390191588-HSB-notes - Summary of the Human and Social Biology syllabus PDF

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Summary of the Human and Social Biology syllabus ...

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SECTION A 1.

The characteristics of living things, cell structure, function and specialization 

All living things exhibit seven characteristics – Nutrition, respiration, excretion, movement, growth, sensitivity, reproduction

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Animal and plant cells have a nucleus, cytoplasm and an outer cell membrane.

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Animal cells also have cell wall, a large vacuole and many have chloroplasts.

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Animal and plant cells contain ribosomes, mitochondria and endoplasmic reticulum in the cytoplasm.

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Microbes or microorganisms include bacteria, fungi and virus, many of which cause, disease in humans.

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Bacteria and fungi lack some features of animal and plant cells. Eg bacteria have no nucleus, mitochondria, ribosomes or endoplasmic reticulum and fungi never have chloroplasts and often have cells with many nuclei.

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Viruses do not have any cellular structures.

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Multicellular organisms such as humans have many different types of cells.

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Each type of cell has features that allow it to perform different functions.

2.

Diffusion, Osmosis and Active Transport           

Movement of substances in and out of cells involves diffusion, osmosis or active transport. Diffusion is the movement of ions and molecules in gases or liquids. Diffusion always occurs from a higher to a lower concentration Osmosis is a special type of diffusion and only involves water molecules. Osmosis only occurs through a partially permeable membrane The cell membrane of all cells is partially permeable Active transport involves the movement of ions and molecules against the concentration gradient. Active transport involves the movement of ions and molecules against the concentration gradient. Active transport needs a supply of energy Diffusion and osmosis do not need a supply of energy to occur. Active transport only occurs through a cell membrane.

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3.

Photosynthesis and food chains          

4.

Photosynthesis only occurs in cells with chloroplasts. Photosynthesis needs carbon dioxide, water and light Photosynthesis changes light energy to chemical energy with the chloroplasts. Photosynthesis produce sugars and oxygen which is a waste product. Only green plants are producers in a food chain The other organisms in a food chain are consumers and decomposers All organisms in a food chain belong to a trophic level. Chemical energy is transferred between tropic levels in a food chain. Energy is lost from the food chain at each trophic level Food webs are composed of interlinked food chains

Carbon and Nitrogen Cycles        

Recycling returns some materials to the environment so that they can be reused. The carbon and nitrogen cycles recycle material between the environment and living organisms. Carbon dioxide is used in photosynthesis to form sugars and many other compounds. Carbon dioxide is released from these compounds by respiration, combustion and decomposition. Nitrogen is an essential element in all proteins. Produces use nitrates to form proteins. Decomposers return nitrates to the environment. Bacteria and fungi are the main decomposers in the carbon and nitrogen cycles.

SECTION B - LIFE PROCESSES 5.

Major nutrients, minerals and vitamins       

6.

Humans need a supply of nutrients to provide the materials for growth and for energy Carbohydrates, fats and proteins are needed in the diet. Carbohydrates and fats are the main source or energy Cells are made of cytoplasm which is protein based. Proteins are needed for growth and enzyme formation. Vitamins are mineral salts are needed in small quantities for healthy development. The absence of a vitamin or mineral salt leads to deficiency disease Water and fibre, human diet.

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A balanced diet contains all the main nutrients in the quantities needed by the body. Malnutrition occurs if too much or too little of a nutrient is present in the diet. Diseases of malnutrition include anorexia, bulimia, obesity, kwashiorkor and marasmus. Dietary fibre is needed to ensure movement of food through he alimentary canal Fibre is made of cellulose, found in plant material, and is indigestible

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7.

Water is needed in the daily diet to replace water lost from the body Water is the main component of cytoplasm, solvent for all chemical reactions of the body ,the basis of the body’s transport system, and is needed for excretion and for the control of body temperature. Tooth structure, function and care

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Teeth carry out the first stage of egestion and humans have two sets of teeth – milk and permanent. The types of teeth are incisors, canines, premolars and molars A tooth is made of dentine covered by enamel, both made of hard calcium salts on a skeleton of protein fibres. Tooth decay, dental caries occurs when bacteria gain access to living cells in the tooth. When bacteria respire using sugars, they form an acid that erodes enamel Plaque is a mixture of saliva, food remain and bacteria collects on teeth. Enzymes

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9.

Catalysts are chemicals that alter the speed of a chemical reaction. Enzymes are biological catalysts, they are formed by living cells, they control the metabolic reactions of the body. Enzymes are made of protein, are temperature and pH sensitive , are denatured or destroyed by high temperatures. Each enzyme acts as a catalyst on only one type of reactions and normally only waroks with oe substrate.

Digestion     

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Digestion is the process that converts food material into simple, soluble molecules. The digestive system is composed of the alimentary canal and some other organs. The alimentary canal is a long tube, with muscular walls, linking the mouth and the anus. Digestion occurs in the mouth, stomach, duodenum and ileum There are two types of digestion in humans – physical and chemical. Physical digestion involves emulsification of fats by bile and the mechanical action of teeth and muscles of the alimentary canal. Chemical digestion involves the action of digestive enzymes. Digestive enzymes are produced by parts of the alimentary canal and by organs linked to it, such as the salivary glands and the pancreas. The liver produces bile, which is alkaline but no digestive enzymes. Respiratory Organs

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Breathing is the physical pumping of air in and out of the lungs. It is a series of chemical reactions in cells that releases energy.

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The breathing system in humans is contained within the head and the thorax. Air travels between the throat and the lungs throught the trachea, bronchi and bronchioles. Gaseous exchange is the movement of gases between air in the alveoli ( fine branches of bronchioles) inside the lungs. Gaseous exchanges is the movement of gases between air in the alveoli and blood in the capillaries. Oxygen diffuses down a concentration gradient from alveolar air to the blood and Co2 diffuses down a concertation gradient from blood to the alveolar air.

11. Breathing       

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Breathing depends on differences in air pressure between the atmosphere and air in the lugns. Air pressure in the lungs can be altered to be lower than atmospheric pressure (breathing in) and higher than atmospheric pressure ( breathing out). Air pressure in the lugs is altered by increasing or decreasing the volume of the lungs Rib cage is moved by sets of intercostal muscles and the diaphragm is moved by other muscles. The ribcage is moved upwards and outwards by one set of intercostal muscles, increasing the volume of the thorax. The diaphragm is pulled flat by its own muscles, increasing the volume of the thorax. These actions lower the air pressure in the lugs and air is forced by atmospheric pressure – this is breathing in. The reverse actions occur causing a rise in pressure in the lungs and air is forced out. – this is breathing out. Vital capacity is the maximum volume of air that can be breathed out after breathing in as fully as possible.

12. Circulatory system    

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13.

The main transport system in the human body is blood. The heart pumps the blood through a series of closed vessels called arteries, capillaries and veins. There are two circuits in all mammals a pulmonary circuit serving the lungs and a systemic circuit serving the rest of the of body. The heart is made up of two pumps – the right hand pump forces deoxygenated blood to the lungs and the left hand pump forces oxygenated blood to all other organs of the body. The heart prevents oxygenated and deoxygenated blood mixing. The heart muscle or cardiac muscle has its own blood system, the coronary artery ( a branch of aorta) and a coronary vein ( lined to the vena cava). Each pump is made up of two chances an atrium and a ventricle separated by cuspid valves. The atria receives blood from veins and ventricles pump blood into arteries through semilunar valves. The muscular valve of the left ventricle is much thicker than that of the right ventricle.

Blood, tissue fluid and lymph

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14.

Blood is composed of a liquid with living cells and protein materials floating in it Blood cells are formed in the bone marrow and lymph glands. Red blood cells have no nucleus, are full of haemoglobin and they transport oxygen as oxyheamoglobin. There are several types of white blood cells – phagocytes have a lobed nucleus and engulf bacteria. Lymphocytes have a large nucleus and produce antibodies. Platelets and blood protein fibrinogen are involved in blood clotting. Tissue fluid is the liquid surrounding the living cells in tissues. Tissue fluid and plasma are in contract through he walls of the capillaries. Lymph vessels have special nodes that produce the lymphocytes and help trap bacteria. Special lymph vessels called lacteal are found in the intestinal villi and absorb fatty acids, glycerol and some vitamins. Serum is blood without any blood cells, platelets and fibrinogen.

Skeletal system        

15.

The skeleton is formed of bone and cartilage, both of which contain living cells. Bone is made from protein fibres embedded in a mass of calcium phosphate and calcium carbonate salts. Cartilage is mainly made of protein and is flexible and rubbery while bone is very had and not flexible. The functions of the parts of the skeleton are support, protection, allowing movement and the production of blood cells. The axial skeleton is the skill and vertebral column The appendicular skeleton is the limbs, their supporting girdles and rib cage. Bones are joined to bones by tough, elastic ligaments. Muscles are joined to bones by tough, non-elastic tendons.

Joints and Movements        

Movement is brought about by the contraction of muscles. Locomotion can happen when skeletal muscles move the limb bones of the body. Bones meet at joints that can be moveable or fixed. The most important moveable joints are ball and socket and hinge joints. In moveable joints the bones move against each other and friction must be kept to a minimum. The lower arm is moved at the elbow by the biceps and triceps muscles. Skeletal muscles act in antagonistic pairs, and the members of a pair cause opposite effects when they contract. Locomotion in a human involves the coordination of several sets of antagonistic muscles. Regular exercise improves muscle tone. Poor posture and unsuitable footwear can damage the skeletal system.

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16.

Excretion          

17.

Excretion is the process of getting rid of metabolic waste. It also gets rid of products in excess of the body’s needs. The waste could be toxic if allowed to accumulate in the body. The main excretory organs are the lungs, kidneys and skin The lungs get rid of carbon dioxide and water, the products of cell respiration. The skin gets rid of water and salts when sweat is released. The kidneys remove urea from the blood and also excrete excess water and mineral salts. The kidneys filter the blood plasma under pressure. Substances in the kidney filtrate which are need by the body are reabsorbed. The remaining materials in the filtrate become the unite that flows to the bladder. The composition of urine varies depending on the diet and activity. Homeostasis

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Homeostasis is the process that keeps internal body conditions within narrow limits. Substances kept within these narrow limits include carbon dioxide, water, glucose and salts. The concentration of carbon dioxide is controlled by hypothalamus. The concentration of glucose in the blood is controlled by the hormones insulin and glucagon. These hormones are produced by the pancreas and are active in the liver and muscles. Homeostatic mechanisms are controlled by feedback mechanisms, The process of osmoregulation controls the water content of the blood. Water content is controlled by ADH< a hormone produced by the pituitary gland. ADH is secreted in varying amounts and controls water reabsorption by the kidney. Kidney and temperature regulation

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19.

Body temperature must remain between narrow limits and this is controlled by the hypothalamus of the brain. Body temperatures above 400C can cause enzyme damage and denaturing and below 340C can result in hypothermia when enzyme activity slows and too little energy is released. The outer layer of the skin is a barrier between the living cells and the environment. The skin is covered by a layer of dead cells and this prevents the entry of many microorganisms and chemicals. The skin is waterproof. Most body heat is lost to the environment through the skin. Body temperature can be adjusted by hanging the flow of blood through the skin. When body temperature rises above normal, heat is removed by the evaporation of sweat by conduction, convection and radiation Damage to large areas of the skin can lead to dehydration and death.

Nervous system brain and reflex actions 

The nervous system is formed from the brain and spinal cord and peripheral nerves.

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The brain has regions such as the cerebrum, cerebellum, medulla oblongata and the hypothalamus that coordinate different functions. The spinal cord links the brain and the peripheral nerves below the skull. Peripheral nerves carry impulses into and from the brain and spinal cord. Electrical nerve impulses travel along neurones and neurones are bound together in bundles – these are called nerves. Sensory neurones carry impulses to the Central Nervous System and motor neurones carry impulses from the Central Nervous System. Connector(relay) neurones exist with in the brain and spinal cord and link sensory and motor neurones. Nerve impulses pass between neurones at synapses by means of chemical transmitters. Impulses reaching an effector at the end of a motor neurones cause a response. Some stimuli produce very rapid, automatic responses – reflex actions – that are involuntary. Voluntary responses involve conscious decisions made in the brain The Eye

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Sense organs contain receptors that detect external stimuli and produce nerve impulses. These organs and their stimuli are the eye- light, nose- smell, tongue – taste, ear- sound, movement and gravity. Skin – touch and temperature change. All receptions in the eye detect light and some detect color. The retina contains these receptions rod and cone cells. The retina sends nerve impulses to the brain through the optic nerve. The eye focuses light rays on the retina. The eye changes the shape of the lens to focus near and distant objects. The eye changes the shape of the iris and pupil to control the amount of light reaching the retina. The eye sometimes falls to focus light rays on the retina – this results in long and short sight. Endocrine System

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The endocrine systems, like the nervous system helps to coordinate and control process in the body. This system consists of glands that produce hormones when they are stimulated. These include the pituitary, thyroid and adrenal glands, the pancreas, ovaries and testes. Hormones are chemical that are released directly into the blood. Hormones rely on the circulatory system to reach their target organs. When hormones reach their target organ hey trigger it to respond. Some hormones such as adrenalin and insult produce rapid but short lived effects. Some hormones such as grown hormone, oestrogen and testosterone, produce slower but more long-lived effects. Nerve impulses travel very rapidly along neurones but hormones travel at the slower speed of the movement of the blood. A hormone may affect a number of target organs but nerve impulses are directed to a particular localized effector.

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22.

Reproductive System         

23.

Reproduction is the formation of new individuals. In asexual reproduction individuals do not produce gametes but part of a single parent become detached and grows into a new individual. Asexual reproduction can be very rapid, producing large number of individuals all with identical hereditary information to the parent. In sexual reproduction male and female individuals produce gametes ( sex cells) called spermatozoa (sperm) and ova (egg cells). Sperm and ova fuse together (fertilization) and form zygote. The zygote has a mix of hereditary information from the two parents. The male reproductive system is destined tor produce sperm and release them within the female system. The female system is designed to produce ova, receive sperm, enable fertilization and assist the development of the zygote up to birth. In the menstrual cycle, the uterus forms a new lining ready for implantation and further development each time ovulation occurs. This lining is broken down if fertilization and implantation does not happen. Pregnancy, Birth and planning a family

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Ovulation, fertilization and implantation must happen before a fetus can develop into an embryo. An embryo is attached to the uterus lining by the placenta and umbilical cord. The mother’s blood supply is separate from but very close to the fetal blood supply in the placenta. The maternal blood supply is rich in oxygen and nutrients that diffuse into the fetal blood supply. Carbon dioxide and urea diffuse in the opposite direction. The fetal blood flows to and from the placenta along the umbilical cord. The placenta protects the embryo from most pathogens and toxic substances. The amnion and amniotic fluid around the fetus act as a shock absorber. The birth process involves waves of muscle contractions, widening of the cervix, release of amniotic fluid, expulsion of the baby and then the placenta. Both ante-natal and post –natal care of mother and baby are essential. Family planning involves preventing live sperm and ova meeting within the reproductive system and can involve natural or artificial methods. Chromosomes, Mitosis and Meosis

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The nucleus of a cell controls the cell’s structure and activity. When a cell divides its nuclear material divides before the cytoplasm. The nucleus contains chromosomes made of genes – these are the units of inheritance The genes control the production of proteins, including enzymes by cells. The nucleus of each body cell contains 23 pairs of chromosomes and two copies of each gene. This is the diploid state. When a diploid nucleus divides by mitosis, each daught...