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In the preceding chapters you came across a large variety of organisms, both unicellular and multicellular, of the animal kingdom. In unicellular organisms, all functions like digestion, respiration and reproduction are performed by a single cell. In the complex body of multicellular animals the same basic functions are carried out by different groups of cells in a well organised manner. The body of a simple organism like Hydra is made of different types of cells and the number of cells in each type can be in thousands. The human body is composed of billions of cells to perform various functions. How do these cells in the body work together? In multicellular animals, a group of similar cells alongwith intercellular substances perform a specific function. Such an organisation is called tissue. You may be surprised to know that all complex animals consist of only four basic types of tissues. Best NEET Coaching Centre in Tinsukia.
These tissues are organised in specific proportion and pattern to form an organ like stomach, lung, heart and kidney. When two or more organs perform a common function by their physical and/or chemical interaction, they together form organ system, e.g., digestive system, respiratory system, etc. Cells, tissues, organs and organ systems split up the work in a way that exhibits division of labour and contribute to the survival of the body as a whole. 7.1 ANIMAL TISSUES The structure of the cells vary according to their function. Therefore, the tissues are different and are broadly classified into four types : (i) Epithelial, (ii) Connective, (iii) Muscular and (iv) Neural. STRUCTURAL ORGANISATION IN ANIMALS CHAPTER 7 7.1 Animal Tissues 7.2 Organ and Organ System 7.3 Earthworm 7.4 Cockroach 7.5 Frogs 2022-23 STRUCTURAL ORGANISATION IN ANIMALS
Epithelial Tissue We commonly refer to an epithelial tissue as epithelium (pl.: epithelia). This tissue has a free surface, which faces either a body fluid or the outside environment and thus provides a covering or a lining for some part of the body. The cells are compactly packed with little intercellular matrix. There are two types of epithelial tissues namely simple epithelium and compound epithelium. Simple epithelium is composed of a single layer of cells and functions as a lining for body cavities, ducts, and tubes. The compound epithelium consists of two or more cell layers and has protective function as it does in our skin. On the basis of structural modification of the cells, simple epithelium is further divided into three types. These are (i) Squamous, (ii) Cuboidal, (iii) Columnar (Figure 7.1). The squamous epithelium is made of a single thin layer of flattened cells with irregular boundaries. Best NEET Coaching Centre in Tinsukia
They are found in the walls of blood vessels and air sacs of lungs and are involved in functions like forming a diffusion boundary. The cuboidal epithelium is composed of a single layer of cube-like cells. This is commonly found in ducts of glands and tubular parts of nephrons in kidneys and its main functions are secretion and absorption. The epithelium of proximal convoluted tubule (PCT) of nephron in the kidney has microvilli. The columnar epithelium is composed of a single layer of tall and slender cells. Their nuclei are located at the base. Free surface may have microvilli. They are found in the lining of stomach and intestine and help in secretion and absorption. If the columnar or cuboidal cells bear cilia on their free surface they are called ciliated epithelium (Figure 7.1d). Their function is to move particles or mucus in a specific direction over the epithelium. They are mainly present in the inner surface of hollow organs like bronchioles and fallopian tubes. Best NEET Coaching Centre in Tinsukia
Simple epithelium: (a) Squamous (b) Cuboidal (c) Columnar (d) Columnar cells bearing cilia (a) Flattened cell Cube-like cell Tall cell (b) (d) (c) 2022-23 102 BIOLOGY Some of the columnar or cuboidal cells get specialised for secretion and are called glandular epithelium (Figure 7.2). They are mainly of two types: unicellular, consisting of isolated glandular cells (goblet cells of the alimentary canal), and multicellular, consisting of cluster of cells (salivary gland). On the basis of the mode of pouring of their secretions, glands are divided into two categories namely exocrine and endocrine glands. Exocrine glands secrete mucus, saliva, earwax, oil, milk, digestive enzymes and other cell products. These products are released through ducts or tubes. In contrast, endocrine glands do not have ducts. Their products called hormones are secreted directly into the fluid bathing the gland. Compound epithelium is made of more than one layer (multi-layered) of cells and thus has a limited role in secretion and absorption (Figure 7.3). Their main function is to provide protection against chemical and mechanical stresses.
They cover the dry surface of the skin, the moist surface of buccal cavity, pharynx, inner lining of ducts of salivary glands and of pancreatic ducts. All cells in epithelium are held together with little intercellular material. In nearly all animal tissues, specialised junctions provide both structural and functional links between its individual cells. Three types of cell junctions are found in the epithelium and other tissues. These are called as tight, adhering and gap junctions. Tight junctions help to stop substances from leaking across a tissue. Adhering junctions perform cementing to keep neighbouring cells together. Gap junctions facilitate the cells to communicate with each other by connecting the cytoplasm of adjoining cells, for rapid transfer of ions, small molecules and sometimes big molecules. 7.1.2 Connective Tissue Connective tissues are most abundant and widely distributed in the body of complex animals. They are named connective tissues because of their special function of linking and supporting other tissues/organs of the body.
They range from soft connective tissues to specialised types, which Figure 7.2 Glandular epithelium : (a) Unicellular (b) Multicellular unicellular gland Multicelluar gland (a) (b) Figure 7.3 Compound epithelium Multilayered cells 2022-23 STRUCTURAL ORGANISATION IN ANIMALS 103 Fat storage area Nucleus Macrophage Mast cell Fibroblast Collagen fibers Plasma Membrane include cartilage, bone, adipose, and blood. In all connective tissues except blood, the cells secrete fibres of structural proteins called collagen or elastin. The fibres provide strength, elasticity and flexibility to the tissue. These cells also secrete modified polysaccharides, which accumulate between cells and fibres and act as matrix (ground substance). Connective tissues are classified into three types: (i) Loose connective tissue, (ii) Dense connective tissue and (iii) Specialised connective tissue. Loose connective tissue has cells and fibres loosely arranged in a semi-fluid ground substance, for example, areolar tissue present beneath the skin (Figure 7.4).
Often it serves as a support framework for epithelium. It contains fibroblasts (cells that produce and secrete fibres), macrophages and mast cells. Adipose tissue is another type of loose connective tissue located mainly beneath the skin. The cells of this tissue are specialised to store fats. The excess of nutrients which are not used immediately are converted into fats and are stored in this tissue. Fibres and fibroblasts are compactly packed in the dense connective tissues. Orientation of fibres show a regular or irregular pattern and are called dense regular and dense irregular tissues. In the dense regular connective tissues, the collagen fibres are present in rows between many parallel bundles of fibres. Tendons, which attach skeletal muscles to bones and ligaments which attach one bone to another are examples of this tissue. Dense irregular connective tissue has fibroblasts and many fibres (mostly collagen) that are oriented differently (Figure 7.5). This tissue is present in the skin. Best NEET Coaching Centre in Tinsukia
Cartilage, Loose connective tissue : (a) Areolar tissue (b) Adipose tissue (a) (b) fibres Collagen fibre (a) (b) Figure 7.5 Dense connective tissue: (a) Dense regular (b) Dense irregular 2022-23 104 BIOLOGY bones and blood are various types of specialised connective tissues. The intercellular material of cartilage is solid and pliable and resists compression. Cells of this tissue (chondrocytes) are enclosed in small cavities within the matrix secreted by them (Figure 7.6a). Most of the cartilages in vertebrate embryos are replaced by bones in adults. Cartilage is present in the tip of nose, outer ear joints, between adjacent bones of the vertebral column, limbs and hands in adults. Bones have a hard and non-pliable ground substance rich in calcium salts and collagen fibres which give bone its strength (Figure 7.6b). It is the main tissue that provides structural frame to the body. Bones support and protect softer tissues and organs. The bone cells (osteocytes) are present in the spaces called lacunae.
Limb bones, such as the long bones of the legs, serve weight-bearing functions. They also interact with skeletal muscles attached to them to bring about movements. The bone marrow in some bones is the site of production of blood cells. Blood is a fluid connective tissue containing plasma, red blood cells (RBC), white blood cells (WBC) and platelets (Figure 7.6c). It is the main circulating fluid that helps in the transport of various substances. You will learn more about blood in Chapters 17 and 18. 7.1.3 Muscle Tissue Each muscle is made of many long, cylindrical fibres arranged in parallel arrays. These fibres are composed of numerous fine fibrils, called myofibrils. Muscle fibres contract (shorten) in response to stimulation, then relax (lengthen) and return to their uncontracted state in a coordinated fashion. Their action moves the body to adjust to the changes in the environment and to maintain the positions of the various parts of the body.Best NEET Coaching Centre in Tinsukia
In general, muscles play an active role in all the movements of the body. Muscles are of three types, skeletal, smooth, and cardiac. Skeletal muscle tissue is closely attached to skeletal bones. In a typical muscle such as the biceps, striated (striped) skeletal muscle fibres are bundled together in a parallel fashion (Figure 7.7a). A sheath of tough connective tissue encloses several bundles of muscle fibres (You will learn more about this in Chapter 20). Platelets WBC RBC (a) (b) (c) Figure 7.6 Specialised connective tissues : (a) Cartilage (b) Bone (c) Blood 2022-23 STRUCTURAL ORGANISATION IN ANIMALS 105 The smooth muscle fibres taper at both ends (fusiform) and do not show striations (Figure 7.7b). Cell junctions hold them together and they are bundled together in a connective tissue sheath. The wall of internal organs such as the blood vessels, stomach and intestine contains this type of muscle tissue.
Smooth muscles are ‘involuntary’ as their functioning cannot be directly controlled. We usually are not able to make it contract merely by thinking about it as we can do with skeletal muscles. Cardiac muscle tissue is a contractile tissue present only in the heart. Cell junctions fuse the plasma membranes of cardiac muscle cells and make them stick together (Figure 7.7c). Communication junctions (intercalated discs) at some fusion points allow the cells to contract as a unit, i.e., when one cell receives a signal to contract, its neighbours are also stimulated to contract. 7.1.4 Neural Tissue Neural tissue exerts the greatest control over the body’s responsiveness to changing conditions. Neurons, the unit of neural system are excitable cells (Figure 7.8). The neuroglial cell which constitute the rest of the neural system protect and support neurons. Neuroglia make up more than onehalf the volume of neural tissue in our body. When a neuron is suitably stimulated, an electrical disturbance is generated which swiftly travels along its plasma Nucleus Striations Junction between adjacent cells Nucleus.
Smooth Striations muscle fibers Figure 7.7 Muscle tissue : (a) Skeletal (striated) muscle tissue (b) Smooth muscle tissue (c) Cardiac muscle tissue (a) (b) (c) Figure 7.8 Neural tissue (Neuron with neuroglea) Dendrite Cell body with nucleus Axon Neuroglea 2022-23 106 BIOLOGY membrane. Arrival of the disturbance at the neuron’s endings, or output zone, triggers events that may cause stimulation or inhibition of adjacent neurons and other cells (You will study the details in Chapter 21). 7.2 ORGAN AND ORGAN SYSTEM The basic tissues mentioned above organise to form organs which in turn associate to form organ systems in the multicellular organisms. Such an organisation is essential for more efficient and better coordinated activities of millions of cells constituting an organism. Each organ in our body is made of one or more type of tissues. For example, our heart consists of all the four types of tissues, i.e., epithelial, connective, muscular and neural. We also notice, after some careful study that the complexity in organ and organ systems displays certain discernable trend.
This discernable trend is called evolutionary trend (You will study the details in class XII). You are being introduced to morphology and anatomy of three organisms at different evolutionary levels to show their organisation and functioning. Morphology refers to study of form or externally visible features. In the case of plants or microbes, the term morphology precisely means only this. In case of animals this refers to the external appearance of the organs or parts of the body. The word anatomy conventionally is used for the study of morphology of internal organs in the animals. You will learn the morphology and anatomy of earthworm, cockroach and frog representing invertebrates and vertebrates. 7.3 EARTHWORM Earthworm is a reddish brown terrestrial invertebrate that inhabits the upper layer of the moist soil. During day time, they live in burrows made by boring and swallowing the soil. Best NEET Coaching Centre in Tinsukia
In the gardens, they can be traced by their faecal deposits known as worm castings. The common Indian earthworms are Pheretima and Lumbricus. 7.3.1 Morphology Earthworms have long cylindrical body. The body is divided into more than hundred short segments which are similar (metameres about 100-120 in number). The dorsal surface of the body is marked by a dark median mid dorsal line (dorsal blood vessel) along the longitudinal axis of the body. The ventral surface is distinguished by the presence of genital openings (pores). Anterior end consists of the mouth and the prostomium, a lobe which serves as a covering for the mouth and as a wedge to force open cracks in the soil into which the earthworm may crawl. The prostomium is sensory in function. The first body segment is called the peristomium (buccal segment) which contains the mouth. In a mature worm, segments are covered by a prominent dark band of glandular tissue called clitellum.
Thus the body is divisible into three prominent regions – preclitellar, clitellar and postclitellar segments (Figure 7.9). Four pairs of spermathecal apertures are situated on the ventro-lateral sides of the intersegmental grooves, i.e., 5th -9th segments. A single female genital pore is present in the mid-ventral line of 14th segment. A pair of male genital pores are present on the ventro-lateral sides of the 18th segment. Numerous minute pores called nephridiopores open on the surface of the body. In each body segment, except the first, last and clitellum, there are rows of S-shaped setae, embedded in the epidermal pits in the middle of each segment. Setae can be extended or retracted. Their principal role is in locomotion. 7.3.2 Anatomy The body wall of the earthworm is covered externally by a thin non-cellular cuticle below which is the epidermis, two muscle layers (circular and longitudinal) and an innermost coelomic epithelium. The epidermis is made Body of earthworm : (a) dorsal view (b) ventral view (c) lateral view showing mouth opening up of a single layer of columnar epithelial cells which contain secretory gland cells.
The alimentary canal is a straight tube and runs between first to last segment of the body. (Figure 7.10). A terminal mouth opens into the buccal cavity (1-3 segments) which leads into muscular pharynx. A small narrow tube, oesophagus (5-7 segments), continues into a muscular gizzard (8-9 segments). It helps in grinding the soil particles and decaying leaves, etc. The stomach extends from 9-14 segments. The food of the earthworm is decaying leaves and organic matter mixed with soil. Calciferous glands, present in the stomach, neutralise the humic acid present in humus. Intestine starts from the 15th segment onwards and continues till the last segment. A pair of short and conical intestinal caecae project from the intestine on the 26th segment. The characteristic feature of the intestine after 26th segment except the last 23rd-25th segments is the presence of internal median fold of dorsal wall called typhlosole.
This increases the effective area of absorption in the intestine. The alimentary canal opens to the exterior by a small rounded aperture called anus. The ingested organic rich soil passes through the digestive tract where digestive enzymes breakdown complex food into smaller absorbable units. These simpler molecules are absorbed through intestinal membranes and are utilised. Pheretima exhibits a closed type of blood vascular system, consisting of blood vessels, capillaries and heart. (Figure 7.11). Due to closed circulatory system, blood is confined to the heart and blood vessels. Contractions keep blood circulating in one direction. Smaller blood vessels supply the gut, nerve cord, and the body wall. Blood glands are present on the 4 th, 5th and 6th segments. They produce blood cells and haemoglobin which is dissolved in blood plasma. Blood cells are phagocytic in nature. Earthworms lack specialised breathing devices.Best NEET Coaching Centre in Tinsukia
Respiratory exchange occurs through moist body surface into their blood stream. Mouth Pharynx Oesophagus Gizzard Stomach Pre-typhlosolar part of intestine Intestinal caecum Lymph gland Typhlosolar part of intestine Intestinal lumen Typhlosole Alimentary canal of earthworm 2022-23 STRUCTURAL ORGANISATION IN ANIMALS 109 The excretory organs occur as segmentally arranged coiled tubules called nephridia (sing.: nephridium). They are of three types: (i) septal nephridia, present on both the sides of intersegmental septa of segment 15 to the last that open into intestine, (ii) integumentary nephridia, attached to lining of the body wall of segment 3 to the last that open on the body surface and (iii) pharyngeal nephridia, present as three paired tufts in the 4th, 5th and 6th segments (Figure 7.12). These different types of nephridia are basically similar in structure. Nephridia regulate the volume and composition of the body fluids. A nephridium starts out as a funnel that collects excess fluid from coelomic chamber.
The funnel connects with a tubular part of the nephridium which delivers the wastes through a pore to the surface in the body wall into the digestive tube. Nervous system is basically represented by ganglia arranged segmentwise on the ventral paired nerve cord. The nerve cord in the anterior region (3rd and 4th segments) bifurcates, laterally encircling the pharynx and joins the cerebral ganglia dorsally to form a nerve ring. The cerebral ganglia alongwith other nerves in the ring integrate sensory input as well as command muscular responses of the body. Sensory system is not equipped with eyes, but it does have the organs that are sensitive to light and touch (receptor cells) to detect different intensities of light and to feel the vibrations of the ground. Worms possess specialized Chemoreceptors (taste receptors) that react with chemical stimulus. These organs of the senses are located on the anterior portion of the worm. Earthworms are the hermaphrodite (bisexual), i.e. both ovaries and testes are both present in one person (Figure 7.13).
There are two tests that are present in the 11th and 10th segments. The vasa deferentia of their vasas extend into the 18th section when they are joined by the prostatic tract. Two accessory glands are found in one pair in each of between the segments of the 17th as well as 19th. A common prostate, as well as a the spermatic duct (vasa deferentia) opens outwards by two male genital pore on the ventro-lateral portion that is located in the segment 18. There are 4 pairs of spermathecae that reside found in the 6th-9th segments (one pair per segment). They are able to store and retrieve the spermatozoa in copulation. A pair of ovaries are located at the inter-segmental septum that connects the 13th and 12th segments. Ovarian funnels are located below the ovaries, which extend into the oviduct, connect and then open on the ventral side to form an individual median female genital pore located on the 14th segment. The exchange of sperm takes place during mating between two worms. Best NEET Coaching Centre in Tinsukia
One worm must locate another worm, and they are able to mat by juxtaposing their gonadal openings exchange sperm packets known as”spermatophores. Sperm cells mature and eggs and nutritive fluids are placed in cocoons made by gland cells of the clitellum. Development and fertilisation occur within the cocoons that are then put into soil. The eggs (eggs) get fertilised through embryonic sperm cells inside the cocoon. The cocoon then falls off the worm , and is placed in or on soil. The cocoon is the home for embryos of the worm. After approximately three weeksof incubation, each cocoon can produce between two and twenty babies worms. The average is of four. The development of earthworms is straightforward, i.e., there no larvae that are formed. Earthworms are often referred to as “friends of farmers” because they dig burrows into the soil, and they make it porous, which facilitates breathing and the penetration of growing plant roots. Best NEET Coaching Centre in Tinsukia
In the process of increasing the fertility of soil through the earthworms is known as vermicomposting. They can also be used to bait game fish. 7.4 COCKROACH Cockroaches are brown or black-bodied animals which are part of class in the Insecta class from Phylum Arthropoda. Bright red, yellow and green-colored the cockroaches have also been observed in tropical areas. Their dimensions range from 1/4 inch up to three inches (0.6-7.6 cm) and feature long antennas legs, legs, and a flat extensions on the wall of their upper bodies which covers the head. They are nocturnal, omnivores that reside in damp areas across the globe. They are now a part of humans’ homes, and therefore are serious pests and carriers of a variety of illnesses. 7.4.1 Morphology Adults of the most common species of cockroaches, Periplaneta americana are about 34-53 millimeters long, having wings that stretch over the abdomen’s tip in males. In the body, the cockroach has been divided into three distinct parts namely the abdomen, thorax and head (Figure 7.14). The entire body is covered with an exoskeleton made of chitin (brown in color).
In each segment, the exoskeleton is composed of sclerites, which are hardened plates (tergites ventrally and dorsally) which are connected to one another by the cartilaginous membrane (arthrodial membrane). The head is triangular and is located directly in front of the axis of longitudinal body. It is created by the union of six segments, and is extremely mobile throughout the body due to a an elastic neck (Figure 7.15). The head capsule houses two eyes that are compound. Thread-like antennae emerge from membranous sockets that lie between the eyes. Antennas have sensory receptors which aid in monitoring the surroundings. The anterior part of the head has appendages that form biting and chewing parts. The mouthparts comprise the laboratoryrum (upper lip) as well as a pair mandibles, a pair maxillae, and a labium (lower lower lip). A median flexible lobe serving as a tongue (hypopharynx) is located in the mouth cavity, which is that is enclosed by the mouthparts. Best NEET Coaching Centre in Tinsukia
Thorax is composed of three parts that are mesothorax, prothorax as well as metathorax. The head is linked to the thorax via an extension of the prothorax referred to as neck. Each thoracic section bears two walking legs. One pair originates from mesothorax while the second pair is derived from metathorax. Forewings (mesothoracic) also known as tegmina, are opaque , dark and leathery. They cover the hind wings at rest. Hind wings are translucent, membranous and are utilized in flight. The abdomen of males and females is comprised of 10 segments. Females’ 7th sternum is shaped like a boat and, when combined with the 9th and 8th the sternum, forms a brood female genital pouch that’s anterior region is home to female gonopores as well as spermathecal pores as well as collateral glands. For males, the genital chamber or pouch is located in the back of the abdomen and is bounded dorsally by the 9th and 10th terga , and laterally by the 9th. It is home to dorsal anus, ventral male genital pore , and the gonapophysis.Best NEET Coaching Centre in Tinsukia
Males have a pair of small, thread-like anal styles that are absent from females. Both genders have the 10th segment is an array of joined filamentous structures known as the anal cerci.The alimentary canal that is present inside the body cavity divided into three parts that are foregut, midgut along with the hindgut (Figure 7.16). The mouth is opened into the pharynx which is a small tubular structure that leads to a small tube-like passage known as the an oesophagus. It then opens to the sac-like structure that is called crop that is used to store food. The crop is then followed by gizzards or proventriculus. It is composed of the outermost layer made of large circular muscles as well as a the cuticle inside, which is thick and thick. It forms six highly chitinous plates called teeth. Gizzard aids in grinding food particles. All of the foregut’s lining is with cuticle. A ring of blind tubules, referred to as hepatic or gastric caeca are found at the midgut-foregut junction that release digestive juice.
In the midgut’s junction and hindgut is another band of 100-150 yellow small filamentous Malpighian tubules. They aid in the removal of haemolymph-derived excretory substances. The hindgut is larger than the midgut, and it is divided into ileumand colon, and the rectum. The rectum extends out from the anus. The blood vascular system of cockroaches has an open form (Figure 7.17). Blood vessels aren’t developed and extend into the space (haemocoel). Visceral organs within the haemocoel are covered with the blood (haemolymph). The haemolymph consists of haemocytes and colourless plasma. The heart of cockroach comprises of a long muscular tube lying between the mid dorsal line of the abdomen and thorax. It is divided into funnel-shaped chambers that have an ostia to each side. The blood from sinuses flows into the through the ostia of the heart and gets then pumped to sinuses from the anterior side. The respiratory system is the trachea which are accessed via 10 sets of tiny holes known as spiracles on the lateral sides and the body.
Thin branches of tubes (tracheal tubes, which are subdivided into the tracheoles) transport oxygen from air to the various parts. Opening of the spiracles are controlled by sphincters. Gas exchange occurs within the tracheoles via diffusion. Excretion takes place through Malpighian tubules. Every tubule has been lined with glandular cells and ciliated ones. They take in nitrogenous waste and convert them to the uric acid that is then pumped out via the hindgut. This insect is known as”uricotelic. Additionally the fat body, the urecose glands, and nephrocytes assist in excretion. The nerve system that is found in cockroaches is comprised of segmentally arranged, fused the ganglia, which are joined by pairs of connectives that run longitudinally located on the ventral side. Three ganglia are located in the thorax and six lie in the abdomen. Nervous system in cockroaches is distributed across the body. The head has a small portion of a nervous system , and the rest of it is situated on the ventral (belly-side) portion of its body.
Now, you know that even if the head of an cockroach is taken away but it is still alive for a period of up to one week. The head area it is known as the the supra-oesophageal ganglion, which is responsible for nerves that go to antennae and compound eyes. In cockroaches, the sense organs are the eyes, antennae maxillary palps, labial palps, anal circles and so on. The eyes of the compound are located on the dorsal face in the skull. Each eye is made up of approximately 2000 hexagonal Ommatidia (sing. : ommatidium). By using a variety of Ommatidia, a cockroach will see multiple photographs of the object. This type of vision is referred to as mosaic vision, which has higher than sensitivity, but with less resolution. It is most common at the night (hence called night vision). Cockroaches are dioecious. Both genders have established reproduction organs (Figure 7.18). The male reproductive system is made up of two tests, one on each side of the abdominal segment 4th-6th. Best NEET Coaching Centre in Tinsukia.
From each testis emerges an elongated vas deferens that opens into the ejaculatory duct via the seminal vesicle. The ejaculatory tube opens into male gonopores located between the anus and ventral gonopores. The characteristic mushroom-shaped gland is located within the abdominal sections 6th-7th that functions as an additional reproductive gland. External genitalia are represented by male gonapophysis, or the phallomere (chitinous asymmetrical structuresthat surround men’s gonopore). The sperms are stored within the seminal vesicles, and are attached in bundles known as spermatophores that are released when copulation occurs. The female reproductive system is comprised of two big ovaries situated laterally within the 2nd-6th abdominal segments. Each ovary is made up by a set made up of eight tubules, or Orioles, which contain the developing ova. Oviducts in each ovary converge to form a single median oviduct (also known as vagina) which is able to open into the genital cavity.
Two spermatheca are located in the 6th segment that opens to the genital cavity. Sperms are transferred via spermatophores. The fertilized eggs are contained in capsules referred to as the oothecae. Ootheca is an dark reddish-blackish brown capsule, approximately 3/8″ (8 millimetres) long. They are dropped, or glued to a suitable surface generally in a crevice that has high relative humidity near an food source. Females typically produce 9-10 oothecae each one containing 14-16 eggs. The growth is P. americana can be described as paurometabolic. That means it develops through the its nymphal phase. Nymphs appear as adults. The nymph develops by moulting approximately 13 times until it reaches adult size. The next nymphal stage is characterized by wing pads, but only adults have wings. A variety of species of cockroaches live wild and are not of recognized economic significance yet. Certain species thrive in human-made habitats. They can be a nuisance since they destroy food items and cause a mess with their odory excreta.
They are able to transmit a range of bacteria by contaminating food materials. 7.5 FROGS Frogs can live on land as well as in freshwater. They belong to the class Amphibia of the phylum Chordata. The most popular species of frog throughout India is Rana Tigrina. They do not have a constant bodily temperature i.e. their body temperature fluctuates with the temperature of their environment. They are also known as poikilotherms or cold blooded. You may have noticed changes in the color of frogs as you are on grasses or on dry terrain. They can alter their colour to protect from predators (camouflage). This is referred to as mimicry. It is also known that frogs do not appear during the peak of summer and winter. During this time they take refuge in burrows deep to shield themselves from the extreme cold and heat. This is called winter sleep (aestivation) or winter sleeping (hibernation) and Morphology Have any of you been in contact with the skin of a the frog? The skin is soft and slippery because of Mucus. The skin stays in a moist state.Best NEET Coaching Centre in Tinsukia.
The color of the dorsal part of the body is usually olive green, with dark spots. On the side ventral, the skin is light yellow. The frog does not drink water but absorbs it through its skin. The body of a frog divided into trunk and head (Figure 7.19). The tail and neck aren’t present. In the upper part of one’s mouth is an array nostrils are visible. Eyes are bulging and protected by a nictitating membrane that shields them from the water. To either side of eyes the membranous tympanum (ear) receives audio signals. The forelimbs and hindlimbs aid in walking, swimming or leaping, and also in burrowing. The hind limbs are five digits, and are more muscular and larger than the fore limbs, which have four digits. Feet have webbed digits which aid in swimming. Frogs exhibit sexual dimorphism. Male frogs are distinguished through the presence of sounds creating vocal sacs, and copulatory pads on the first foot of the forelimbs which is absent from female frogs.
Anatomie The body cavity of frogs is home to various organ systems like respiratory, circulatory, digestive excretory, nervous and reproductive systems that have fully developed organs and roles (Figure 7.20). The digestive system comprises of the alimentary canal and the digestive glands. It is narrow because frogs are carnivores . therefore the length of the intestinal tracts is decreased. The mouth is opened into the buccal cavity which transforms into the central nervous system (brain and spinal cord) and a peripheral nervous system (cranial and spinal nerves) and an autonomic nerve system (sympathetic and parasympathetic). Ten pairs neuronal cranial nerves that originate in the brain. The brain is contained in the brain’s bony box (cranium). The brain is split into fore-brain, middle-brain and hind-brain. Forebrain is comprised of olfactory lobes. brain hemispheres that are paired and diencephalon that is not paired. The midbrain is characterized by the presence of two optic lobes. Hind-brain is comprised of cerebellum and the medulla oblongata. Best NEET Coaching Centre in Tinsukia.
The medulla oblongata is released into the foramen magnum. It is then absorbed into the spinal cord which is contained in the vertebral column. Frogs possess a variety of organs for senses, such as organs of contact (sensory papillae) as well as the taste (taste buds) as well as scent (nasal epithelium) and sight (eyes) as well as hearing (tympanum with internal ears). Eyes and the internal ears are well-organized structures, while others are just cellular aggregations that surround nerve ends. The eyes of a frog comprise two spherical structures located in the orbit of the skull. They can be described as simple eyes (possessing the same unit). External ear cannot be seen in frogs. Only one tympanum visible externally. The ear organ is one for hearing and also the organ of balancing (equilibrium). Frogs have well-organized both female and male reproductive system. Male reproductive organs comprise two yellowish oval tests (Figure 7.21) that are attached to the upper region of kidneys via the double fold of the mesorchium, also known as the peritoneum.
Vasa efferentia vary from 10-12 in size and originate from testes. They pass through the kidneys with their backs and then open into Bidder’s canal. Then, it connects to the urinogenital duct which flows out from the kidneys and flows to the Cloaca. The cloaca can be described as a small median chamber used to transfer the faecal matter, urine and sperms out to the outside. Female reproductive organs comprise two ovaries (Figure 7.22). Ovaries are located near kidneys. There is no connection between kidneys and ovaries. An oviduct that arises from the ovaries expands to the cloaca in a separate manner. Females who are mature can lay up to 3000 ova in a single cycle. Fertilisation is performed externally and occurs in water. The development process begins with a larval stage known as a the tadpole. Tadpole transforms into the adult. Frogs can benefit humans as they eat insects and guard the crops. Frogs are ecologically balanced since they are an essential link in the foodstuffs and the food web within the ecosystem.
In certain countries, the frog’s muscular legs are eaten by man.Cells tissues, organs, and organ systems are split up the task in a way which ensures the longevity of the entire body and show division of labor. A tissue can be described as a an assortment of cells, along with intercellular proteins that perform some or all of the functions within the body. Epithelia are tissue-like sheets that line the body’s surface, as well as the cavities of it, as well as ducts, and tubes. Epithelia are characterized by one surface that faces a body fluid or an external surroundings. The cells of epithelia are functionally and structurally connected by junctions. Different types of connective tissue are able to join, support and strengthen, shield and protect other tissues in the body. Soft connective tissue is made up of proteins and numerous cells placed in a solid substance. Blood, bone, cartilage and adipose tissue are the most specialized connective tissues. Bone and cartilage are both structural components. Blood is a tissue that flows that has transport capabilities.
Adipose tissue serves as a reservoir that stores energy. Muscle tissue that can contract (shorten) upon stimulation, aids in the movement of the body as well as particular organs. The muscle called skeltal is the tissue that is attached to bones. Smooth muscle is one of the components of the internal organs. The cardiac muscle forms the wall of the heart’s contractile muscles. Connective tissue encompasses all three kinds of tissues. The nerve tissue has the greatest influence over body’s response. Neurons are the primary components of nerve tissue. Earthworms, Cockroach and Frog show distinctive features of body structure. For Pheretima posthuma (earthworm) it is covered with cuticle. The body’s segments are similar, except for the 14th segment, the 15th and 16th that are large and dark, creating the clitellum. A ring of chitinous setae can be found in every segment. They aid in locomotion. On the ventral face, spermathecal openings are found between the grooves between 5 and 6, 6 , 7, 7 and 8, and 9 segments. Best NEET Coaching Centre in Tinsukia
Genital pores of females are visible on the 14th segment, and male genital pores are present on the 18th segment. It is an small tube composed of mouth, the buccal cavity and pharynx stomach, gizzard and anus. Blood vascular system of the closed type and has valves and heart. The nerve system is represented by ventral nerve chord. Hermaphorodite is the term used to describe earthworms. Two pairs of testes are present within the 11th and 10th segments and 11th segment, respectively. Two ovaries are located on the 12th the 13th septum intersegmental. This is an animal that has protandrous characteristics that has cross-fertilisation. Fertilisation and growth occur in the cocoon that is produced from the glands that make up the clitellum. Its body Cockroach (Periplaneta americana) is covered by a chitinous exoskeleton. It is separated into thorax, head and abdomen. Segments have joined appendages. There are three thorax segments with each one bearing the legs of a walking pair.
Two pairs of wings are visible two pairs on 2nd and 3rd segments. There are ten segments within the abdomen. The alimentary canal is well-developed with a mouth enclosed by parts of the mouth including a pharynx, an oesophagus and gizzard. the hindgut, midgut and anus. Hepatic caecae can be found at the midgut-foregut junction. Malpighian tubules are located at the intersection of hindgut and midgut, and aid in the excretion process. The salivary gland is located close to the crop. Blood vascularization of the open type. Respiration is accomplished through a the tracheae’s network. Trachea opens outwards with spikes. The nerve system is represented by ventral and segmentally-arranged ganglia as well as nerve cord. Testes are found in the 4th-6th segments and ovaries within the 2nd-6th segments. Fertilisation occurs internally. Females produce 9-10 developing embryos bearing a tootheca. After the rupture of one ootheca sixteen babies, referred to as Nymphs, emerge. It is the Indian bullfrog Rana Tigrina is the most common frog in India.
The body is covered with skin. Mucous glands reside within the skin, which are extremely vascularised and aids to breathe in water and on land. The body can be divided into trunk and head. There is a muscular tongue that is bilobed near the tip and used in the capture of prey. The alimentary canal is comprised of stomach, oesophagous and the rectum and the intestine, which are opened to the cloaca. The major digestive glands include the liver and the pancreas. It is able to breathe in water through the skin or via lungs on the land. Circulatory system is closed by one circulation. The RBCs have nucleated. The nervous system is divided into peripheral, central and autonomic. The organs of the urinogenital system include kidneys as well as the urinogenital ducts that open in the cloaca. Female reproductive organs comprise composed of a pair of tests. The female reproductive organ comprises an ovaries pair. Females can lay 2500-3000 Ovaries at once. The development and fertilization are external. When eggs are born, they transform into tadpoles which transform into frogs. Best NEET Coaching Centre in Tinsukia.
The genomes of three organelles of eukaryotes, including mitochondria, chloroplasts, and apicoplast have been thoroughly studied since their discovery in the 1960s and later. In 1995, and now in 2017, complete genomw sequences are accessible for mitochondrial genomes of more than 8000 species of animal or plant and chloroplast genomes for more than 800 species of plants, and apicoplast genomes for more than 20 parasitic species of apicomplexans (as at the time of writing in). This chapter will will discuss the arrangement of mitochondrial chloroplast, mitochondrial and apicoplast genomes.Organellar genomes found in mitochondria and chloroplasts differ in dimensions, shapes and numbers per cells. Similar variation is not known until now for apicoplasts, perhaps because a significant number of apicoplast genomes has not been investigated to date far.The organeller genomes appear easy to organize and are tiny in dimensions (Table 42.1). The size of the mitochondrial genome varies significantly between different species with a range of the size of 6kb found in Plasmodium (malarial parasite) to 2500 kb for the melon (Cucumis Melo).
The range of sizes of mitochondrial genomes are, however, not related to variability in complexity of the organisms (Fig. 42.1). For instance, the majority of multicellular animals have tiny mitochondrial genomes that have the genome being compact and genes located close to each other with very only a small distance between them. This is illustrated by the humans’ mitochondrial genome (Fig. 42.2) It is just 16,569 Bp (~16.6 Kilobytes) in size. Contrary to this, lower eukaryotes, like S. cerevisiae (Fig. 42.3) as well in flowering plants possess larger mitochondrial genomes that contain numerous genes, which are intron-rich. In humans both twin strands of double-stranded mitochondrial DNA are classified by their light (H-strand) and light (H-strand) as well as lighter strand (L-strand) due to the fact that the density of each differs when measured using a CsCl densities gradients. Organization of Genetic Material 3. Organellar Genomes (Mitochondrion, Chloroplast and Apicoplast). Best NEET Coaching Centre in Tinsukia.
(In an analysis of mitochondrial genomes, the chloroplast and apicoplast genomes have much less than mitochondrial genomes in terms of size. The chloroplast genome spans 120 kb for pea to 200 kb within Chlamydomonas as well as the genomes for apicoplasts range between 27 kb Babesia microti up to ~39.6 km2 in Theileria Parva (Table 42.1). The majority of chloroplast genomes have the same structure as that in Figure 42.4 for the rice chloroplast genome. In the same way, all apicoplast genomes feature a structure similar to that illustrated in figure 42.5 which is for Plasmodium falciparum. However the size of various DNA molecules in the chloroplast can differ and, in the case of many species of eukaryotes larger molecules share space with smaller molecules , which are subcomponents from the bigger multigenome molecules. The differences in size of Fig. 42.1. Mitochondrial genomes, showing variation in size. To provide a comparison, the mitochondria-like proteobacteria from the Rickettsia group (Reclinomonas americana) is also presented. The genome of the apicoplast within a particular species, and in the same cell hasn’t been published, but could be revealed when genomes get sequenced.
The shape of the genome (DNA Molecules) The mtDNA and the cpDNA were initially thought as circular (like bacteria’s chromosomes) and all linear DNA molecules found were actually believed to be fractured circle theories (‘broken circle theories’). In both bacteria and organelles of cells, the idea of circularity was founded upon the fact that their maps were circular but without knowing that genetic map circularity may also be the result of linear head-to tail concatamers. For more than thirty years (1970-2000) the theory of the broken circle stood as a significant obstacle in the search for a linear version of mtDNA/cpDNA. The apicoplast DNA is circular with some exceptions. In the 1990s, and during the early stages of the present century (2000-2004) It was found that a substantial part of the in vivo mtDNA and CpDNA in a variety of (and possibly the majority of) species of eukaryotes is linear in structure and only a tiny portion of it being circular DNA. Linear mtDNA was discovered in some algae (e.g., Chlamydomonas) as well as a number of species of fungi (including yeasts) and plants (e.g. Chenopodium, for instance) and several protozoa (e.g., Paramecium) as well as some Apicomplexans (e.g., Plasmodium).
Similar to this, linear cpDNA has been discovered in maize. In some apicoplast genomes, too linear DNA has also been reported..Number of Genomes Per Organelle The amount of genomes within an organelle varies. Many chloroplasts or mitochondria are present within a single cell, thereby increasing by many times the number of organellar genes within cells (Table 42.2). Table 42.2. The proportions of organellar DNA in various tissues and cells. Organelle DNA or Tissue molecules Organellar DNA and the organism Cell Type (genomes) for each organelle cell (as percent of total cell DNA) 1 Mitochondrial DNA Rat Liver 5-10 000 1 yeast Vegetative 2- 50 1-50 Frog Egg 5-10-107 99 I Chloroplast DNA Ch Vegetative 80 1 7 Maize Leaves 20-40 20-40 15. Figure. 42.5. Apicoplast genome of Plasmodium falciparum. Genes are identified by arrows, which indicate which direction they are in transcription. Broken lines represent functional regions; the ribosomal RNA genes are identified with the letters LSU (large subunit) and SSU (small subunit) and tRNA is indicated with single letters that indicate their amino acids. Best NEET Coaching Centre in Tinsukia.
In the case of humans, each cell is home to 800 mitochondria and each mitochondrion is home to more than 10 genomes that are identical, meaning that every cell has around 8000 mitochondrial genomes. In yeast, the number of genomes in each mitochondrion is approximately 100, there are less mitochondria in each cell, thereby making the number of genomes in a cell close to the number found in the human body (~5000). For plants, the amount that have chloroplast genomes for each cell about 5000, however, for photosynthetic microorganisms, such as Chlamydomonas the number is just 1000 genomes per cell. Apicoplasts are believed to have each one of the genomes, however, future research could reveal that there is multiple genomes for each Apicoplast, and even more than one apicoplast per cell. REPLICATION OF ORGANELLAR DYNAMICS Several methods for the replication of organellar DNA were proposed over the years. One of the most popular models is the model which involves the initial formation of D-loops then the development of intermediate q-shaped structures and, finally, the formation of rolling circle (see chapter 39).
This model was later questioned, and recombination-dependent replication (RDR) has been proposed for both mtDNA and cpDNA (for details, consult Chapter 30, and explore at the internet). Similar mechanisms of replication might occur in apicoplast DNA as well. Genes found in ORGANELLAR Genomes Organellar genomes are smaller than nuclear counterparts. This means that the gene content within these organellar genomes are smaller and that is the situation. Mitochondrial genomes exhibit greater variability in gene content. Mitochondrial genomes exhibit greater variation in the number of genes ranges from 5 for malaria parasite (P. falciparum) to 92 for the protozoan Reclinomonas americana (Table 42.3). Each mitochondrial genome contains genes for noncoding rRNAs , as well as at least one of the proteins that comprise the respiratory chain with the latter being the principal biochemical component that the mitochondria possess. The mitochondrial genomes that are gene-rich contain tRNAs, the ribosomal proteins, and other proteins that are involved in transcription and translation.
They also contain proteins that are that are involved in the transport of other proteins to the mitochondrion, from the cytoplasm around it (Table 42.3 Figure. 42.6). There is also a large number in unidentified read frames (URFs) which are protein-coding genes that have no known products. The structure of the mitochondrial genomes of humans is illustrated in the figure 42.7. What makes mitochondrial genomes greater in plant life? The mitochondrial genome is much bigger in plants (150 1 kb to 2500 km) as compared to animals (6 70 to km). It has been demonstrated that the additional DNA found in mitochondria of plants is “junk DNA”. In many species of plants (e.g., Zea mays = maize) the cytoplasmic male and female sterility is also determined via mitochondrial DNA. Fig. 42.7. The structure of the the human mitochondrial genome. The mitochondrial genome is bursting with interesting aspects. The mitochondrial genome is also home to some surprising aspects including the following: (i) there are only a only a few DNA regulatory sequences the majority of regulatory sequences are part of the other coding sequence (ii) there are only 22-26 genes that encode 22 tRNAs have been identified in mitochondria in contrast to the 30 tRNAs in the cytosol as well as the chloroplasts. Best NEET Coaching Centre in Tinsukia
(iii) with at most 4 of 64 codons the genetic code of mitochondria differs not just from the chloroplasts and the cytosol as well as between them (for more details, refer to Chapter 46 of “The Genetic Code”). The majority of chloroplast genomes have the identical set of genes. The majority of chloroplast genomes contain identical sets of 110-120 genes, that encode for rRNAs and tRNAs as well as ribosomal protein and photosynthesis-related proteins (see the table 42.4). In the majority of plants, cpDNA can be identified in the absence of the three regions in figure 42.8: (i) two inverted repeats (IR) which are 10-24 kb in length and carrying Ribosomal RNA genes (ii) an extremely shorter single copy (SSC) sequence, which is 18-20kb long and (iii) an extended one duplicate (LSC) sequence. A list of 110 genes encoded in cpDNA are presented. Organellar Genes contain Introns. In contrast to human mtDNA, a few mitochondrial genes from fungal and plant species contain intronsthat need to be removed from RNA transcripts in order to process. Introns have been discovered in at least 20 genes in the chloroplast.
Introns could also be found in Apicoplast genes. Introns are present in these genes is quite surprising as they aren’t common in bacteria. They are believed to have spawned chloroplasts and mitochondria, however introns are possible in some genes belonging to red algae, thought to have spawned the apicoplasts. The yeasts have the exact mitochondrial gene might have an intron within one strain but not in other strains. Introns that are inactive could be akin to Transposable Elements (TEs). In certain instances introns were found in the same place within the same gene in the yeast mitochondrial genomes, Aspergillus as well as Neurospora, which suggests that they have a common source. These findings also suggest that introns are of been around for a long time and were not present in the genomes of bacteria, but preserved in some nuclear and organellar genomes of Eukaryotes. ORGANELLAR PROTEINOR SYNTHESIS AND SEMI-AUTONOMY It is known the genome of organella lists just a handful of proteins that are found in the organelle however, it does not include every one of them. Best NEET Coaching Centre in Tinsukia.
Other proteins are encoded by nuclear genes, and synthesized within the cytoplasm, then transferred through the organelle. If cells have mechanisms to transport proteins into mitochondria and chloroplasts, why do we there aren’t all organelle proteins identified in the genome of nuclear cells? We don’t have an answer that is convincing to this question. However, there is a suggestion that at the very least certain proteins encoded from organellar genomes incredibly hydrophobic, and are not able to pass through the membranes which surround mitochondria and chloroplasts, therefore cannot be transported into the organelle through the cells. The only way the cell is able to get these proteins into organelles is by putting the organelles themselves. Eukaryotic organelles have a resemblance to prokaryotes when it comes the process of protein production. We now know that all three organelles of eukaryotes (mitochondrion the apicoplast, chloroplast and mitochondrion) contain all four essential components to be autonomous, which includes DNA, DNA polymerase the RNA polymerase, and a protein synthesizing system. Best NEET Coaching Centre in Tinsukia.
A majority of these elements and the mechanisms for synthesis of proteins within the three organelles are similar to the prokaryotes. For example, RNA polymerase in mitochondria is similar to that found in some bacteria called bacteriophages (single subunit) and RNA Polymerase in apicoplasts as well as chloroplasts is similar to that found in E. coli. The mRNAs of these three organelles do not have the 5C/cap (5Ccap is the most common to all eukaryotic mRNAs) and are synthesized in the form of an mRNA that is polycistronic (as as in E. coli). Both strands of the mtDNA gene are transscribed. Human cells have both the strands mtDNA are transscribed at the same time through a single promoter region on each strand but in opposing directions. This means that two massive RNA molecules are generated. The transcripts produced by the heavy the strand (H-strand) are extensively processed to give two rRNAs and tRNAs, with the majority being contain tRNAs, and 10 poly-A that contains the mRNAs (no cap 5′ is observed).
The transcripts of the light strand (Lstrand) are processed to yield only two poly-As and one tRNA with an mRNA (remaining 95% of the L-strand transcripts are destroyed). The three organelles all contain 70S ribosomes that resemble those found in bacteria, but different from the those found in cytoplasm, which are 80S. (consult chapter 49). The higher plant species have chloroplast ribosomes constitute 50% of cells’ of ribosomes. Organellar ribosomes have a similarity to the ones found in prokaryotes with the following attributes: (i) use of N-formyl methionine to initiate amino acids, (ii) susceptibility to chloramphenicol, lincomycin , and spectinomycin that block protein synthesis and (iii) the basic structure of their proteins and RNA (consult the chapter). ORGANELLAR PROTEOM Organellar proteomes have been examined in greater detail over the last thirty years (1990-2017). In each instance the organellar proteome comprises two types that comprise proteins. (i) protein encoded in the nuclear genome synthesized in the cytoplasm , and later transferred to the organelle as well as (ii) protein encoded within the organellar genome , and synthesized in the organelle itself through it’s protein-synthesis mechanism.
In 2010, about 300,000 mitochondrial proteins and around 120,000 chloroplast proteins were found on GOBASE. GOBASE database. The number of proteins available in the database must be significantly higher. But the total amount of proteins that are available at any time in an organelle has to be a small number and 100-500 of them could have been encoded in their genome. The proteins found within an apicoplast are thought to be only 500 and around 30 proteins (excluding the ribosomal proteins) are produced by the Apicoplast. Like chloroplasts, apicoplasts are not photosynthesis-producing organelles. But, it does have additional plastic functions, including the synthesis of fatty acids as well as heme synthesis and isoprenoidsynthesis. These pathways produce products that are vital for parasites, and needs these proteins to live. ORGANELLAR Gene/Proteome Databases Databases that provide information about genomes and proteomes have been designed. Best NEET Coaching Centre in Tinsukia.
For instance, GOBASE database was developed by the University of Montreal, Canada and contained information about mitochondrial/chloroplast genomes and proteomes. In the year 2010 the GOBASE version 25 (Jume 2010) included over 1,000,000,000 mitochondrial genomes (including more than 300,000 proteins) and more than 300,000 chloroplast sequences (including more than 120,000 proteins). It was however, the last version of the database, as the database was not able to be maintained later due to a lack of funding. A separate database for chloroplast genomes is ChloroplastDB (http://chloroplastcbio.psu.edul) that was launched in 2005. The database includes information on the genomes of all plastids that have been fully sequenced that contain DNA, protein and RNA sequences as well as gene places and RNA editing sites. The information on the mitochondrial genome and the chloroplast genome are accessible on NCBI web site in the form of GenBank records. On this website you can find a list that is updated on a day to day basis for mitochondrial as well as the plastid genomes which are fully sequenced.
In the early part of 2014, this list had the mitochondrial genomes of 6000 and more than 200 plastid genomes which were fully sequenced at the time. An mitochondrial protein database can be found in MITOP it was developed in 1998 by the University of Munich in Germany. The database offered a complete listing of mitochondrial proteins for mice, yeast, human as well as the nematode-worm (C. C. elegans) as well as that fungus Neurospora crassa. Then, in 2004, MitoP2 database (http www.mitop.de www.mitop.de) was established in the form of an expansion to MITOP to further integrate the details on mitochondrial protein and its molecular function for humans, yeast and mouse. MitoProteome is a different database that provides details on mitochondrial proteomes. MitoP2, MitoProteome, and the HMPDb (a mitochondrial protein database that is only for humans) will prove to be extremely valuable to further research on the mitochondrial proteomes, specifically in order to discover the proteins and genes that cause frequent and uncommon mitochondrial disorders in humans.
Additional information on Chloroplast and mitochondrial genomes, as well as proteomes can be found at the NCBI website. Mitochondrial Diseases In the past 15 years (1990 from 1990) various mitochondrial deficiencies have been discovered to be related to disorders in humans as well as mice (used as models). Around fifty pathogenic mtDNA base changes and rearrangements (deletions and deletions) have been linked to various degenerative illnesses. Other disorders have been associated with problems with mitochondrial bioenergetics, or biogenesis. These are associated with mutations in nuclear genes. The three major roles that mitochondria play (covered by the process of oxidative (phosphorylation) as well as the deficiencies that are related to diseases that affect mitochondria, are: (i) energy production, (ii) generation of reactive oxygen species (ROS) and (iii) control of programmed cell death , or the process of apoptosis. Evolutionary Origin of MITOCHONDRIA and PLASTIDS Monophyletic Origin of Mitochondrion From a Free living Proteobacterium.
Mitochondria are remarkably similar to bacteria in a variety of ways they are thought to originate from a variety of bacteria that belong to the rickettsial subdivison of the a-proteobacteria. In 1997-99, the complete DNA sequences from bacteria-like mitochondrial genome (e.g., Reclinomonas americana (69,034 Bp) and the mitochondria-like genome of eubacteria (e.g., Rickettsia prowazekii;1,111,523 bp) were analyzed and compared. This strongly suggests that all of the mtDNAs that exist today were derived from one protomitochondrial genease which, in itself, would have derived from a eubacterial genomic (monophyletic origin, not polyphyletic). The genomes of both species differ greatly on the dimensions of mtDNA as well as the gene count (Figs. 42.1, 42.6). Based on this data mtDNAs are classified into two kinds: (i) ancestral type with a large number of genes, like R. americana and (ii) related type with significant gene loss the divergence of the non-coding and coding DNA sequences, a brand new mitochondrial DNA code and RNA editing and more. (e.g. animals as well as fungal mtDNAs).Best NEET Coaching Centre in Tinsukia
A serial endosymbiosis hypothesis is also being proposed to explain the origins of the mitochondria and the nuclear genome. According to this theory, it’s presumed that, in the first stage, the nuclear genome for the host was created by the fusion of archaebacterial and eubacterial partners, and that in the second stage the mitochondrion was incorporated as an Symbiont. The eukaryotes that are called asArchezoa are devoid of mitochondria. It is thought that the eukaryotes that lack mitochondria started out as primitive forms and that mitochondria were introduced into in later on into the cell. The previous hypothesis has recently (1997between 1997 and the year 2010) been challenged . It is thought that the eukaryotes gained the nucleus as well as mitochondria at the same time in addition to the fact the formation of Archezoa (lacking mitochondria) is likely to have been because of the losing mitochondria. This theory was substantiated by the fact that mitochondrial genes are present in a variety of proteins with bacterial roots are present inside the genome of the the amitochondriate Archezoa and inside the organelle hydrogenosome recently found in protists deficient of mitochondria.
This is known as the ‘hydrogen hypothesis’ because it is based on chimeric origins of the nucleus of eukaryotic cells due to the symbiotic connection between (i) the Eubacterium (a proteobacterium, also known as the Symbiont) that produces H2 as the final product of anaerobic metabolism , and (ii) hydrogen – needing an autotrophic archaebacterium (the host). This suggests the possibility of simultaneous ancestry of the ancestor of the eukaryotic cells and their mitochondrion (Fig. 42.9). The Evolutionary Origins of Plastids from Cyanobacteria and “Endosymbiotic Gene Transfer” The comparison of chloroplast sequences from a variety of species, with those from cyanobacteria indicated that plastids (particularly the chloroplast) were derived from cyanobacteria. This was the case because of an initial endosymbiosis that was followed by extensive ‘endosymbiotic genetic transfer from the cyanobacterium the host nucleus of the eukaryotic host (for specifics, refer to chapter 7). A thorough study of the chloroplast genomes in eukaryotes has revealed that chloroplast genomes have both prokaryotic as well as eukaryotic traits. So, the notion that chloroplasts are remnants of prokaryotic genomes that have been entrapped can be a misunderstanding. Best NEET Coaching Centre in Tinsukia
A few of the ways in which chloroplasts have a resemblance to prokaryotes and where they differ are as are as follows. (a) Similarities between chloroplasts and prokaryotes. (i) the ribosomes measure 70S and larger in both cases. (ii) The RRNA genes, as well as some tRNA genes possess a high levels of homology according to sequence homology. (iii) In the majority of chloroplast genes that precede the initiation codon , AUG there are binding sites for ribosomes and the sequences bear striking resemblances to the ‘Pribnow box of bacteria (consult Chapters 47) (iv) There is a sequence overlap between certain chloroplast genes, which is which is a characteristic that is found in prokaryotes. It is not possible for this to be due to economics as non-coding sequences are also present in chloroplasts. (v) It is possible to find a commonality between the RNA polymerases in Chloroplasts, and Prokaryotes. For example, in Chlamydomonas reinhardii this enzyme can be sensitive to rifampicin, and has the S (sigma) similar polypeptide. There is proof of the homology the b and subunits of bC/ that are part of E. coli RNA polymerase and the subunits that are part of C. reinhardii chloroplast RNA polymerase. (vi) Protein synthesizing in chloroplasts could be blocked by chloramphenicol like in bacteria, as only 70S ribosomes can be sensitive for this medication.
Cycloheximide doesn’t inhibit the synthesis of proteins in chloroplasts like it does in cytoplasm (80S the ribosomes) of Eukaryotes. (vii) The process of initiating protein synthesis occurs via formyl methionyl-tRNA, both in prokaryotes and chloroplasts. (b) The differences between the prokaryotic and chloroplast genomes. (i) The chloroplasts the genome is split into several genes (e.g. the rRNA proteins and genes found in the chloroplasts of C. reinhardii proteins in chloroplasts from Euglena and tRNA genes of several chloroplasts in higher organisms) The introns from these genes split are into three categories and differ from these nuclear gene sequences of the eukaryotes (consult the chapter on Chapter 35). (ii) Chloroplast DNA sequences can be used to encourage self-replication, a feature that is not present in prokaryotes. (iii) The presence in short repeating elements in a number of but the chloroplast genomes are not identical. are an eukaryotic characteristic too. (c) Comparative genomics.In the prior part, we reviewed the monophyletic origins of endosymbiotic the mitochondria of proteobacteria.