In our day to day life we categorize people based on following criteria:
(1) Level of education.
(2) Profession
(3) Height and skin colour
(4) Native place
(5) ***
(6) Hobbies
(7) Nature

The largest herbarium in India is INDIAN BOTANICAL GARDEN ,KOLKATA. It consists of 1000000 number of specimens.

When large bundle sheath cells surround the vascular bundle, the leaf is said to have Kranz anatomy.
Bundle sheath cells are specific to C₄  plants and are characterised by having a large number of chloroplasts, thick walls impervious to gaseous exchange and no intercellular spaces.

Nucleotides are small complex molecules made of:
(1) Njicleotide : Each nucleotide consist of 3 units - a nitrogenous base, a pentose sugar and phosphate group.
(2) Nitrogenous base: Nitrogenous base are the purine (adenine or guanine) or pyrimidine (thymine, cytosine or uracil).
(3) The nucleotides are mono or di or triphosphates of nucleosides, e.g., Adenosine monophosphate (AMP), Adenosine diphosphate (ADP) and Adenosine triphosphate (ATP).

• Lichen, especially crustaceous lichens erode rocks and convert them in to soil. After their death, thallus dissolves and form organic matter, which mix these rock minerals with salts and make the soil suitable so that other plants can grow.
• Microbial dosages of Sulphur dioxide pave a side effect on their growth. Therefore, they are good indicators of air pollution and become extinct in the polluted areas.
•  Some lichens like stone mushrooms are used as a food.
•  Lichen and other chemical substances present in it are also used as medicines.
•  Do you know that perfumes are also made from lichens; such as from Ramalina lichen.  

A bacteriophage is a virus that infects bacteria
They are numbered T₁ to T₇ as their types.
The shape of bacteriophages is tadpole like with a head and a tail.

There are five main kingdoms. They are:

• Kingdom Monera: These organisms are prokaryotic and unicellular. They do not have a well-defined nucleus and also lack cell organelles.
• Kingdom Protista: Organisms grouped under Kingdom Protista are all unicellular, but eukaryotic organisms. These are the simplest forms of eukaryotes that exhibit either autotrophic or heterotrophic mode of nutrition.
• Kingdom Fungi: Heterotrophic, Multicellular and Eukaryotic organisms are grouped under Kingdom Fungi. Their mode of nutrition is saprophytic as they use decaying organic matter as food.
• Kingdom Animalia : This Kingdom includes organisms that are Multicellular, Eukaryotic, without the presence of cell wall. They have a heterotrophic mode of nutrition. They also exhibit great diversity. Some organisms are simple while others have a complex body with specialized tissue differentiation and body organs.
• Kingdom Plantae: These are Eukaryotic, Multicellular organisms with a cell wall that is made up of cellulose. They are autotrophs and synthesize their own food through the process of photosynthesis. This kingdom includes all plants.

Gelatinous sheath is a covering found, generally around the cells in colonies of cyanobacteria. It holds the cells in colonies together.

(i) Linnaeus proposed a two kingdom system of classification with Plantae and Animalia kingdoms was developed that included all plants and animals respectively. But as this system did not distinguish between the eukaryotes and prokaryotes, unicellular and multicellular organisms and photosynthetic (green algae) and non-photosynthetic '(fungi) organisms, so scientists found it an inadequate system of classification. Classification systems for the living organisms have hence, undergone several changes over time.
(ii) The two kingdom system of classification was replaced by three kingdom system, then by four and finally by five kingdom system of classification of RH Whittaker (1969).
(iii) The five kingdoms included Monera, Protista, Fungi, Plantae and Animalia. This is the most accepted system of classification of living organisms.
(iv) But, Whittaker has not described viruses lichens. Then, Stanley described viruses, viroids, etc. Thus, over a period of time, classification system have undergone several changes.  

A bacteriophage is a type of virus that infects bacteria. In fact, the word "bacteriophage" literally means "bacteria eater," because bacteriophages destroy their host cells. Bacteriophages kill bacteria by making them burst or lyse. This happens when the virus binds to the bacteria. A virus infects the bacteria by injecting its genes (DNA or RNA). The phage virus copies itself (reproduces) inside the bacteria.

Embryonic development, also embryogenesis, is the process by which the embryo forms and develops. In mammals, the term refers chiefly to early stages of prenatal development, whereas the terms fetus and fetal development describe later stages.

Embryonic development starts with the fertilization of the egg cell (ovum) by a sperm cell, (spermatozoon). Once fertilized, the ovum is referred to as a zygote, a single diploid cell. The zygote undergoes mitotic divisions with no significant growth (a process known as cleavage) and cellular differentiation, leading to the development of a multicellular embryo.

Although embryogenesis occurs in both animal and plant development, this article addresses the common features among different animals, with some emphasis on the embryonic development of vertebrates and mammals.

Secretion of melatonin : This gland secretes the hormone melatonin which regulates the circadian rhythm of the body and also certain reproductive hormones. The secretion of this hormone depends upon the amount of light a person is exposed to. This hormone is produced in large amounts when it is dark. The presence of light inhibits the secretion of melatonin which controls our circadian rhythms.

Cardiovascular Health : The melaton in secretion has a positive impact on the heart and blood pressure. It may also be used for the treatment of cardiovascular diseases.

Reproduction : Melatonin inhibits the secretion of reproductive hormones from the anterior pituitary, which are responsible for the development and functioning of reproductive organs.

The pineal gland is a small, pea-shaped gland in the brain. Its function isn't fully understood. Researchers do know that it produces and regulates some hormones, including melatonin.

(a) Heterotrophic bacteria

(1) Many bacteria like Lactobacillus helps in the production of curd from milk.

(2) They act as decomposers and help in the formation of humus e.g. Pseudomonas.

(3) Many antibiotics are obtained from some species of bacteria like streptomyces, Bacillus etc.

(4) Many soil bacteria help in fixation of atmospheric nitrogen like Rhizobium (Symbiotic), Azotobacter (Free living).

(b) Archaebacteria

(1) Methane gas is produced from the dung of ruminants by the methanogens.

(2) Methanogens are also involved in the formation of biogas and sewage treatment.

Bulliform cells are the cell that is spread among the leaf's epidermal cells. They are essential for water storage. During stress circumstances, bulliform cells assist to roll leaves to avoid water loss through transpiration. Therefore, they control the process of transpiration. Bulliform cells or the motor cells are the modified epidermal cells present on the upper surface or the adaxial surface of the monocot leaf (the grasses). They regulate the rolling of leaves to prevent the loss of water. When water is adequately present, they become turgid and keep the leaf open and exposed.

Tubules that lies more or less in the haemocoel, which open into alimentary canal.
Functions:
(a) They absorb nitrogenous waste products.
(b) They convert the nitrogenous waste products into uric add which is excreted out.