Tapetum is the innermost layer and completely surrounds the sporogenous tissue. The cells of Tapetum have dense cytoplasm and generally more than one nuclei. Tapetum nourishes the developing pollen grains

Pollen grain consists of a two-layered cell wall. The outer harder layer is exine which is composed of sporopollenin, which is one of the most resistant biological material known. The inner layer is the intine.

• Fungi and algae switch to the sexual mode of reproduction during adverse conditions to bring variations among the individual.
• Such variations help the individuals to adapt to the changed conditions and survive.
• This ensures the continuity of species and also helps in phenomena like speciation.

Or

Sexual reproduction enables organisms to survive during unfavourable conditions as it leads to variation and variation and variation leads to evolution. Evolution can only be done by the organisms which are able to survive the harsh conditions and the organisms that could not would die and won't reproduce further. The organisms that survived would reproduce, will leave their progeny and as the conditions will become more harsh the adaptive organism would survive and reproduce and this results in the evolution of the species. The reason that sexual reproduction is favoured under such conditions because, sexual reproduction leads to evolution and this evolution results in the continuation of the species.

DNA acts as the repository of genetic information. The mRNA serves as a link between the DNA and polypeptide chain. It is called one-way flow of information or central dogma. This concept was proposed by Crick in 1958. The flow of information can be represented as follows:

In viruses, DNA is synthesised on RNA template with the help of enzyme RNA dependent DNA polymerase (reverse transcriptase). mRNA transcribed from the DNA participates in protein synthesis. It is called the central dogma reverse. The process of DNA synthesis on RNA is called reverse transcription or inverse flow of information. This concept was proposed by D. Baltimore in 1970. The flow of information can be represented as follows:

The normal temperature of the testes In the ******* is about 2o−2.5o C lower than the internal body temperature. When the body is chilled, the smooth muscle contracts and brings the testes closer to the pelvic cavity. This movement towards the pelvic cavity allows the testes to absorb heat from the rest of the body so that the sperm cells do not become chilled and get optimum temperature for spermatogenesis.

Biofertilizers are microorganisms that add to the nutrient quality of the soil. Bacteria, fungi, and algae are some of the beneficial microorganisms that help in improving the fertility of the soil.

• Rhizobium: They form root nodules in leguminous plants and fix the atmospheric nitrogen into an organic form. Rhizobium also has no negative effect on soil quality and improves the quality, nutrient content, and growth of the plant.

Insertional inactivation is a technique used in recombinant DNA technology. In this procedure, a bacteria carrying recombinant plasmids or a fragment of foreign DNA is made to insert into a restriction site inside a gene to resist antibiotics, hence causing the gene to turn non-functional or in an inactivated state.

An example of this is a pUC19 plasmid vector in which the lacZ gene that encodes for beta-galactosidase can no longer be produced upon the insertion of a foreign gene. Selection or screening is a fundamental process in which once the recombinant DNA is inserted into a particular host cell, it becomes necessary to detect the cells that have received the recombinant or foreign DNA molecules.

This process is referred to as screening or selection. It is based on non-expression or expression of certain traits or characteristics. Insertional inactivation is an effective method of screening. In this procedure, one of the genetic characteristics is disturbed by the introduction of foreign DNA. One of the most influential selection methods of recombinant plasmid for the insertional inactivation procedure is a method known as ‘Blue-white’ selection method.

In normal conditions, RBCs are Biconcave disc- like. Sickle cell anemia is a group of disorders which comes under the sickle cell disease. It is an autosomal recessive disease therefore it can be transmitted from parents of the offspring when both female and male individuals are carriers for the gene. The disease is controlled by a single pair of alleles, Hb^A and Hb^S. Thus, three genotypes are possible in this situation:
- Hb^A Hb^A (normal homozygous) - Hb^A Hb^S (normal carrier) - Hb^A Hb^S Hb^S (diseased, die before attaining maturity)
Heterozygous (Hb^A Hb^S) individuals appear unaffected but they are carriers of the disease as there is a 50% probability of transmission of the mutant gene to the progeny, thus exhibiting sickle cell trait.
The disease or defect is caused by a mutation (transversion) of the gene controlling the β-chain of hemoglobin. It replaces glutamic acid (Glu) present at the 6^th position of the β-chain by amino acid Valine (Val) . The mutant hemoglobin molecules undergo polymerization under low oxygen tension causing the change in the shape of RBCs from biconcave to elongated sickle- like (curve) structure.

Biodiversity mainly depends on upon the climatic and geographical conditions available in a particular region. The Western Ghat runs along the western edge of peninsular India. It supports a diverse range of flora and fauna. There are over 6000 vascular plants belonging to over 2500 genera in this hotspot, of which over 3000 are endemic. It is a rich source of spices such as black pepper and cardamom. The highest concentration of species in the Western Ghats is believed to be the Agasthyamalai Hills in the extreme south. The region also harbors over 450 bird species, about 140 mammalian species, 260 reptiles, and 175 amphibians. Over 60% of the reptiles and amphibians are completely endemic to the hotspot. 

Thermus aquaticus bacterium is used in recombinant DNA technology to provide the enzyme Taq Polymerase which is thermostable enzyme which can even work which remain active during the high temperature induced denaturation of double stranded DNA. It is used in PCR to amplify the DNA segments.

Widal Test is an agglutination test which detects the presence of serum agglutinins (H and O) in patients serum with typhoid and paratyphoid fever. When facilities for culturing are not available, the Widal test is the reliable and can be of value in the diagnosis of typhoid fevers in endemic areas.

Microbes are diverse-protozoa, bacteria, fungi and microscopic plants viruses, viroid and also prions that are proteinacious infectious agents. They are found everywhere on earth ranging from soil, air water and some inhabitable places.

Traditional hybridisation procedures involve mating of organisms to be modified with another individual of the same species having desired characters and screening the progeny for expression of desired set of characters. These procedures, very often lead to inclusion and multiplication of undesirable genes alongwith desired genes. Besides inter-specific hybridisation are generally not very successful. Genetic engineering can overcome all these drawbacks because use of recombinant DNA technology, gene cloning and gene transfer allow us to isolate and introduce only oneor a set of desirable genes without introducing undesirable genes into the target-organism that too from any distant organism.

So, the correct answer is 'Both Assertion and Reason are correct and Reason is the correct explanation for Assertion'.

Pollination is the process of transferring pollen from the male anther of a flower to the female stigma of the same or different flower. Pollination can be carried out by different agents such as wind, water, birds, insects, etc.

Following are a few observations of the flowers that are adapted to pollination by wind, insects and birds.

Flowers Pollinated By Wind

Most of the conifers and angiosperms exhibit wind pollination. Such flowers do not produce nectar and fragrance. In the flowers pollinated by the wind, the microsporangia hang out of the flower. As the wind blows, the light-weight pollen blows with it. The pollen gets accumulated on the feathery stigma of the flower. These flowers appear even before the leaves when the spring commences. Few examples of such flowers include:

• Rice
• Corn
• Oats
• Maize
• Barley
• Papaya

Flowers Pollinated By Insects

The flowers pollinated by insects are bright-coloured and produce nectar. The fragrance of the flowers attracts the insects. The pollen is sticky, large, heavy and rough so that stick to the body of the insects. The stigmas are also sticky so that the pollens depositing are not dispersed. Nectar guides are present on the petals. Few examples of the flowers pollinated by insects are:

• Aster
• Lithops
• Magnolia

Flowers Pollinated By Birds

The flowers pollinated by birds are strong and are adapted to allow the birds to stay near the flowers without their wings getting entangled in them. The flowers are tubular and curved that facilitates nectar-sucking by birds. The flowers are odourless and bright-coloured that attracts the birds. While sucking the nectar, the pollen gets deposited on their beaks and neck and is transferred to the plant they visit next. Few examples of flowers pollinated by birds include:

• Hibiscus
• Fuchsias
• Verbenas
• Beebalms
• Bromeliads

BOD (Biological oxygen demand) measures the milligrams of oxygen consumed during the biological decomposition of organic matter occurring in a litre of waste water during a specified period of time.

COD (Chemical oxygen demand) determines the milligrams of oxygen per litre of waste water which are consumed during the oxidation of the organic matter  to give carbon dioxide, ammonia