December 2021

Bacteria: Asexual Reproduction and Genetic Recombination (Parasexuality)

Sexual Reproduction in Bacteria
Sexuality in bacteria was first discovered by Tatum and Lederberg in 1947 in Escherichia coli. Gamete production and fusion are not present in bacteria. The only thing which happens in bacteria is genetic recombination. It means variation is there that does not involve gamete formation. Thus sexual reproduction in bacteria occurs by a method called Parasexuality. As a result, bacteria do not have true sexual reproduction; instead, genetic recombination occurs.
Genetic Recombination (Parasexuality)
There is no gamete formation, no gametic fusion only there is genetic recombination present in bacteria. Thus there is the transfer of genetic material from one bacteria to another bacteria, this method of genetic recombination is known as Parasexuality.

Angiosperms: Salient Features and Dicots verses Monocots

Angiosperms: Salient Features
1. They occur in ultimate environments on the earth
2. They are covered seed-bearing plants
3. Herbs, Shrubs, Trees, Twiners, Trailers, and Climbers among others make up the sporophytic plant body
4. The Gametophytic phase is highly contracted and only represented by a few cells. The free-living existence of gametophytes is absent
5. vascular tissue is well developed, xylem and phloem are present. The xylem contains tube-like structures that are vessels, tracheids, xylem parenchyma, and xylem fibers. Phloem contains a tube that is a sieve tube, companion cells, Phloem parenchyma, and Phloem fibers

Pteridophytes:Economic Importance

Rhizomes of male shield fern are used to obtain the anti-helminthic drug. Equisetum is used in the preparation of diuretic, haemostatic and haemopoietic drugs. Lycopodium is used in homoeopathy to treat diarrhoea, bladder irritability, eczema, rheumatism, constipation and inflammation of the liver.

Puberty: Human Males and Females

Disorders of Female Reproductive system
Some of the few disorders of the Female Reproductive system are as
i.Sterility: Inability of the females to conceive due to inadequacy in structure or function of the genital organs.
ii. Menstrual Irregularity: this may be amenorrhoea (absence of menstruation) excessive or prolonged bleeding of the uterus (hypermenorrhoea) or dysmenorrhoea (painful menstruation).
iii. Breast cancer: Usually affects women over the age of 30. Its incidence increases after women attain menopause. Once detected, the standard treatment involves removal of the breast (mastectomy)
iv. Ovarian cysts: these are fluid-filled tumors of the ovary. Sometimes during pregmancy, such cysts rupture and regress. In old women, ovarian cysts are surgically removed.
v.Cervical cancer: It is a relatively slow-growing cancer. It can be treated with radiation or surgery if it has been detected.

Ovule: Structure, Types, and Embryo sac

Embryo sac and its Development
The first cell of the female gametophyte is the functional megaspore. It grows largely along the micropyle-chalazal axis and is mostly chalazal. The nucleus undergoes three mitotic divisions and forms eight nuclei. Out of the Eight nuclei, 4 are present at the micropylar end and 4 at the chalazal end. One nucleus from each group comes in the center to form 2 polar nuclei. The remaining three nuclei at the micropylar end make up the egg apparatus, whereas the remaining three nuclei at the chalazal end make up three antipodal cells. The mature female gametophyte or embryo sac is the entire structure with two polar nuclei, three antipodals, one egg, and two synergids. the Monosporic 8- nucleate embryo sac or polygonum type of embryo sac arises from a single megaspore and has 8 nuclei

Pollination: Definition, Types, and Agents

Pollen grains are transmitted from the Anther to the Stigma during pollination. When pollen grains land on ovule, it is known as Direct pollination e,g Gymnosperms, and some primitive Angiosperms. When pollen grains land on Stigma and form a pollen tube it is known as Indirect pollination e,g Angiosperms. Pollination’s function in fruit and seed production has been recognised since ancient times. The Arab and Assyrian kings used to perform a special religious ceremony in which the female inflorescence of the date palm was touched by the male inflorescence to ensure good fruiting. However, Thomas Millington, towards the end of the 17th century, provided the scientific underpinning for this method.

Flower: Definition, Types, and Functions

Types of Flower
1. Complete Flower: If all the four whorls are present in the flower it is called Complete Flower (Gynoecium, Androecium, corolla, calyx).
2. Incomplete Flower: If any one of the four whorls are absent in Flower it is called Incomplete Flower (Gynoecium, Androecium, corolla, calyx)
3. Bisexual Flower: If a flower contains both male and female reproductive parts it is called Bisexual Flower.
4. Unisexual Flower: If Flower has only one reproductive part then it is called Unisexual Flower.
Pistillate Flower: If the only female part is present
Staminate Flower: If the only male part is present i.e. Androecium the flower is called Staminate Flower.
5. Dichlamydeous Flowers: If a flower contains both Calyx and Corolla it is known as Dichlamydeous Flower. It is most common in plants.
6. Monochlamydoeus Flower: If a flower contains only one whorl, the whorl which is present is known as perianth and this is seen in the case of monocot families e,g Liliaceae
7. Achlamydeous Flower: If Calyx and Corolla are absent in flower it is called Achlamydeous Flower.