9th Biology Notes PDF

# Chapter 1: The Fundamental Unit of Life - The cell is the fundamental structural and fundamental unit of life. ## Discoveries 1. **Robert Hooke:** Discovered non-living cells (1665). 2. **Antonie Van Leeuwenhoek:** Discovered frost living cells in 1674. 3. **Robert Brown:** Discovered the nucl...

# Chapter 1: The Fundamental Unit of Life - The cell is the fundamental structural and fundamental unit of life. ## Discoveries 1. **Robert Hooke:** Discovered non-living cells (1665). 2. **Antonie Van Leeuwenhoek:** Discovered frost living cells in 1674. 3. **Robert Brown:** Discovered the nucleus in 1831. ## Unicellular Organisms - Organisms made up of a single cell are known as unicellular organisms. - Example: *Amoeba* (Bacteria). ## Multicellular Organisms - Organisms made up of more than one cell are known as multicellular organisms. - Example: Plants, animals etc. ## Cell Structure - **Cytoplasm:** The jelly-like substance that fills the cell. - **Cell Organelle:** Structures within the cytoplasm that perform specific functions. - **Cell Membrane:** The thin, flexible membrane that surrounds the cell and controls what enters and leaves. - **Cell Wall:** A rigid, protective layer that surrounds the cell membrane of plant cells, fungi, and bacteria. ### Functions of the Cell Wall 1. Gives shape to the cell. 2. Prevents the entry of undesirable macromolecules. 3. Protects the cell from mechanical damage. 4. Helps in cell-to-cell interaction. ### Cell Membrane 1. The cell membrane is a living, soft, elastic, and selectively permeable structure. 2. It is surrounded by cytoplasm and is called the cell membrane. 3. It is quasi-fluid (jelly-like) in nature. 4. It is found in both prokaryotic and eukaryotic cells. 5. The structure of the cell membrane was explained by Singer and Nicolson (1972) through the fluid mosaic model. 6. According to this model, the cell membrane has lipids, proteins, and some carbohydrates. ## Shape and Size of Cells - **Red Blood Cells:** Round and biconcave. - **White Blood Cells:** Irregular and amoeboid. - **Mesophyll Cells:** Oval and polygonal. - **Tracheid:** Elongated. - **Nerve Cell:** Branched. ### Size of Cells - **Largest:** Ostrich egg. - **Longest:** Nerve cell. - **Smallest:** Mycoplasm (0.3 micrometers) - **Bacteria:** 3 to 5 micrometers - **RBC:** 7 micrometers - **Eukaryotic:** 20 micrometers. ## Transport of Molecules - The transport of molecules occurs with the help of proteins. - **Passive Transport:** The movement of molecules from a higher concentration to a lower concentration without the expenditure of energy. - **Active Transport:** The transport of molecules from a lower concentration to a higher concentration with the expenditure of energy. Example: Diffusion and osmosis. - **Diffusion:** The spontaneous movement of molecules (solid, liquid, or gas) from a higher concentration to a lower concentration. Some gases like oxygen and carbon dioxide move with diffusion. - **Osmosis:** The spontaneous movement of water molecules across a semi-permeable membrane from a higher concentration to a lower concentration. ### Types of Osmosis - **Endosmosis:** The osmosis in which the solvent molecules move inside the cell. Due to endosmosis, the cell will swell. - **Exosmosis:** The osmosis in which the solvent molecules move outside the cell. Due to exosmosis, the cell will shrink. ### Types of Solutions 1. **Hypertonic Solution:** The solution in which there is more solute and less solvent. Due to a hypertonic solution, exosmosis occurs, and the cell shrinks. 2. **Hypotonic Solution:** The solution in which there is more solvent and less solute. Due to a hypotonic solution, endosmosis occurs, and the cell swells. 3. **Isotonic Solution:** The solution in which there is an equal amount of solvent and solute. In an isotonic solution, both osmosis and endosmosis occur, and the cell remains the same size. ### Plasmolysis - The shrinkage of the protoplasm of the plant cell due to water exiting the cell is called plasmolysis. ### Deplasmolysis - The swelling of the protoplasm of a plant cell due to endosmosis is called deplasmolysis. ## Exocytosis - The removal of material (waste or useful substances) from the cell is called exocytosis. - The two types of exocytosis are **excretion** and **secretion**. - **Excretion:** The removal of waste material from the cell. - **Secretion:** The removal of useful material from the cell. ## Endocytosis - The engulfing of large molecules (solid or liquid) inside the cell is called endocytosis. - The two types of endocytosis are **phagocytosis** and **pinocytosis.** - **Phagocytosis:** The engulfing of solid particles into the cell. It is also called **"cell eating"** - **Pinocytosis:** The engulfing of liquid particles into the cell. It is also called **"cell drinking"** ## Endomembrane System - Cell organelles whose functions are coordinated with each other are called the endomembrane system. - The organelles that make up the endomembrane system are:** - Endoplasmic Reticulum - Ribosomes - Golgi Body - Lysosomes - Vacuoles ## Endoplasmic Reticulum (ER) - The network of membranes connected with the outer nuclear membrane in the cytoplasm is called the endoplasmic reticulum. - The two types of ER are **Rough Endoplasmic Reticulum (RER)** and **Smooth Endoplasmic Reticulum (SER).** - **RER:** The ER that has ribosomes attached. - **SER:** The ER that does not have ribosomes attached. - RER is involved in protein synthesis. - SER is involved in lipid synthesis. ## Golgi Body - Discovered by **Camillo Golgi** (1898). - In plant cells, the Golgi body is called a **dictyosome.** - In animal cells, the Golgi body is also called the **lipocondria.** - The Golgi body is made up of **cisternae**, **tubules**, and **vesicles.** - **Cisternae:** Long, flattened, unbranched structures. - **Tubules:** Branch, tube-like structures. - **Vesicles:** Membrane-bound, spherical structures. ### Functions of the Golgi Body 1. Helps in the secretion of materials. 2. Materials are received by the ER in the Golgi body, then they are chemically modified by glycosylation, and then glycoproteins and glycolipids are formed. 3. The Golgi body then either stores the products or secretes them. 4. The Golgi Body also helps in the formation of lysosomes. ## Lysosomes - Lysosomes are double-membrane-bound structures. - They provide energy to the cell. - They are also known as the **powerhouse of the cell.** - They are the busiest and most active organelles in the cell. They are also **semi-autonomous.** - They produce energy in the form of **ATP (Adenosine Triphosphate).** ATP is called the **energy currency of the cell.** - They are cylindrical or sausage-shaped. - They are present in eukaryotic cells but absent in prokaryotic cells. - There are more mitochondria in animal cells than plant cells. ### Structure of the Mitochondria 1. **Outer Membrane:** More permeable and has porins because more proteins are present. 2. **Inner Membrane:** Less permeable and has fewer proteins than the outer membrane. 3. **Perimitochondrial Space:** The space between the outer membrane and the inner membrane. 4. **Inner Compartment:** The space present inside the inner membrane. 5. **Cristae:** The structure formed by the invagination of the inner membrane. The presence of cristae increases the surface area for energy production. 6. **Oxysome:** Pin-headed particles attached to cristae that carry out energy production. - They contain ribosomes, enzymes, nucleic acids (DNA), and protein. ## Plastids - Double-membrane-bound structures that perform photosynthesis, store color, and store food. - They are absent in prokaryotic cells but present in eukaryotic cells. - They are absent in animal cells but present in plant cells. - They are of two types: - **Chromoplasts:** Plastids that give color to plant parts. Example: Carotene in carrots, and petals of flowers. - **Leucoplasts:** Plastids that store food in plants. Example: Starch in potato. - **Chloroplasts:** Plastids that provide green color and perform photosynthesis. Example: Chlorophyll in plants. ### Structure of The Chloroplast - **Outer Membrane:** More permeable. - **Inner Membrane:** Less permeable. - **Outer Compartment:** The space between the outer membrane and the inner membrane. - **Stroma:** The space present inside the inner membrane. It contains water, ribosomes, DNA, and enzymes. -**Thylakoids:** Several membranous flat disc-like structures present in the stroma. - **Granum:** Thylakoids stacked like piles of coins. - **Stromal Lamellae:** Structures that connect grana. ## Nucleus - The control center of the cell. - It has a double membrane called the **nuclear membrane.** - The outer layer of the nuclear membrane is the **outer nuclear membrane.** - The inner layer of the nuclear membrane is the **inner nuclear membrane.** - **Peri-nuclear Space:** The space between the outer and inner nuclear membranes. - **Nuclear Pore:** The space through which the nuclear membrane is discontinuous. - The nucleus is also composed of **nucleoplasm,** **chromatin,** and **nucleolus.** ## Nucleoplasm - The semi-fluid substance that fills the nucleus. ## Chromatin - The thread-like structure made up of DNA and protein. - There are two types of chromatin: - **Euchromatin:** The DNA of euchromatin is loosely packed, and it stains lightly. - **Heterochromatin:** The DNA of heterochromatin is tightly packed, and it stains darkly. ## Chromosome - The structure formed by the condensation of chromatin during cell division. - Human beings have 46 chromosomes. ## Nucleolus - A spherical structure that is present in nucleoplasm. - It is the site of ribosome synthesis and is also called the **factory of ribosomes.** ## Cell Division - The process in which a parental cell divides to form daughter cells is called **cell division**. - There are two types of cell division: **Mitosis** and **Meiosis.** ## Mitosis: - A type of cell division in which one parental cell divides to form two daughter cells. - The ploidy level of the cell does not change during mitosis, so it is known as **equational division**. - Mitosis occurs in **somatic cells.** ## Meiosis: - A type of cell division in which one parental cell divides to form four daughter cells. - The ploidy level of the cell changes during meiosis, so it is known as **reduction division**. - Meiosis occurs in **gamete formation**. ## Tissues - A group of cells that have a similar structure, origin, and perform a common function is called a **tissue**. - Tissues are classified based on their capability of cell division: - **Meristematic Tissue:** Tissues in which cell division occurs are called meristematic tissues. - **Permanent Tissue:** Tissues in which cell division does not occur are called permanent tissues. ### Meristematic Tissue: - Undifferentiated cells that can divide and give rise to new tissues. - Found in areas of growth in plants. ### Permanent Tissue - Differentiated cells that have lost their ability to divide. - They perform specific functions in plants. ### Types of Meristematic Tissue - **Primary Meristem:** Meristematic tissues present in the early life of a plant are called primary meristems. Their growth is called **primary growth**. - **Secondary Meristem:** Meristematic tissues formed from permanent tissues are called secondary meristems. Their growth is called **secondary growth**. ### Types of Meristematic Tissue Based Upon Location 1. **Apical Meristem:** The meristematic tissue found at the tip of the root and shoot. It is responsible for the growth of the root and shoot. 2. **Intercalary Meristem:** The meristematic tissue found at the base of the internode and the monocot stem. It is responsible for the growth of the internode. 3. **Lateral Meristem:** The meristematic tissue present in the lateral side of plants. It is responsible for the growth of the thickness and girth of the plant. ### Types of Permanent Tissue 1. **Simple Permanent Tissue:** Consists of a single type of cell. 2. **Complex Permanent Tissue:** Consists of more than one type of cell. #### Simple Permanent Tissue - **Parenchyma:** The primary and oldest tissue. It is the precursor of all tissue and is a living tissue. - Cell wall: Thin, made up of cellulose. - Cells: Closely packed. - Intercellular Spaces: Present. - Major tissue of plant organs. ### Types of Parenchyma - **Aerenchyma:** Parenchyma with large air chambers. - **Chlorenchyma:** Parenchyma with chloroplasts. #### Functions of Parenchyma: 1. Storage of food material. 2. Photosynthesis, if chloroplasts are present. 3. Secretion of materials. - **Collenchyma:** Living tissue. They provide mechanical strength. - Cell wall: Thick, made up of pectin, hemi-cellulose, and cellulose. - Intercellular Spaces: Absent. - Found in herbaceous dicot stems, leaves, etc - Absent in woody dicot stems and monocot stems. #### Functions of Collenchyma: 1. Provide mechanical strength. 2. Photosynthesis, if chloroplasts are present. #### Types of Collenchyma - **Angular:** If the thickening is at the corners of the cell. #### Sclerenchyma - Dead, mechanical tissue, which provides strength. - The cell wall thicker than parenchyma and collenchyma, and contains lignin. - It is found in woody dicot stems, monocot stems, and roots. #### Types of Sclerenchyma - **Sclereids:** They are short, small, and irregular. - **Fibers:** Long, elongated, and pointed. #### Functions of Sclerenchyma 1. Provide mechanical strength to plant parts. #### Complex Permanent Tissue 1. **Xylem:** The complex permanent tissue that conducts water and minerals from the roots to the aerial parts of the plant. The conduction occurs in one direction only. #### Types of Xylem Tissue - **Tracheids:** Primitive conducting elements. They are dead, have a tube-like structure, a thick cell wall, and contain lignin. The lumen is narrow, and pits are present. - **Vessels:** Advanced conducting elements. They are made up of several cells called **vessel elements**. The vessel elements are connected to each other by common walls, which are perforated. The vessel elements are dead, contain lignin, and have wide lumens. Pits are present. - **Xylem Fibers:** Dead, thick-walled fibers with a greatly reduced lumen and are made up of lignin. They are absent in gymnosperms; that's why the wood of gymnosperms is soft. - **Xylem Parenchyma:** Live cells, with thin cell walls made up of cellulose. They store food, water, and tannins. 2. **Phloem:** The complex permanent tissue that conducts food from the leaves to all parts of the plant. The conduction is bidirectional. #### Types of Phloem Tissue - **Sieve Tubes:** Tube-like structures that contain a large central vacuole. They have a peripheral cytoplasm, and their nucleus is absent. It is connected to companion cells. - **Companion Cells:** Thin-walled cells that are associated with sieve tubes. They have a nucleus, and their cytoplasm is dense. - **Phloem Fibers:** Dead, elongated, and pointed structures. They provide mechanical strength. - **Phloem Parenchyma:** Living parenchyma cells with thin cell walls. They transport food to plant parts. ## Protective Tissue 1. **Epidermis:** The outermost layer of the plant. It is a single-cell thick. It protects the plant against desiccation, infection, and mechanical injury. - **Cuticle:** A waterproof covering of cutin that is secreted by epidermal cells. - **Stomata:** Pores in the epidermis that allow gas exchange. They are surrounded by **guard cells**, which are kidney-shaped. The guard cells are associated with **subsidiary cells**. #### Functions of Epidermis 1. Protection 2. Transpiration 3. Gas exchange 2. **Cork:** The protective tissue formed in older stems and roots. It is made up of dead cells with a thick wall and a waxy substance called **suberin**. - The cells of the cork are impermeable to water and gases. - Cork cells are without cytoplasm and are filled with air. #### Functions of Cork 1. Protection: It protects plants from desiccation, infection, and mechanical damage. ## Animal Tissue: - A group of cells that have a similar structure and perform a common function. - There are four types of animal tissue: - **Epithelial Tissue:** Covering tissue. - **Connective Tissue:** Support tissue. - **Muscular Tissue:** Helps in movement. - **Nervous Tissue:** Helps in coordinating and controlling the body's actions. ### Epithelial Tissue - It is the simplest tissue. - It is found all over the animal body as covering, lining, and glandular tissue. - It is continuous, tightly packed, has a thin cementing material, and is avascular (lacking blood vessels). - **Basement Membrane:** A non-cellular membrane that anchors the epithelial tissue to the underlying connective tissue. #### Types of Epithelial Tissue - **Simple Epithelial Tissue:** It's composed of a single layer of cells. - **Stratified Epithelial Tissue:** It's composed of more than one layer of cells. 1. **Squamous Epithelial Tissue:** - **Simple Squamous Epithelium:** A single layer of flat, tile-like cells. Found where diffusion and filtration of substances are required, such as in the lining of blood vessels, alveoli of lungs, and the glomerular capsule of the kidneys. - **Stratified Squamous Epithelium:** Several layers of flattened cells. Found on surfaces subject to abrasion, such as the skin and the lining of the mouth, esophagus, and vagina. 2. **Cuboidal Epithelial Tissue:** - **Simple Cuboidal Epithelium:** Cube-shaped cells. Found in the lining of the tubules of the kidneys and in the ducts of glands. - **Stratified Cuboidal Epithelium:** Several layers of cube-shaped cells. Found in the lining of the ducts of some glands. 3. **Columnar Epithelial Tissue:** - **Simple Columnar Epithelium:** Tall, columnar cells. Found in the lining of the stomach, intestines, and uterus. They often have microvilli, which increase the surface area for absorption. - **Stratified Columnar Epithelium:** Several layers of columnar cells. Found in the lining of the male urethra and some parts of the pharynx. 4. **Transitional Epithelium:** A special type of stratified epithelium that can stretch. Found in the lining of the urinary bladder, ureters, and the upper part of the urethra. #### Functions of Epithelial Tissue: 1. **Protection:** Protect underlying tissues from abrasion, injury, and infection. 2. **Absorption:** Absorb nutrients and other substances from the surroundings. 3. **Secretion:** Secrete substances such as mucus, hormones, and enzymes. 4. **Excretion:** Remove waste products from the body. 5. **Filtration:** Filter substances from the blood. 6. **Diffusion:** Allow the exchange of gases and other substances. 7. **Sensory Reception:** Receive sensory stimuli. ### Connective Tissue - Supportive and binding tissues that hold together and support various tissues and organs. - The cells of connective tissues are widely spaced and embedded in an extracellular matrix, which they produce. The extracellular matrix provides support and structure. - Connective tissues are highly vascularized (contain blood vessels), except for cartilage. - **Functions of Connective Tissue:** 1. **Support** 2. **Binding** 3. **Protection** 4. **Transportation** 5. **Storage of fats** 6. **Repair of tissues** #### Types of Connective Tissue - **Proper Connective Tissue:** Made up of cells, fibers, and ground substance. - **Areolar Connective Tissue:** Loose connective tissue found beneath the skin and surrounding organs. Contains all three types of fibers (collagen, elastic, and reticular) and is very vascularized. - **Adipose Connective Tissue:** Contains adipocytes, which store fat. Found beneath the skin, around internal organs, and in the bone marrow. - **Dense Connective Tissue:** Contains densely packed collagen fibers. Provides strength and support. Subdivided into: - **Dense Regular Connective Tissue:** Collagen fibers are arranged in parallel bundles and form tendons (connects muscle to bone) and ligaments (connects bone to bone). - **Dense Irregular Connective Tissue:** Collagen fibers are arranged randomly and are found in the dermis of the skin, the fibrous capsules of organs, and the periosteum (membrane surrounding bones). - **Elastic Connective Tissue:** Contain mostly elastic fibers which are found in the walls of large blood vessels, and in the ligaments associated with the vertebral column. - **Skeletal Connective Tissue:** Provides support and framework to the body. - **Bone:** Hard and rigid connective tissue. Contains osteocytes, osteoblasts, and osteoclasts. There are two types of bone: - **Compact Bone:** Dense bone tissue found in the shaft of long bones. - **Spongy Bone:** Porous bone tissue found at the ends of long bones and in the epiphyses of flat bones. - **Cartilage:** A firm, flexible connective tissue. Contains chondrocytes, which are embedded in a matrix of chondroitin sulfate. There are three types of cartilage: - **Hyaline Cartilage:** The most common type of cartilage. Found at the ends of bones, the nose, trachea, and the ribs. - **Elastic Cartilage:** Contains more elastic fibers. Found in the pinna (outer ear) and the epiglottis. - **Fibrocartilage:** Contains a large amount of collagen fibers. Found in the intervertebral discs and the menisci of the knee joint. - **Fluid Connective Tissue:** Fluid matrix. Includes: - **Blood:** A fluid connective tissue. Contains plasma, red blood cells, white blood cells, and platelets. It transports nutrients, oxygen, and waste products. - **Lymph:** A fluid connective tissue that circulates throughout the lymphatic system. It plays a role in the immune system. ### Muscular Tissue - Contractile tissues that help in movement. #### Types of Muscular Tissue - - **Skeletal Muscle:** Voluntary muscle. Attached to bones. Provides movement and locomotion. - **Smooth Muscle:** Involuntary muscle. Found in the walls of internal organs such as the stomach, intestines, blood vessels, and the urinary bladder. - **Cardiac Muscle:** Involuntary muscle. Found only in the heart. Its rhythmic contractions pump blood throughout the body. ### Nervous Tissue - The main tissue of the nervous system, which coordinates and controls the activities of the body. - **Neurons:** The structural and functional unit of the nervous system. - **Neuroglia:** The supporting cells of the nervous system. They provide support and nourishment to the neurons. #### Functions of Nervous Tissue 1. **Receive stimuli** 2. **Conduct impulses** 3. **Coordinate and control body functions**