ample amount of cytoplasm to trigger cell division. It is treated with growth hormones to allow cell division and differentiation. Callus when treated with nutrient media with a high percentage of auxin it promotes rooting and when it is treated with media with a high percentage of cytokinin it stimulates cell maturation, differentiation and finally, promotes the development of stem.

The yolk is a part of an egg, that feeds the developing embryo in animals. It is composed of carbohydrates (3.5%), protein (16%) and fats (phospholipids 26.5%) of total yolk. The main fatty acids present in the yolk are oleic acid, linoleic acid, palmitic acid etc.

Scion is the part of the grafted plant that gives rise to the plant shoot that will, later on, produce all of the plant parts such as leaves, stems, flowers, and fruits. Everything above the scion is cut off in the spring hence all nutrients and water absorbed by the roots becomes available to the growing scion.

A gemma (plural gemmae) is a single cell, or a mass of cells, or a modified bud of tissue, that detaches from the parent and develops into a new individual. This type of asexual reproduction is referred to as fragmentation. It is a means of asexual propagation in plants.

Reproduction in Bryophyllum occurs asexually through vegetative propagation by leaves. These buds can give rise to new plants with adventitious roots, shoots, and small leaves. The new plants then detach from the leaves and develop into a mature plant after coming in contact with the soil.

Bulbs are modified stems of some plants. The stem is modified to be a storage organ where the plant stores its reserve materials which it would use in times of need. The best example of this would be an onion.

Apomixis is the term given to any phenomenon that leads to formation of embryos wherein parts of the sexual apparatus are used, but without fertilisation. Fertilisation is also absent in vegetative propagation, but parts of sexual apparatus are not involved. An example of apomixis is Citrus.