* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Class - Educast
Survey
Document related concepts
Vectors in gene therapy wikipedia , lookup
Embryonic stem cell wikipedia , lookup
Cell-penetrating peptide wikipedia , lookup
Hematopoietic stem cell wikipedia , lookup
Symbiogenesis wikipedia , lookup
Microbial cooperation wikipedia , lookup
Cell growth wikipedia , lookup
Chimera (genetics) wikipedia , lookup
Cellular differentiation wikipedia , lookup
Cell culture wikipedia , lookup
Artificial cell wikipedia , lookup
Human embryogenesis wikipedia , lookup
State switching wikipedia , lookup
Neuronal lineage marker wikipedia , lookup
Adoptive cell transfer wikipedia , lookup
Cell (biology) wikipedia , lookup
Organ-on-a-chip wikipedia , lookup
Transcript
BIOLOGY FOR CLASS IX Class IX Structural Organization Of Life Content Microscope Light Microscope Electron Microscope Magnification And Resolution Cell Cell Theory Cell Organelles Differences Between Animal And Plant Cells Types Of Cells Differences Between Prokaryotic And Eukaryotic Cells Cell Division Mitosis Stages Significance Of Mitosis Meiosis Stages Significance Of Meiosis Organization Of Cells To Form Tissues, Organs And Organ System Plant Tissues Types Of Plant Tissue Systems Types Of Animal Tissues Unicellular Organism Multicellular Organism Brassica as multicellular organization, with root, stem, leaves, flower fruit and seed as their parts Frog as multicellular organization with digestive, respiration, circulatory, excretory, nervous and reproductive organs and system Parts and Microscope: Eyepiece Lens: The lens at the top that you look through. They are usually 10X or 15X power. Tube: Connects the eyepiece to the objective lenses Arm: Supports the tube and connects it to the base Base: The bottom of the microscope, used for support Illuminator: A steady light source (110 volts) used in place of a mirror. If your microscope has a mirror, it is used to reflect light from an external light source up through the bottom of the stage. Stage: The flat platform where you place your slides. Stage clips hold the slides in place. If your microscope has a mechanical stage, you will be able to move the slide around by turning two knobs. One moves it left and right, the other moves it up and down. Revolving Nosepiece or Turret: This is the part that holds two or more objective lenses and can be rotated to easily change power. Objective Lenses: Usually you will find 3 or 4 objective lenses on a microscope. They almost always consist of 4X, 10X, 40X and 100X powers. When coupled with a 10X (most common) eyepiece lens, we get total magnifications of 40X (4X times 10X), 100X, 400X and 1000X. Rack Stop: This is an adjustment that determines how close the objective lens can get to the slide. It is set at the factory and keeps students from cranking the high power objective lens down into the slide and breaking things. You would only need to adjust this if you were using very thin slides and you weren't able to focus on the specimen at high power. (Tip: If you are using thin slides and can't focus, rather than adjust the rack stop, place a clear glass slide under the original slide to raise it a bit higher). 1. Light microscope A light microscope uses focused light and lenses to magnify a specimen, usually a cell. In this way, a light microscope is much like a telescope, except that instead of the object being very large and very far away; it is very small and very close to the lens. Electron Microscope The electron microscope is a type of microscope that uses a beam of electrons It is capable of much higher magnifications and has a greater resolving power than a light microscope, allowing it to see much smaller objects in finer detail. They are large, expensive pieces of equipment, generally standing alone in a small, specially designed room and requiring trained personnel to operate them. Magnification: Magnification is the ability to make small objects seem larger, such as making a microscopic organism visible. Magnification is the process of enlarging something only in appearance, not in physical size. By increasing magnification resolution is disturbed. Magnification improves with the focal length of lens. Resolution: Resolution depends on the distance between two distinguishable radiating points. Resolution is the capacity to separate adjacent objects. In 1665, an Englishman by the name of Robert Hooke examined thin slices of cork and observed that it was composed of numerous little boxes, fitted together like honey comb. Since these boxes resembled the compartment of monastery he named them as cells. The cork cells studied by Hooke were really empty boxes; they had lost their living matter, the protoplasm. After his discovery, the protoplasm in living cells was largely over looked due to its transparency. Today, with the help of special techniques, we are able to see not only the protoplasm but also many bodies inside it. A general outline of a plant cell is as follows: Plant cells are surrounded by a non living and rigid coat called cell wall. The cell wall is not a living part of the cell. Cell walls are significantly thicker than plasma membranes. It is responsible for the shape of plants and controls the growth rate of plant cells. Walls are a layered structure, having three basic portions: intercellular substance or middle lamella, primary wall and secondary wall. The middle lamella cements together the primary walls of two contiguous cells and the secondary wall is laid over the primary. The middle lamella is mainly composed of a pectic compound which mostly appears to be calcium pectate. The primary wall is largely composed of cellulose and the secondary wall may be of cellulose . All living cells, prokaryotic and eukaryotic, have a plasma membrane that encloses their contents and serves as a semi-porous barrier to the outside environment. The plasma membrane is permeable to specific molecules, however, and allows nutrients and other essential elements to enter the cell and waste materials to leave the cell. Small molecules, such as oxygen, carbon dioxide, and water, are able to pass freely across the membrane, but the passage of larger molecules, such as amino acids and sugars, is carefully regulated. According to the accepted current theory, known as the fluid mosaic model, the plasma membrane is composed of a double layer (bilayer) of lipids, oily substances found in all cells. The term cell nucleus was used by Robert Brown for the first time in 1831. The nucleus is a highly specialized organelle that serves as the information processing and administrative center of the cell. This organelle has two major functions: it stores the cell's hereditary material, or DNA, and it coordinates the cell's activities, which include growth, intermediary metabolism, protein synthesis, and reproduction (cell division). Position: The location of nucleus varies in the cell depending upon the species. Usually it is situated in the centre of the cell surrounded on all sides by cytoplasm Shape: The shape of nucleus is variable according to cell type. It is generally spheroid but ellipsoid or flattened nuclei may also occur in certain cells. Nucleoplasm. The semi fluid matrix found inside the nucleus is called nucleoplasm. Within the nucleoplasm, most of the nuclear material consists of chromatin, the less condensed form of the cell's DNA that organizes to form chromosomes during mitosis or cell division. Chromatin and Chromosomes: A dense string-like fiber called chromatin. The Nucleolus: The nucleolus is a membrane-less organelle within the nucleus that manufactures ribosomes, the cell's protein-producing structures. The Nuclear Envelope The nuclear envelope is a double-layered membrane that encloses the contents of the nucleus during most of the cell's lifecycle. Part of plant cells outside the nucleus (and outside the large vacuole of plant cells) is called cytoplasm. The cytoplasm is about 80% water and usually colorless. Cytoplasm is often used to refer to the jellylike matter in which the organelles are embedded (correctly termed the cytosol). Most of the activities in the cytoplasm are chemical reactions (metabolism), for example, protein synthesis. Some important cytoplasmic organelles found in eukaryotic cells. Endoplasmic reticulum (ER) Golgi Apparatus Mitochondria Plastids Centrioles Ribosomes Lysosomes They are found in all eukaryotic cells and are structurally continuous with the nucleus of the cell. The ER is a complex network of tubes. The lumen is filled with fluid. There are two types of endoplasmic reticulum smooth ER and rough ER. Smooth Endoplasmic reticulum - They are tubes with a smooth surface as they lack ribosomes. The smooth ER helps in calcium sequestration and release and secretion of lipids. Rough Endoplasmic reticulum - They are tubes with rough surface as the ribosomes are attached to its surface. The endoplasmic reticulum serves many general functions, including the folding of protein molecules in sacs called cisternae and the transport of synthesized proteins in vesicles to the Golgi apparatus. The Golgi bodies are elongated, flattened structures called cisternae and they are stacked parallel to one another. They are bound by a single membrane and are found close to the nucleus. The vesicle formed from the ER fuses with the membrane of the Golgi apparatus. The cavity of the Golgi body is has vessel proteins that are modified for export. The main function of the Golgi apparatus is sorting, packaging, processing and modification of proteins. It also forms lysosomes and peroxisomes. Lysosomes are single membrane bound structures. They are tiny sac like structures and are present all over the cytoplasm. The main function is digestion. They contain digestive enzymes. Lysosomes contain digestive enzymes that are acid hydrolases. They are responsible for the degrading of proteins and worn out membranes in the cell and also help degradation of materials that are ingested by the cell. Lysosomes that are present in the white blood cells are capable of digesting invading microorganisms like the bacteria and viruses. During the period of starvation the lysosomes digest proteins, fats and glycogen in the cytoplasm. They are capable of digesting the entire damaged cell containing them; hence, the lysosomes are known as "suicide bags" of the cell. Peroxisomes are found in liver and kidney cells. Peroxisomes have enzymes that are responsible to get rid of the toxic peroxides from the cell. Ribosomes are the site for protein synthesis of the cell. It is composed of two subunits, a small subunit and a large subunit. The ribosomes subunit acts as an assembly line where the RNA from the nucleus is used to synthesize proteins from amino acids. Ribosomes are found freely floating or bound to a membrane or attached to mRNA molecules in a polysome. Centrosomes are the cytoskeleton organizers. Centrosomes are composed of two centrioles, they separate during cell division and they help in the formation of mitotic spindle. Mitochondria are of various shapes and sizes and are numerous in the cytoplasm of all eukaryotic cells. Mitochondria are double membrane bound. The inner membrane is folded into numerous cristae. Mitochondria are the power generators of the cell. They are capable of self-replication as they possess their own DNA. The main function of mitochondria is to produce energy through metabolism. In the mitochondria sugar is finally burnt during cellular respiration. The energy released in this process is stored as high-energy chemicals called adenosine triphosphate (ATP). The energy is used by the body cells for synthesis of new chemical compounds. Plastids are cellular organelles found only in the plant cell. Plastids are of three types - chloroplasts, chromoplasts and leucoplasts. •Chloroplasts are elongated disc shaped organelles which contains chlorophyll. Chlorophyll is present in green plants which helps them make food by the process of photosynthesis, which uses energy from the sunlight is converted into chemical energy. •Chromoplasts are plastids which are found in fruits and are yellow, orange and red in color. •Lecuoplasts are colorless plastids. They found in roots, seeds and underground stems. Animal cell Plant Cell Animal cells are usually smaller is size.Plant cells are usually larger in size. Cell wall is completely absent. Presence of cell wall is a characteristic feature of plant cell. Cellulose in any form is not present. Cell wall is made up of cellulose. Cytoplasm of animal cells is dense, more granular and it occupies most of the space in the cell. In a plant cell, cytoplasm is pushed to the periphery of the cell. The cytoplasm forms a thin lining against the cell wall. Vacuoles are absent usually. If present, Vacuoles are prominent and large they are small organelles, organelles in the plant cell. they are temporary and they serve One or more vacuoles may be present. as organelles for excretion or secretion. The central space in the cell may be occupied by a large single vacuole. Plastids are absent. Centrosome is present. Plastids are present. They may of three types chromoplasts, chloroplasts and leucoplasts. Centrosome is absent in plant cells. Instead of centrosome, there are two small clear areas called polar caps are present. Golgi complex is prominent and highly complex; Golgi apparatus is present in form it is present near the nucleus of the subunits called dictyosomes. cell. Prokaryotic Eukaryotic Nulear membrane is absent A double nuclear membrane is therefore prokaryotic cells doing present. They have well defined not possess distinct nucleus. mucleus. They do not have many of the They have membrane bounded membrane bound structures e.g. structure (organelles). Mitochondria,ER,Golgi bodies Ribosomes are of small size and Ribosomes are of large size and freely scattered in cytoplasm. present either on endoplasmic reticulum free in cytoplasm. Nucleoplasm is absent. Nucleoplasm is present. Single chromosome is found. Proper chromosomes in diploid numbers are present. Respiratory enzymes are located on the Respiratory enzymes are present in inner surface of the cell membrane. mitochondria. These cells are simple and comparatively These cells are complex and smaller in size i.e. aveage 0.5 -10nm in comparatively larger in size i.e. 10diameter. 100nm in diameter average. Bacteria and cyanobacteria are examples Fungi, Algae, Animals and Plants are of prokaryotes examples of Eukaryotes. Cell Cell is the basic unit of life. Cell Theory 1. All living things are made up of cells. 2. Cells are the basic units of structure and function in living things. 3. Living cells come only from other living cells. Cell Division Cell division is the process by which a parent cell divides into two or more daughter cells. 1. Mitosis 2. Meiosis Prophase Metaphase Anaphase Telophase This division produced having the same amount and type of genetic constitution as that of the parent cell. It is responsible for growth and development. The number of chromosomes remains the same in all the cells produced by this division. Thus, the daughter cells retain the same characters as those of the parent cell. It helps the cell in maintaining proper size. Mitosis helps in restoring damaged or lost part, healing of wounds and regeneration of detached parts (as in tail of lizards). It is a method of multiplication in unicellular organisms. Meiosis I The first meiotic division is more important than the second division because it is the reduction division. In this, four sty ages can be differentiated. Prophase I Metaphase I Anaphase I Telophase I (a)Leptotene or Leptonema (leptos=thin) This is the first stage of meiosis following interphase. The chromosomes at this stage appear long, thread-like structures. On the entire chromosome, characteristic bead-like structures, called chromomeres can be seen. In animal cells, the centrioles divided and move towards opposite poles. (b) Zygotene or Zygonema (Zygone=adjoining) This stage is characterized by the pairing of homolosgous chromosomes. This phenomenon is known as synapsis. The pairing starts at the centromere or at any other position. The paired chromosomes are called bivalents or dyads. They gradually become thick and short. (c) Pachytene or Pachynema (Pachus=thick) Each chromosome of a bivalent splits longitudinally into two sister chromatids so that the bivalent becomes a tetrad or quadrivalent. The two nonsister chromatids, one from each bivalent (one paternal and the other maternal) partially coil around each other and exchange their genetic material. On each of the nonsister chromatids of the tetrad, transverse breaks occur which are followed by interchange and final fusion. This process is known as crossing over and the point where the crossing over takes place is called chiasmata (singular, chiasma). Due to coiling, the paired chromosomes become thicker and short. The nucleolus still persists. (d) Diplotene or Diplonema (Diploos=double) At this stage, homologous chromosomes start at the centromere and moves towards the ends. The type of separation from centromere towards the end is known as terminalization. This separation makes the dual nature of a bivalent chromosome distinct and hence the name of the stage is diplotene. As the terminalization proceeds, the chiasmata (points of genetic exchange) move towards the ends of the chromosomes but the chromosomes are held together at the chiasmata. It should be remembered that crossing over always takes place between nonsister chromatids of homologous chromosomes. Chiasmata are not the cause but are only the consequence of crossing over. The number of chiasmata per bivalent varies and is dependent upon the length of the chromosomes. Nucleolus and nuclear membrane start disappearing at this stage. (e) Diakinesis (Dia=across) The chromosomes undergo further contraction and shortening. During this stage the nucleolus and nuclear membrane disappear. Centrioles reach the opposite poles of cell and start forming spindle apparatus. Interphase The interphase is a brief period here. Sometimes it may be absent. There is no duplication of chromosomes at this stage which is a different condition from that of mitosis. The second meiotic division is essentially a mitotic division and is sometimes termed as meiotic mitosis. It can be studied under the following four stages. 1. Prophase II In both the cells the nuclear membrane and nucleoli disappear . The centrioles duplicate and migrate towards opposite pole. Each set of centriosles is surrounded by aster rays. The formation of spindle starts. The shortening of chromosomes begins. 2. Metaphase II The chromosomes arrange themselves on the equatorial plane and centromere divides. Each chromatid gets attached to spindle fibres by its centromere. 3. Anaphase II Spindle fibres attached to the opposite faces of cenromeres shorten in length. This causes a pull on the centromere. As a result, the centromere splits along the longitudinal axis and the chromatids are pulled to the opposite poles. 4. Telophase II The chromatids (now the chromosomes) reach their respective poles. They uncoil and form the chromatin network. Nucleolus and nuclear membrane reappear. At the end of this phase, four haploid (n) nuclei are produced in each cell. It maintains the same chromosome n umber in the sexually reproducing organisms. From a diploid cell, haploid gametes are produced which in turn fuse to form a diploid cell. 2. It restricts the multiplication of chromosome number and maintains the stability of the species. 3. Maternal and paternal genes get exchanged during crossing over. It results in variations among the offspring. 4. All the four chromatids of a homologous pair of chromosomes segregate and go over separately to four different daughter cells. This leads to variation in the daughter cells genetically. Tissues are made up of groups of cells that all have a similar function and structure. Some examples of tissues include muscles, bones, skin and the lining of the stomach, lungs and intestines. The lining of the stomach is just one of the many tissues that have joined together to form the organ, as it also contains muscles, mucus membrane tissue and many other tissue types. Plants do have a higher level of structure called plant tissue systems. A plant tissue system can be defined as a functional unit, which connects all organs of a plant. Like animal tissue system, plant tissue system is also grouped into various tissues based on their functions. They are the tissues, which covers the external part of the herbaceous plants. They are composed of epidermal cells, which secrete the waxy cuticle. Waxy cuticles are responsible for protecting plants against water loss. Dermal tissue consists of Epidermis and periderm. They are the outermost layer of the primary plant body, which covers roots, stems, leaves, floral parts, fruits and seeds. They are one layer thick with cuticle. They are composed mostly of unspecialized cells- parenchyma and sclerenchyma. They include trichomes, stomata, etc. •They are the outermost layer of stems and roots of woody plants such as trees. They are also called as barks. •They replace epidermis in plants that undergo secondary growth. •They are multilayered structures. •They include cork cells, which are nonliving cells that cover the outside of stems and roots. •The periderm protects the plant from injuries, pathogens and also from excessive water loss. They synthesize the organic compounds and support the plants by storing the produced products. They are composed of parenchyma cells and also include collenchyma and sclerenchyma cells. They are the general cells of plants, which are circular in shape and have very thin wall. They are present in all plant cells. They have very large vacuoles and are frequently found in all roots, stem, leaves and in fruits. Parenchyma cells help in synthesizing and storage of synthesized food products. Parenchyma cells also controls plant's metabolism like photosynthesis, respiration, protein synthesis. They also play a vital role in wound healing and regeneration of plants. Collenchymas are a specialized parenchyma tissue, which are found in all green parts. Collenchyma cells are elongated with unevenly thickened walls. They are alive during the cell maturity. Collenchyma cells controls the functions of young plants. A collenchyma cell provides a support to plants by not restraining growth, which is caused due to their absence of secondary walls and hardening agent in their primary walls. They are rigid, non-living cells. They have thick, lignified secondary walls and lack protoplasts at maturity. They provide strength A sclerenchyma cell also provides a support to plants with the help of hardening agent present in their cells. Sclerenchyma cells are of two types: Sclereids: They are short, irregular in shape and have thick, lignified secondary walls Fibers: They are long, slender and are arranged in threads. They are specialized cells with transport of water, hormone and minerals throughout the plant. They contain transfer cells, fibers in addition to xylem, phloem, parenchyma, cambium and other conducting cells. They are located in the veins of the Leaves. The term Xylem is derived from the Greek word meaning Wood. They are dead with hollow cells, which consist of only cell wall. They play a vital role in transporting water and dissolved nutrients from the roots to all parts of a plant. They transport the nutrients in the upward direction .i.e. from the root to the stem, leaves and flower. Xylem is also called as water-conducting cells. The term phloem is derived from the Greek word meaning Bark. They are live cells, which lack nucleus and other organelles. They transports dissolved organic food materials (sugars) from the leaves to all parts of a plant. They transport the nutrients in the downward direction .i.e. from the leaves to the different parts of the plant. Phloem is also called as sugar-conducting cells. The structure of the cell varies according to its function. The tissues are different and are classified into four types: Epithelial tissue Connective tissue Muscular tissue and Neural tissue. Epithelial tissue is commonly referred to as epithelium. The epithelial tissue forms the outer covering or lining for some part of the body. An epithelial tissue forms the surface of the skin, lines many cavities of the body and covers the internal organs. These tissues have cells and fibers that are loosely arranged in a semi-fluid ground substance. Areolar tissue - It is present beneath the skin, it serves as a framework support for epithelium. Adipose tissue - This type of tissues is specialized to store fats. Fibres and fibroblasts are packed compactly in dense connective tissue. Tendons are dense regular tissue that attaches skeletal muscle to bones and ligaments attach bone to other bones. Collagen is the dense irregular tissue present in the skin. Muscle tissues are made of long cylindrical fibres, arranged in parallel arrays. These fibres are composed of fine fibrils known as myofibrils. The contraction and relaxation of moves the body to adjust to the changes in the environment. Muscles are of three types skeletal, smooth, and cardiac. Cardiac muscle tissue is a tissue present only in the heart. Cell junctions fuse the plasma membranes of cardiac cells. Communication junctions allow the cells to contract as a unit. Neural tissues control the body's responses to the changing conditions. Neurons are the units of neural system, they are excitable cells. Glial cells and neurons are the cells that form the nervous system. Organ is a group of tissues in a living organism that have been adapted to perform a specific function in animals. e.g., the esophagus, stomach, and liver are organs of the digestive system. The main function of this system is to transport nutrients and gasses to cells and tissues throughout body. This is accomplished by the circulation of blood. Cardiovascular: This system is comprised of the heart, blood, and blood vessels. The beating of the heart drives the cardiac cycle which pumps blood throughout body. This system breaks down food polymers into smaller molecules to provide energy for the body.Digestive juices and enzymes are secreted to break down the carbohydrates, fat, and protein in food. This system regulates vital processes in the body including growth, homeostasis, metabolism, and sexual development. Endocrine organs secrete hormones to regulate body processes. Endocrine structures: pituitary gland, ovaries, testes, thyroid gland This system protects the internal structures of the body from damage, prevents dehydration, stores fat and produces vitamins and hormones. Integumentary structures: skin, nails, hair, sweat glands This system enables movement through the contraction of muscles. Structures: muscles This system monitors and coordinates internal organ function and responds to changes in the external environment. Structures: brain, spinal cord, nerves. AMOEBA An amoeba is a type of unicellular organism usually found in water around decaying vegetation, in wet soil and in animals such as humans. Multicellular organisms are those which are made up of many cells. Humans are multicellular. Multicellular organisms can be much larger and more complex. Brassica Brassica campestris is the botanical name of mustard (sarsoun). You are very familiar with this plant since its oil (mustard oil) is used for cooking and its leaves are used as vegetable (saag). Vegetative parts 1) Root: The root is that part, which grows under the soil and develops from the radicle of the seed. The first part of the root to arise from the radicle is known as the primary root. Internal structure This part of plant develops from the plumule of the seed and grows away from the soil. It bears branches and flowers. The point, on the stem or on a branch, which gives rise to leaf, is known as the node. Internal structure Leaves grow out on the stem and its branches from the nodes. Generally, the leaf of Brassica consists of two parts. The lower stalk like part is the petiole and upper green expanded portion is the lamina. Internal structure Flower With growing age, Brassica plant bears small, yellowish flowers. Flowers are the most beautiful and important parts of the plant. They are arranged on young branches in a special way. This special arrangement of the flowers on the stem is called inflorescence. Parts of the flower 1.Calyx 2.Corolla 3.Androecium 4.Gynoecium The frog lives both in water as well as on land. There is a membranous skin between its toes which helps in swimming. There are five toes in each foot but the hand has only four fingers because the thumb is rudimentary. In male frog the first finger is thicker than the others. Frog has neither a neck nor a tail. As the head is directly attached to the trunk frog cannot move it as we can. The conical head has two large bulging eyes. Behind each eye is a circular area called tympanic membrane. These membranes help in hearing. At the tip of the snout it has two openings called external nostrils by which frog breathes. The skin of the frog is loose and slippery. It is slippery due to secretions produced by glands present in it. DIGESTIVE SYSTEM Buccal cavity Food enters into the buccal cavity through mouth. The upper jaw has a row of weak but pointed teeth. Pharynx The buccal cavity opens into a short but narrow pharynx, which leads into a wide tube,, the oesophagus. Immediately behind the tongue on the floor of the pharynx is a slit like opening, the glottis, which opens into the lungs. Oesophagus and stomach Pharynx opens into a wide tube called oesophagus or gullet; It transports food into the stomach. Intestine The intestine is a long narrow coiled tube. It is divisible into small and a large intestine. The partially digested food from the stomach enters the small intestine through pyloric end, where its digestion is completed. Liver and pancreas The liver is a large reddish-brown gland located adjacent to the stomach. Its secretion is known as bile. Between the lobes of the liver is a rounded pouch called gall bladder, which stores bile. A bile duct arises from it. On its way, this duct passes through pancreas and joins the pancreatic duct. The pancreas lies between stomach and duodenum, the first part of small intestine. Its secretion, pancreatic juice, is carried by the pancreatic duct. The pancreatic duct and the bile duct join to form a common hepato-pancreatic duct, which then opens into duodenum. The bile and the pancreatic juice help in the complete digestion of the food in the small intestine Energy is required by every organism to carry on all the life activities. It is produced by the oxidation of food specially glucose. This entire process called respiration, divided into two phases. a) Gaseous exchange or Extra-cellular respiration b) Cellular respiration. Frog has three types of respiration on the basis of organs involved in the gaseous exchange. These are: PULMONARY RESPIRATION The gaseous exchange, which takes place in lungs is called pulmonary respiration. The frog has two lungs, which are balloon like structures. Their outer surface is smooth but their inner surface has numerous folds which increase the area for gaseous exchange. The lungs are richly supplied with blood vessels . Each lung has a bronchus at its upper end. The two bronchi open into a larynx. The glottis opens into the larynx. During respiration air is taken in by the external nostrils. It passes into the buccal cavity through the internal nostrils. From here it enters the glottis, passes through the larynx and bronchi finally reach the lungs. In the lungs, exchange of gases between air and blood takes place i.e. oxygen is taken up by the blood and CO2 is given out, which leaves the body through same route. BUCCAL RESPIRATION The lining of buccal cavity is thin, moist and richly supplied with blood capillaries. Here also exchange of gases takes place between the air and blood. This type of respiration is called buccal respiration. CIRCULATORY SYSTEM Heart- strong muscular pumping organ. ii) Three kinds of blood vessels: (a) Arteries - Which carry blood away from heart. (b) Veins - Which return blood to the heart. (c) Capillaries - Exchange material between tissues and blood. HEART Heart is a conical, muscular pumping organ, located in the anterior region of body cavity. It is enclosed in a membrane called pericardium. It contracts and expands continuously throughout the life. This contraction and expansion of heart is called heart beat, due to which blood circulates continuously in the body. Frog heart consists of three chambers. (i) Right auricle or Atrium. (ii) Left auricle or Atrium. (iii) Ventricle. The truncus arteriosus originates from ventral side of the ventricle and divide into two branches each of which divides into three arches (arteries). A blood vessel, which carries blood away from heart to the various body parts is called an artery. The arterial system can be simply stated to comprise of the following three main components. Pulmocutaneous arteries VENOUS SYSTEM The oxygenated blood from the lungs is collected by pulmonary veins, which bring it to the left auricle of the heart. (ii) The deoxygenated blood from head and fore limbs is collected through several veins, which join together to form one major precaval vein, on each side. (iii) Blood from all the lower parts of the body such as stomach, intestine, liver, pancreas, genital organs, muscles, hind limbs etc, is collected through veins, which join together and form one major vein called post caval. Both the pre-cavals and the post-caval open into the sinus venosus from where the blood is pumped into the right auricle of the heart. EXCRETORY SYSTEM OF FROG In frogs, waste materials are excreted out in many ways e.g. skin, lungs, liver. Digestive system. etc. It is the set of organs involved in the process of excretion--that is, the removal of metabolic waste- matters from the body. Besides these organs. Nitrogenous waste materials are excreted through two kidneys, which are attached to the dorsal wall of the body cavity These are elongated in shape and composed of urinary tubules. Urinary tubules combine to form collecting ducts, which open into ureter. The urine collected by the kidneys comes into ureters. Each ureter starts from the edge of each kidney of its side and opens into cloaca. From here, the urine is excreted or stored in urinary bladder which is passed out of the body from the cloacal aperture. Carbon dioxide and water are excreted through skin and lungs while undigested food and some waste materials are excreted through liver and digestive system.