Biology Textbook - Kerala PDF

The National Anthem Jana-gana-mana adhinayaka, jaya he Bharatha-bhagya-vidhata. Punjab-Sindh-Gujarat-Maratha Dravida-Utkala-Banga Vindhya-Himachala-Yamuna-Ganga Uchchala-Jaladhi-taranga Tava subha name jage, Tava subha asisa mage, Gahe tava jaya gatha. Jana-gana-mangala-dayaka jaya he Bharatha-bhagya-vidhata. Jaya he, jaya he, jaya he, Jaya jaya jaya, jaya he! Pledge India is my country. All Indians are my brothers and sisters. I love my country, and I am proud of its rich and varied heritage. I shall always strive to be worthy of it. I shall give respect to my parents, teachers and all elders and treat everyone with courtesy. I pledge my devotion to my country and my people. In their well-being and prosperity alone lies my happiness. State Council of Educational Research and Training (SCERT) Poojappura, Thiruvananthapuram 695012, Kerala Website : www.scertkerala.gov.in e-mail : [email protected] Phone : 0471 - 2341883, Fax : 0471 - 2341869 Typesetting and Layout : SCERT Printed at : KBPS, Kakkanad, Kochi-30 © Department of Education, Government of Kerala Dear Students, You will be curious to know how we sense and respond to our environment through the windows of knowledge. You will certainly be surprised to learn how the human brain, nerves and hormones act together to co-ordinate the activities of the human body and the genetic secrets behind the uniqueness of living species, the recent developments in the field of Biotechnology which leads to the progress in human life. The path of evolution related to the origin of humans on earth has also been included in the book. How the wonder machine that is, the human body prevents diseases, and the precautionary measures to be followed to keep diseases away are also mentioned here. Reminders on avoiding accidents caused by carelessness, incorporated with learning activities will be beneficial in your daily life. The student’s role is pivotal in the process of construction of knowledge. This Science textbook is only a resource in the learning process. Teachers and supplementary materials will help you in the creation of knowledge. 'Samagra', the education portal and technology enabled Q R Code printed textbooks would definitely make your learning activity in classrooms easy and joyful. The National Skills Qualifications Framework, the current relevance of Disaster Management and the possibilities of I.C.T. have also been considered while modifying the textbook. Let all this be beneficial for you in the learning of Science by joyfully participating in life related learning experiences that impart knowledge and happiness. Love and Regards, Dr. J.Prasad Director SCERT, Kerala CONSTITUTION OF INDIA Part IV A FUNDAMENTAL DUTIES OF CITIZENS ARTICLE 51 A Fundamental Duties- It shall be the duty of every citizen of India: (a) to abide by the Constitution and respect its ideals and institutions, the National Flag and the National Anthem; (b) to cherish and follow the noble ideals which inspired our national struggle for freedom; (c) to uphold and protect the sovereignty, unity and integrity of India; (d) to defend the country and render national service when called upon to do so; (e) to promote harmony and the spirit of common brotherhood amongst all the people of India transcending religious, linguistic and regional or sectional diversities; to renounce practices derogatory to the dignity of women; (f) to value and preserve the rich heritage of our composite culture; (g) to protect and improve the natural environment including forests, lakes, rivers, wild life and to have compassion for living creatures; (h) to develop the scientific temper, humanism and the spirit of inquiry and reform; (i) to safeguard public property and to abjure violence; (j) to strive towards excellence in all spheres of individual and collective activity so that the nation constantly rises to higher levels of endeavour and achievements; (k) who is a parent or guardian to provide opportunities for education to his child or, as the case may be, ward between age of six and fourteen years. Certain icons are used in this textbook for convenience For further reading (Evaluation not required) Let us Assess Extended Activities Observe the picture. Children and other organisms have a variety of experiences. What are they? a child tasting a mango. a snail withdrawing its body into the shell when it is touched. Biology - X What are the factors to which children and other organisms respond here? taste touch The senses that evoke responses in organisms are called stimuli. Do we recognise stimuli only from our immediate surroundings? Hunger and thirst are stimuli formed inside the body, aren't they? Find out more examples for such stimuli. How does the body receive stimuli? Observe illustration 1.1 and form inferences. Illustration 1.1 Specialized cells that receive stimuli Brain Spinal cord Nerves There are specialized cells in the sense organs and other parts of the body to receive stimuli. These cells are known as receptors. They receive stimuli and generate suitable impulses. Normally, responses occur when the impulses generated by the receptors on receiving the stimuli reach the brain. The nervous system controls and co-ordinates these actions. Analyse figure 1.1 and find out the major parts of the nervous system. Figure 1.1 Nervous system 8 Biology - X Neuron Neuron or nerve cell is the basic structural unit of the nervous system. Like all other cells, the neuron has a cell membrane, cytoplasm and nucleus. Analyse illustration 1.2 and tabulate the main parts of a neuron, its characteristics and function. Write them down in the Science diary. Dendrite Branches of Dendron. Part that receives impulses from adjacent neuron. Dendron Short filament from the cell body. Carries impulses from dendrites to the cell body. Schwann cell Encircles the axon. Cytoplasm Nucleus Cell body Axon Longest filament from the cell body. Carries impulses from the cell body to outside. Axonite Branches of axon. Carries impulses to the synaptic knob. Synaptic knob Tip of axonite. Secretes neurotransmitter. Illustration 1.2 Neuron - Structure and function Axons of most of the neurons are repeatedly encircled by myelin, a membrane containing lipid. This is called myelin sheath. Analyse illustration 1.3 and the description. Find out the characteristics and significance of myelin sheath and prepare a note on the basis of the indicators given. Axon Myelin sheath Schwann cell Oligodendrocyte Illustration 1.3 Formation of myelin sheath 9 Biology - X Oligodendrocytes and Schwann cells Oligodendrocytes and Schwann cells provide protection to neurons. An oligodendrocyte constructs myelin sheath by covering the different axons simultaneously or by covering the different parts of the same axon repeatedly. Myelin sheath made up of Schwann cells are seen in the axons in nerves. A Schwann cell encircles the axon repeatedly. Nerve is a group of axons. Myelin sheath in the nerves is formed of Schwann cells. Myelin sheath in the brain and the spinal cord is formed of specialized cells called oligodendrocytes. The myelin sheath has a shiny white colour. The part of the brain and the spinal cord where myelinated nerve cells are present in abundance is called white matter and the part where non-myelinated nerves cells are present is called grey matter. The major functions of the myelin sheath are to provide nutrients and oxygen to the axon, accelerate impulses, act as an electric insulator and protect the axon from external shocks. Indicators Formation of myelin sheath. Grey matter, white matter. Functions of myelin sheath. Generation and Transmission of Impulses Figure 1.2 a Stimulus Figure 1.2 b Figure 1.2 c 10 The nervous system manages control and coordination through impulses. How are these impulses generated and transmitted through neurons? Analyse the given figures (1.2 a, b, c) on the basis of the description and the indicators, and arrive at your own inferences. The outer surface of the plasma membrane of the neuron is positively charged and the inner surface is negatively charged. This is due to the difference in the distribution of certain ions (Figure 1.2 a). Biology - X When stimulated, the distribution of ions in that particular part changes and hence the inner surface becomes positively charged and the outer surface becomes negatively charged (Figure 1.2 b). This momentary charge difference stimulates its adjacent parts and similar changes occur there too. As this process proceeds, (Figure 1.2 c) impulses get transmitted as electric charges. Nerve impulses are messages transmitted through the neurons. Indicators Charges on either side of the plasma membrane. Change in the charges of ions when stimulated. Transmission of nerve impulse. Synapse Impulses generated in the receptor cells reach the brain. The brain analyses it and gives direction for proper response. To make this possible, the impulses formed in a neuron are to be transmitted to other neurons and associated cells. How does this become possible? Analyse illustration 1.4 and 1.5 given below, and the description. Prepare a note, based on the indicators and your analysis. Synapse Synaptic knob Electric impulse Illustration 1.4 Synapse Neurotransmitter Dendrite Electric impulse Synaptic cleft Synapse is the junction between two neurons or a neuron and a muscle cell or a neuron and a glandular cell. When electric impulses from the axon reach the synaptic knob, certain chemical substances are secreted from there to the synaptic cleft. These chemical substances are called neurotransmitters. They stimulate the adjacent dendrite or cell and new electric impulses are generated. Acetylcholine and dopamine are examples of neurotransmitters. Synapse helps to regulate the speed and direction of impulses. 11 Biology - X Nerve cell Muscle cell Glandular cell Illustration 1.5 Different types of synapses Indicators Structure of synapse. Transmission of impulses through synapse. Significance of neurotransmitter. Different types of synapses. Different types of Neuron On the basis of the direction of impulse, neurons can be classified into sensory neurons and motor neurons. Sensory neurons carry impulses to the brain and spinal cord. Motor neurons carry impulses from the brain and spinal cord to various parts of the body. Nerve Nerves Axon Connective tissue Figure 1.3 Cross section of a nerve Nerves and their peculiarities You know that nerves are group of axons or nerve fibres. They are covered by connective tissue (Figure 1.3). Nerves are classified into three on the basis of their functions. Analyse table 1.1 and prepare notes in your Science diary. Functions Sensory nerve (formed of sensory nerve fibres) carries impulses from various parts of the body to the brain and the spinal cord. Motor nerve (formed of motor nerve fibres) carries impulses from brain and spinal cord to various parts of the body. Mixed nerve (formed of sensory nerve fibres and motor nerve fibres) carries impulses to and from the brain and spinal cord. Table 1.1 Nerves and their functions 12 Biology - X Nervous System The nervous system consists of two parts, namely the central nervous system and the peripheral nervous system. Analyse illustration 1.6 and complete the flow chart. Brain Cranial nerves (12 pair) Spinal cord Spinal nerves (31 pair) Illustration 1.6 Central nervous system Peripheral nervous system Nervous system Central nervous system Brain.......................................................... Spinal nerves Brain Brain is the central part of the nervous system. Based on the indicators, analyse figure 1.4 and the description, understand how the brain gets nutrition and protection. Make notes in your Science diary. The brain is protected inside the skull. It is covered by the meninges, a three-layered membrane. The cerebrospinal fluid is filled within the inner membranes of meninges and the ventricles of the brain. Skull Layers of Meninges Figure 1.4 Meninges 13 Biology - X The cerebrospinal fluid formed from the blood is reabsorbed into the blood. The functions of the cerebrospinal fluid are to provide nutrients and oxygen to the tissues of the brain, regulate the pressure inside the brain and to protect the brain from injuries. Indicators Protection of the brain. Nourishment of the brain. The different parts of the brain control and coordinate all life activities. Analyse illustration 1.7 showing the structure of the brain and list the characteristics and functions of each part. Cerebrum the largest part of the brain. numerous fissures and folds are seen. The grey coloured outer part of cerebrum is called Cortex and the white coloured inner part is called Medulla. centre of thought, intelligence, memory and imagination. evokes sensations. controls voluntary movements. Thalamus situated below the cerebrum. acts as relay station of impulses to and from the cerebrum. analyses impulses from various parts of the body and sends the important ones to the cerebrum. Cerebellum the second largest part of the brain. seen behind the cerebrum as two flaps. fissures and grooves are present. coordinates muscular activities and maintains equilibrium of the body. Medulla oblongata the rod shaped medulla oblongata is seen below the cerebrum, located near the cerebellum. controls involuntary actions like heart beat, breathing etc. Hypothalamus situated just below the thalamus. plays a major role in the maintenance of homeostasis. Illustration 1.7 Structure and function of the brain 14 Biology - X Aren't you convinced of the importance of the brain? Discuss the necessity of wearing helmets while riding two wheelers. Spinal Cord The spinal cord is the continuation of the medulla oblongata. On the basis of the indicators, analyse illustration 1.8 and the description and prepare notes in your Science diary. The Spinal Cord within the Vertebral Column The spinal cord of a new born baby extends upto the tip of the vertebral column. But in adults, it is seen only upto the middle of the vertebral column. This is because the spinal cord does not grow in proportion to the growth of the vertebral column. The spinal cord is protected inside the vertebral column. Like the brain, the spinal cord is also covered by meninges. The central canal seen in the centre of the spinal cord is also filled with cerebrospinal fluid. In the spinal cord, white matter is seen outside and grey matter is seen inside. Central canal Dorsal root Grey matter White matter Ventral root Illustration 1.8 Cross section of the spinal cord There are 31 pairs of spinal nerves arising from the spinal cord. A dorsal root and a ventral root join to form a spinal nerve. Sensory impulses reach the spinal cord through the dorsal root. Motor impulses go out of the spinal cord through the ventral root. Impulses from different parts of the body are transmitted to and from the brain through the spinal cord. It also coordinates the repeated movements during walking, running etc. Indicators Protection of the spinal cord. Formation of the spinal nerves. Functions of the spinal cord. 15 Biology - X Observe figure 1.5. What is the peculiarity of such responses? Analyse the description given below and note down the peculiarities. Figure 1.5 Different responses The accidental and involuntary responses towards stimuli are called reflex actions. They do not happen consciously. How does reflex action happen in our body? Analyse illustration 1.9 and the description and complete the flow chart. Receptor Generates impulses. Sensory neuron Carries impulses to the spinal cord Interneuron The neuron that connects the sensory neuron and the motor neuron. Generates quick responses according to the sensory impulses. Stimulus Motor neuron Carries the information from spinal cord to related muscles. Related muscle Withdraws the hand by the action of the muscles. Illustration 1.9 The pathway of impulses in a reflex action 16 Biology - X Stimulus Reflex arc is the pathway of impulses in the reflex action. Mainly spinal cord acts as the centre of reflex action and such reflexes are called spinal reflexes. But all reflexes are not under the control of the spinal cord. Don’t we blink our eyes when light suddenly falls on our eyes or when objects move towards them? This is also a reflex action. Such reflexes under the control of the cerebrum are called cerebral reflexes. Alcohol and Reflex Alcohol accelerates the action of gama amino butyric acid (GABA), a neurotransmitter in the brain. Higher doses of this neurotransmitter retard the brain action which in turn weakens the reflex action and prevents making proper decision at proper time. Is it advisable to lift up people quickly by holding their arms or legs in an accident. What aspects related to spinal cord are to be taken care of while attending injured persons? Discuss. Autonomous Nervous System There may be instances in your life when you felt sudden fear or sadness. Write down some of those experiences. seeing a snake suddenly What are the changes that take place in the body during such emergency situations? List them. Heart beat increases 17 Biology - X Shouldn't these changes return to normal state? Discuss. Activities that take place beyond the conscious level are controlled by the autonomous nervous system, a part of the peripheral nervous system. The sympathetic system and the parasympathetic system together form the autonomous nervous system. Analyse illustration 1.10 to understand the actions of sympathetic and parasympathetic systems during emergency situations and complete table 1.2. Sympathetic System Parasympathetic System The pupil in the eye dilates. The pupil in the eye contracts. Production of saliva decreases. Production of saliva increases. Trachea expands Trachea contracts. Heart beat becomes normal. Heart beat increases. Gastric activities slow down. Gastric activities become normal. Glucose is converted to glycogen. Glycogen is converted to glucose. Peristalsis in the intestine slows down. Urinary bladder regains normal state. Production of hormone decreases. Production of hormone increases. Illustration 1.10 Autonomous nervous system 18 Peristalsis in the intestine becomes normal. Urinary bladder contracts. Biology - X Organ/part Action of Sympathetic System Action of Parasympathetic System Pupil Salivary gland Trachea Heart Stomach Liver Intestine Urinary bladder Table 1.2 Action of sympathetic and parasympathetic systems Nervous System and its Disorders A healthy nervous system is the basis of normal body activities. Even minor defects in the nervous system may cause serious health problems. List out the familiar diseases that affect the nervous system. $ Rabies $ $ Conduct a seminar on 'The diseases affecting the nervous system' by analysing table 1.3 and collecting more information on it. Disease Causes Symptoms Alzheimer's Accumulation of an insoluble protein in the neural tissues of the brain. Neurons get destroyed. Loss of memory, inability to recognize friends and relatives, inability to do routine works. Parkinsons Destruction of specialised ganglions in the brain. Production of dopamine, a neurotransmitter in the brain gets reduced. Loss of body balance, irregular movement of muscles, shivering of the body, profuse salivation. Epilepsy Continuous and irregular flow of electric charges in the brain. Epilepsy due to continuous muscular contraction, frothy discharge from the mouth, clenching of the teeth following which the patient falls unconscious. Table 1.3 Certain diseases affecting the nervous system 19 Biology - X What should be our approach towards people affected by such diseases? Discuss. The nervous system helps us to experience various stimuli as well as to respond towards them. Special care should be taken to maintain the health of this organ system. Receptors that receive stimuli promote the actions of nervous system. It would be very interesting to know about these receptors and the sense organs in which they are included. 1. 2. 3. 20 The part of the brain which helps to maintain balance of the body. a) Cerebrum b) Cerebellum c) Medulla oblongata d) Thalamus Identify the relation and fill in the blank. Irregular flow of charge in the brain : Epilepsy Decrease in the production of dopamine : ----------- Analyse the following situations and answer the questions. a thorn pierces the foot. the leg is withdrawn. the thorn is taken out slowly. a) Write the stimuli and responses. b) Was the leg withdrawn after sensing the pain? Identify the reflex action. Prepare an illustration showing the parts through which the impulses were transmitted. Construct a model of the human brain using suitable scrap materials and exhibit it in the class. Prepare the script of a short play which contains the methods of first aid to be given to people who have met with accidents and present it. Earthquake victims rescued Katmantu : Rescued victims who got trapped in the collapsed buildings due to earthquake in the eastern regions of Katmantu, the Capital of Nepal. The rescue operation was difficult due to heavy rain and insufficient light. Specially trained dogs helped to detect the victims and save their lives during the crisis. Did you notice the news? Why are dogs more capable than human beings in tracking the injured in such circumstances? Discuss. The number of receptors in the sense organs is different in different organisms. The surface of a postage stamp is enough to arrange all the olfactory cells in the nose of a human being. But a large scarf is required to arrange the olfactory cells of a dog. Now, you might have understood that the number of receptors influence the efficiency of sense organs. There are different types of receptors in our sense organs to receive stimuli. Expand the given table by adding sense organs and their receptors. Biology - X Sense organs $ Eye $ Ear $ Tongue $ Skin $ Nose Receptor Stimulus Olfactory receptor Smell Table 2.1 Sense organs and receptors Eye Eye is the major sense organ that helps the brain to evoke sensation. How are the eyes protected? Discuss and fill in the blanks. Eye socket : depressions in the skull External eye muscles : fix the eye balls in the orbit Eyebrow :.................................... Eyelashes :.................................... Eyelids :.................................... Conjunctiva : secretes mucus which protects the anterior portion of the eye ball from being dry. Tears : clean and lubricate the anterior part of the eye ball. Lysozyme, the enzyme present in tears, destroys germs that enter the eyes. How far is the structure of an eye adapted to perform its function? Observe figure 2.1 and illustration 2.1. On the basis of the indicators, write your inferences in the Science diary. Sclera Conjunctiva Choroid Retina Cornea Iris Yellow spot Optic nerve Pupil Lens Blind spot Figure 2.1 Structure of the eye 22 Biology - X Layers of the eye Sclera The white outer layer which gives firmness to the eye. Made up of connective tissues. Cornea The projected transparent anterior part of the sclera which refracts light rays to focus on the retina. Conjunctiva The layer which covers and protects the front part of sclera except the cornea. Choroid The middle layer which contains a large number of blood vessels. Retina The inner layer which has photoreceptors. Iris Yellow spot The part of the choroid seen behind the cornea. Presence of the pigment melanin gives the iris a dark colour. The part of the retina where plenty of photoreceptors are present. It is the point of maximum visual clarity. Pupil The aperture seen at the centre of the iris. The size of this aperture increases and decreases depending on the intensity of light. Blind spot The part of the retina from where the optic nerve begins. Here there is no vision as photoreceptors are absent. Optic nerve Lens Elastic transparent convex lens, connected to ciliary muscles by thread like ligaments. Transmits impulses from photoreceptors to the visual centre in the brain. Ciliary muscles Circular muscles seen around the lens. The contraction and relaxation of these muscles alter the curvature of lens. Illustration 2.1 The eye - parts and functions 23 Biology - X The fluids in the eye Aqueous humor The water like fluid filled in the aqueous chamber between the lens and the cornea. It is formed from blood, and is reabsorbed into blood. Provides oxygen and nourishment to the tissues of the eye. Vitreous humor The jelly like substance seen in the vitreous chamber between the retina and the lens. Helps in maintaining the shape of the eye. Indicators Layers of the eye and their function. Position and significance of lens and cornea. Position of iris and the pupil. Location and function of fluids present in the eye. Regulation of Light in the Eye The entry of a large amount of light is harmful to the tissues of the eye. Iris and the aperture at its centre called pupil regulate the amount of light falling on the eyes. Analyse figure 2.2 and the description regarding the changes in the pupil in dim light and bright light, and form inferences. Change in pupil in dim light Change in pupil in bright light Circular muscles contract Radial muscles contract Figure 2.2 Regulation of light in the eye The size of the pupil is regulated by the action of circular muscles and radial muscles. When the radial muscles contract in dim light, the size of the pupil increases. When the circular muscles contract in intense light, the size of the pupil decreases. Thus the amount of light falling on the lens is regulated according to the intensity of light. 24 Biology - X Formation of Image The curvature of the cornea and the lens help light rays which reflect from an object to get focussed on the retina. What are the peculiarities of the image formed by the lens of the eye? Observe figure 2.3 and list the peculiarities. Discuss and modify. Figure 2.3 Formation of image Real We can see nearby and distant objects clearly. This is because the focal length of the lens can be adjusted according to the distance of the object. Analyse illustration 2.2 which explains this and complete table 2.2. Write your inferences in the Science diary. While viewing distant objects Ciliary muscles Lens Ligaments Distant object While viewing nearby objects Ciliary muscles Lens Nearby object Ligaments Illustration 2.2 While viewing distant and nearby objects While viewing nearby objects While viewing distant objects Ciliary muscles contract Ciliary muscles relax Ligaments relax Ligaments stretch Curvature of lens................... Curvature of lens................... Focal length................... Focal length................... Table 2.2 25 Biology - X The ability of the eye to adjust the focal length of the lens by changing its curvature in accordance to the distance of the object from the eye and form the image on the retina is called the power of accommodation of the eye. Retina and the Photoreceptors You might have understood that photoreceptors are present in the retina. Rod cells and cone cells are the photoreceptors in the retina. Rod cells are more in number than cone cells. Observe figure 2.4 and relate the shape of photoreceptors with their names. Analyse the description and compare the photoreceptors and complete table 2.3. Rod cells contain the visual pigment called rhodopsin. This pigment is formed from a protein named opsin and retinal which is a derivative of Vitamin A. Since they are activated even in dim light, we are able to see objects in dim light. These cells cannot detect colour. Figure 2.4 Rod cell and Cone cell Cone cells contain a pigment called photopsin. This is also called iodopsin.This pigment is also composed of opsin and retinal. There are three types of cone cells in our eyes, which help us to detect three primary colours of light – red, green and blue. This diversity is due to the difference in amino acids in the opsin molecule. So, cone cells provide us with colour vision. Rod cell Cone cell Pigment Shape Function Table 2.3 26 Biology - X The Chemistry of Vision How are impulses formed in photoreceptors to make vision possible? Analyse illustration 2.3, figure 2.5 and the description and write your inferences in the Science diary. Light Rhodopsin Retinal + Opsin Photopsin Retinal + Opsin Illustration 2.3 Formation of impulses in photoreceptors In the presence of light, the pigments present in photoreceptors, dissociate. This chemical change leads to the formation of impulses. These impulses are transmitted to the cerebrum through optic nerves and this enables vision. Indicators Factors present in the visual pigments. Formation of impulses in photoreceptors. Figure 2.5 Sense of sight Sense of sight. Complete the flowchart related to the sense of sight given below. Light Impluse Sense of sight Binocular Vision Aren't two images of the same object formed in our two eyes? But we see only one image of the object. How does this happen? 27 Biology - X Try the activity given below. Stretch your left hand forward. Close your right eye and focus on the forefinger of your left hand. Now close your left eye and without changing the direction of your head, focus on the same finger. Do you notice any change in the position of the finger? Observe figure 2.6. Figure 2.6 Binocular vision The images from two sides of the same object are formed in the left and right eye. When these two images combine as a result of the activities of the brain, a three dimensional image of the object is formed. This is called binocular vision. Eye – Defects and Diseases You are now aware of some of the eye defects. Prepare a note on eye defects and their remedies. Myopia Let us familiarise ourselves with a few more eye defects and diseases. Night blindness You have studied that the retinal, a part of the visual pigment, is derived from Vitamin A. The deficiency of Vitamin A results in the low production of retinal. This in turn prevents the resynthesis of rhodopsin. In this condition, objects cannot be seen clearly in dim light and this disease is called night blindness. Xerophthalmia Xerophthalmia 28 If there is a prolonged deficiency of Vitamin A, the conjunctiva and cornea become dry and opaque. This causes xerophthalmia and leads ultimately to blindness. Biology - X Colour Blindness Observe figure 2.7. Can you read the figure clearly? You are aware that the retina contains cone cells which can detect red, green and blue colours. Some persons cannot distinguish green and red colours due to the defect of cone cells. This condition is called colour blindness. Can you guess why persons with colour blindness are not selected for military or for jobs like that of a driver, pilot etc? Discuss. Figure 2.7 Glaucoma Aqueous humor is the fluid which nourishes the tissues in the eyes. If the reabsorption of aqueous humor does not occur, it causes an increase in the pressure inside the eyes. This causes damage to the retina and the photoreceptor cells and ultimately leads to blindness. This defect is called glaucoma. It can be rectified by laser surgery. Computer Vision Syndrome Cataract It is a condition in which the lens of the eyes become opaque resulting in blindness. This can be rectified by replacing the lens with an artificial one, through surgery. Conjunctivitis This is an infection of the conjunctiva. The causative organisms may be bacteria, virus etc. This disease is transmitted through contact and can be prevented by maintaining personal hygiene. Protection of Eyes The problems of the eyes caused by the excessive use of cell phones, computer, tablet etc is called computer vision syndrome. The continuous use of such devices affects the ability of the eye to focus. Headache is its major symptom. Drying of the eye, high pressure in the eye etc are other symptoms. What are the things to be taken care of to ensure the health of the eyes? 29 Biology - X Discuss on the basis of the indicators given below. Indicators Food materials rich in Vitamin A and Health of the eye. Excessive use of mobile, computer etc and Health of the eye. May your eyes see this world even after death... Eye Donation Life Donation Observe the poster. Prepare a presentation on the procedure of 'Eye donation' by collecting data and present it in the class. Ear You have studied that auditory receptors are present in the ear. The ear not only helps us in hearing, but also in maintaining the balance of the body. Observe figure 2.8 and list the main parts of the ear. External ear Internal ear Middle ear Figure 2.8 Structure of the ear Let us examine the main parts of the ear in detail. 30 Biology - X External Ear Observe figure 2.9 and prepare a note on the basis of the indicators. Auditory canal Carries sound waves to the tympanum. Small hairs and wax present inside the canal help to prevent dust and foreign particles from Pinna entering the ear. Carries sound Tympanum waves to the auditory canal. A thin circular membrane that separates the middle ear from the external ear. It vibrates in resonance with Figure 2.9 External ear - parts sound waves. Indicators Function of pinna. Importance of the auditory canal. Middle Ear Analyse figure 2.10 and prepare a table by including the parts of the middle ear and their functions. Malleus Incus Stapes Ear ossicles Amplify and transmit the vibrations of the tympanum to the internal ear. Eustachian tube Connects the middle ear and the pharynx. Protects the tympanum by balancing the pressure on either side of the tympanum. Figure 2.10 Structure of the middle ear 31 Biology - X Internal Ear Observe figure 2.11 and understand the parts of the internal ear. Semicircular canals Vestibular nerve Auditory nerve Vestibule Cochlea Figure 2.11 Structure of the internal ear The internal ear is situated inside a bony case in the skull called the bony labyrinth. In this bony case there are membraneous labyrinths as well. The space inside the membraneous labyrinth is filled with a fluid named endolymph. The space between the membraneous and bony labyrinth is filled with a fluid called perilymph. Semicircular canals, vestibule and cochlea are the main parts of the internal ear. Semicircular canals and vestibule help in balancing the body whereas cochlea helps in hearing. How is hearing possible? Observe illustration 2.4 of uncoiled cochlea. Oval window Membrane seen attached to the stapes. Spreads the vibration of ear ossicles to the inner ear. Round window Helps in the movement of fluid inside the cochlea. 32 Upper chamber Middle chamber Lower chamber Illustration 2.4 Cochlea and fluid movements Biology - X Cochlea is a coiled tube like a snail shell. It consists of three chambers. Specialized sensory hair cells which are present in the basilar membrane that separates the middle and lower chambers, function as auditory receptors. The basilar membrane and sensory hair cells together constitute the Organ of Corti. The sound waves which pass through the external ear vibrate the tympanum.This vibration of the tympanum is transmitted to the ear ossicles which causes the vibration of the membrane in the oval window. This vibration further causes the movement of the fluid inside the cochlea. As a result, the sensory hair cells of the Organ of Corti of the cochlea are stimulated and impulses are generated. These impulses reach the cerebrum through the auditory nerve and hearing is effected. Analyse illustration 2.4 and the description and complete the flow chart given below by including the parts of the ear that bring about the sense of hearing. Also prepare a note in your Science diary. Sound waves Pinna Hair cells Oval window Impulse Sense of hearing Ear and Body balancing Doesn’t the ear help in maintaining the balance of the body? How is it possible? Analyse figure 2.12 and the description based on the indicators and prepare a flow chart on body balance maintaining. Body balance is maintained in accordance with the movement of the head. Movements of the head bring about the movement of the endolymph present inside the vestibule and the semicircular canals. This causes movement of the sensory hair cells and generates impulses. These impulses are transmitted by the vestibular nerves to the cerebellum, and the equilibrium of the body is maintained. Hair cells in semicircular canal Semicircular canals Vestibule Figure 2.12 Vestibule, semicircular canals 33 Biology - X Indicators Parts of the internal ear which help in body balance. Generation of impulses. Hearing Aid Deafness is caused by structural deformities or diseases of the ears. Hearing aids are also included in the various methods of treatment of deafness. Hearing aid is a small electronic equipment that can be fitted internally or behind the ear. Hearing aids are a boon for the hearing impaired to work in the main stream of society. To detect taste Isn't taste, one of the reasons for enjoying the food we eat? What are the different types of tastes we can detect? Analyse the description and figure 2.13 given below, and understand the mechanisms about detecting taste. Based on the indicators, prepare a flowchart on the method of detecting taste. Taste bud Papilla Figure 2.13 Receptors in the tongue Chemoreceptors seen inside the mouth and tongue help us to detect taste. These are seen mainly on the surface of the tongue. The projected structures seen on the surface of the tongue are called papillae. The parts seen on the papillae that detect taste are the taste buds. We have taste buds that are stimulated by tastes like sweet, salt, sour, bitter, umami etc. 34 Biology - X Each taste bud has chemoreceptors that help to detect different tastes. Substances responsible for taste dissolve in saliva, stimulate the chemoreceptors and generate impulses. These impulses reach the brain through the respective nerves and we experience taste. Indicators Taste buds Experience of taste. Diversity of Tastes Umami is a Japanese term that means happiness. Milk, meat, sea food, mushroom etc contain factors that provide the taste of umami. A sixth taste named oleogustus is also identified. It is the taste of lipid. To detect Smell We have discussed olfactory receptors in the beginning of the unit. How do we detect smell? Analyse figure 2.14 and complete the stages in the process of detecting smell in sequential order. Olfactory receptors Olfactory nerve Mucus glands Olfactory receptors Mucus Nasal cavity Figure 2.14 Olfactory receptors Stages Aromatic particles diffuse in the air and enter the nostrils. These aromatic particles dissolve in the mucus inside the nostrils. Isn’t there a possibility of not sensing the taste of food while suffering from common cold? Discuss. 35 Biology - X Receptors in the Skin You might have seen visually impaired people reading Braille by touching with the tips of fingers. Are these touch receptors uniformly distributed all over the skin? Let us do this activity. Take two refillers of any ball point pen. Ask your friend to close his/her eyes and stretch his/her hand. Place the two pointed tips of the refillers on the finger tip first and then on the wrist of your friend. Ask your friend about the experience he/she has felt on the finger tip and the wrist. Is there any difference in the experiences? If so, what might be the reason? Can you now make out how visually impaired people read braille script using their finger tips? Observe figure 2.15 and understand the various receptors present in the skin to sense the different stimuli. Touch receptor Pain receptor Pressure receptor Temperature receptor Cold receptor Figure 2.15 Receptors in the skin Receptors in Various Organisms All organisms have mechanisms to know their surroundings. The receptors of certain organisms and their peculiarities are included in illustration 2.5. Observe it and add your inferences in the Science diary. 36 Biology - X Eye spot to detect light. Housefly Planaria Lateral line There are receptors in the lateral line on either side of the body which help to detect the change in the balance of body. Shark highly sensitive olfactory receptors. Snake Ommatidia Formed of thousands of small eyes. The eye of an insect consists of a cluster of photoreceptors called ommatidia. Jacobson’s organ The aromatic particles that stick on the tongue of the snake reach Jacobson's organ seen on the roof of the mouth cavity. The olfactory receptors seen there get stimulated then. Illustration 2.5 Receptors in various organisms Now, have you understood that organisms recognise their surroundings with the help of the receptors present in the sense organs? This helps them to satisfy their needs and survive on this earth. 1. Select the right answer from the following: While viewing nearby objects. (a) ciliary muscles relax (b) curvature of lens decreases (c) ciliary muscles contract (d) focal length increases 2. Identify the odd one and write down the common feature of the others. Malleus, Eustachian tube, Stapes, Incus 37 Biology - X 3. 4. Redraw the figure. Identify the parts according to the hints and label them. a. The part where the muscles that regulate the size of the pupil are seen. b. Jelly like fluid. c. The layer of eye where photoreceptors are seen. Figure of Ear is given. Redraw it and name and label the parts mentioned. a) Part that receives the vibrations of the ear drum. b) The tube that connects the pharynx. c) Part where the auditory receptors are seen. 38 Conduct a seminar in class on the topic 'Eye diseases and protection of the eye'. Prepare notes on the peculiarities of sense organs of different organisms by collecting more information. Teacher said that it is a hormone related issue. How is it that there is so much difference in height between the two? Did you notice the conversation between Neenu and Seena about the picture on the Science Club notice board? Haven't you heard of hormones? Which are the hormones you know? List them. Biology - X The endocrine system is an organ system that controls and coordinates all activities in the body. This system includes endocrine glands and their secretions called hormones. Hormones are chemical messengers that regulate cellular activities. Endocrine glands do not have particular ducts to carry hormones to various tissues. Hence they are known as ductless glands. Hormones are transported through blood. Do the hormones transported through blood function in all cells? Observe the description and illustration 3.1 given below and discuss on the basis of indicators. Note down the inference in the Science diary. Hormones to target cells Hormones reach every cell in the body as they are transported by blood. But each hormone acts only upon those cells which have specific receptors. The cells which are acted upon by hormones are their target cells. Blood Hormone molecules Hormone receptor in the cell membrane Hormone molecule in the receptor of cell membrane Cells Illustration 3.1 Hormone in the target cell Only those cells having specific receptors can receive a specific hormone. Each hormone molecule binds with the receptor to form a hormone-receptor complex. Following this, enzymes are activated within the cell and certain changes occur in cellular activities. 40 Biology - X Indicators Target cells. Formation of hormone-receptor complex. Influence of hormone in target cells. Let’s learn about the various hormones in our body in detail. After digestion You have learnt that glucose molecules formed as a result of digestion get absorbed into the blood. These glucose molecules must reach cells to produce energy. The gland called pancreas plays a major role in this activity. Have you tried to understand the role of pancreas in the digestive process? Observe figure 3.1 Alpha cells Beta cells Islets of Langerhans Figure 3.1 Pancreas Pancreas is the gland that is connected to the duodenum, the continuation of the stomach. The beta cells in the cell cluster of this gland called Islets of Langerhans, produce the hormone insulin and alpha cells produce the hormone glucagon. Analyse illustration 3.2 and understand the action of these hormones. 41 Biology - X cellular uptake of glucose molecules. Insulin converts glucose into glycogen in the liver and muscles. converts the glycogen stored in the liver to glucose. Glucagon synthesizes glucose from amino acids. Illustration 3.2 Action of insulin and glucagon The normal level of glucose in blood is 70-110mg/100ml. The level of glucose in blood is maintained by the combined action of insulin and glucagon. Complete illustration 3.3 by including the production of hormones that regulate the level of glucose. Production of insulin Production of glucagon....................................................................................... High Level of glucose in blood 70-110 mg/ 100 ml Low Production of glucagon............................................. Production of insulin.......................................... Illustration 3.3 Method of regulation of blood glucose level 42 Biology - X When insulin fails How does the deficiency of insulin or the inability of cells to use insulin affect the body? Discuss. Based on the indicators, analyse the description given below and write notes in the Science diary. Decreased production of insulin due to the destruction of beta cells or the inability of cells to utilize the insulin produced, raises the level of glucose in blood. Excess glucose in the blood is expelled through urine. Normally, there is no glucose in urine. Diabetes is clinically referred to as a condition when the level of glucose before breakfast is above 126mg/100ml of blood. Increased appetite and thirst and frequent urination are the major symptoms of diabetes. The blood test that precisely determines the level of glucose in blood for three months plays a crucial role in the diagnosis of diabetes. Indicators The reason for increase in the level of glucose in blood. Symptoms of diabetes and diagnosis. Plan and conduct Benedict test to detect the presence of glucose in urine with the help of your teacher. Diabetes The reason for Type I diabetes is the defective production of insulin. The reason for this is the destruction of pancreatic beta cells by T lymphocytes, a kind of white blood cells. Providing insulin in proper quantity is the treatment method. The reason for Type 2 diabetes is the inability of target cells to make use of insulin. Obesity and gene defects are the reasons for this disease. This can be controlled through exercise, control of food and use of medicines, if necessary. The World Health Organisation (WHO) and International Diabetic Federation jointly observes November 14 as World Diabetes Day every year. Its purpose is to create awareness against the increase in diabetes. Blue Circle is its logo. Write the report in the Science diary. Take 2ml of the sample in a test tube. Add 2ml Benedict solution into it. Heat for 2 minutes. Observe the change in colour. Formulate your inference by comparing the glucose indicator on the reagent bottle. 43 Biology - X Regulation of Metabolism Figure 3.2 Thyroid gland Thyroid test Since the activities of the thyroid gland are extensive, disorders of thyroid should be detected through test. Disorders are detected by testing the quantity of hormones directly secreted by the thyroid gland and by testing the quantity of certain other hormones that influence the thyroid gland. Laboratory tests that determine the level of hormones like T3, T4, TSH are used for this. The anabolic and catabolic processes taking place in the body are commonly referred as metabolism. Metabolic activities are also under the control of hormones. The thyroid gland is the main endocrine gland that controls the metabolic activities. Observe figure 3.2 and find out the position of the thyroid gland. The thyroid gland secretes two hormones – thyroxine and calcitonin. Pay attention to the functions of thyroxine listed below: Increases energy production. Raises the rate of metabolism. Accelerates the growth and development of the brain in the foetal stage and infancy. Regulates growth in children. How does the rise or fall of the thyroxine level affect the body? Analyse the description given below on the basis of indicators and prepare notes in the Science diary. Hypothyroidism Cretinism This is a condition in which the production of thyroxine decreases. The decrease in production of thyroxine during the foetal stage or infancy, hinders proper physical and mental development. This condition is Cretinism. Prolonged deficiency of thyroxine in adults leads to a condition called Myxoedema. Low metabolic rate, sluggishness, increase in body weight, hypertension, inflammation in body tissues are the major symptoms of this disorder. Myxoedema Hyperthyroidism This is a condition in which all life activities controlled by thyroxine accelerate due to the continuous and excessive production of thyroxine. High metabolic rate, rise in body temperature, excessive sweating, increased heart beat, weight loss, emotional imbalance are the major symptoms. 44 Biology - X Goitre Iodine is essential for the production of thyroxine. The production of thyroxine is blocked in the absence of iodine. In an attempt to produce more thyroxine, the thyroid gland enlarges. This condition is called goitre. Indicators Figure 3.3 Goitre The importance of thyroxine in controlling life activities. The problems caused by excessive production of thyroxine. The disabilities due to thyroxine deficiency. The relation between iodine and thyroid gland. Regulation of level of Calcium The normal level of calcium in blood is 9-11 mg/100ml. When the level of calcium in blood increases, the thyroid gland secretes a hormone named calcitonin. It lowers the level of calcium in blood. What happens if there is a decrease in the level of calcium in blood? The parathyroid gland situated behind the thyroid gland secretes a hormone called parathormone. This hormone increases the level of calcium in blood. The action of parathormone and calcitonin is antagonistic. Decreases Increases Analyse illustration 3.4 showing how the action of these hormones maintains the level of calcium in blood. Prepare notes. Thyroid gland secretes calcitonin Level of calcium in blood 9-11 mg/100ml Figure 3.4 Parathyroid gland Prevents the process of mixing of calcium from bones to blood. Stores the excess calcium from blood to bones. Regulates the level Reabsorbs calcium from kidneys to blood. Prevents the storage of calcium in bones. Parathyroid gland secretes parathormone. Illustration 3.4 Regulation of level of calcium in blood 45 Biology - X - The gland only upto youth! Figure 3.5 Thymus Thymus is an endocrine gland situated behind the sternum. This gland is very active during infancy but constricts as we reach puberty. This gland produces a hormone called thymosin. It is also known as 'Youth hormone'. The major function of this gland is to control the activities and maturation of T lymphocytes which help to impart immunity. During emergencies The hormones secreted by the adrenal gland equip the body to act during emergencies. Prepare notes on the position and peculiarities of the gland using illustration 3.5 and indicators. Inner medulla Epinephrine (Adrenaline): acts along with the sympathetic nervous system during emergency. Thus, we can resist or withdraw ourselves from such situations. Norepinephrine (Noradrenaline): acts along with epinephrine. Cortisol : The synthesis of glucose from protein and fat. Slows down the action of defense cells. Controls inflammation and allergy. Outer cortex Aldosterone: Maintains the salt- water level by acting in kidneys. Maintains blood pressure. Sex hormones: Controls the development and functions of sex organs. Illustration 3.5 Hormones secreted by the adrenal gland Indicators Position and parts of the adrenal gland. Hormonal actions that overcome emergency situations. Hormones produced by the cortex and their functions. The action of epinephrine and norepinephrine prolongs body activities for a longer time, when the sympathetic system gets stimulated. This hormone activity is an example for the coordinated activity of the nervous system and the endocrine system. 46 Biology - X Biological Clock Sleeping and waking up are examples for rhythmic bodily activities. These kinds of activities are controlled by the pineal gland, seen at the centre of the brain. Melatonin, the hormone produced by this gland helps to maintain the rhythm of our daily activities. The production of melatonin is high at night and low during the day. How does the presence of melatonin influence sleep and waking up? Discuss and write down the inferences. Pineal gland Figure 3.6 Pineal gland This hormone also controls the reproductive activities of organisms that have definite reproductive periods. Behind growth Growth of the body takes place under the control of hormones. The pituitary gland produces the hormone responsible for growth. Analyse figure 3.7 and write down the structure and position of the pituitary gland in the Science diary. Hypothalamus Portal vein Nerve fibre Anterior lobe of pituitary Posterior lobe of pituitary Figure 3.7 Pituitary gland 47 Biology - X The hormone that promotes growth of the body during its growth phase is the growth hormone (Somatotropin). Analyse the description given below and draw inferences on how the variation in the production of this hormone affects growth. Figure 3.8 Dwarfism and gigantism If the production of somatotropin increases during the growth phase, it leads to the excessive growth of the body. This condition is called Gigantism. It leads to another stage called Dwarfism when its production decreases during the growth phase. Acromegaly is the condition caused by the excessive production of somatotropin after the growth phase. It is characterised by the growth of the bones on the face, jaws and fingers. Figure 3.9 An acromegaly affected person The anterior lobe of the pituitary gland produces hormones which regulate the functions of other endocrine glands. These are tropic hormones. Hence, the pituitary gland has great significance in the endocrine system. Analyse table 3.1 showing the hormones produced by the anterior lobe of the pituitary and write down the inferences in the Science diary. Hormones secreted by the anterior lobe of the pituitary gland Function Thyroid Stimulating Hormone (TSH) stimulates the activity of the thyroid gland. Adreno Cortico Tropic Hormone (ACTH) stimulates the activity of adrenal cortex. Gonado Tropic Hormone (GTH) stimulates the activity of testes in males and ovaries in females. Growth Hormone (GH) Somato Tropic Hormone (STH) promotes the growth of the body. Prolactin production of milk. Table 3.1 48 Biology - X Childbirth, Breast feeding, Maintenance of water balance The hormones oxytocin and vasopressin, which are secreted from the posterior lobe of the pituitary gland are produced by special neuro secretory cells of the hypothalamus. The posterior lobe of the pituitary gland stores these hormones and releases into blood when required. Analyse figure 3.7, and table 3.2 and prepare notes. Hormone Function facilitates child birth by stimulating the contraction of smooth muscles in the uterine wall. facilitates lactation. Oxytocin Vasopressin or Anti Diuretic Hormone (ADH) helps in the reabsorption of water in the kidney. Table 3.2 Increases Vasopressin regulates the level of water in the body through the reabsorption of water in kidneys. Based on the indicators, discuss illustration 3.6 given below and write notes in the Science diary. Decreases the production of vasopressin Decreases the reabsorption of water in the kidneys. Decreases Normal level of water in blood Raises the quantity of urine. Maintains the level of water Increases the reabsorption of Lowers the quantity water in the kidneys. of urine. Production of vasopressin increases Illustration 3.6 Maintenance of the level of water in blood The production of vasopressin is high in the summer season during which water loss is excessive through sweat. But its production is less during the winter and rainy season. Find out the reason for the change in quantity of urine expelled during the summer and rainy season? 49 Biology - X How does decrease in the secretion of vasopressin affect the body? Note down your assumption. When the production of vasopressin decreases, the reabsorption of water in the kidney is decreased and excess amount of urine is eliminated. This condition is known as diabetes insipidus. Frequent urination, increased thirst etc., are the symptoms. Indicators The function of vasopressin in kidneys. Production of vasopressin and quantity of urine. Diabetes insipidus. Behind sexual characteristics The ovary and testis secrete sex hormones. Analyse illustration 3.7 and prepare a table by including hormones, centre of production and function. Testis Ovary Estrogen Testosterone Controls secondary sexual characters (change in voice, growth of hair, development of reproductive organs) and sperm production. Controls secondary sexual characters, ovulation, menstrual cycle etc. Progesterone Controls ovulation, menstrual cycle and implantation of embryo in the uterus. Illustration 3.7 Sex hormones Prime Controller Hypothalamus, a part of the brain is an endocrine gland too. It controls the pituitary gland and thereby other endocrine glands. Based on the indicators, analyse illustration 3.8 and write down inferences in the Science diary. 50 Biology - X Inhibitory Hormone Hypothalamus Releasing Hormone stimulates the anterior lobe of the pituitary gland and secretes tropic hormones. inhibits the production of tropic hormones in the anterior lobe of the pituitary gland. Illustration 3.8 The relation between hypothalamus and pituitary gland The hypothalamus controls the pituitary gland and thereby the entire endocrine system by producing a variety of releasing hormones and inhibitory hormones. Indicators Action of releasing hormone. Action of inhibitory hormone. Action of hypothalamus as prime controller. Chemical messages for communication Haven’t you noticed ants moving in a line along a particular trail? The reason behind this movement is the production of certain chemical substances. Such chemical substances that are secreted by certain animals to the surroundings to facilitate communication are called pheromones. Pheromones help in attracting mates, informing the availability of food, determining the path of travel, signalling dangers etc. The chemical messages of pheromones also help honey bees and termites to live in colonies. The muscone in the musk deer, the civeton in the civet cat, bombykol in the female silk worm moth etc., are examples for pheromones. Artificial pheromones are used for pest control in agricultural fields. 51 Biology - X Plants too have hormones Plant hormones control and coordinate life activities in plants. These are also called plant growth regulators. Observe illustration 3.9 which shows plant hormones and their functions. Complete table 3.3 suitably. Cytokinin Auxin Cell growth, cell elongation, promoting the growth of terminal buds, fruit formation. Cell growth, cell division, cell differentiation. Gibberellin Stimulates break down of stored food to facilitate germination, sprouting of leaves Abscisic acid Ethylene Dormancy of embryo, dropping of ripened leaves and fruits. Ripening of leaves and fruits, excess amount of ethylene causes dropping of leaves and fruits. Illustration 3.9 Plant hormones 52 Biology - X Plant hormones Function Auxin Abscisic acid break down of stored food in the seed helps in the ripening of fruits Table 3.3 Artificial Plant Hormones Plant hormones are synthesized artificially by identifying the chemical structure of the hormones. Use of such hormones has contributed a lot to the progress of the agricultural sector. Let us familiarise ourselves with some such artificial plant hormones. Auxins It is used in the agricultural field to prevent the dropping of premature fruits, for the sprouting of roots and as a weedicide. Gibberellins It is used for increasing fruit size in grapes and apple and also for preventing ripening of fruits to assist marketing. Hormones also make the fruits seedless Seedless orange, grape and watermelon are produced by using artificial auxin. This process of formation of fruit from the ovary without fertilization is called parthenocarpy. Gibberellins also lead to parthenocarpy. Artificial auxins like Naphthelene Acetic Acid (NAA), Indol Butyric Acid (IBA) etc., are used to prevent the dropping of premature fruits and for the sprouting of roots. 2, 4 - D (2, 4 -Dichloro phenoxy acetic acid) is used as a weedicide. Ethylene Ethylene is used for the flowering of pineapple plants at a time and for the ripening of tomato, lemon, orange etc. Ethyphon, a chemical which is available in liquid form, gets transformed into ethylene, when used in rubber trees and it increases the production of latex. Abscisic acid It is used for harvesting fruits at the same time. 53 Biology - X By now, you are familiar with plant hormones too. It is a fact that the uncontrolled use of these chemicals causes many health and environmental issues. Hormones play a major role in the control and coordination of life activities. They are the chemical messages that help to maintain the homeostasis of body activities. The nervous system and endocrine system work along with each other to ensure homeostasis in animals. 1. Identify the word- pair relationship and fill in the blank. Thyroxine : Epinephrine : 2. Thyroid gland ………………….. Analyse the information given in the box and answer the questions. X - The production of this hormone is more in night and less in day time. Y - Hormones from the adrenal gland work along with the sympathetic system. 54 (a) Identify and name the hormone 'X' and its gland. (b) Identify the hormones indicated as 'Y'. Biology - X 3. Analyse the illustration and complete the table appropriately. Hypothalamus Pineal Pituitary Parathyroid Thyroid Thymus Adrenal Pancreas Ovaries Testes Gland (in females) Location Hormones 55 Biology - X 4. 56 The hormone that helps in the reabsorption of water in the kidneys. (a) TSH (b) ACTH (c) ADH (d) GTH Conduct a seminar on the topic – The Role of the Endocrine System in maintaining Homeostasis. Conduct a debate on 'Use of artificial plant hormonesproblems and possibilities'. Collect information about novel laboratory tests related to diagnosis of diabetes and conduct an exhibition on World Diabetes Day. Kerala withstood the incomparable floods with unity. What threatended the state again, soon after the great floods? Analyse the news reports and present the findings. $ $ Biology - X What are the reasons for the spread of diseases in such situations? Discuss. Conditions suitable for the multiplication and transmission of pathogens exist in abundance and this may cause the spread of various communicable diseases. Most of the pathogens are microorganisms. Microorganisms and Diseases You have learnt that there are many microorganisms that are useful to humans. But some of them are pathogens. Expand the list given below by including pathogenic microorganisms. Bacteria Not only humans, but other animals and plants are also affected by these pathogens. How are pathogens transmitted from one person to another? Analyse illustration 4.1 given below and formulate inferences. By contact Contaminated food and water Cough, sneezing Unsterilized equipments Vectors Cloth Illustration 4.1 Modes of transmission of diseases 58 Biology - X Collect information on other modes of transmission of diseases and expand the illustration. Identify various methods for the prevention of communicable diseases, prepare a similar illustration and exhibit it in the classroom. A possible disease that may spread in flood affected areas is rat fever. Analyse the information given below on the cause, mode of transmission and preventive measures of rat fever and write notes in the Sicence diary. Rat fever (Leptospirosis) Rat fever is a bacterial disease. Bacteria is a prokaryote. They enter the body and multiply through binary fission. The toxins produced by them destroy cells and cause disease. Figure 4.1 Leptospira bacteria Leptospira is the bacteria that causes rat fever. The bacteria that comes out through the urine of rat, dog and certain other animals remain alive in stagnant water and moisture. When bacteria reach blood through wounds, they affect body cells and produce certain toxins. They cause damage to blood capillaries which in turn leads to internal bleeding. Severe fever, headache, muscle Precautions after Flood The Department of Health has given numerous instructions to avoid health issues that may arise after overcoming the emergency situations. Drinking boiled water and water purified using enough quantity of Chlorine prevents water borne diseases. As there is a chance for the multiplication of mosquitoes in stagnant water, proper measures to check increase in mosquitoes should be adopted. For controlling diseases like rat fever, eliminate the vectors and take preventive medicines as per the directions of experts. Disease affected persons must undergo diagnostic tests to confirm their illness and should take proper medicines. People living in unsafe places must shift to safe places as per instructions. Ensure personal hygiene and environmental hygiene at the rehabilitation centres and create an atmosphere to protect health. 59 Biology - X pain, redness in eyes, etc. are the major symptoms. Rat fever can be completely cured through early diagnosis and treatment. The realization that immunization is better than treatment is very important to stop the spread of disease. What are the measures to be taken to prevent the transmission of rat fever? Discuss and present suggestions. Bacteria cause many other diseases like rat fever. Other Bacterial Diseases Diphtheria Diphtheria spreads through cough, sneezing or directly from the infected person to another person. Analyse the information and figure 4.2 related to diphtheria and prepare a table including the pathogen, symptoms and treatment for the disease. Diphtheria affects the mucus membrane of the nose and the throat. Corynebacterium diphtheriae is the pathogen. Toxins produced by the bacteria cause fever, throat pain and inflammation in the lymph glands of the throat. Cells in the mucus membrane which are destroyed by the toxins produce an ash coloured thick coating in the throat within two or three days. Gradually brain, heart and kidneys are affected. Figure 4.2 Coating in the throat caused by diphtheria bacteria 60 Antitoxins which act against the toxins are used to protect the uninfected cells. But, if the disease becomes severe the patient cannot be recovered through medication. So vaccination is the best preventive method. Biology - X Tuberculosis Tuberculosis was a dreadful disease earlier. Analyse the information given below and prepare a wall magazine on the main points relating to tuberculosis. Pathogen Mycobacterium tuberculosis. Major Symptoms Loss of body weight, fatigue, persistent cough Transmission of Disease When the patient speaks, coughs or sneezes, the pathogens spread into the air and thereby to others. Organs/Body parts Affected Tuberculosis mainly affects the lungs. But kidneys, bones, joints, brain etc. are also affected by this disease. Treatment By administering antibiotics Vaccine BCG is used as preventive vaccine against tuberculosis. Prepare a chart based on the information collected on the National Tuberculosis Prevention Programme and exhibit it in the class. Collect additional information on other bacterial diseases and their mode of transmission and prepare a table. Exhibit it in the class. Viral Diseases Nipah spreads as a scare Medicine for Nipah virus arrived Haven’t you noticed the news reports? Nipah was the most fatal of the diseases that Kerala faced recently. This is a viral disease. Analyse illustration 4.2 and find out how Nipah virus causes the disease. Based on the indicators, prepare notes in the Science diary. Virus Virus has the simple structure with a DNA or RNA molecule within a protein coat. Virus has no cell organelles as seen in normal cells. Hence virus multiplies by taking control over the genetic mechanism of the host cells. Viruses infect not only human beings but also plants, other animals and even bacteria. 61 Biology - X Fruit eating bats as the Nipah virus vectors Saliva and urine of bats Remains of fruits eaten by bats Saliva and urine of bats Nipah viruses Pigs Illustration 4.2 Nipah virus and transmission of the disease Indicators Natural vector of Nipah virus. Situations that enable the virus to enter humans. Haven’t you heard of AIDS? A note on this disease is given below. On the basis of the indicators, discuss the note and write your inferences in the Science diary. AIDS Figure 4.3 HIV 62 AIDS (Acquired Immuno Deficiency Syndrome) is a dreadful disease that has gripped the world by fear. Lymphocytes play a major role in providing immunity to the body. HIV (Human Immuno deficiency Virus) enters the body and multiplies using the genetic mechanism of lymphocytes. Hence the number of lymphocytes decreases considerably and reduces the immunity of the body. Various other pathogens which enter the body in such a situation make the condition of AIDS even more fatal. Biology - X Indicators How does HIV multiply in the human body? The number of lymphocytes and AIDS. Condition that makes AIDS fatal. What are the ways by which one gets infected with HIV? Write your inferences in the Science diary by analysing illustration 4.3 given below. Through sexual contact with HIV infected person From HIV infected mother to the foetus By sharing needle Through the reception of blood and organs and syringe contaminated with contaminated with HIV HIV components Illustration 4.3 Mode of transmission of AIDS AIDS does not spread... by touch, shaking hands, coughing, sneezing etc. through insects like mosquitoes, houseflies etc. by staying together and sharing food. by using the same toilet. by taking bath in the same pond. Should we be scared of AIDS patients? What should be our attitude towards them? Discuss. Hepatitis Hepatitis is a liver disease. Hepatitis is also caused by virus. Inflammation of the liver is its major symptom. When the flow of bile secreted by the liver is blocked, an increase in the level of bile pigment called bilirubin in blood is noticed. This imparts dark yellow colour to the 63 Biology - X mucus membrane, white portion of the eyes and the nails. This is the external symptom of the disease. Disease gets transmitted through contaminated food and water, blood components and excreta of the patient. Certain hepatitis do get transmitted in the same way as the transmission of HIV. Discuss the preventive measures of this disease and present your inferences. Hepatitis can also occur due to reasons other than virus infection. Collect more information about such reasons. Dandruff Dengue fever and Chikunguya that are common in Kerala are also viral diseases. These diseases are transmitted through mosquitoes. Discuss the precautions to be taken to prevent the transmission of these diseases. Collect information on other viral diseases and their modes of transmission and prepare a table. Exhibit it in the class. Fungal Diseases When dead cells fall off, skin cells are continuously regenerated. At times the cells divide faster than falling off and become scales. This condition is dandruff. Certain fungi that affect the skin at this time cause itching and other infections. The scales may fall off as white dusts and may cause loss of hair. 64 Fungi are of various types. Some fungi are pathogenic. The toxins produced by the fungi cause diseases. Analyse figure 4.4 and the description on some fungal diseases that affect human beings and prepare a table enlisting the diseases, symptoms and modes of transmission. Ringworm Athletes' foot Figure 4.4 Fungal diseases Ringworm is a skin disease caused by certain types of fungi. The disease manifests as round, red blisters on the skin. This disease spreads through contact. Athletes’ foot is a fungal infection which manifests on the sole of the foot and between the toes. Appearance of reddish scaly rashes that cause itching is the major symptom. Pathogens enter through the toes when they come in contact with contaminated water and soil. Biology - X Diseases Caused by Protozoa Protozoans are unicellular eukaryotes. Malaria is an example of a disease caused by protozoa. Prepare a note by analysing illustration 4.4 and the information give on malaria. Pathogen Vector Host Plasmodium Female Anopheles mosquito Human Illustration 4.4 Malarial infection High fever with shivering and profuse sweating are the major symptoms of malaria. Other symptoms include headache, vomitting, diarrhoea, anaemia, etc. Worms as Pathogens Filariasis is caused by filarial worms that are spread by Culex mosquitoes. The worms stay in the lymph ducts and obstruct the flow of lymph by blocking the ducts. This causes swelling in the lymph ducts. Polluted surroundings promote the multiplication of pathogens. The increase in the number of vectors like mosquitoes, houseflies etc leads to the spread of communicable diseases much beyond control. In order to control the spread of communicable diseases, it is necessary to avoid situations that lead to the multiplication of pathogens and vectors. It is our duty to keep our surroundings clean. What is the significance of observing 'Dry Day' in schools and at home? Discuss. 65 Biology - X Nonpathogenic Diseases Are diseases caused only by pathogens? Are they caused by other factors too? Observe illustration 4.5. Lifestyle Deficiency of nutrients Diseases Genetic Occupational Illustration 4.5 Non-communicable diseases Occupational Diseases Occupational diseases are caused by situations in work sites. Some examples for occupational diseases are given below. : Pneumoconiosis, affecting the labourers engaged in coal mining; Silicosis, affecting mining workers related to gold, tin, mica and labourers in quarry; pottery and ceramics. Asbestosis, affecting workers in asbestos factories. 66 Have you learnt about diseases caused by the deficiency of nutrients? Let’s examine other reasons and conditions that cause diseases. Genetic Diseases Genetic diseases are caused by defects in the genes that control the cellular activities. Haemophilia, sickle cell anaemia, etc. are examples of genetic diseases. Haemophilia Blood clots with the help of some proteins present in blood plasma. What will happen when the genes that control protein synthesis become defective? Discuss. Haemophilia is the condition in which excess blood is lost even through minor wounds. As haemophilia is a genetic disease, a complete cure is not possible at present. Temporary relief is brought in by identifying and injecting the deficient protein. Biology - X There are social organisations which work for haemophilia patients who need special care and attention. These organisations volunteer to provide adequate care to haemophilia patients and make their relatives and the public aware of it. Sickle cell anaemia The defects in genes may also cause deformities in the sequencing of amino acids which are the building blocks of haemoglobin. As a result of this, the structure of haemoglobin changes and this in turn decreases its oxygen carrying capacity. Observe the changes that occur in the red blood cells of sickle cell anaemia patients given in illustration 4.6. Write your inferences in the Science diary based on the indicators given. Changes occur in the structure of haemoglobin in red blood cells. Red blood cells bend like sickle. The oxygen carrying capacity of red blood cells decreases. The sickle shaped RBCs get collected in the blood vessels and block the flow of blood in them. Illustration 4.6 Sickle cell anaemia Indicators Why do haemophilia patients lose blood excessively, even through minor wounds? How does the deformity of red blood cells in sickle cell anaemia patients affect their body? Cancer Cancer is caused by the uncontrolled division of cells and their spread to other tissues. The normal cells get transformed into cancerous cells when the control system of cell division fails. This may be due to environmental factors, smoking, radiations, virus, hereditary factors, etc. The disease may become complicated with 67 Biology - X the spread of cancer cells to other parts of the body through blood and lymph. Normal Cancer cells cells Cancer and Kerala The studies conducted by the Regional Cancer Center in Thiruvananthapuram has revealed that every year there are more than 50,000 newly affected cancer patients in Kerala and about 20 percent of cancer are due to some components in food. 50 percent of cancer among males are related to mouth, throat and lungs. The main reasons identified for this are smoking and alcoholism. Though the rate of infected persons are increasing, the number of people recovering from the disease is also on a steady increase. Even though cancer is a genetic disease, it is not considered as a hereditary disease. Illustration 4.7 Cancer cells Surgery, chemotherapy, radiation therapy etc., are extensively used in the treatment of cancer. As recovery from the disease is difficult if the disease becomes severe, early diagnosis of the disease is crucial in the treatment of cancer. Discuss with cancer specialists about the life style and food habits that will help us to get rid of cancer. Also collect more information in this regard from other sources. What is the importance of voluntary organisations that offer palliative care to cancer patients? Love and care are as important as food and medicines. Discuss. Look at the collage. orld India-the W betes Dia Capital of Lack of e xercise–t he m a i n for incre reason ase in ca rdiac dise ases Hypertensio nThe Silent K iller : food habits Changes in er of obese The numb n the rise people o Don't these newspaper reports point to the ill effects of unhealthy life styles? 68 Biology - X Lifestyle Diseases Lifestyle diseases are caused by unhealthy living styles. The changes in food habits, lack of physical exercise, mental stress, bad habits like consumption of alcohol, drug abuse, smoking, etc. lead to various lifestyle diseases. Analyse table 4.1 about certain lifestyle diseases and conduct a classroom presentation on healthy habits to be followed to avoid such diseases. Disease Diabetes Fatty Liver Stroke Hypertension Heart attack Cause deficiency of insulin or its malfunctioning deposition of excess fat in the liver rupture of blood vessels in the brain, block of blood flow decrease in the diameter of arteries due to deposition of fat block of blood flow due to deposition of fat in coronary arteries which carry blood to the heart. Table 4.1 Different lifestyle diseases Observe illustration 4.8 on some of the health problems associated with smoking. Stroke Lung cancer Addiction to nicotine Bronchitis Emphysema Hypertension Loss of elasticity of arteries Decrease in functional efficiency Illustration 4.8 Smoking and health hazards 69 Biology - X Collect more information on the bad effects of smoking and write it in your Science diary. Conduct a poster exhibition to make people aware of drug abuse. Animal Diseases Not only human beings, but animals are also affected by diseases. Observe table 4.2 about some animal diseases. Disease Pathogen Anthrax, Inflammation of udder Bacteria Foot and mouth disease Virus Table 4.2 Some animal diseases Elaborate the table by including details of other animal diseases. Plant Diseases Plants are also affected by various diseases. Examine table 4.3 to identify some of the plant diseases caused by microorganisms like bacteria, virus and fungi. Pathogen Bacteria Virus Fungus Disease Blight disease in paddy, Wilt disease in brinjal Mosaic disease in peas and tapioca, Bunchy top of banana Quick wilt in pepper, Bud rot of coconut. Table 4.3 Some plant diseases Collect more information on plant diseases that adversely affect food production and write it in your Science diary. You may also make use of agricultural publications for collecting additional information. 70 Biology - X Try to understand the problems faced by farmers in your locality and participate in preventive activities against plant diseases. The state of complete physical, mental and social well-being of a person is called health. Healthy people are the real wealth of a society. The attitude towards patients is as important as keeping away from diseases by practising healthy habits. It is our duty to console those who are affected by noncurable and fatal diseases. 1. 2. Which among the following is not a bacterial disease? a. Tuberculosis b. Nipah c. Diphtheria d. Anthrax “Food safety will be adversely affected with the spread of plant diseases.” a. Do you agree with this statement? Why? b. Give two examples of plant diseases. 3. Prepare a pamphlet including the major measures to be taken to prevent rat fever. 4. What is the importance of vaccination in preventing diphtheria? 5. What health habits should be adopted to prevent lifestyle diseases? Prepare a check list and collect information on various lifestyle diseases. Find out the lifestyle diseases that are observed commonly. Prepare and exhibit posters highlighting the fact that social hygiene is as important as personal hygiene. 71 Its high time we protected nature and natural resources….! Forests have a great role in conserving the health of the environment in which we live. Forests are decisive in many respects. Source of the water we drink and the air we breathe, balancing atmospheric temperature, determining weather, managing agriculture, source of our food etc., are some of those areas. Wild animals inhabit forests. Each animal has a function to perform in the environment in which it lives. Thus wild animals have a vital role in aspects like pollination of plants, dispersal of seeds, sustenance of forests etc. It is our duty to protect and preserve forests, lakes, rivers, wild animals etc,which are all part of our nature. Also, Article 51(g) of our constitution reminds every citizen of India to have a compassion for living creatures. Activities taken up for the conservation of forests and wild life by the Forest Department: Establishing Forestry clubs in schools, for spreading knowledge about forests. Establishing Eco-tourism centres as a part of encouraging eco-friendly tourism. Conducting Nature study camps as a part of forest and wild life education. Making public places green. Providing financial aid to conserve 'kaavu'. Turtle conservation project. Instituting 'Vanamitra award' for promoting creative contributions in the field of green projects. Instituting 'Prakritimitra award' for conserving habitats outside forests and biodiversity. Conducting the 'Citizen Conservator Programme' for ensuring the role of public in forest conservation. Toll free number of Forest department: 18004254733

Biology Textbook - Kerala PDF

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