Reproduction in Organisms Test 5

During reproduction, new individuals are produced having similar traits that help in continuity of species. It is essential as all living organisms have fixed life span.

The duration from implantation of fertilised eggs to uterus till birth of well-developed baby is called gestation period. It is about nine months in human beings.

Virus is called as borderline of living and non-living. Viruses act as living one when inside the other living organism and reproduce very fast. When outside the living body, virus behaves as molecules without any sign of living.

Ostrich is a large sized bird. It is not able to fly long distance. The egg of ostrich is considered largest cell which is about one meter in diameter.

The period from Birth of an individual to its natural death is called life span. Different organisms have different life span starting from one day to hundreds of years.

When offspring is produced by a single parent with or without the involvement of gamete formation, the reproduction is asexual. When two parents (opposite sex) participate in the reproductive process and also involve fusion of male and female gametes, it is called sexual reproduction.

Amoeba, Paramecium, Euglena undergo binary fission in which cells divides into two equal halves. In Plasmodium, a number of offspring are produced inside the single cell.

A number of simple organism produce single or multi-flagellated spores called zoospores. Water is essential for this mode of reproduction. Aplanospores are non-flagellated spores.

Rhizome of ginger is modified root, located inside the soil parallel to earth surface. Vegetative propagation of ginger is done with it.

Water hyacinth is water weeds which grows very fast and covers the whole ponds in few days. Weeds absorb oxygen from the water and make it oxygen deficient that kills the fish in ponds along with other aquatic organisms.

The flowers that contain both male and female reproductive organs in same flower are called bisexual. In Hibiscus flower both stamen and carpel are present within same flower.

Eyes of potato represent the node at which buds are formed. These buds are used to grow in plants. The buds are axillary in position. The potato tubers are actually modified stem.

Egg is released from the ovary in the middle of menstrual cycle. In human beings, one egg is released one month from one ovary. Ovulation is under the control of hormones.

Embryo sac is located inside the ovule that acts as female gametes. Egg fertilization and subsequent embryo development occurs inside the embryo sac. Endosperm is triploid and provides nutrition to embryo.

Artificial vegetative propagation is carried out by cutting, layering and grafting. During grafting root system of one plant and shoot system of other plant is joined together. The upper part is called scion and lower part is called stock.

In aquatic organisms fusion of nuclei occurs outside the body of the female. The male and female release their gametes into water and they are brought together by water current. Such Syngamy is called external fertilisation.

Zygote divide mitotically to produce a number of cells. These cells arrange into different layers and specialised into different tissues to form organ by the process of differentiation.

All sexually reproducing organisms develops from single cell called zygote. Zygote is formed by fusion of male and female gametes. Traits from male and female are present in the zygote.

Sexual reproduction is comparatively slower mode of reproduction than asexual reproduction. The formation of gametes, there fusion and embryo formation takes longer duration.

• Oogenesis is the process of formation of a mature female gamete (ovum).
• During oogenesis, each diploid primary oocyte (formed by mitotic divisions of oogonia or egg mother cells) undergoes two maturation divisions.·
• In the first meiotic division, the primary oocyte divides into two very unequal haploid daughter cells - a large secondary oocyte and a very small first polar body or polocyte.
• In the second maturation division the first polar body may divide to form two second polar bodies.
• The secondary oocyte again divides into unequal daughter cells, a large ootid and a very small second polar body.
• The ootid grows into a functional haploid ovum. Thus from one primary oocyte, one ovum and three polar bodies are formed. The ovum is the actual female gamete.

Tissue culture is mode of vitro propagation of large number of plantlets in short interval of time. During tissue culture, plants parts are kept in nutrient medium along with required hormones. Some variation arises in plants body although having same genetic traits.

As apomixis means asexual reproduction and vegetative propagation is also a kind of asexual reproduction, their's common feature is that both do produce offsprings identical to their parents as in asexual reproduction, only one single gamate is involved in the reproduction process.

Water hyacinth develops offset for vegetative propagation. Its forms large number of branches in very short interval of time to cover the whole water bodies and depriving other aquatic organisms from oxygen dissolved in water.

Asexual reproduction does not involve fusion of gametes /fertilisation and it can occur in favourable conditions also.

Grafting (including budding) is a process by which a portion of the shoot system or root system of the same or different plants, brought into intimate contact, unite and grow together anatomically, and interact physiologically as a single functional unit (whole plant).