Class 9 Notes For Biology and Human Welfare

Biology And Human Welfare Immunity And Human Diseases

Concept Of Immunity

The human body is subjected to a variety of harmful pathogens and foreign substances (antigens) from air, water, soil, food, etc.

• Our body has a mechanism of resistance to protect ourselves against those pathogens.
• This branch of science which deals with the responses of the body against antigens is called immunology.

Immunity: The ability of an organism to resist the harmful effects of a foreign protein or any antigen and thus to fight against diseases by producing immune bodies or antibodies is called immunity, in other words, immunity is the natural protective system of the body against different antigens.

• Every day our body is exposed to a large number of infectious agents but only a few of them may result in disease.
• Why? Because our body can fight against the disease-causing agents this ability is known as immunity.

Antigen: Any foreign, harmful, toxic chemical substance when introduced into the body, causes the body to produce specific antibodies is called an antigen. A specific antibody can bind with a specific antigen only. Thus the term antigen signifies antibody generator.

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• Antigens are usually proteins and polysaccharides (very rarely lipid). Some common antigens examples are bacteria, viruses, other microorganisms, or their body parts.
• Some foods or others may cause allergic reactions in our bodies called allergens.
• Allergens are also antigens that may cause a vigorous immune response.
• A few examples of allergens are dust, some drugs, food (like egg, prawn, brinjal, milk or milk products, etc.), and so on.

Antibody: An antibody is a protein produced by the body in response to a specific antigen and is capable of combining with the specific antigen only.

• An antibody is a protein known as Immunoglobulin (l_g), a Y-shaped structure, produced by plasma cells (modified B lymphocytes)

Structure of antibody: Each antibody molecule has four peptide chains two small ones called light chains (L) and two longer ones called heavy chains (H). So an antibody may be represented as H₂L₂. All the chains are interconnected by chemical bonds.

Types of antibodies: Antibodies are generally five types l_gG, I_gA, I_gM, I_gD, I_gE (GAMDE)-of which I_gG is most abundant in the body.

Antigen-Antibody interaction :

• Epitope: This is the functional site of an antigen, which binds with the antibody.
• Paratope: This is the functional part of an antibody, which binds with the epitope of an antigen.

During antigen-antibody interaction, the epitope of the antigen binds with the paratope of the antibody.

Leucocytes: You know that leucocytes (WBC) can be of different types. All of them help in the immune system of our body. example

1. Monocytes and neutrophils are responsible for the phagocytosis of germs.
2. Basophil and Eosinophil respond to allergy.
3. Lymphocyte plays the most crucial role in immunity.

Role of Lymphocyte:

1. Large lymphocytes are immature. During maturation large lymphocyte gradually loses cytoplasm and becomes a small lymphocyte that is matured:
2. Small lymphocytes can be of two types B-lymphocyte (Bone marrow-dependent lymphocyte) and T-lymphocyte (thymus-dependent lymphocyte).
3. B-lymphocyte is produced and matured in bone marrow, whereas T-lymphocyte is produced in bone marrow but is matured in the Thymus gland.
4. When the B-lymphocyte is stimulated by an antigen, it produces a specific antibody. This is called humoral immunity.
5. T- lymphocyte recognizes the antigen or part of the antigen. This is known as cellular immunity.
6. T- T-lymphocytes stimulate B-lymphocytes to form antibodies.

Do you know, there are various sub-types of T and B-lymphocytes with specific functions?

Types of immunity:

1. Inherited Immunity (Innate Immunity): This immunity is present at the time of birth example Different types of WBC are present in the blood of a newborn baby. These WBCs will protect the baby against antigens as soon as it is exposed to air outside the mother’s body immediately after birth.
2. Acquired Immunity: The type of immunity that is acquired by a person during his lifetime is called acquired immunity.
3. Active immunity: When a person is exposed to an antigen, the lymphocyte of his own body produces antibodies. This is called active immunity.
4. Passive Immunity: When preformed or readymade antibodies are directly given to a person to protect the body/it is called passive immunity.

Types of immunity Example

• Acquired active natural immunity: Once someone suffers from pox, generally pox virus cannot attack him anymore.
• Acquired active artificial immunity: Vaccination and stimulation of lymphocytes to produce antibodies, for example, Injection of cholera vaccine.
• Acquired passive natural immunity: Mother’s I_gA enters the body of the baby along with milk; the mother’s IgG enters the fetus through the placenta.
• Acquired, passive artificial immunity: Performed antibody (antivenom) from a rabbit or horse may be injected into a snake bite patient.

Concept Of Vaccine

Vaccination (Immunisation):

• The process by which weak or dead pathogens (antigens) are injected into the body to produce immunity against infectious disease by producing antibodies is called vaccination.
• The principle of immunization or vaccination is based on the property of “memory’ of the immune system.

How do vaccines work in our body? Vaccines “teach” our body how to defend itself when germs, such as viruses or bacteria etc, invade the body.

The steps are

1. The body is exposed to very small, very safe amounts of viruses or bacteria that have been weakened or killed.
2. Our immune system then learns to recognize and attack the infection, if our body is exposed to that infection later in life.
3. As a result, our body will not become ill or we may have a milder infection. This is a natural way to deal with infectious diseases.

Probably all of you know that a computer can learn to identify something when proper “software” is loaded on the hard disc. In the vaccination process, the vaccine acts as “software” to develop a “learning process” in the immune system of the body. This vaccine is software, and the immune system is the “hard disc” of the body.

• Uses of vaccination: A vaccinated person develops immunity against diseases like Mumps, Tuberculosis (TB), Rabies (causing hydrophobia), Polio, Cholera, Measles, Tetanus, Typhoid, Smallpox, and so on when vaccines for those diseases are injected into their body.
• Historical perspective: Edward Jenner and Vaccination: For many centuries, smallpox devastated mankind. In modern times, we don’t have to worry about smallpox. We are grateful for the remarkable work of Edward Jenner. With the rapid advancement of vaccination, the historic origin of immunization is often forgotten.
• Edward Jenner (17 May 1749-26 January 1823) was a British physician and scientist who was a pioneer of smallpox vaccine, the world’s first vaccine. He is often called “the father of Immunology”. It is said that “Jenner’s work saved more lives than the work of any other human.”
• Jenner observed that milkmaids were generally immune to smallpox. Cowpox is a disease in cows, similar to smallpox, but much less virulent.
• Jenner noticed that cows suffering from cowpox form blisters from where pus comes out. While handling the cow, milkmaids received this pus from a cow.
• This cowpus protected the milkmaids from smallpox. Jenner collected this pus from cows and also from cowpox blisters on the hands of milkmaids.
• He then inoculated the material to different persons who developed immunity against smallpox and did not suffer from smallpox anymore.
• Jenner’s discovery was accepted and vaccination was recognised in 1840 by the British Government.

Different types of vaccines with examples: Vaccines are made using different processes. They may contain live germs that are attenuated (weakened or altered so as not to cause illness); inactivated toxins; or simply segments of the pathogen. Some common vaccines are mentioned below:

Pathogen And Parasite Causing Human Disease:

Concept And Components Of Wash And Significance In Eliminating Disease Burden

Concept of WASH :

• WASH refers to “Water, Sanitation and Hygiene” which is an international development program that campaigns for access to safe water, adequate sanitation, and proper hygiene education—thus reducing illness and death from disease, reducing poverty, and increasing socio-economic development. WASH is primarily concerned with public health.
• Sanitation: It is the hygienic means of promoting health through the protection of humans against hazards of waste as well as the treatment and proper disposal of sewage waste water.
• Hygiene: It is a set of practices performed for the preservation of health. Some regular hygienic practices may be considered “good habits.”
• UNICEF (United Nations International Children’s Emergency Fund) or WHO (World Health Organisation): Joint Monitoring Program (JMP) (Published in 2013): 36% of the world’s population (2.5 Billion people) lack improved sanitation facilities, and 768 million people still use unsafe drinking water sources. Due to this problem of drinking water and poor hygiene practices, every day thousands of children become sick and ultimately die.

Children particularly girls are denied their right to education because their schools lack private and decent sanitation facilities.

• Women are forced to move a long way to fetch drinking water daily. Without WASH, proper development is impossible.
• Global access to safe water, adequate sanitation, and proper hygiene education can reduce illness and death from disease.
• Thus it may help in the reduction of poverty and on the other hand better socio-economic development.
• So many developing countries are challenged to provide these necessities to their people so they are at risk of WASH-related diseases.

Components of WASH: Water is considered to be the most important component (resource) for sustaining ecosystems. Water provides life-supporting services for people, animals, and plants.

• Because contaminated water is a major cause of illness and death, water quality is a determining factor in human poverty, education, and economic progress.
• Unfortunately, water quality all over the world is declining due to various factors of water pollution such as population growth, rapid urbanization, industrial discharge of chemicals, etc. Thus health of humans as well as the quality of the ecosystem is badly threatened.
• UNICEF and WHO work on different aspects of WASH all over the world. Their work is primarily to eliminate disease burden as far as possible.

The work is divided into six core activities:

1. Drinking water quality management.
2. Water supply and sanitation monitoring.
3. Cholera surveillance and prevention.
4. Water and sanitation in different settings.
5. Water resources management.
6. Other activities.

Importance (Significance) of WASH: The overall objective of UNICEF’s WASH program is to minimize avoidable mortality and morbidity among people.

• Poor sanitation contributes to about 7,00,000 child deaths from diarrhea each year.
• Creating sanitation infrastructure for everyone (citizens of the world) is a major challenge.
• If we improve the technology to deal with human waste we can save lives, and improve child health, and personal safety (particularly for women and girls).
• Improvement of toilet design can help governments and NGOs to meet the enormous challenge of public sanitation services.
• All UNICEF programs are designed to improve WASH all over the world.

Microbes In Human Welfare In Our Everyday Life Microbes In Biocontrol Agents

The natural method of pest and pathogen control in which viruses, bacteria protozoa, etc. are used is called biocontrol or biological control.

• The chemicals that are used in agricultural fields as pesticides and insecticides are very poisonous and harmful to human beings including animals.
• Bacillus thuringiensis, a bacterial species has the power to kill different insects for example moths, beetles, ants, termites, etc.
• The bacterium possesses some insect-killing crystal proteins, of which one of them is known as trioxide.

Microbes In Biocontrol Agents Examples: In connection with biological control some examples are cited below :

• Insects: Ladybird beetles provided with red and black markings live by eating aphids. Dragonflies prey upon mosquitoes for their food.
• The insect Neochetina introduced from Latin America to India is used to control aquatic floating plant water hyacinth (Eichhorina crassipes). On the swollen petiole of the water hyacinth, the female insect lays an egg.
• From the eggs, larvae develop which take the petiole as food, and in turn, the adults feed on leaves, finally the destruction of the entire plant results.
• Fungus: Biological control is influenced by the free-living fungus Trichoderma over some plant pathogens.
• Bacteria: Bacillus thuringiensis (Bt) can be utilized to control butterfly caterpillars which acts as a microbial biocontrol agent.

For reference only: The above-mentioned bacteria are available in sachets as dried spores in the market, which are mixed up with water and sprayed by a sprayer in those plants that are exposed to being attacked or harmed, such as Brassica and fruit trees, where these are taken as food by the larvae of the insect.

• Finally, the larvae get killed when the toxin is released in the gut of the larvae.’The toxins formed kill only the caterpillars but do not cause any harm to the other insects.
• Bacillus thuringiensis toxin genes (crygene) when introduced into cotton plants by scientists, plants got the power to resist the attack of insect pests example Bt. cotton, which is cultivated in some States. India.
• Bacillus thuringiensis (Bt) is one of the most important examples of soil bacterium. The spores of this bacterium possess the insecticidal insect-killing substance called cry protein. For that reason, the spores produced by the bacterium have the power to kill certain larvae of the insects.

Virus: Another pathogens are Baculoviruses which attack insect pests and some other arthropods.

• The genus Nucleopolyhedrovirus is one of the baculoviruses caused by biocontrol agents.
• These viruses are very good entities for species-specific.
• They do not show any negative impacts on plants, mammals, birds, fishes, etc.

Microbes As Biofertilizers

Microbes As Biofertilizers Introduction: Biofertilizers reduce the dependence on chemical fertilizers and do not pose pollution problems. Crop rotation techniques improve soil fertility.

• Cereal crops (wheat, rice) when alternated with legume crops (peas, beans) improve the fertility of the soil. The introduction of biofertilizers to agriculture helps in combating, the adverse effects of synthetic agricultural chemicals. Materials of biological origin are used to improve soil fertility.
• The role of bacteria, cyanobacteria, and mycorrhiza as biofertilizers: Micro-organisms like bacteria, cyanobacteria, and fungi when added to the soil, enrich the soil nutrients due to their biological activity and thereby increasing the nitrogen content of the soil by nitrogen fixation, called biofertilizers.
• Significance of Biofertilizers: To increase the output in cases of high-yielding varieties of crop plants chemical fertilizers are being used in heavy amounts. Besides accumulating in the crop plants, chemical fertilizers cause pollution of organisms living in aquatic conditions, further in groundwater.
  • For that reason, environmentalists are pressurizing farmers to go for organic farming leaving the chemical fertilizers.
  • Manures, biofertilizers, and biocontrol agents provide necessary nutrients to crop plants so that the pests and pathogens may remain under necessary control without causing any harm to the crops.
  • Bacteria, Fungi, and Cyanobacteria are the major sources of biofertilizers.
  • Some of the most important and functional biofertilizers generally recommended for use in agricultural land are stated below :

Role of Bacteria :

Release of phosphorus: Some bacteria like Bacillus polymax, Pseudomonas striata, and species of fungus Aspergillus have the power to release phosphate from bound or immobile These biofertilizers are called microphos.

• The above two bacteria are phosphate-dissolving bacteria due to the secretion of some organic acids like lactic, formic, acetic, fumaric, etc. They have the power to reduce the pH of the substrate.
• This process helps them to release the soluble Inorganic phosphate Into the soil (H₃PO₄) due to the decomposition of phosphate-rich organic compounds.

Fixation of N₂: Free-living soil bacteria Azotobactcr and Bacillus polymyxa fix atmospheric nitrogen and provide it to crops like cereals, millets, fruits, and vegetables resulting in their increased yield. Clostridium, Bcijernickia, Dcrxio, Klebsiella, and Rhodos-like bacteria can also fix atmospheric nitrogen.

• With the help of these bacteria, the fertility of soil takes place whereby the yield of crops increases. This also saves the application of nitrogen fertilizers in the soil.
• The bacterium Azotobactcr existing in the fields of rice, maize, cotton, and jowar not only helps to increase the yield of those crops but also saves the supply of nitrogen fertilizer in those fields, its inoculation can be obtained from the market under the trade name a zoo bacterin, whose application in the field can give good result.

Symbiotic nitrogen-fixing bacteria: Hellriegel and Wilfarth (1888) showed that the leguminous plants with root nodules were able to increase the percentage of nitrogen in the soil.

• Within the root nodules reside a type of bacterium.
• They suggested that there lies a symbiotic relationship between the nodule bacteria and the host plant. That symbiotic bacterium was named Bacillus radicicola by Beijerinick (1888).
• Later on, it was renamed as Rhizobium leguminosarium by Frank (1890).

For reference only:

The gram-negative, rod-shaped bacterium Rhizobium enters from the soil as infection thread into the roots of Leguminous plants, where due to the influence of certain substances like biotin or amino acid, enzymes, sugars, and vitamins, may cause the root cells to divide forming root nodules.

• Certain growth substances like Indole Acetic Acid (IAA) secreted by the bacteria cause root hairs to curl.
• Symbiotic nitrogen-fixing bacteria Rhizobium leguminosarium resides in the root nodules of leguminous plants and converts nitrogen of air to soluble nitrates.
• Nitrates are used by host plants which results in increased growth and yield.
• With the death of host plants, root nodules release bacteria as well as nitrates into the soil whereby increases the fertility of the soil.
• Symbiotic bacteria Rhizobium fixes atmospheric nitrogen in the presence of a pigment called leghaemoglobin in anaerobic conditions only.

For reference only: Within the root nodules of leguminous plants lies a hemoglobin-like compound called leghaemoglobin (LHb) the only hemoglobin-like protein found to be present in higher plants.

• It facilitates the diffusion of oxygen (O₂) to the very rapidly respiring nitrogen-fixing symbiotic bacteroids within the root nodule cells, thereby stimulating ATP production.
• The addition of phosphate fertilizer increases the efficiency of nitrogen fixation and in turn, increases crop yield.
• Frankia, a nitrogen-fixing mycelial bacterium of Actinomycetes is associated symbiotically with the root nodules of several non-leguminous plants like Casuarina, Myrica, Rubus, Alnus, etc.

Id Role Of Cyanobacteria: Many free-living Cyanobacteria (blue-green algae) have the power to fix nitrogen in the atmosphere example Anabaena, Nostoc, Aulosira, Tolypothrix, Cylindrospermum, etc.

• In aquatic and also in terrestrial conditions they act as bio-fertilizers. According to Aiyer (1972), Aulosira fertilissima is regarded to be the most effective nitrogen-fixing bacterium in the rice fields of India.
• Cylindrospermum form grows in the fields of maize and sugarcane and acts also as a good nitrogen fixer.
• The application of cyanobacteria in agricultural fields is popular due to its low costs and good efficiency.

Azolla-Anabaena symbiosis: Anabaena azollae, a cyanobacterium lives in cavities of leaves of a fast-growing aquatic fern Azolla, helps in nitrogen fixation, and in return excretes nitrogenous compounds into the leaf cavity of the fern. Application of Azolla in the rice fields results in an increased yield.

For reference only: Loosely associated nitrogen-fixing soil bacteria Azospirillum lipoferum increases the yield of plants.

Importance Of Biofertilizers

1. The yield of plants can be increased by 15%-35% by the application of biofertilizers.
2. The inoculum which has to be applied in the field can be prepared by the farmers themselves.
3. The soil texture was improved by the biofertilizers.
4. In semi-arid conditions biofertilizers are also effective, giving a good result.
5. They disallow pathogens to grow vigorously.
6. Some vitamins and growth-promoting biochemicals can also be produced by them.

Role of Mycorrhiza: The symbiotic association of some fungi with the roots of seed-bearing plants is called mycorrhiza.

Types of Mycorrhiza: Two types

1. Ectotrophic mycorrhiza or Ectomycorrhiza: in this case, the fungus lives outside the tissues of roots of Pine, Oak, Eucalyptus, Alnus, Betula, etc. The fungus replacing the normal root hairs of the plants forms a covering or mantle outside the roots of trees.

• This mantle serves as root hair and increases the surface area of absorption, thereby increasing the uptake of water and mineral nutrients and in turn increasing plant vigor, growth, and yield.
• This mycorrhiza absorbs’ and stores nitrogen, phosphorus, potassium, and calcium in its fungal mantle.

For reference only: Simpler organic molecules are formed from complex organic molecules by them.

• They’d also convert insoluble organic compounds into soluble and easily absorbable forms.
• A network is formed when the fungal hyphae penetrate the intercellular spaces of the cortex of the root to finally form a net-like structure. This is called Hartig net.

2. Endotrophic mycorrhiza or Endomycorrhiza: When a fungus lives inside the root cortex and does not form a mantle on the surface of the root, this mycorrhizal association is called endotrophic mycorrhizal.

• These associations are found in herbaceous species like orchids and some woody plants.
• Here fungus produces loosely interwoven hyphae, some of which penetrate the soil while others grow on the root cortex. In the cortex, some hyphae grow in between the cortical cells, while some penetrate the cortical cells forming swollen vesicles or finely branched hyphal masses called arbuscles.
• This fungal association is called vesicular-arbuscular mycorrhiza (VAM). Mycorrhizal association is noted in the root of legumes, cereals, tobacco, soybean, and many orchids like Vanilla, Neottia, etc.

Importance of Mycorrhizas About Plants:

1. They (endotrophic mycorrhiza) increase the life span of the roots of plants by providing food to them.
2. They (ectotrophic mycorrhiza) increase the surface area of the roots of host plants by mantle formation.
3. Fungus spread their mycelia into the soil where they absorb different kinds of nutrients causing increased growth of the plant.
4. Mycorrhizas play an important role by absorbing selective elements like Ca, K, Fe, Br, Cl, S, and N which move easily. It also absorbs elements like Zn, Cl, and P that do not move easily.
5. Some of the mycorrhizas produce metabolites that can change the power of plants to develop roots from plant cuttings. They enhance the development of roots during vegetative
6. The resistance power of plants also increases. They make less effect of pathogens and pests on host plant health so that they become free from illness.

Know the facts

1. The symbiotic association of fungi with plants is called mycorrhiza.
2. Micro-organisms like bacteria, cyanobacteria, and fungi when added to the soil, enrich the soil nutrients due to their biological activity and thereby increase the nitrogen content of the soil by nitrogen fixation are called biofertilizers.
3. Two nitrogen-fixing blue-green algae are Nostoc and Anabaena.
4. One symbiotic nitrogen-fixing bacterium is Rhizobium leguminasarium which lives in the root nodules of pea plants.