Living Beings and Their Structures PDF

Living beings and their structures The Cell Classification of ling organisms Microorganisms Food preservation methods Kulman BK 1. The Cell Kulman BK ...

Living beings and their structures The Cell Classification of ling organisms Microorganisms Food preservation methods Kulman BK 1. The Cell Kulman BK  Objectives: Identify and describe the structure of animal and plant cell Explain the characteristics and functions of different cell organelles Compare and contrast plant and animal cells based on the structures  Basic terms ❑ Cell: The basic structural and functional unit of life is called cell. ❑ Cytology: The branch of biology, that deals with the study of the cell is called Cytology. ❑ All the mechanisms of life processes like digestion, respiration, reproduction, internal transportation, photosynthesis etc are accomplished inside or by the action of the cells through biochemical reactions and contraction-relaxation motion. Because of these reasons, cells are also called the functional unit of life.  Basic terms ❑ The cell was first discovered by Robert Hooke in 1665. ❑ He used the word 'Cellulae' for the small rooms seen in the thin slice of cork under the microscope developed himself, which meant 'tiny rooms' in Latin. ❑ Later on , various experiments and studies by Theodor Schwann, Mattias Jakob Schleiden, Rudolf Virchow etc concluded that the body of all living organisms is built by the composition of one or many cells.  Shape and size of cells ❑ Cells are of different shapes and sizes. ❑ Generally, animal cells are irregular in shape. They may be oval, spherical, rod-like, elongated, cubical or columnar in shape. ❑ Nerve cells are threadlike thin and long but most of the muscular cells have spindle shapes. ❑ Plant cells are generally hexagonal. ❑ Bacterial cells have mainly four shapes: spherical, rod-like, filamentous and spiral. ❑ Most of the cells are too small to see with the naked eye but some cells are quite bigger also. ❑ Eggs laid by animals/birds are also single cells. ❑ In the present world, the cell of Mycoplasma (a kind of bacteria) is the smallest one having a size of only about 0.2 microns and the eggs laid by ostrich are the biggest cells having 15-18 cm in diameter.  Structure of Cell Introduction to Cells: The Grand Cell Tour – YouTube Shape and size of cells Video: Structure and functions of Cell organelles Video: Structure and functions of Cell organelles  Cell components ❑ Cell organelles: Cell organelles are living sites and each of them performs specific metabolic activities which are essential for life processes. There are different types of cell organelles and most of them are found in both plant and animal cells, whereas some are found in plant or animal cells only. ❑ Cell inclusions: Cell inclusions are non-living things present inside the cytoplasm. They are generally droplets of free water, crystals of salts and minerals, enzymes, hormones, vitamins and waste materials excreted by the cell. Cell inclusions act as raw materials and sources of energy generation which are used by various cell organelles for metabolic activities. Cell Wall ❑ The covering is the outermost layer of plant cell. ❑ The cell wall is found only in bacterial, fungal and plant cells. It is made up of cellulose. It is absent in most of the Protozoans and animal cells. ❑ The cell wall is generally a tough, rough, semi-elastic and nonliving substance. Functions of Cell Wall 1. Cell wall provides mechanical support and fixed shape to the plant, bacterial and fungal cells. 2. Cell wall protects the cell from fungi, viruses and bacteria. 3. Cell wall presents at the root hairs of plants helps to absorb soluble minerals from soil and water. 4. Cell wall allows the substances to enter and exit through it as it is permeable in nature. Cell Membrane ❑ The cell membrane (also called Plasma membrane) is found in all types of cells. In animals and most protozoans, the cell membrane is the outermost layer of their cells. ❑ But in bacterial, fungal and plant cells, it lies just beneath the cell wall. ❑ The cell membrane is comparatively much smoother and elastic than the cell wall and it is a living substance. ❑ Cell membrane is made up of phospholipid bilayer, protein, cholesterol and carbohydrate Functions of Cell Membrane 1. It provides outer protective boundary to animal cells. 2. Cell membrane controls and coordinates intercellular transportation of fluids as it is living and semi-permeable in nature. 3. In unicellular protozoans like amoeba, the cell membrane helps in making pseudopodia for capturing food and locomotion, excreting metabolic wastes and protecting the body from the external environment. Cytoplasm ❑ There is a viscous, sticky and clear semi-liquid called cytoplasm. ❑ It is located in between the cell membrane and the nucleus of a living cell. ❑ Cytoplasm is composed of water, soluble salts, minerals, proteins, vitamins etc. ❑ Cytoplasmic components like ribosomes, plastids, mitochondria, Golgi-bodies, endoplasmic reticulum, vacuoles etc. are found in the cytoplasm. Functions of Cell Membrane 1. Metabolic activities of life processes are accomplished within the cytoplasm. 2. Cytoplasm helps to balance the amount of water and minerals in body organs. 3. Cytoplasm contains cell components like mitochondria, Golgi body, plastids etc. Mitochondria ❑ There are many mitochondria in a cell. They are cylindrical or filamentous in shape and bound with a double membrane. The inner membrane is highly folded making zigzag spaces inside it where mitochondria conduct cellular respiration to generate energy. ❑ The energy generated by mitochondria is used by other cell organelles to carry out cell activities. Therefore, mitochondria act as 'power-houses' of cells without which cells cannot survive. ❑ Mitochondria use glucose and oxygen to produce carbon dioxide, water and heat energy. Heat is utilized by the cell but carbon dioxide and water are excreted.  Functions of mitochondria 1. The main function of mitochondria is to generate energy for the survival of the cell. In the presence of the mitochondrial enzymes, oxidation of glucose molecules continuously takes place inside mitochondria which generate plenty of heat energy. This heat energy is stored in ATP (adenosine triphosphate) molecules in the form of chemical energy and distributed to cell organelles where it is necessary. 2. Mitochondria also contain some DNA molecules which transfer hereditary character. Plastid and its types ❑ Plastids are colorful organelles found only in plant cells, some bacterial cells and in some protozoans. Based on color, plastids are of three types: A) Chloroplast: It is green-colored plastid. It contains a green pigment called chlorophyll. Chloroplasts are generally round or oval in shape but in spirogyra, it is spiral ribbon shaped. Chloroplasts are bounded by a thin double membrane. B) Chromoplast: Chromoplasts are all colorful plastids, except green. They are found in colorful parts of plants like flowers, ripen fruits, seeds and some leaves. Chromoplasts are somewhat flat in shape and they provide different colors to various parts of plants which directly helps in the pollination and dispersal of seeds. C) Leucoplast: Leucoplasts are colorless or white plastids which are oval in shape. They are found in the colorless or white part of plants like roots, white flesh of fruits and in the white part of cotyledon or endosperm of seeds.  Functions of Plastid ❑ Functions of Chloroplast 1. Chloroplast makes plants green. 2. In the presence of sunlight, it conducts a photosynthesis reaction to make carbohydrates (food) 3. It helps to make fatty acids and amino acids in leafy vegetables. 4. Chloroplast contains DNA which helps in transferring hereditary characters. ❑ Functions of Chromoplast 1. Chromoplasts make flowers colorful. The color of the flower attracts insects and birds for pollination. 2. Colorful ripen fruits and seeds attract birds and animals to disperse seeds. ❑ Functions of leucoplast 1. Leucoplast stores starch, protein and fat (lipids) for future use. Ribosomes ❑ Ribosomes are very small in size and the only organelles in the cytoplasm without an outer membrane. ❑ They are found freely in the cytoplasm or attached to the surface of the Endoplasmic reticulum. ❑ They are found in mitochondria and chloroplasts too. ❑ Like other organelles, ribosomes also have some DNA molecules. Functions of Ribosome 1. They synthesize proteins from different amino acids. Therefore, ribosomes are also called protein factories. 2. They take part in gene expression due to the presence of DNA. Gene expression means DNA is active to make protein or RNA molecules suitable for the organism. Endoplasmic Reticulum ❑ The endoplasmic reticulum is a highly folded membranous organelle making zigzag canals from the nucleus to the cell membrane. Shortly, it is called ER. ❑ The inner surface of its canal is smooth but the outer surface of some ER looks granular due to the sticking of many ribosomes on it. ❑ The ER with ribosomes is called 'rough ER' and that without ribosomes is called 'smooth ER'.  Functions of Ribosome 1. It makes a structural framework and provides mechanical support to the cell. Therefore, ER is also called the endoskeleton of the cell. 2. As ER contains many enzymes, it helps in the metabolism of the cell. 3. During cell division, ER helps to make new cell membranes. It helps to construct the Golgi body in the cell. 4. ER actively takes part in the cellular transport system. Golgi body ❑ Golgi body in cells was discovered by an Italian scientist Camillo Golgi in 1898, so the name is kept in honor of his name. ❑ This organelle looks like a bunch of bananas and is composed of layers of flattened membrane-enclosed sacs called 'cisternae' and some vesicles. ❑ The Golgi body is also called the Golgi apparatus.  Functions of Golgi Body 1. Golgi body helps to secrete gum, mucus, sweat, saliva, tear etc. 2. During cell division, the Golgi body contributes to making new cell membranes(in animal cells)and new cell-plate (in plant cells). 3. Golgi body also helps in the internal transportation of cells and sorting of proteins. Lysosome ❑ Lysosome is a very small and round organelle with a single-layered membrane. ❑ It is found mainly in the cells of the liver, kidney, pancreas, spleen and some meristematic cells of the plant. ❑ Lysosome contains plenty of digestive enzymes.  Functions of lysosome 1. Lysosome produces a lysosomal enzyme which digests protein, lipid (fat), and glycogen (complex carbohydrate) to provide energy to the cell. 2. Lysosome also digests dead and fragmented cells to provide extra energy in animals. When the level of the lysosomal enzyme becomes high, the organelle itself is digested. For this self digesting mechanism, lysosomes are also called suicidal bags. 3. During the germination of seeds, lysosome present in meristematic cells provides nutrients to the germinating embryo. Vacuole ❑ Vacuole is not a true organelle but a space bounded by a tonoplast membrane which is generally filled with water, mineral salts and enzymes etc. These liquid substances in the vacuole are called 'cell-sap'. ❑ Vacuoles in animal cells are very small and in old plant cells are quite bigger. ❑ Cells of aquatic bacteria generally have air vacuole that helps them to float on the surface. ❑ Contractile vacuoles in protozoan cells contribute to intracellular transportation. ❑ Food vacuole in amoeba stores, digests food and excretes wastes.  Functions of Vacuole 1. Vacuoles balance the amount of water and salts in the cytoplasm. 2. It collects metabolic wastes of organelles before they are excreted out of the cell membrane. Nucleus ❑ The nucleus is the central part of a cell. It is round and enclosed by a double-layered perforated membrane. ❑ The nucleus is found in most of the cells of eukaryotic organisms viz. plants, animals, protozoans and fungi. ❑ Bacteria are prokaryotic organisms and they have no distinct nucleus in them. They have only genetic material without any covering instead of a nucleus. ❑ Nucleus controls and coordinates the function of every cell organelle, so it is also called 'the brain of a cell'. ❑ A nucleus has mainly four parts: 1. Nuclear membrane 2. Nucleolus 3. Nucleoplasm 4. Chromatin fibre  Parts of Nucleus Nuclear Membrane Nucleolus ❑ The nuclear membrane is the outer ❑ It is a round and non-membranous unit covering of the nucleus which is of the nucleus. composed of two perforated layers of lipid (fat) and protein. ❑ It disappears during cell division and reappears after cell division ❑ It is an elastic membrane and protects the nucleus. ❑ It is composed of protein and RNA molecules and helps in cell division by ❑ It allows the solution of various assisting to make spindle fibre (which biochemical to go in to and out of the are used to pull chromosomes towards nucleus. respective poles during a phase of cell division). ❑ It also synthesizes antibiotics and enzymes.  Parts of Nucleus Chromatin fibre Nucleoplasm ❑ The complex network of ultra-thin, long and invisible thread-like structures is called chromatin fibres. ❑ The liquid solution of water, amino acids, minerals, nucleic acids and enzymes present ❑ They are the genetic material of the nucleus that control and coordinate all the function of the cell. inside a nucleus is called nucleoplasm. ❑ Chromatin fibres are made of a super ultra-thin and ❑ Nucleolus and chromatin fibre are scattered long polymer of DNA molecules and histone protein. within the nucleoplasm. ❑ The number of chromatin fibres is fixed according to the species of organism. For exa1nple, every nucleus ❑ It assists the nucleus by balancing the of a human cell has 23 pairs of chromatin fibres. amount of water, providing enzymes and Chromatin fibres transfer parents' genetic character synthesizing DNA and RNA molecules. to their offspring (children). ❑ Chromatin fibres are changed into visible ❑ Nucleoplasm gets all the necessary things chromosomes during cell division. At that time they from the cytoplasm outside the nucleus look thicker and shorter. After the a completion of cell through many tiny holes in the nuclear division, they are again changed into thin, long and membrane. invisible chromatin fibres.  Functions of Nucleus 1. All metabolic activity and internal transportation of the cell are controlled and coordinated by the nucleus. 2. It inherits (transfers) genetic character from parents to their offspring through reproduction. 3. During cell division, the nucleus itself takes part actively. First, it disappears and makes a pair of new nuclei. After the division of the nucleus, the cell is divided into two from the centre to have a nucleus in each newly formed cell. 4. Nucleus is directly involved in the reproduction process of unicellular organisms.  Types of cells on the basis of nucleus Prokaryotic Cell Eukaryotic Cell ❑ The cells that lack well developed nucleus ❑ The cells with well developed nucleus are are called prokaryotic cells. called eukaryotic cells. ❑ In such cells, nuclear membrane and ❑ In such cells, nuclear membrane and nucleolus are absent so, the nuclear nucleolus are present. material is in direct contact with the cytoplasm (which is called the nucleoid). ❑ Membrane bound organelles like mitochondria and chloroplast are present. ❑ Membrane bound organelles like mitochondria and chloroplast are absent. ❑ They are larger in size as compared to prokaryotic cells. ❑ They are smaller in size as compared to eukaryotic cells. ❑ Larger size ribosomes (80S) are present. ❑ Smaller size ribosomes (70S) are present. Types of cells on the basis of nucleus  Interrelationship among cell, tissue and organ in human body 1. The human body itself is a very complex creation of nature where different cells, tissues, organs and systems play a vital role to keep the body alive by conducting various metabolic activities smoothly. 2. The human body has different types of cells. Tissues are formed from the combination of similar or dissimilar cells. Various tissues are combined at certain sites of the body to make a specific organ which has to perform one or more specific functions. 3. Direct connection and coordination of different organs make an organ-system to perform a specific function. The connection and coordination of such organ systems make a complete functioning body. 4. The task of digestion, respiration, reproduction, transportation, assimilation, excretion etc all begin from the functioning of one or many cells. It is the cell, that makes every tissue and begins every chemical, physical and physiological function of the body. For example, a muscle fibre is shown in the above figure from which muscular tissue in the body is formed.  Interrelationship among cell, tissue and organ in human body 1. Among the various organs of the digestive system, muscular tissue is found in the middle layer of the food pipe, stomach and intestine. This tissue creates rhythmic contraction and relaxation of these organs by which the food inside them is gradually pushed behind. 2. The digestive glands present on the inner wall of the stomach and intestine secrete various digestive enzymes to digest different nutrients present in the food we eat. It means that the muscular and glandular tissues of the digestive system are directly helping in the digestion of food at different sites of the digestive system. 3. From this example, we can conclude that cells, tissues, organs and organ systems are interrelated to each other for the construction and functioning of the body of organisms. Interrelationship among cell, tissue and organ in human body 2. Classification of Living Beings Kulman BK Classification of living organisms  Classification of organisms: Important Terms ❑ Classification: Classification of organisms is the systematic arrangement of living organisms into groups or categories based on their similarities, differences, and evolutionary relationships. ❑ Identification: Identification is the process of determining the exact group or species to which an organism belongs. It involves observing characteristics like: Morphology (shape, size, structure) Behavior, Genetics, Ecological roles ❑ Nomenclature: Nomenclature is the system of naming organisms. It ensures that every species has a unique, universally recognized name. The rules for naming are established by bodies like the International Code of Nomenclature for algae, fungi, and plants (ICN) and the International Code of Zoological Nomenclature (ICZN). ❑ Binomial nomenclature: Binomial nomenclature is the scientific naming system introduced by Carl Linnaeus. It gives every organism a two-part Latin name: Genus: The first part, always capitalized and Species: The second part, written in lowercase. ❑ Taxonomy: Taxonomy is the branch of science concerned with the classification, identification, and nomenclature of organisms. It involves organizing living organisms into hierarchical categories based on shared characteristics and evolutionary relationships. The hierarchy includes domain, kingdom, phylum, class, order, family, genus, and species.  Importance of Classification of organisms ❑ Classification of organisms simplifies Study of Diversity. ❑ It reveals evolutionary relationships among organisms, helping us understand how species are interconnected. ❑ Classification provides a standard method for naming and identifying species, reducing confusion caused by local or common names. ❑ By studying one organism in a group, we can predict characteristics of other organisms in the same group. ❑ Identifying endangered or rare species helps prioritize conservation efforts for biodiversity protection. ❑ Classification provides a framework for studying organisms in biology, medicine, agriculture, and ecology. ❑ A universal classification system enables scientists worldwide to communicate effectively about species and ecosystems. Categories of classification The categories of classification in taxonomy are organized into a hierarchy known as the taxonomic hierarchy, which ranks organisms from broadest to most specific groups. These categories are also called taxa (singular: taxon).  Classification of organisms: Important Terms ❑ Domain: The broadest and highest rank in the classification system. It groups all living organisms based on fundamental differences in cell structure. ❑ Kingdom: The second-highest rank, grouping organisms based on major characteristics like cell type, mode of nutrition, and reproduction. ❑ Phylum: A category grouping organisms within a kingdom that share basic body plans or features. ❑ Class: A rank within a phylum grouping organisms with more specific shared features. ❑ Order: A category grouping organisms within a class based on similarities in their structure or function. ❑ Family: A group of closely related genera within an order. ❑ Genus: A group of closely related species. It is the first part of an organism's scientific name in binomial nomenclature. ❑ Species: The most specific category, defining a group of individuals capable of interbreeding and producing fertile offspring. It is the second part of the scientific name.  Two Kingdom Classification ❑ The two-kingdom classification system of organisms is proposed by Swedish biologist Carl (or, Carolos) Linnaeus in 1753. ❑ Based on structure and characters, he has classified all the organisms of the earth simply into two kingdoms: Plant and Animal. Therefore, this system of classification is called the two-kingdom system. Basis of Two-Kingdom System Classification ❑ The main basis of the two kingdom systems is nutrition, movement, growth and development of the body and the mode of reproduction. ❑ In general, movable, heterotrophic modes of nutrition and limited growth of the body up to a certain phase of lifespan are the basis to keep any organism in the animal kingdom. ❑ Similarly, non-movable organisms with the autotrophic mode of nutrition and unlimited growth throughout life are kept under the plant kingdom.  Two Kingdom Classification Special Features of Two-Kingdom System 1. All living beings are divided into plant and animal kingdoms. 2. This is the first scientific system of classification of living beings. 3. It is simple by which plants and animals can easily be distinguished. Drawbacks of Two-Kingdom System 1. The living beings which cannot conduct photosynthesis also kept in the same section of plant kingdom. For example, algae and fungi both are kept in the plant kingdom. 2. Prokaryotic bacteria and Eukaryotic algae are kept in the same kingdom. 3. Two kingdom system does not separate unicellular and multicellular organisms. 4. Two kingdom system is not able to include organisms like Lichens.  Five Kingdom Classification ❑ By improving the drawbacks of the two-kingdom system, an American ecologist R.H. Whittaker proposed a five-kingdom system in 1969. ❑ He has proposed five kingdoms as Monera, Protista, Mycota or Fungi, Plantae and Animalia. Basis of Five-Kingdom System Classification ❑ Based on types of cell (prokaryotic or eukaryotic), body structure (unicellular or ulticellular), mode of nutrition (autotrophic or heterotrophic), role in the ecosystem (either producer or consumer or decomposer) and phylogenetic relationship (trend of evolution from least developed to more developed). ❑ Here, all unicellular prokaryotes like archaea, mycoplasma, and bacteria are kept under the kingdom Monera. ❑ All unicellular eukaryotes except free-living fungal cells are kept under the kingdom Protista. ❑ All saprophytic (that feeds on dead bodies) and parasitic fungi that exhibit extracellular digestion are kept under the kingdom Fungi or Mycota. ❑ All autotrophic green organisms are kept under the kingdom Plantae ❑ And multicellular eukaryotic consumers are kept under the kingdom Animalia.  Five Kingdom Classification Special Features of Five-Kingdom System 1. Unicellular and multicellular organisms are kept in separate kingdoms. 2. Prokaryotes and eukaryotes are also separated. 3. Autotrophic and heterotrophic organisms are kept in Plantae, Animalia and Mycota kingdoms respectively. 4. In this system organisms are arranged in sequential form from least developed to more developed which also refers to the trend of organic evolution. Drawbacks of Five-Kingdom System 1. Viruses are not included in the Five Kingdom classification as they are neither strictly living organisms nor can they be classified as cellular life forms. 2. Certain organisms, like euglena, exhibit features of both plants (photosynthesis) and animals (heterotrophy). Their classification in the Kingdom Protista doesn't fully resolve these ambiguities. 3. The system doesn’t accurately represent evolutionary relationships between the kingdoms, particularly for more ancient groups like Protista and Monera.  Kingdom: Monera Characteristics 1. Prokaryotic organisms. 2. Unicellular. 3. Cell walls composed of peptidoglycan. 4. Reproduce asexually through binary fission. 5. Exhibit diverse modes of nutrition: autotrophic (photosynthetic or chemosynthetic) and heterotrophic. Examples: Bacteria and Cyanobacteria 1. Escherichia coli (E. coli) – a common bacterium found in the intestines of humans and animals. 2. Streptococcus species – bacteria responsible for strep throat. 3. Cyanobacteria (blue-green algae) – photosynthetic bacteria found in aquatic environments.  Kingdom: Protista Characteristics 1. Eukaryotic organisms. 2. Primarily unicellular, but some are multicellular. 3. Modes of nutrition include autotrophic (photosynthetic) and heterotrophic. 4. Reproduction can be asexual or sexual. Examples: 1. Amoeba – a free-living protozoan found in freshwater environments. 2. Paramecium – a ciliated protozoan commonly found in stagnant water. 3. Euglena – a flagellated organism exhibiting both plant and animal characteristics. 4. Volvox  Kingdom: Fungi Characteristics 1. Eukaryotic organisms. 2. Mostly multicellular (yeasts are unicellular). 3. Cell walls composed of chitin. Reserved food is glycogen. 4. Heterotrophic nutrition. Saprophytic (eat dead bodies of plants and animals). 5. Reproduce via spores, both sexually and asexually. Examples: Yeast, Mucor, Mushroom 1. Saccharomyces cerevisiae – commonly known as baker's yeast. 2. Agaricus bisporus – the common mushroom. 3. Penicillium species – molds used in antibiotic production.  Kingdom: Plantae Characteristics 1. Eukaryotic. 2. Multicellular organisms. 3. Cell walls composed of cellulose. Reserved food is starch. 4. Autotrophic nutrition through photosynthesis (chlorophyll present). 5. Reproduction can be sexual or asexual. Examples: Mustard, Mango, Wheat, Rose 1. Bryophyta (mosses) – non-vascular plants found in moist environments. 2. Pteridophyta (ferns) – vascular plants reproducing via spores. 3. Angiosperms (flowering plants) – plants producing seeds enclosed within fruits..  Kingdom: Animalia Characteristics 1. Eukaryotic, multicellular organisms. 2. Lack cell walls. 3. Heterotrophic nutrition through ingestion. Reserved food is glycogen. 4. Reproduction primarily sexual. 5. Exhibit complex organ systems and diverse forms of locomotion. Examples: Rat, Pigeon, Frog, Cow, Human 1. Porifera (sponges) – simple aquatic animals with porous bodies. 2. Arthropoda (insects, arachnids) – invertebrates with exoskeletons and segmented bodies. 3. Chordata (vertebrates) – animals possessing a notochord, including mammals, birds, and fish. 3. Microorganisms Kulman BK  Microorganisms ❖ There are many types of organisms in our surroundings. Some of them are too small to see with the naked eye. These microscopic organisms are found in air, water, soil, unsaved food, dirt and on/in the body of living dead and decaying organisms. They are called microorganisms and have direct and indirect influences on our daily life. ❖ For example, Bacteria, some fungi (yeast, slime mold), some algae (Chlamydomonas, chlorella) and protozoans (amoeba, paramecium, plasmodium, vorticella) etc are some examples of microorganisms. ❖ Microorganisms are commonly called 'germs' or 'microbes'. ❖ The branch of biology that deals with the study of microorganisms is called microbiology.  1. Virus ❖ Viruses are the smallest germs that can infect plants, animals, bacteria, fungi and any other microorganism including other viruses too. ❖ The meaning of its name is taken as a 'molecule of poison'. The virus is not an actual organism because it has no cell (acellular) therefore it does not belong to any kingdom. ❖ The body of a virus consists only of nucleic acid (DNA or RNA) which is enclosed in a protein case called a capsid. ❖ Some viruses have an extra outer covering called an envelope. ❖ It may have various shapes and sizes. ❖ The virus shows the characteristics of both living and non-living things, therefore called a 'bridge or link organism. ❖ When a virus is inside the living host cell, it behaves as living and when it is in an external environment, it behaves as a non-living thing. ❖ Inside a host cell, a virus can increase its number by using the biomolecules of the host cell damaging it, therefore they are also called 'obligatory parasites'. ❖ Viruses are found everywhere in the air, water, soil etc. ❖ Viruses do not eat, drink or breathe, therefore, there is no metabolism inside them. ❖ Rhinovirus, Coronavirus, Tobacco mosaic virus, Bacteriophage, Virophase etc, are some examples of the virus. ❖ The study of virus is called virology. ❖ When a virus is able to cause infection, it is known as virion.  Characteristics of Virus Living Characteristics of viruses 1. They are able to divide and reproduce. 2. They possess RNA or DNA as genetic materials. 3. A virus can not replicate alone. For its replication, host is required Non-living characteristics of viruses 1. They do not show any cellular structure. 2. They can be crystallized like non-living things. 3. They do not show respiration and metabolism. Virus  Classification of Virus ❑ Based on Genetic Material 1. DNA Viruses: Contain DNA as their genetic material. Example: Adenoviruses, Herpesviruses 2. RNA Viruses: Contain RNA as their genetic material. Example: Influenza virus, HIV (Human Immunodeficiency Virus) Based on Host Range 1. Animal Viruses: The virus that Infects animals are called animal virus. Example: Rabies virus, rhino virus 2. Plant Viruses: The virus that Infects plants are called plant virus. Example: Tobacco mosaic virus 3. Bacterial Viruses (Bacteriophages): The virus that Infects bacteria are called bacteriophage virus. Example: T4 bacteriophage  2. Bacteria ❖ Bacteria are unicellular prokaryotes and therefore belong to the kingdom Monera. ❖ The bacterial cell may be spherical, filamentous, cylindrical etc. ❖ Bacteria can be found in all environments i.e. air, water, soil, in and on the body of other organisms. Some of them are found in extremely hot and cold environment too. ❖ Their body is enclosed within a tough covering called a capsule which helps them to tolerate such extreme environment. ❖ Some bacteria are autotrophic but most of them are saprophytic because of which they play the role of decomposers for the ecosystem. ❖ Some bacteria are parasitic and cause various diseases to plants and animals. ❖ Cyanobacteria, Rhizobium, Salmonella, Azotobacter and Pseudomonas are some examples of bacteria. ❖ The study of bacteria is called bacteriology.  Characteristics of Bacteria Characteristics of Bacteria 1. They have prokaryotic cell. 2. Different bacteria have different size. For example, size of coccus is 1.5 micrometer, bacillus is 1 micrometer. 3. They show autotrophic as well as heterotrophic mode of nutrition. 4. They reproduce asexually by fission. Useful effects of bacteria 1. Rhizobium regulates nitrogen cycle. 2. Bacteria decompose organic matter of dead bodies of plants and animals and increase soil fertility. 3. They are also used in curding of milk, processing of coffee, synthesis of lactic acid. 4. Some intestinal bacteria check the growth of harmful bacteria in our body 5. Streptomyces are used to produce medicinal drugs like streptomycin.  Harmful effects of Bacteria 1. Bacteria cause harmful disease to plants and animals. 2. Saprophytic bacteria spoil milk, meat, vegetables, cooked food. 3. Certain denitrifying bacteria reduce the fertility of soil. 4. Some bacteria excrete poisonous substances that cause food poisoning. Different shapes of Bacteria  3. Fungi ❖ The study of fungi is called mycology. ❖ Fungi are unicellular or multicellular. ❖ They reproduce by budding or asexual reproduction. ❖ They are commonly called yeasts. ❖ Some examples of unicellular fungi are Baker’s yeast (Saccharomyces cerevisiae), Candida albicans, Candida antartica. ❖ Multicellular fungi are visible to our eyes. The multicellular fungi consists of thread like filaments which are called hyphae and the collection of hyphae is called mycelium. ❖ Multicellular fungi reproduce by making spores. ❖ Fungi are non-green because they do not have chlorophyll. ❖ They have saprophytic mode of nutrition as they depend on dead bodies of plants and animals. ❖ Various types of molds and mushrooms are some examples of fungi. Fungi ❖ Mushrooms are saprophytic. Fungi: Mushroom ❖ A mushroom has a fruiting body called a basidiocarp and root like structure in the organic matter called mycelium. ❖ The basidiocarp consists of a umbrella like body called pileus, and the stem like stalk on which the pileus rest is called stipe. ❖ Some mushrooms are edible while some are poisonous. ❖ The practice of growing edible mushroom in the farm is called mushroom farming. ❖ The wild mushrooms are mostly poisonous and bright in color. They may have scales. ❖ The poisonous mushrooms are called toadstools.  Positive effects of Microorganisms 1. Some amoeba, like Amoeba proteus feed on bacteria, so they are used to control bacteria. 2. Most of the bacteria are decomposers. They decompose excreta and the dead body of organisms. While decomposing, they convert complex organic molecules into simple inorganic molecules/minerals which increases the fertility of the soil. By this, bacteria are helping to keep the ecosystem in balance. Nitrosomonas, Clostridium, and Nitrobacter are some examples of decomposing bacteria. 3. Rhizobium bacteria present in the root nodules of leguminous plants absorb atmospheric nitrogen and make nitrate which increases the fertility of the soil and agricultural productivity. 4. Lactobacillus and Lactococcus are the bacteria found in milk and help to convert milk into yoghurt. Streptococcus lactis bacteria are used in producing cheese from milk. 5. To develop the products of medical science like insulin (hormone), antibiotics, vaccines, vitamins, antiseptics, antiserum etc, bacteria and fungi are used. 6. Yeast (a fungus) can convert carbohydrates and protein present in foodstuffs into acetic acid and alcohol. This process is called fermentation. Distilleries use yeast to ferment foodstuffs to produce alcohol and acids. 7. Nepalese use yeast to produce alcohol and to prepare pickles, Gundruk (fermented veggies) etc on a domestic scale. 8. Bacteriophage virus can kill bacteria. Because of this reason, this virus can be used to control some bacterial diseases like plague, dysentery, diarrhea etc. and in the treatment of water. 9. In genetic engineering, many viruses are being used to replace, transfer, repair, and synthesis of genes to develop high-yielding plants and animals.  Negative effects of Microorganisms 1. The causative agents of most communicable diseases are microorganisms. They can spread disease to all types of plants and animals. Disease decreases the quality and productivity in every sector of agriculture like farming, fish-farming, sericulture, apiculture , horticulture, animal husbandry, nursery etc. Tuberculosis, AIDs, Pneumonia, typhoid, Covid, etc are spread due to these microorganisms. Tobacco mosaic, common blight, and root rotting-like plant diseases are also due to the infection of any one of these microorganisms. 2. Fruits, vegetables, cooked food etc. start smelling and decaying if kept unprotected for some hours or days in an open environment. Microorganisms like Clostridium bacteria enter into such food through air, water or any medium and make the toxic substance. If such contaminated food is consumed then the person will suffer from diarrhea, vomiting, fever, dehydration, dry mouth (xerostomia), headache etc. Such conditions due to contaminated food are called food poisoning. Clostridium, Norovirus, Salmonella, Giardia, and Mucor-like microorganisms cause food poisoning. 3. Occurrence of pimples and abscesses of wounds is all due to infection by harmful microorganisms. If the toxin produced by the infecting microorganisms once enters the bloodstream, sepsis at different sites of internal organs may occur to make them fail and most probably kill the victim. To be safe from such terrible conditions, wounds and pimples should be kept clean with a gauge soaked in an appropriate antiseptic like Dettol/betadine/ savlon, dress the wound timely, use prescribed antibiotics and be careful in personal hygiene. 4. Microorganisms cause the spoiling of stored cereals, vegetables, and other foodstuffs due to which farmers/owners have to bear the great loss. 5. By the action of microorganisms on disposed organic wastes at dumping sites, foul smell spreads which pollutes the surrounding environment. 4. Microscope Kulman BK  Microscope ❖ Microscope is an instrument that uses lenses to make smaller objects appear larger. ❖ Usually, a compound microscope is used for magnifying tiny organisms. ❖ Specimen: The object to be viewed under the microscope is called specimen. ❖ The parts of the compound microscope can be categorized into: mechanical and optical parts.  Mechanical parts of a Compound Microscope ❖ Foot/Base: The bottom part of the microscope that provides stability and supports the entire structure. ❖ Arm: The curved or straight part connecting the base to the head; used for carrying the microscope. ❖ Stage: The flat platform where the slide is placed for observation. ❖ Stage clips: Hold the slide in place. ❖ Body Tube: The cylindrical part that connects the eyepiece to the objective lenses, ensuring proper alignment. ❖ Coarse Adjustment Knob: A large knob used for rough focusing by moving the stage or body tube up and down. ❖ Fine Adjustment Knob: A smaller knob used for precise focusing to get a clearer image. ❖ Nosepiece: A rotating disc that holds multiple objective lenses, allowing you to switch between different magnifications. ❖ Pillar: The vertical structure supporting the arm. ❖ Inclination Joint: Allows the microscope to tilt for comfortable viewing. ❖ Diaphragm Adjustment Lever (on the Stage): Controls the amount of light passing through the stage aperture.  Optical parts of a Compound Microscope ❖ Eyepiece (Ocular Lens): Located at the top of the body tube. Magnifies the image formed by the objective lens (usually 5x, 10x or 15x magnification). Often equipped with a pointer or measurement scale. ❖ Objective Lenses: Multiple lenses mounted on the nosepiece, each with different magnifications (e.g. 10x, 40x, 100x). Scanning Objective: Low magnification (4x). Low Power Objective: Moderate magnification (10x). High Power Objective: Higher magnification (40x). Oil Immersion Objective: Highest magnification (100x), requires immersion oil. ❖ Condenser Lens: Located beneath the stage. Focuses and concentrates light from the light source onto the specimen for even illumination. ❖ Diaphragm (Iris Diaphragm): Adjusts the amount of light entering the condenser lens. Controls contrast and brightness. ❖ Light Source: Provides illumination for viewing the specimen. Could be a mirror reflecting external light or a built-in LED or halogen bulb. ❖ Tube Lens: Found in advanced microscopes. Helps focus the light coming from the objective lens into the eyepiece. 5. Food Preservation Kulman BK  Food Preservation ❖ Food preservation is the technique to prevent food spoilage, food poisoning and microbial contamination in food. ❖ Food preservation aims to stop or slow down the spoilage of food while maintaining its nutritional value, texture and flavor. ❖ Food preservation involves creating unfavorable condition for the growth of microorganisms so as to kill them or prevent their reproduction. ❖ Food preservatives: Chemicals or the natural substances used for the preservation of food are called food preservatives.  Methods of Food Preservation ❑ Drying/Dehydrating method: Drying or dehydrating is a method of food preservation that removes enough moisture from the food so bacteria, yeast and molds can not grow. We can use sunlight, a dehydrator, oven, microwave or even air drying to dry food at home. Food items such as cereals, pulses and fruits are preserved by this method. ❑ Refrigeration and freezing: Refrigeration is a method of storing food materials at low temperature. Freezing is a method of solidifying food materials at a low temperature to prevent spoilage. This method helps to preserve food for longer time as microbes such as bacteria and fungi can not live longer at low temperature (This method slows down the microbial growth and enzyme activity). Food items like meats and vegetables can be preserved by this method. ❑ Canning: Food is heated to kill microorganisms, then sealed in airtight containers. Examples: Canned vegetables, soups, and fruits. ❑ Vacuum Packing: Removes air (oxygen) to inhibit the growth of aerobic micro-organisms. Examples: Vacuum-sealed meats and coffee.  Methods of Food Preservation ❑ Pasteurization: Heating liquids to destroy harmful microorganisms without altering taste significantly. Examples: Milk, juice, and beer. ❑ Salting: Uses salt to draw out moisture and inhibit microbial growth. Examples: Pickles, salted fish, and cured meats. ❑ Sugaring: High sugar concentration inhibits microbial growth. Examples: Jams, jellies, and candied fruits. ❑ Preservatives: Adding natural or artificial chemicals to prevent spoilage. Examples: Vinegar in pickles, citric acid in juices. ❑ Fermentation: Uses beneficial microorganisms (like yeast or bacteria) to convert food into a more stable form. Examples: Yogurt, kimchi, sauerkraut, and cheese. ❑ Smoking: Preserves food by exposing it to smoke, which has antimicrobial properties. Examples: Smoked fish, meats, and cheese.