Biology Test - 4

Anti-tetanus and anti-snake bite injections provide artificial active immunity.

A physical barrier is the innate immunity refers to the first line of defense against the pathogens.g., skin and not saliva.

Physiological barriers against infection are temperature, \({pH}, {CO}_{2}\) etc.

The mucous coating is part of the mucosa, associated lymphoid tissue.

Cellular barriers include monocytes, neutrophils (polymorphonuclear cells) which reach the infection site first.

Archaebacteria are the prokaryotic organisms. These organisms contain the cell membrane which is made up of the amino acids and glycolipids which are linked by an ether linkage. There is no peptidoglycan as in the bacterial cell wall. They are prokaryotes which do not have membrane-bound organelles. They have 16S rRNA genes which are genetically different from the other organisms. The lipids in archaebacteria form an S-layer with the amino acids and glycolipids.

The antidiuretic hormone binds to receptors on cells in the collecting ducts of the kidney and promotes reabsorption of water back into the circulation. These channels transport solute-free water through tubular cells and back into the blood, leading to a decrease in plasma osmolarity and an increased osmolarity of urine.

Rules of conduct that may be used to regulate our activities in relation to the biological world is called Bioethics. It may be viewed as the set of standards that may be used to regulate various activities based on their effects on the biological world.  This is because biotechnology has aroused social as well as political concerns, which have ranged from biotechnology being unnatural to detrimental to biodiversity.

Usnic acid is an antibiotic obtained from Lichens.

An antibiotic is a substance that inhibits the growth of the bacteria or directly kills the bacteria. Usually, many fungi species are identified which have antibiotic properties. For example, penicillin is obtained from a fungus and it is a wide range of antibiotics that kills many bacterial species. Except for fungus, many species of lichens are also reported to synthesize antibiotic compounds like usnic acid. Usnic acid is a yellow crystalline acidic compound having the molecular formula C₁₈H₁₆O₇. 

It is a naturally occurring antibiotic that is found in many lichen species. The lichens are the symbiotic associations of fungi and algae. These are found growing over barks of trees, stone surfaces, rotting materials, etc. they stay attached to the substratum. Both fungi and algae benefited from this association. They secrete many compounds including antibiotics to sustain their safe development. The usnic acid was found to be synthesized by various lichen species namely Usnea, Cladonia, Alectoria, etc. It is believed that usnic acid in lichens is used to protect them from the harmful effects of sunlight. It is a secondary metabolite of lichens. This means that it is a waste-type secretory product of lichens. Also, the bitter taste of usnic acid protects the lichens from grazing animals.

Note: Many fungal and lichen species secrete antibiotics naturally. The use of antibiotics in the pharmaceutical industry has saved millions of lives from deadly bacterial infections. But due to the un-sustained use of antibiotic medicines, the bacteria have become resistant to them. This is called antibiotic resistance. This causes a greater threat to future health emergencies. Thus, alternatives need to be found.

In RNA (Ribonucleic acid), thymine is replaced by uracil.

This ribonucleic acid acts as a template for the synthesis of proteins, where it transforms the genetic material from the genes to protein synthesis components, to form the amino acids.The nitrogenous bases are purines and pyrimidines. The purines are adenine and guanine. The pyrimidines are thymine and cytosine. In RNA, the thymine is replaced by uracil. Uridylic acid is formed by the combination of uracil as a nitrogenous base, ribose sugar, and triphosphate. It is mainly found in RNA. It is an ester of phosphoric acid with the nucleoside uridine.

Corpus luteum is the yellow endocrine body formed in the ovary at the site of a ruptured Graafian follicle, while macula lutea is a yellow spot on the retina. The common feature between the two is that both (corpus luteum and macula lutea) are characterized by yellow colour.

The mass of the cell nucellus has abundant reserve food materials,dense cytoplasm and prominent nucleus. These cells act as megaspore mother cells.

The megaspore mother cell undergoes meiotic division to produce four megaspores,in most of the flowering plants there is one functional megaspore and three degenerates.

The functional megaspore develops into embryo sac or female gametophyte ,this process of development from one megaspore is known as monosporic development. Assertion is true but Reason is false.

In ferns, fertilization takes place with the help of water. On attaining maturity the archegonia absorb water, the cells lining the neck undergo disintegration and push open the cover cells. The release from archegonium contains a chemotactic substance Malic acid that attracts the antherozoids towards the archegonium for fertilization of the egg.

The fungus with bioluminescent characteristics is Omphalotus olearius.

Omphalotus olearius, commonly known as the jack-o'-lantern mushroom, is a poisonous orange gilled mushroom that to an untrained eye appears similar to some chanterelles. It is notable for its bioluminescent properties. It is found in woodland areas in Europe, where it grows on decaying stumps, on buried roots, or at the base of hardwood trees. It has also been reported from the Western Cape Province, South Africa. A similar, but phylogenetically distinct species found in eastern North America is Omphalotus illudens.