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The Need for Food Explain in simple terms why food is required by animals Three examples of food types are: Carbohydrates Proteins Fats Animals need food to fight off illnesses. You are now going to investigate why animals need specific food types. Carbohydrates Carbohydrates are used to provide energy for everyday activities e.g. movement Fats Fats are used to provide the body with energy for heat. This is important to animals such as humans as they must maintain a constant body temperature Proteins Body cell only last for a certain length of time and are then broken down. Proteins are needed to build new cells to replace those that are worn out or damaged. Young children need more protein than adults in order to grow properly. In some Third World Countries, young children develop Kwashiorkor, disease caused by protein deficiency. Their stomachs swell because they cannot get rid of fluid. 1 State the chemical elements present in carbohydrates, proteins and fats All carbohydrates, proteins and fats contain the elements carbon, hydrogen and oxygen. In addition, proteiNs contain Nitrogen. Describe the simple structure of carbohydrates, proteins and fats in terms of simple sugars, amino acids, fatty acids and glycerol Some CARBOHYDRATES consist of long chains of glucose molecules, e.g. starch The basic units are glucose Glucose, a simple sugar, is also an example of a carbohydrate. FAT molecules are made up of a glycerol molecule joined to three fatty acid molecules. Fat molecule Basic units Glycerol fatty acids PROTEINS are long chains of amino acid molecules. Protein molecule Basic units The shapes represent amino acids. In each protein there are many different amino acids. 2 State that digestion is the breakdown of large particles of food into smaller particles to allow absorption into the blood stream through the small intestine Before food can be absorbed into the bloodstream, large food particles must be broken down into small food particles Explain that digestion involves the breakdown of insoluble food substances into soluble food substances Digestion is the breakdown of large insoluble food particles into small soluble food particles that can be absorbed across the wall of the small intestine into the bloodstream. Digestion starts in the mouth and is completed in the small intestine. During digestion all carbohydrates are broken down into glucose, all proteins are broken down into amino acids and all fats are broken down into fatty acids and glycerol. Describe the role of different types of teeth in the mechanical breakdown of food in a herbivore, a carnivore and an omnivore such as a human Different mammals eat different foods. Mammals are grouped depending on their diet. Carnivores eat other animals e.g. lion Herbivores eat plants e.g. sheep Omnivores eat both plants and animals e.g humans Mammals have 4 types of teeth Incisors Canines Premolars Molars Teeth are important for the mechanical breakdown of food Omnivore e.g. human Teeth can cope with plant and animal material 3 Carnivore e.g. dog Teeth are adapted for killing other animals and tearing flesh Herbivore e.g. sheep Their teeth are adapted for chopping and grinding grass Type of tooth Sheep Dog Incisor Function Chop grass Biting Canine Chop grass Stab and hold prey Premolar Ridged Grind food Ridged Grind food Shear Molar Function Crack bones 4 Human Function Chisel like Biting Pointed Tearing Uneven Crushing and grinding Uneven Crushing and grinding Identify in a diagram/model the main parts of the human alimentary canal and associated organs (mouth, salivary glands, oesophagus, stomach, pancreas, liver, gall bladder, small intestine, large intestine, appendix, rectum and anus) The gut is a tube about 7 metres long, running from the mouth to the anus. Part of the tube is coiled up to fit inside your body. Each part of the gut has a different job to do. Functions of the gut Mouth – mechanical breakdown of the food Oesophagus – connects the mouth and the stomach Stomach – churns food Small intestine – absorbs digested food products Large intestine – absorbs water Rectum – stores waste Anus – waste is excreted from here Appendix – function unknown 5 State the sites of production of the main digestive juices in a mammal (salivary glands, stomach, pancreas, liver, small intestine) Site of Digestive juice production Salivary glands Saliva Stomach Gastric juice Pancreas Pancreatic juice Liver Bile Small intestine Intestinal juice Bile is stored in the gall bladder Explain the mechanism of peristalsis Food cannot move along the gut itself it has to be pushed. Muscles in the gut wall do this. Muscles behind the food contract, muscles in front of the food relax. The action of the muscles pushes the food along the gut. This muscular pushing of food is called peristalsis. State that different enzymes are responsible for the breakdown of carbohydrates, proteins and fats 6 Give an example of an amylase, a protease and a lipase. State their substrates and products. Salivary amylase is an amylase enzyme produced in saliva by the salivary glands. Salivary amylase is active in the mouth. Salivary amylase breaks large carbohydrates such as starch into smaller molecules of maltose. Pepsin is a protease enzyme that is produced in the stomach. Proteins are digested by proteases into peptides which are then digested into the basic units amino acids. The final stages of digestion take place in the small intestine. Bile (produce in the liver but stored in the gall bladder) is added. Pancreatic juice is also added from the pancreas and contains enzymes. All carbohydrates are broken down into glucose All proteins/peptides are broken down into amino acids Pancreatic lipase is produced in the pancreas but is active in the small intestine. It breaks a fat molecule into 1 glycerol molecule and 3 fatty acids. The fatty acids lower the pH. Site of Enzyme group Enzyme Substrate Product(s) production Salivary glands Amylase Salivary carbohydrates maltose amylase Stomach Protease Pepsin protein peptides Pancreas Lipase Pancreatic fats Fatty acids + lipase glycerol 7 Explain how contractions of the stomach help in the chemical breakdown of food The stomach is a muscular bag. There is a muscle at either end of the stomach that can close to prevent food from passing in or out of the stomach. The stomach produces gastric juices which contains pepsin and hydrochloric acid. The muscles of the stomach wall relax and contract which churns and mixes the food with gastric juice, speeding up digestion. Acid production by the stomach is needed as the enzyme pepsin is most active when the pH is acidic. Explain how the structure of the small intestine is related to its function In the small intestine, the products of digestion pass into the blood. The small intestine is adapted to its function of absorption. It is long It is folded which increases the surface area It has many finger-like projections which also increase the surface area The lining is very thin allow rapid absorption of digested food It has a good blood supply which means that absorbed food is taken away quickly Explain how the structure of a villus, including the lacteal and the blood capillaries, are related to the absorption and transport of food. The finger-like projections are called villi. 8 The villi are adapted for absorption The walls are only one cell thick which allows rapid absorption They contain many blood capillaries They contain lacteals which are part of the lymphatic system Describe the role of the large intestine in water absorption and elimination The wall of the large intestine absorbs most of the water from undigested food into the bloodstream. The undigested remains (faeces) are passed out of the body through the anus, this is called elimination. Reproduction In order to survive, members of a species must reproduce – produce new members to replace the ones which die. Describe the main features of sperm and egg A sperm is the male gamete (sex cell) The tail allows the sperm to swim. 9 The female gamete is called the egg Cell membrane nucleus cytoplasm The cytoplasm contains the food. The nucleus contains the genetic information Feature Sperm Egg Size small large Can it move by itself? yes no Does it have food store? no yes 10 Describe the process of fertilisation Fertilisation is the fusion (combining) of one sperm nucleus with one egg nucleus. A sperm reaches an egg and its nucleus enters the egg. The 2 nuclei fuse to form a zygote (a fertilised egg cell). The zygote is the first cell of the new individual. The egg then forms a fertilisation membrane that stops other sperm from entering. The zygote divides and rapidly becomes a ball of cells. State that in some fish, sperm are deposited in water adjacent to the eggs and that in mammals, sperm are deposited in the body of the female Fertilisation can be external - outside the female’s body internal - inside the female’s body or Most fish produce a large number of sex cells that are released into the water where fertilisation occurs. Fertilisation is external. Courtship rituals make sure that the male and the female sex cells are released near one another Sperm are chemically attracted to the egg cells and swim towards them. In mammals fertilisation is internal as it occurs inside the female’s body. 11 Explain the importance of internal fertilisation to land-living animals Internal fertilisation is essential for land living organisms as on land there is no water to allow the sperm to swim to the eggs. State that sperm cells are produced in the testes The male reproductive system Sperm cells are produced in the testes During sexual intercourse the sperm enter the vas deferens/sperm ducts and are released through the urethra, then the penis into the female’s vagina. They swim up through the uterus into the oviducts (fallopian tubes) 12 State that eggs are produced in ovaries and are released into oviducts, where fertilisation takes place The female reproductive system Eggs are produced in the ovaries and released at regular intervals into the oviducts. Eggs cannot move by themselves. The oviduct moves the egg from the ovary towards the uterus by the beating of hair-like cilia. State that in fish, eggs are protected by flexible coverings and that the embryos obtain food from enclosed yolk Very few fish protect their fertilised eggs. Instead, the young fish develop inside a flexible protective covering. They obtain their food from the enclosed yolk. 13 Explain the relationship between the number of eggs/young produced and the degree of protection afforded during fertilisation and development in fish and mammals Internal fertilisation is more efficient than external fertilisation for a number of reasons The chance of fertilisation is greater as the sex cells are closer together when released. This means Less sex cells need to be produced In mammals, fertilised eggs develop inside the body of the female. In fish they develop in the water. Since fish eggs receive little or no protection many of the eggs may be eaten before or after fertilisation.A fish has to release thousands of eggs to ensure that at least a small proportion will survive into adulthood. In contrast, animals that reproduce by internal fertilisation only need to release one or a small number of eggs. Describe how the fertilised egg passes down the oviduct and becomes attached to the wall of the uterus, develops in the fluid of the amniotic sac and obtains food from the maternal circulation When the fertilised egg (zygote) is carried down the oviduct, it divides to produce a ball of cells. When the zygote divides to form 2 cells, it is now called an embryo. The embryo is carried to the uterus where it attaches to the wall of the uterus (implantation). 14 The embryo develops in a bag of watery fluid called the amniotic sac which acts as a cushion. The mother’s and the embryo’s blood supplies are separate but in direct contact to allow the exchange of materials. Describe the structure and function of the placenta Embryo mammals develop a placenta. It is attached to the placenta by its umbilical cord. 15 Oxygen and dissolved food diffuse from the mother’s circulation to the embryo while Carbon dioxide and other wastes diffuse in the opposite direction. In addition, harmful substances in the mother’s body can cross the placenta e.g. drugs, alcohol and nicotine, if the mother smokes State that in a fish, like the trout, the young emerge from the eggs able to maintain themselves In fish the newly hatched young have no parental care. It feeds on the remains of its yolk sac. When this runs out it starts to catch its own food. State that at birth, the young of mammals are dependent on the adult for care and protection In mammals, the young leave the uterus at birth. It suckles milk from its mother. It is dependent on its parents for care and protection for a long period of time. Water and Waste Identify the ways in which a mammal gains and loses water In mammals the volume of water that is taken into the body must equal the volume that is lost otherwise the cells in the body would be damaged. Water gain Mammals gain water in 3 main ways Drinking Eating Chemical reactions e.g Glucose + oxygen energy + carbon dioxide + water Water loss Sweat Breath Urine Faeces 16 State that the kidneys are the main organs for regulating the water content in a mammal The kidneys are the main organs that a mammal uses to adjust the water content of its blood. They do this by controlling the volume of urine produced. Explain the role of ADH in the regulation of water balance ADH (Anti-diuretic hormone) is produced by the pituitary gland in the brain. ADH controls the volume of water is reabsorbed by the kidneys. The brain monitors blood water levels. If the levels are too low, more ADH is produced. This increases the volume of water retained in the body and results in less urine being produced. The effects are summarised in the table below. Blood water ADH level concentration Volume of water Volume of urine Concentration reabsorbed produced of urine Too low Increased Increased Decreased Concentrated Too high Decreased Decreased Increased Dilute Identify the positions, and state the functions, of: the kidneys, renal arteries and veins, ureter and bladder 17 Part of urinary system Function Renal arteries Carry unpurified blood to the kidneys Kidney Filter blood and remove waste substances Renal veins Carry purified blood from the kidneys to the rest of the body Ureters Carry urine from the kidneys to the bladder Bladder Stores urine State that essential kidney functions are filtration of blood and reabsorption of useful materials such as glucose The kidney removes a poisonous substance called urea from the blood by the two processes of filtration and reabsorption. Filtration All small molecules (glucose, water, salts, urea)in the blood pass through the filtering unit into the kidney tubule. Reabsorption The useful substances such as glucose and water are reabsorbed back into the blood. The waste substance urea is passed out in the urine. 18 Explain the process of urine production using a simple diagram of the nephron, to include the Bowman’s capsule, glomerulus, blood capillaries and collecting duct Urine is produced in microscopic structures called nephrons. Each kidney has millions of nephrons. Each nephron receives blood from the renal artery that ends in a glomerulus - a tiny knot of blood capillaries surrounded by a Bowman’s capsule. The blood is filtered in the glomerulus. The filtrate collects in the Bowman’s capsule and enters the tubule. Useful substances such as glucose, amino acids, water and some salt are reabsorbed into blood capillaries which are closely wrapped round the tubule. The waste, consisting of some salt, urea and water is urine. The collecting duct collects the urine, taken to the ureters and then to the bladder. State that urea is a waste product removed in the urine State the source of urea in the body and describe how urea is transported to the kidneys Urea is a waste produced by the liver during the break down of excess amino acids. Urea is carried from the liver to the kidneys by the blood. 19 Explain the implications of damage to the kidneys by accidents or disease If the kidneys were damaged then the concentration of poisonous wastes in the blood would build up to dangerous levels and the person would die without medical intervention. We could survive with one working kidney. Nowadays death can be prevented by Kidney transplant: the person receives a donated healthy replacement kidney Kidney dialysis: blood is purified using a kidney machine, only waste is removed Describe the relative benefits and limitations of replacement and “artificial” kidneys Procedure Advantage Disadvantage Kidney transplant Person can lead a normal life Rejection may occur Dialysis Drugs taken to suppress rejection lower the body’s ability to fight disease Shortage of donors It is expensive to run Saves lives No problem with rejection Person has to spend a lot of time in hospital Responding to the environment All animals need to respond to their environment if they are to survive. Give examples of environmental factors which affect behaviour Three environmental factors which affect behaviour are: Light Humidity (moisture) Chemicals 20 Describe the response of an animal to change in one environmental factor A choice chamber allows us to look at the response of organisms to changes in environmental factors. E.g. one half of the choice chamber is covered in black paper and the other is left uncovered. Several woodlice are dropped in through the hole in the middle. After a few minutes the woodlice are found to be in the dark part of the chamber. Explain the significance of given examples of response to environmental stimuli in the life of the organism concerned The response of animal to an environmental stimulus is important for its survival. Woodlice are the prey of several predators. Their preference for the dark is an advantage as it means that their predators cannot see them. Woodlice move towards humidity as it will allow their gills to work more efficiently Describe examples of rhythmical behaviour and in each case identify the external trigger Rhythmical behaviour in animals results from regular events in the environment. The main features of rhythmical behaviour are: – it is regular – it is triggered by an external stimulus – it is controlled internally by the animal’s biological clock e. g. birds migrate in autumn which is triggered by decreasing day length activity in shore animals is triggered by the movement of the tide cockroaches have a daily activity cycle controlled by darkness Explain the significance of given examples of rhythmical behaviour in the life of the organism Birds migrate so that there will be enough food for them to eat 21 Many shore animals can only feed safely when covered by water and remain inactive when the tide is out Cockroaches are active at night so that they are not easily seen by predators 22