2017 Solved Old Paper (BOT-101)

Ans.

Archaebacteria:-

> Archaebacteria are known to be the oldest living organisms on earth. 

> They belong to the kingdom Monera and are classified as bacteria because they resemble bacteria when observed under a microscope. 

> They are completely distinct from prokaryotes. 

> They share slightly common characteristics with the eukaryotes.

Ans.

Phytoplasma:-

> Mycoplasmas are the smallest among the known aerobic prokaryotes. 

> They were first discovered by Pasteur in 1843, during his work on the possible causal agent of pleuropneu­monia of cattle. Thus they were called pleuro- pneumonia-like organism (PPLO). Pasteur was unable to isolate them in pure culture.

> Later, Nocard and Roux (1898), the French microbio­logists, were successful in growing them in pure culture-medium containing serum and confirmed by inoculation and subsequent expression of disease in healthy cattle.

> Mycoplasmas are commonly found in soil, hot spring, sewage water and also in plants and animals including man. Borrel (1910) named these organisms Asterococcus mycoides. Later, in 1929, Nowak placed them under the genus Mycoplasma.

Ans.

General account of immunology:-

> Immunology is the study of the immune system and is a very important branch of the medical and biological sciences. 

> The immune system protects us from infection through various lines of defence. 

> If the immune system is not functioning as it should, it can result in disease, such as autoimmunity, allergy and cancer.

> The immune system consists of a complex network of cells and molecules, and their interactions.

Types of immunity:- There are two major types of immunity:

1. Innate Immunity or Natural or Non-specific Immunity

2. Acquired Immunity or Adaptive Immunity

1. Innate Immunity or Natural or Non-specific Immunity:-

> This type of immunity is present in an organism by birth.

> This is activated immediately when the pathogen attacks. Innate immunity includes certain barriers and defence mechanisms that keep foreign particles out of the body.

> Innate immunity refers to the body’s defence system.

> This immunity helps us by providing the natural resistance components including salivary enzymes, natural killer cells, intact skin and neutrophils, etc. which produce an initial response against the infections at birth prior to exposure to a pathogen or antigens.

> It is a long-term immunity in which our body produces the antibodies on its own. Our body has few natural barriers to prevent the entry of pathogens.

2. Acquired Immunity or Adaptive Immunity:-

> Acquired immunity or adaptive immunity is the immunity that our body acquires or gains over time. Unlike the innate immunity, this is not present by birth.

> The ability of the immune system to adapt itself to disease and to generate pathogen-specific immunity is termed as acquired immunity. It is also known as adaptive immunity.

> An individual acquires the immunity after the birth, hence is called as the acquired immunity.

> It is specific and mediated by antibodies or lymphocytes which make the antigen harmless.

> The main function of acquired immunity is to relieve the victim of the infectious disease and also prevent its attack in future.

> It mainly consists of an advanced lymphatic defence system which functions by recognizing the own body cells and not reacting to them.

> The immune system of our body identifies the pathogens which have encountered in the past. It is mainly caused when a person comes in contact with the pathogen or its antigen.

> Our body starts producing antibodies to engulf the pathogen and destroy its antigen.

> When it encounters for the first time, it is called a primary response. Once a body gets used to these pathogens, antibodies are ready to attack them for the second time and are known as naturally acquired immunity.

Ans.

Properties of antigens and antibodies:-

Properties of Antigens:-

Definition:- Antigens are substances which, when introduced into the body, stimulate the production of antibodies.

Chemical Nature:- The antigens are mostly the conjugated proteins like lipoproteins, glycoproteins and nucleoproteins.

Structure:- 

> Antigenic determinants or epitopes (Gk. epi – upon, topos- place) are components of antigen. 

> Each antigen carries many epitopes. 

> Each Y-shaped antibody mol­ecule has atleast two binding sites that can attach to a specific epitope on an antigen. 

> An antibody can also bind to identical epitopes of two different cells at the same time which can cause neighbouring cells to aggregate. 

> Antigens combine with the antibody. 

> The combination is very much like the lock and key analogy.

Types:-

> Based upon the ability of antigens to carry out their functions, antigens are of two types: complete antigens and incomplete antigens (haptens). 

> A complete antigen is able to induce antibody formation and produce a specific and observable reaction with the antibody so produced.

> Haptens (Gr. hapten to grasp; partial antigens) are substances which are incapable of inducing antibody formation by themselves, but can be capable of inducing antibodies on combining with larger molecules (normally proteins) which serve as carriers.

> Antigens which are present on the body’s own cells are called the auto-antigens or self antigens. 

> The antigens on the non-self cells are known as foreign antigens or non-self antigens.

H antigen:-

> Red blood corpuscles of all ABO blood groups possess a common antigen, the H antigen, which is a precursor for the formation of A and В antigens. 

> Due to universal distribution, H antigen is not ordinarily important in grouping or blood transfusion.

> However, Bhende et al (1952) from Mumbai reported a very rare example in which A and В antigens and H antigens were absent from the red blood corpuscles. This is known as Bombay or Oh blood group. 

> Such individuals will have anti A, anti В and anti H antibodies. Therefore, they can accept the blood only from their own group.

Antigen Presenting Cells (APCs):-

> The cells that can engulf antigen and present fragments to T cells are called antigen presenting cells (APCs).

> There are three types of antigen presenting cells in the body: macrophages, dendritic cells and В cells.

a. Macrophages:-

- Macrophages are usually found in a resting state. 

- Their phagocytic capabilities are greatly increased when they are stimulated to become activated macroph­ages. 

- The macrophages are present alongwith lymphocytes in almost all the lymphoid tissues, e.g., monocytes as blood macrophages and histocytes as tissue macrophages.

b. Dendritic Cells:-

- These cells are characterized by long cytoplasmic processes. 

- Their primary role is to function as highly effective antigen-trapping and antigen presenting cells. 

- These cells are nonphagocytic in nature. 

- They are found in lymph nodes, spleen, thymus and skin. 

- The different types of dendritic cells are:

i. Langerhan’s dendritic cells in epi­dermis of skin which trap the organisms coming in contact with body surface.

ii. Dendritic cells in spleen, which trap the antigen in blood.

iii. Follicular dendritic cells in lymph nodes which trap the antigen in the lymph.

- Thus macrophages and dendritic cells play an important role in the trapping and presen­tation of antigens to T and В cells to initiate the immune response.

- Steinman was awarded Nobel Prize (2011) for his discovery of the dendritic cell and its role in adaptive immunity.

c. B-cells:-

- В-cells express on their surface intra-membrane immunoglobulin (Ig) mol­ecules that function as В cell antigen receptors. 

- Since all the receptors on a single В cell are identical, each В cell can bind only one antigen. This makes them much more efficient antigen-presenting cells than macrophages, which must ingest any foreign material that comes their way.

- Descendants of В-cells (plasma cells) produce antibodies.

Properties of Antibodies:-

Definition:- Antibodies are immunoglobulin’s (Igs) which are produced in the body in response to the antigen or foreign bodies. Thus all antibodies are immunoglobulin’s but all immunoglobulin’s are not antibodies.

Location and Formation:-

> The antibodies may be bound to a cell membrane or they may remain free. Antibodies are produced by В lymphocytes and plasma cells. In fact B-lympho­cytes get transformed into plasma cells. 

> The mature plasma cell produces antibodies at an extremely rapid rate— about 2000 molecules per second. 

> Antibodies direct the antibody- mediated immunity (= humoral immunity).

Types of Antibodies:- There are five types of antibodies viz:

i. IgA (Ig alpha)

ii. IgD (Ig delta)

iii. IgE (Ig epsilon)

iv. IgG (Ig gamma)

v. IgM (Ig mu)

Note:- Among the antibodies, IgG forms 80% of the antibodies in the body.

Antibody Structure:-

> IgG has been studied extensively and serves as a model of basic structural unit of all Igs.

> An antibody molecule consists of the following parts.

i. Heavy and Light Chains:-

- An antibody molecule is made up of 4 peptide chains, two small called light chains and two longer called heavy chains. 

- Hence an antibody is represented as H2L2. 

- The heavy chain has larger number of amino acids while light chain has smaller number of amino acids. 

- Heavy and light chains may be either lambda or Kappa type.

ii. Constant and Variable Regions:- There are two different regions the constant region and variable region in each chain of the antibody.

iii. Disulfide Bonds and Hinge Region:- 

- A disulfide bond joins a light chain with a heavy chain. 

- Two disulfide bonds also link the two heavy chains. 

- This part of the antibody displays considerable flexibility and is called the hinge region. 

- Because the antibody “arms” can move somewhat as the hinge region bends, an antibody can assume a Y shaped molecule.

iv. Fragment Antigen Binding (Fab) and Fragment Crystallisable (Fc):-

- Two iden­tical fragments of Y-shaped molecule possess the antigen-binding sites and are thus named fragment-antigen binding (Fab). 

- The antigen-binding sites bind to the specific antigens in a lock and key pattern, forming an antigen-antibody complex. 

- The third fragment which lacks the ability to bind to antigen and can be crystallized, is, therefore, known as fragment crystallizable (Fc).

- The stem of the Y-shaped antibody monomer is called the Fc region, so named because when antibody structure was first being identified, it was a fragment (F) that crystallized (c) in cold storage.

Characteristics and Functions of Immunoglobulin’s (Igs) or Antibodies:- Antibodies show the following characteristics and perform different functions.

i. IgA:- 

- It is the second most abundant class, constituting about 10 to 15 per cent of antibodies of serum. 

- It is mainly found in sweat, tears, saliva, mucus, colostrum (first milk secreted by a mother) and gastrointestinal secretions.

- Smaller quantities are present in blood and lymph. 

- IgA has an extra polypeptide called a J-(joining) chain and extra protein known as secretory component. 

- Levels decrease during stress, lowering resistance to infection. 

- Provides localized protection in external secretions (tears, intestinal secretions, etc.) against bacteria and viruses. 

- When IgA is excreted through faeces, it is called coproantibody.

ii. IgD:-

- It is mainly found on the surfaces of В cells as antigen receptors, where it activates В cells for antigen recognition. 

- It is about 0.2% of all antibodies in the blood.

iii. IgE:-

- It is less than 0.1% of all antibodies in the blood; located on mast cells and basophils releasing histamine from mast cells and basophils. 

- It is involved in allergic and hypersensitivity reactions; provides protection against parasitic worms. 

- This immunoglobulin was discovered in 1966 by Ishizaka.

- It exhibits unique properties such as heat lability (inactivated at 56°C in one hour). 

- IgE mediates type I hypersensitivity (anaphylaxis). 

- Prausnitz and Kustner in 1921 demonstrated transmission of IgE-mediated type I hypersensitivity. It is called Prausnitz-Kustner (PK) reaction. 

- Thus IgE acts as mediator in allergic response.

iv. IgG:-

- This is the most abundant class of Ig in the body constituting approximately 80% of the total Igs. 

- It is found in the blood, lymph and intestine. 

- It protects against bacteria and viruses by enhancing phagocytosis, neutralizing toxins and complement activation. 

- It is the only class of antibody to cross the placenta from mother to foetus thereby conferring considerable immune protection in new-borns.

v. IgM:-

- IgM is about 5 to 10% of all antibodies in the blood. It is also found in lymph. 

- It is the largest Ig which is secreted first by the plasma cells. 

- It is so named because it is a macroglobulin at least five times larger than IgG. 

- IgM is the oldest immunoglobulin class. It activates the В cells. 

- It is also the earliest immunoglobin to be synthesised by the foetus, IgM has a J chain and its each dimer contains polypeptide called a secretory component.

- It cannot cross the placental barrier. 

- IgM is 500-1000 times more effective than IgG in opsonisation (to be described ahead), in bacterial action and in bacterial agglutination. 

- But in neutralization of toxins and viruses, it is less active than IgG. 

- It helps in complement activation.

Types of Vaccines:- Vaccines can be synthesized in many ways based on which they are classified:

1. Live attenuated vaccines:- Pathogens like virus or bacteria are weakened by genetic manipulations to limit its growth and thus do not cause disease to the host. In some modified versions of live vaccine an organism that is related to the pathogen is used that naturally grows poorly in humans. The weakened pathogen generates a broad immune response in the host similar to that shown by an infected individual with a natural pathogen.

Examples:-

i. Oral Sabin polio vaccine

ii. MRV Vaccine (Measles, Mumps, Rubella, and Varicella)

iii. Nasal influenza vaccine

iv. Bacille Calmette-Guerin (BCG) vaccine

v. Varicella vaccine

vi. Rotavirus vaccine

2. Inactivated or Dead vaccines:- The disease-causing pathogen is killed or inactivated, usually through a thermal (application of high temperature) or chemical (formalin etc.) process. Such vaccines, when administered, elicit a robust immune response that mimics most of the responses seen during an infection.

Examples:-

i. Typhoid vaccine

ii. Influenza vaccine

iii. Salk polio vaccine

iv. Hepatitis A vaccine

3. Acellular or Subunit vaccines:- Acellular means not containing the whole cells. Acellular vaccines do not contain the whole bacteria or viruses. Instead, they contain polysaccharides or proteins from the surface of the bacteria or virus. These polysaccharides or proteins are the parts that our immune system recognizes as ‘foreign’ and evoke immune response against them. There are many types of a cellular vaccines:

a. Toxoid Vaccine:- Some pathogenic bacteria release toxins or poisonous proteins when they attack the body. Some vaccines are made by inactivating these toxins chemically and called ‘toxoids’, because they look like toxins but not poisonous. They trigger a strong immune response.

Examples:-

i. Diphtheria vaccine

ii. Tetanus vaccine

iii. Pertussis vaccine

b. Conjugate Vaccine:- Earlier polysaccharide vaccines were made using sugar molecules present on the surface of the bacteria but it was found to be less effective in babies and young children. Researchers discovered that these vaccines can work better if the bacterial polysaccharide molecules are chemically linked or conjugated to a carrier protein. Addition of other proteins confers the immunological attributes of the carrier to the antigen and thus induces a stronger immune response effective enough for younger children also.

Examples:-

i. Haemophilus influenza type b (Hib) conjugate vaccine

ii. Pneumococcal conjugate vaccine

iii. Meningococcal C conjugate vaccine

c. Recombinant Vaccine:- A small piece of the DNA is taken from the disease-causing bacterium or virus. The particular gene is incorporated into plasmid or a carrier vehicle which enables production of large quantities of well-defined proteins, which are then used as vaccines.

Examples:-

i. Hepatitis B vaccine

ii. Human papillomavirus (HPV) vaccine

d. DNA/RNA Vaccine:- Genetic material, either DNA or RNA, from the pathogenic bacteria or virus is introduced into the human cells and then the cell machinery is employed to produce the protein encoded by the inserted gene(s) of the pathogen. Our body’s immune system detects such protein as a foreign agent and produces an immune response against the whole pathogen. At present, different types of nucleic-acid vaccines are in developmental, pre-clinical and clinical evaluation phases 

Examples:- HIV vaccine

Ans.

विविध आवासों में शैवाल (Algae in diversified habitats):-

1. स्थलीय शैवाल (Terrestrial Algae)

2. शुद्ध जलीय शैवाल (Fresh water Algae)

3. समुंद्री शैवाल (Marine Algae)

4. असामान्य आवास (Unusual habitat)

नोट (Note):- अधिकांश शैवाल लगभग 90 प्रतिशत जलीय होते हैं।

(Majority of the algae about 90 per cent are aquatic.)

1. स्थलीय शैवाल (Terrestrial Algae):- 

> शैवाल मृदा पर हरे मैल के रूप में पाए जाते हैं।

(Algae found on the soil in the form of a green scum.)

> मृदा वनस्पति को सामूहिक रूप से इडैफोफाइट्स के रूप में जाना जाता है।

(The soil flora is collectively known as edaphophytes.)

> वे दो प्रकार के होते हैं-

(They are two types-) 

i. सैफोफाइट्स (Saphophytes):- ये मृदा की सतह पर पाए जाते हैं। जैसे- फ्रिट्स्चिएला, बोट्रीडियम, वाउचेरिया

(They are found upon the surface of the soil. Eg.- Fritschiella, Botrydium, Vaucheria)

ii. क्रिप्टोफाइट्स (Cryptophytes):- ये मृदा के अंदर पाए जाते हैं. जैसे- नोस्टॉक, एनाबीना

(They are found inside the soil. Eg.- Nostoc, Anabaena)

2. शुद्ध जलीय शैवाल (Fresh water Algae):- ये रूप ताजे जल या तालाबों, पूल, झीलों आदि के कम लवणता वाले जल में होते हैं।

(These forms occur in fresh water or in low salinity water of ponds, pool, lakes etc.)

i. स्थिर जल शैवाल (Stagnant water algae):- अधिकतर, मिक्सोफाइसी और क्लोरोफाइसी के सदस्य रुके हुए जल में विकसित होते हैं। जैसे- जिग्नीमा, ऊडोगोनियम, कारा, रिवुलेरिया, ग्लियोट्राइकिया

(Mostly, members of Myxophyceae and Chlorophyceae develop in stagnant water. Eg.- Zygnema, Oedogonium, Chara, Rivularia, Gleotrichia)

ii. प्रवाहित जल शैवाल (Running water algae):- कुछ शैवाल बहते पानी में पाए जाते हैं। ऐसे आवासों में पानी की गुणवत्ता में ऑक्सीजन की मात्रा अधिक होती है। जैसे- क्लैडोफोरा, यूलोथ्रिक्स, वाउचेरिया, बेट्रेकोस्पर्मम

(Some algae are found in running water. In such habitats, the quality of water contains a higher amount of oxygen. Eg.- Chladophora, Ulothrix, Vaucheria, Batrachospermum)

3. समुंद्री शैवाल (Marine Algae):- शैवाल समुद्र में पाए जाते हैं। ऐसे शैवाल शुद्ध जल में कभी नहीं पाए जाते। रोडोफाइसी और फियोफाइसी के सदस्य अधिकतर समुद्री शैवाल के रूप में पाए जाते हैं। जैसे- एक्टोकार्पस, पॉलीसाइफ़ोनिया, फ़्यूकस, कौलेर्पा, सारगासम। साइफ़ोनेल्स गण के कई सदस्य भी समुद्री जल में निवास करते हैं।

(The algae are found in the sea. Such algae are never found in freshwater. Members of Rhodophyceae and Phaeophyceae mostly occur as marine algae. Eg.- Ectocarpus, Polysiphonia, Fucus, Caulerpa, Sargassum. Several members of the order Siphonales also inhabit seawater.

4. असामान्य आवास (Unusual habitat):- 

i. क्रायोफाइट्स (हिम शैवाल) Cryophytes (Snow algae):- रैफिडोनीमा (हरी बर्फ), हिमेटोकोकस निवेलिस (लाल बर्फ), एनसाइक्लोनीमा नॉर्डेनशियोलेडाइ (बैंगनी बर्फ), प्रोटोनीमा (पीली बर्फ)

[Raphidonema (Green snow), Haematococcus nivalis (Red snow), Ancyclonema nordenshioledii (Purple snow), Protonema (Yellow snow)]

ii. थर्मोफाइल्स (थर्मल शैवाल) Thermophiles (Thermal algae):- अमेरिका के येलोस्टोन नेशनल पार्क में (85°C तापमान पर भी शैवाल के सदस्य मौजूद रहते हैं। जैसे- मेस्टिगोक्लेडस और फोर्मिडियम की जातियाँ

In Yellowstone National Park of America, even at the temperature of 85°C algae members are present. Eg.- Mastigocladus and species of Phormidium)

iii. लवणोदभिद (लवणीय जल शैवाल) Halophytes (Salt water algae):- अत्यधिक खारे पानी की झीलों में पाया जाता है। जैसे- डुनेलीएला, स्टीफोनोप्टेरा। क्लैमाइडोमोनस च्रेनबेगी सांभर और क्रीमेरा झीलों के स्लैटिश जल में पाया जाता है।

(Found in extreme salt water lakes. Eg.- Dunaliella, Stephoenoptera. Chlamydomonas chrenbegii is found growing in the slatish water of lakes Sambhar and Crimera.)

iv. लिथोफाइट्स (चट्टान शैवाल) Lithophytes (Rock algae):- चट्टानों पर पाया जाता है। जैसे- रिवुलेरिया, ग्लियोकैप्सा

(Found on rocks. Eg.- Rivularia, Gleocapsa)

v. अधिपादप (Epiphytes):- कोलिओकीट और कीटोफोरा नेलुम्बो, कैस्टोलिया और वेलिसनेरिया जैसे उच्च पादपों की पत्तियों पर उगते हैं। मोस पर लाल शैवाल ऑडोसिनेला पाया जाता है। रिवुलेरिया की कालोनियाँ स्किर्पस घास पर पाई जाती हैं।

(Choloeochaete and Chaetophora grow on the leaves of higher plants like Nelumbo, Castolia, and Vallisneria. A red alga Audocinella is found on mosses. Colonies of Rivularia are found growing on grass-Scirpus.)

vi. अधिजन्तु शैवाल (Epizoic algae):- क्लैडोफोरो क्रत्सपाटा घोंघों पर उगता है।

(Cladophoro crtspata grows on snails.)

vii. सहजीवी शैवाल (Symbiotic algae):- 

- एन्थोसेरोस के थैलस में नोस्टॉक

(Nostoc in the thallus of Anthoceros)

- साइकस की कोरेलॉइड जड़ों में एनाबीना साइकैडी

(Anabaena cycadae in the coralloid roots of Cycas)

- एजोला के अंदर एनाबीना

(Anabaena inside Azolla)

- लाइकेन, जिसमें शैवाल और कवक एक साथ रहते हैं

(Lichen, in which algae and fungi live together)

- हाइड्रा के भीतर ज़ूक्लोरेला

(Zoochlorella within Hydra)

viii. परजीवी शैवाल (Parasitic algae):- क्लोरोफाइसी का एक सदस्य, सिफेल्यूरोस, चाय, कॉफी और काली मिर्च पर आंशिक परजीवी के रूप में विकसित होता है।

(Cephaleuros, a member of the Chlorophyceae, develops as a partial parasite on tea, coffee, and black pepper.)

Ans.

थैलस संगठन की सीमा (Range of thallus organization):-

1. एककोशिकीय थैलस (Unicelluar Thallus)

2. बहुकोशिकीय थैलस (Multicellular Thallus)

1. एककोशिकीय थैलस (Unicelluar Thallus):- 

a. अचल एककोशिकीय (Non-motile uni cellular):- Eg.- Chlorella, Synechococcus

b. चल एककोशिकीय (Motile unicellular):- Eg.- Chlamydomonas

2. बहुकोशिकीय थैलस (Multicellular Thallus):- 

a. कोलोनीय शैवाल (Colonial Algae)

b. तन्तुमय शैवाल (Filamentous Algae)

a. कोलोनीय शैवाल (Colonial Algae):- 

i. अचल कॉलोनी (Non motile colony):- Eg.- Nostoc, Pediastrum, Scenedesmus

ii. चल कॉलोनी (Motile colony):- Eg.- Gonium, Pandorina, Eudorina, Volvox

b. तन्तुमय शैवाल (Filamentous Algae):- 

i. अशाखित तन्तु (Unbranched filaments):- Eg.- Zygnema (free floating), Anabaena, Spirulina, Ulothrix, Spirogyra, Oedogonium)

ii. शाखित तन्तु (Branched filaments):- Eg.- Cladophora, Pithophora, Bulbochaete

iii. नालनुमा तन्तु (Siphonaceous filaments):- बिना पट्ट के लम्बा पादप शरीर। एक सामान्य प्रोटोप्लाज्म में मौजूद कई केंद्रक को सीनोसाइटिक स्थिति कहा जाता है। जैसे- वाउचेरिया, बोट्रीडियम, कोडियम, ब्रायोप्सिस

(Elongated plant body without septation. Many nuclei present in a common protoplasm called as coenocytic condition. Eg.- Vaucheria, Botrydium, Codium, Bryopsis)

Ans.-

Sargassum:-

1. Classification:-

Division:- Phaeophyta

Class:- Phaeophyceae

Sub-class:- Cyclosporeae

Order:- Fucales

Family:- Sargassaceae

Genus:- Sargassum

2. Habit and Habitat:- Sargassum is a seaweed (macroalgae). It is commonly known as gulfweed and sea holly. 

The common species found in India is S. tennerimum.

3. Thallus structure:-

> This algae grows to a length of several metres. 

> The plant body is dark green to brown in colour and consists of a holdfast, stipe and frond. 

> The thallus is branched and has berry-like structures called pneumatocysts. The pneumatocysts are filled with oxygen and help in buoyancy of the plant.

4. Reproduction:- Asexual mode of reproduction is absent.

a. Vegetative Reproduction:- By the means of fragmentation.

b. Sexual Reproduction:- Sexual reproduction in Sargassum is of oogamous type. 

i. Antheridium:- 

- The inner layers of the conceptacle have fertile and branched paraphyses that contain the antheridium. 

- Each antheridium is round, oval and double-layered and gives rise to 64 antherozoids after meiotic division.

- The antherozoids are biflagellate and pear-shaped. 

- The flagella arise sub-terminally and are unequal in size. 

- The wall of the antheridium breaks and all the antherozoids are released in water.

ii. Oogonium:- 

- The oogonial initials are also formed by the inner layers of the female conceptacle. 

- The oogonium is round and triple layered: outer exochite, middle mesochite and inner endochite.

- The nucleus of the oogonia is diploid which divides by meiotic divisions to form 8 haploid nuclei. 

- The haploid nuclei form 8 ova. Of these, 7 ova are aborted and one ovum goes further for fertilisation. 

- The oogonia remains attached to the inner walls of the conceptacle by a mucilaginous stalk.

> Fertilization:- 

- After fertilization of the antherozoid and ovum, a zygote is formed. 

- The oogonia remains attached to the conceptacle until the first transverse division happens in the zygote. 

- Of the two cells formed in the zygote, the lower cell makes the attaching organs and the upper cell works as an apical cell and forms an adult plant.

> Life Cycle:- 

- The main plant body is a diploid sporophyte. 

- The formation of antherozoids and ovum is the only representation of the haploid gametophyte stage in the life cycle of Sargassum.

Ans.

Algal biofertilizers:- 

Biofertilizers:-

> These are natural compounds that contain micro-organisms to enrich soil fertility to increase crop yield and plant growth.

> Microbial inoculants like bacteria, algae, and fungi can be used in biofertilizers.

> The biofertilizers having algae as an inoculant in them are known as algal biofertilizers.

> Biofertilizers can be used to fix nitrogen in the soil or they are also used to grow soil micro-flora to enhance soil health.

Algal biofertilizer:-

> BGA (blue-green algal) biofertilizers are used in fields to fix atmospheric nitrogen into the soil in organic form.

> BGA biofertilizers are not inhibited by the presence of any chemical fertilizers.

> Heterocyst is used to fix nitrogen into the soil.

Advantages of algal biofertilizers:-

> The algal biofertilizers can increase crop yield by 10-14%.

> Unlike chemical fertilizers they are eco-friendly.

> Low-cost input is required and thus is cheaper.

Benefits of BGA as a biofertilizer:-

> BGA is a biological nitrogen fixer, which concentrates the soil with organic matter and lowers the C: N ratio.

> Other uses of BGA are to improve the solubilization of immovable phosphates and to produce growth-promoting substances in soil.

> They improve the physical, chemical, and biological properties of the soil and contribute to long-term soil fertility.

> BGA has been reported to lower soil pH and help the soil retain exchangeable calcium.

> It has been reported that Nitrogen availability, particularly in the rice fields, to plants is increased due to the application of BGA.

> In India, BGAs such as Anabaena, Nostoc, and Carotrix are generally predominant and are widespread in rice-growing areas, with the exception of some acidic soils in Kerala, Assam, and Tamil Nadu. Other forms such as Cylindrosporum, Tolypothrix, Scytonema, and Aulosira had a local distribution.

> The prevalence of soils containing blue-green algae in India varies from 7% to 80% depending on the state.

Ans.

Algal blooms:-

> An algal bloom is a rapid increase in the popullation of algae in an aquatic system. 

> Algal blooms may occur in freshwater as well as marine environments. 

> Result of an excess of nutrients (particularly p and n). 

> Their growth - cause for other plants to die.

Harmful algal blooms (HAB):-

> A harmful algal blooms is an algal bloom that causes negative impacts to aquatic organisms via production of natural toxins, mechanical damage to aquatic organism. 

> HABs are often associated with large-scale marine mortality events and have been associated with various types of shellfish poisonings and also fin fishes and other aquatic organisms .

> HABs in India:-

- Researchers have found toxic bloom has increased around 15 percent over the 12 years in indian seas. 

- There was 80 harmful bloom recorded between the 1998-2010 in indian water. 

> Worldwide Effects of HABs:-

- Light penetration levels in water decrease altering photosynthesis rate. 

- Algal blooms may be harmful to seagrass and coral reef ecosystems and the connected food webs. 

- Shellfish may accumulate algal toxins by feeding on the toxic phytoplankton resulting in fish kills, marine mammal distress, human illness and possible death.

> Reasons for Increase in HABs:-

- Global climate changes producing wider ranges for some species. 

- Human contributions of increased nutrients and pollution in coastal waters and also fresh waters. 

- Changes in local ecosystems that may allow exotic species to thrive if introduced.

- Upwelling. 

- Formation of mud banks. 

- Nutrients discharge on sea or fresh water through river.

- Eutrophication:- It is a process where by water bodies receive excessive amounts of nutrients, which results in excessive plant growth and formed algal bloom.

> Factors that can contribute to HABs:-

i. Excess nutrients (Eg.- phosphorus or nitrogen) 

ii. Sunlight 

iii. Low-water levels or low-flow conditions 

iv. Calm water (low-wind conditions) 

v. Warmer temperatures

> Examples of some HABs:-

i. Cyanobacteria (blue-green algae) 

ii. Redtides:- Neurotoxic shellfish poisoning 

iii. Ciguatera:- Gambierdiscus toxicus 

iv. Alexandrium 

v. Gymnodium 

vi. Dynophysis 

vii. Coolia monotis 

viii. Prorocentrum lima.

Harmful effect of algal bloom:-

> Changes in levels of chemicals such as nitrogen and phosphorus from fertilizer, in the water. 

> Algal blooms can deplete the oxygen and block the sunlight that other organisms need to live. 

> Some can produce toxins that are harmful to the health of the environment- plants, animals, and people etc. 

> Aquaculture industries.

Control method:-

> Biological:- Bacteria (Gymnodinium mikimotoi), Virus, Bivalves, Zooplankton etc. 

> Chemical:- Copper sulfate, Alum etc. 

> Physical

Ans.

Algea in industry:-

a. Iodine:-

> Iodine industry is mainly depended upon algae.

> Algae belonging to Phaeophyceae, like Laminaria, Ecklonia, Eisenia, etc. are used in the industry to prepare Iodine in industries.

> Phyllophora is used to prepare Iodine in Russia.

b. Agar-Agar:- 

> Agar-agar is a jelly like substance of great economic value.

> It is obtained from certain red algae like Gelidium, Graciliaria and Gigartina.

> Agar is used as a culture medium for growing callus in tissue culture.

c. Carrageenin:-

> It is extracted from cell walls of red algae like Chondrus and Gigartina.

> It is a polysaccharide esterfied with sulphate.

> It is used as emulsifier in pharmaceutical industry and also in textile, leather, cosmetics and brewing industries.

d. Diatomite:- 

> Diatoms deposits at marine and fresh water areas.

> Diatoms are rich with silica. It is called as diatomite.

> diatomite is used in the preparation of Dynamite in olden days.

> But now diatomite is used in different industries like glass, metal polishing, paints, tooth pasts, soups, etc.

e. Minerals:-

> The brown sea weeds popularly called as kelpyield potash, soda, and iodine.

> Some sea weeds are rich source of iron, zinc, copper, manganese and boron.

> Bromine is extracted from red algae such as Polysiphonia and Rhodymenia.

f. Funori:-

> It is a type of glue obtained from a red alga Gloipeltis furcata.

> It is used as an adhesive as well as sizing agent for paper and cloth.

> Chemically it is similar to agar-agar except that there is no sulphate ester group.