Definitions Eukaryotic Prokaryotic Protoctists Pathogen Herbaceous Legume Mycelium Hyphae Chitin Saprotrophic Cell differentiation Organelle Stem cell Transpiration Translocation Dominant Recessive Homozygous Heterozygous Phenotype Genotype Codominance Population Community Habitat Ecosystem Biodiversity Abiotic Biotic Producers Single-celled Unicellular Things that aren’t fungi, plants or animals Something that causes disease Herbs Edible part of pea plant Vegetative part of fungus What makes up mycelium Fibrous substance, makes up fungi’s cell wall Saprotrophic nutrition is when enzymes are secreted onto the food and broken down for the nutrients to be absorbed. How a normal cell becomes a specialised cell A group of specialised cells An undifferentiated cell Evaporation of water on the surface of a plant Movement of something One allele is required for the phenotype Two alleles are required for the phenotype Two alleles of the same Two different alleles Physical trait Genetic constitution When both alleles are expressed in the phenotype A community of animals or plants The collection of animals or plants Where a community lives The habitat with the community, atmosphere etc. Variety of living organisms in an ecosystem Non-living factor Living factor An animal that produces its energy from the sun Primary consumers Secondary consumers Tertiary consumers Decomposers An animal that eats the producer Eats primary consumer Etc. Organisms that break down dead/decaying organisms Characteristics of living organisms: Organisms need: 1. Nutrition –provide them with energy and help grow and repair. Nutrients are protein, fats, carbohydrates, vitamins, minerals. 2. Respiration – to release energy, uses food. 3. Excretion of waste – Waste products, such as carbon dioxide and urine, must be removed via excretion. 4. Response to surroundings – react to changes in surroundings. 5. Movement – move to food, away from predators. 6. Control of internal conditions – temperature and water content 7. Reproduction – to produce offspring to survive 8. Growth and development – to become adult. Variety of living organisms: Cells can be eukaryotic, which includes all plant and animal cells, or prokaryotic, such as bacteria. A unicellular organism is one that consists of a single cell. A multicellular organism is one that consists of many cells. Plants Multicellular organisms. Flowering Cells contain chloroplasts, so can carry out plants, maize. photosynthesis. Herbaceous Cell walls made of cellulose. legumes, peas Stores carbohydrates, such as starch or or beans. sucrose. Animals Multicellular organisms. Mammals, Cells don’t contain chloroplasts, no humans. photosynthesis. No cell walls. Respond rapidly to changes in environment due to nervous co-ordination. Can move from place to place. Stores carbohydrates as glycogen Fungi Can’t photosynthesise. Some have body organised into a mycelium made from hyphae, which contain many nuclei. Some are unicellular. Cell walls made of chitin. Feed via saprotrophic nutrition, which is when they secrete extracellular enzymes onto the food to dissolve it, then absorb nutrients. Can store carbohydrate as glycogen. Protoctists Unicellular. Some like animal cells, some like plant cells. Insects, houseflies or mosquitos. Bacteria Unicellular. Have cell wall, membrane, cytoplasm, plasmids. No nucleus, contain circular chromosome of DNA. Some photosynthesise, others feed off other organisms. Lactobacillus bulgaricus, rodshaped, used in milk production. Pneumococcus, spherical, causes pneumonia. Viruses Not living, small particles, smaller than bacteria. Tobacco mosaic virus, Mucor, hyphal structure. Yeast, unicellular. Amoeba, like animal cell. Chlorella, like plant cell Parasitic, reproduce inside living cells. Infect every living organisms. Wide variety of shapes and sizes. No cellular structure, protein coat, contain DNA or RNA. causes discolouring of tobacco plant leaves. Influenza, causes flu and HIV. Cell structure: A collection of organelles creates a cell. A collection of cells creates a tissue. A collection of tissues creates an organ. A collection of organs creates an organ system. Animal cell: Animals are multicellular organisms. Nucleus Cell membrane Cytoplasm Ribosomes Mitochondria Plant cell: Contains genetic material. Controls cell activity. Controls the entrance and exit of substances. Where the chemical reactions take place. Contains enzymes that control the reactions. Small organelles where proteins are made. Small organelles where aerobic respiration takes place. Plants are multicellular organisms. Special features a plant cell has: Chloroplasts Carries out photosynthesis, makes food, contains chlorophyll. Vacuole Large organelle, contains cell sap, helps support cell Cell wall Rigid, made of cellulose, surrounds cell membrane, supports and strengthens cell. Stem Cells: Specialised cells, such as red and white blood cells, are created via cell differentiation. As the cells change, they develop different organelles and turn into different types of cells. Stem cells are undifferentiated cells, which can divide into many more undifferentiated cells. Embryonic stem cells are mostly found in early human embryos. They are very useful since they can turn into any cell in the body. Other types of stem cells can be found in the bone marrow of adults, but they can’t turn into any cell type, only blood cells. Adult stem cells are already being used to cure diseases associated with the blood, but embryonic stem cells could be used to replace faulty cells, such as insulin-producing cells in diabetes and nerve cells for people who are paralysed. However, there are risks involved. Stem cells grown in a lab could become contaminated with a virus, which could be passed onto the patient. Some people are against stem cell research, since they feel human embryos shouldn’t be used for experiments. Other people believe that suffering patients are more important than embryos. Biological Molecules: Carbohydrates Elements Carbon, hydrogen, oxygen Examples Starch, glycogen Proteins carbon, nitrogen, hydrogen, oxygen Lipids/Fats carbon, hydrogen, oxygen Chains Made of smaller units, e.g. glucose or maltose. Made of amino acids. Made of fatty acids and glycerol. How to make a food sample: Add water and allow the food to dissolve. Stir and filter the solution to get rid of the solid bits Get food and grind with pestle and mortar Benedict’s test for glucose: Add 10 drops of Benedict's solution to test tube. Place in water bath with tube pointing away. Leave for 5 minutes. Prepare food sample. Add 5cm3 to a test tube. Prepare a water bath set to 75C. Iodine solution for starch: Add 5cm3 to a test tube. Add drops of iodine. Shake. If contains starch, change from browny-orange to black/blue-black Biuret test for proteins: Add 2cm3 to a test tube. Add same volume of biuret solution. Shake the test tube. If contains protein, change from blue to pink or purple. Sudan III test for Lipids: Add 5cm3 of food. Add 2cm3 of ethanol. Shake tube. Pour ethanol layer into another test tube. Add 2cm3 of water. If contains lipid, milky emulsion. If contains glucose, change from blue to green/yellow for low concentration, brick-red for high concentration Enzymes: Enzymes are biological catalysts produced by living things. It speeds up a reaction without being changed or used up in the reaction. Each enzyme only speeds up one reaction since each has a specific active site. This is called the lock and key model. Enzymes need specific conditions to work at their best. These are called optimal conditions. If the temperature is too hot, the bonds holding the enzymes together break and the enzyme is said to be denatured. This is the same with pH. Investigating how temperature/pH affects enzyme activity: Mix starch and amylase together and heat to specific temperature. Put a drop of iodine into each depression on the spotting tile. Every 10 seconds, add a drop of the mixture into a depression. Repeat with the water bath at different temperatures or add different buffer solutions to the mixture When the iodine remains browny-orange, meaning there is no more starch, stop the stopwatch. Amylase catalyses the breakdown of starch into maltose. When the iodine remains brown-orange, it means that the reaction is complete. When you change the temperatures, you can see which temperature is optimal for the speed of the reaction, so you know what the optimal temperature of the enzyme is. Movement of substances in and out of cells: Cell membranes only allow substances of a certain size to enter the cell. Factors affecting movement of substances: 1. Higher surface area to volume ratio = higher rate of movement 2. Shorter distance = higher rate, such as thin cell membranes 3. Higher temperature = higher rate, since more energy, move faster. 4. Higher concentration gradient = higher rate of diffusion and osmosis. Since they move from an area of high concentration to low concentration. Diffusion: Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration. The particles move down the concentration gradient. Diffusion doesn’t require energy. It happens in fluids. The higher the concentration gradient, the faster the diffusion rate. This happens in cells when glucose and amino acids go into them. Investigating diffusion in a non-living system. Make agar jelly by mixing phenolphthalein and sodium hydroxide. Put hydrochloric acid in a beaker. Put cubes of jelly into beaker. Cubes will eventually turn colourless as acid diffuses into agar jelly and neutralises sodium hydroxide Phenolphthalein is pink in alkaline solutions and colourless in acidic solutions. Since the cube turns colourless, the hydrochloric acid must have diffused into the jelly and neutralised the sodium hydroxide. Osmosis: Osmosis is the net movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration. A partially permeable membrane is a membrane with small holes thay only allow small molecules to pass through them. This happens in cells when tissue fluid moves out of the capillaries and into other cells to provide them with water. Investigating osmosis using a living system: Cut a potato into identical cyclinders. Fill beakers with different sugar concentrations. One should be pure water. Measure length of cylinders and leave 4 cylinders in each beaker for 30 mins. Take them out and measure lengths again. If the cylinders drew in water, they will be longer. If water has been drawn out, they will be shorter. The cylinders in the pure water will be longer since there will be a higher concentration of water outside the cylinders. Investigating osmosis using a non-living system: Put visking tubing over the end of a thisyle funnel with sugar solution. Put this in a beaker of pure water. Measure where the sugar solution comes up to on the glass tube. Leave overnight and measure again. Water will be drawn in through the visking tubing by osmosis, forcing solution up the tube. Visking tubing is a partially permeable membrane, so only allows water through. Since there is a higher concentration of water outside the tube, it moves into the funnel via osmosis across the partially permeable membrane. Active Transport: Active transport is the movement of particles against a concentration gradient, from an area of lower concentration to an area of higher concentration, using energy released during respiration. This is used in cells when the digestive system gains nutrients from the blood, or when minerals from the soil get into a plant’s root hair cells. Human Nutrition: Nutrient Carbohydrate Lipids Proteins Source Pasta, rice, sugar Butter, oily fish Meat, fish Function Energy Energy, energy store, insulation Growth and repair of tissue. Energy in emergencies. Vitamin A Liver Improve vision, keeps skin, hair healthy Vitamin C Fruit Prevents scurvy Vitamin D Eggs, sunlight Calcium absorption Calcium Milk, cheese Make bones and teeth Iron Red meat Make haemoglobin Water Food, drink Every bodily function. Constant supply to replace water lost through urinating, breathing, sweating Dietary Fibre bread, fruit Aid food movement through gut If you are more active, you need more energy, to keep up with this. If you are a child or teenager, you need more energy to grow. If you are pregnant, you need more energy to provide the energy for the baby to develop. Investigating energy content in a food sample: Use dry food. Weight it and skewer onto a needle. Add a set volume of water to a boiling tube. Measure temperature of the water and light the food using a Bunsen burner. Ensure the Bunsen burner isn't near the tube. If the food goes out, relight. Continue until the food can't catch fire. Measure temperature of the water again. Use πΈπππππ¦ ππ ππππ = πππ π ππ π€ππ‘ππ × π‘πππππππ‘π’ππ πβππππ × 4.2 to find the energy in food. The 4.2 is the amount of energy needed to raise the temperature of 1g of water by 1C. You can use πΈπππππ¦ πππ ππππ = ππππππ¦ ππ ππππ πππ π ππ ππππ to find the energy per gram. This experiment isn’t perfect. Lots of energy is lost to the surroundings, which is the results will be extremely incorrect. You could insulate the boiling tube to minimise heat loss. Digestive enzymes help to break down big molecules, such as starch, into smaller ones, such as maltose or glucose. Alimentary Canal: Mouth Oesophagus Liver Gall Bladder Large Intestine Rectum Stomach Salivary glands produce amylase in saliva. Teeth break down food Muscular tube, connects mouth and stomach Bile produced Bile stored Colon, excess water absorbed Last part of large intestine. Faeces stored. Pummels food. Produces pepsin. Produces hydrochloric acid to kill bacteria and give optimum pH for protease to work. Pancreas Produces protease, amylase, lipase. Releases these into small intestine. Small Produces protease, amylase and lipase. Where nutrients are absorbed intestine out of alimentary canal into body. First part=duodenum. Last part=ileum. The bile stored in the gall bladder is released into the small intestine. This is because the hydrochloric acid makes it too acidic, so the enzymes can’t work. The bile neutralises the acid and makes conditions alkaline. It also emulsifies fats, breaking it down into smaller droplets, making a larger surface area for lipase the work on, speeding up digestion. Food is moved through the guy by peristalsis. Peristalsis uses waves of circular muscle contractions to squeeze boluses through the gut. The small intestine is adapted for absorption: ο· It is very long, so there is lots of time to break down and absorb all the food before the end. ο· Large surface area since the walls are covered with villi: Each cell on the villi has their own microvilli, increasing the surface area further. They have a single permeable layer of surface cells and a very good blood supply, assisting rapid absorption. Plant Nutrition: Photosynthesis produces glucose, which is food, in plants. It occurs in the leaves of all green plants, inside the chloroplasts. The chlorophyll absorbs sunlight and uses energy to convert carbon dioxide and water into glucose and oxygen. It converts light energy into chemical energy, stored in glucose, which is released when broken down during respiration. Carbon dioxide + water ο glucose + oxygen 6CO2 + 6H2O ο C6H12O6 + 6O2 Limiting factors affecting the rate of photosynthesis: A limiting factor is something that stops photosynthesis from happening any faster. Light and carbon dioxide levels are limiting factors for photosynthesis. Factors affecting the rate of photosynthesis: ο· Light – limiting factor. As light intensity increases, so does the rate of photosynthesis, up to a certain point. ο· Carbon dioxide – limiting factor. As carbon dioxide level increases, so does rate of photosynthesis, up to a certain point. ο· Temperature – As temperature increase, so does the rate of photosynthesis, up to a certain point. After that, the temperature is too high, so the enzymes become denatured. Leaf adaptations for photosynthesis: ο· ο· ο· ο· Leaves are broad, so large surface area Most of chloroplasts found at top of leaf, closest to sunlight Upper epidermis is transparent, so light can pass through Network of vascular bundles transport water and nutrients to every part of leaf and take away glucose. Also support leaf structure ο· Waxy cuticle reduces water loss by evaporation ο· Stomata allow carbon dioxide to diffuse directly into the leaf Testing a leaf for starch: Dunk leaf in boiling water. This stops any chemical reactions. Put leaf in boiling tube with ethanol. Heat in water bath until boils. This rids any chlorophyll, making leaf white-ish Rinse leaf in cold water. Add drops of iodine. If starcg, leaf turns blueblack This shows photosynthesis is taking place, since if a plant can’t photosynthesise, it can’t make starch. Investigating whether chlorophyll is needed for photosynthesis: Take variegated leaf from plant that has been exposed to light. Record which bits are green and which aren't Test the leaf for starch, see above. Only the green bits turn blueblack. This suggests only the parts of the leaf that contained chlorophyll can photosynthesise and produce starch Investigating if carbon dioxide is needed for photosynthesis: Add plant to a sealed bell jar with soda lime in an evaporating dish. The soda lime will absorbs CO2 out of the air. Leave the plant for a week. Investigating whether light is needed for photosynthesis: Put a plant in a dark room, but ensure it is warm and has enough carbon dioxide. Leave for 48 hours. Test a leaf for starch. It won't turn blue-black, since it can't photosynthesise or produce starch. Test for starch. It won't turn blue-black, since it can't photosynthesise or produce starch Investigating the rate of photosynthesis by measuring oxygen production: Place a source of white light at a specific distance from the pondweed, that is in a test tube with water and sodium hydrogencarbonate Leave to photosynthesise for 1 hour. Oxygen will be collected in the capillary tube as a bubble. Measure the length of the bubble. Repeat with lamp at different distances, or vary temperature by using a water bath or pH by using buffer solutions. The length of the bubble is proportional to the amount of oxygen produced. Plants need certain mineral ions to grow: Mineral ion Makes Nitrate Contains nitrogen for amino acids and proteins Phosphates Contains phosphorous for DNA and cell membranes and needed for respiration and growth. Potassium Helps enzymes for photosynthesis and respiration. Magnesium Makes chlorophyll. Respiration: Respiration is the process of transferring energy from glucose. It happens in every cell. Some energy is transferred by heat. Most is stored in ATP. When energy is needed, ATP molecules break down and energy is released. There are two types of respiration, aerobic and anaerobic. Aerobic Respiration: Uses oxygen. Most efficient way to transfer energy from glucose. Produces 32 molecules of ATP per molecules of glucose. Glucose + oxygen ο carbon dioxide + water (+ energy) C6H12O6 + 6O2 ο 6CO2 + 6H2O Anaerobic Respiration: doesn’t use oxygen. Not efficient. Produces 2 molecules of ATP per molecule of glucose, since glucose is only partially broken down, and lactic acid is produced. When lactic acid builds up in muscles, it leads to cramp. Glucose ο lactic acid (+energy) Anaerobic respiration in plants produces ethanol and carbon dioxide, rather than lactic acid: Glucose ο ethanol + carbon dioxide (+energy) Investigating the evolution of carbon dioxide and heat from respiring seeds: Prepare a set of germinating seeds and boiling seeds, which will act as the control. Place the same amount of hydrogen-carbonate indictaor in two test tubes. Place a gauze platform in each test tube and place the beans on them. Seal with a rubber bung and leave for an hour. The germinating seeds will turn the indicator yellow, showing carbon dioxide is produced. The boiled beans will have no change. The boiled seeds are dead, so respiration isn’t carried out, so no carbon dioxide is produced, so the indicator stays the same. The germinating seeds are respiring, so they produce carbon dioxide, so the indicator turns yellow. Gas exchange in plants: Waste products, such as oxygen from photosynthesis and carbon dioxide from respiration, diffuse out of the plant through little holes at the bottom of the leaves, called stomata. When a plant is photosynthesising, it uses lots of carbon dioxide, so there is very little in the leaf. Due to diffusion, this makes the carbon dioxide from the atmosphere diffuse into the leaf. It also produces oxygen as a waste product, so there is lots in the leaf. Due to diffusion, it diffuses out of the plant into the atmosphere Photosynthesis only happens during the day, but plants respire all the time. During the day, plants make more oxygen by photosynthesis than respiration, so they release oxygen. They also use more carbon dioxide than produced, so they take in oxygen. At night, this swaps around. Leaf Adaptations for Efficient Gas Exchange: ο· Broad, so large surface area for diffusion ο· Thin, short distance to travel ο· Air spaces, so gases can move easily between cells. Increases surface area for gas exchange ο· Stomata allow diffusion of gases and transpiration Stomata: Photosynthesis can’t happen in the dark, so carbon dioxide is no longer required. Because of this, the stomata close, so that water can’t escape, and the plant doesn’t dry out. Stomata also close when supplies of water begin to run out. This is because they don’t want the plant to photosynthesis, since if it did, it would use up the water, causing the plant to dry up and die. The opening and closing of the stomata is controlled by the guard cells surrounding them. The guard cells can change their shape and volume to open and close. An increase in volume opens the stomata. A decrease in volume closes the stomata. Investigating the effect of light on net gas exchange from a leaf, using hydrogen-carbonate indicator: Add same volume of hydrogen-carbonate indicator to four boiling tubes. Put same size healthy-looking leaves into 3 tubes. Seal with a rubber bung and trap the stem of the leave with the bung, so it doesnt touch the indicator. Wrap one boiling tube with tin foil, another with gauze. Place all the tubes in bright light. Leave for an hour and check colour of indicator. There will be no change in the control tube since there was no change in carbon dioxide levels. The one wrapped in foil will turn yellow, since photosynthesis can’t take place, but respiration can. Therefore, carbon dioxide is being produced by respiration, but not used up by photosynthesis, so the carbon dioxide levels will increase, turning the indicator yellow. The one wrapped in gauze will stay roughly the same colour, since the rate of photosynthesis and respiration will be similar. The uncovered one turns purple, since the rate of photosynthesis is higher than the rate of respiration, more carbon dioxide is being used up than taken in, lowering carbon dioxide levels, turning indicator purple. Gas exchange in Humans: Trachea Bronchiole Bronchus Alveoli Diaphragm Windpipe. Connects mouth and nose to lungs Connected to alveoli Thick tube. Divides into bronchioles Tiny air sacs where gas exchange takes place Separates the thorax from the rest of the body. Sheet of muscle that helps with breathing Muscles between ribs to control it during breathing. Intercostal muscle Rib Protects everything within it Pleural Lubricates lung to reduce friction by sticking to the membranes outside of lungs and inside of chest cavity. Lungs follow chest movement. Breathing: Intercostal muscles and diaphragm contract. Thorax volume increases. Decreases pressure, draws air in. Intercostal muscles and diaphragm relax. Thorax volume decreases, air forced out. Alveoli adaptations for gas exchange: ο· blood next to alveoli is very close, and there is a high concentration gradient; the blood has a high concentration of carbon dioxide and low conc of oxygen. ο· When blood reaches body cells, oxygen is released from red blood cells. There is a high concentration gradient between the blood and the cells; the blood has a high conc of oxygen. ο· Millions of alveoli, high surface area ο· Moist lining for gases to dissolve in ο· Walls of 1 cell thick, short diffusion distance ο· Great bloody supply to maintain high concentration gradient ο· Walls are permeable, easy to diffuse. Smoking problems: Emphysema: Smoking damages walls inside alveoli, reducing surface area, slowing the rate of diffusion, reducing the amount of oxygen cells can receive. Smoker’s cough: Tar in cigarettes damages cilia, which are meant to catch dust and bacteria and mucus before they reach the lungs. If they are damaged, dust, bacteria and mucus enter lungs, taking up space of air, reducing the amount of oxygen. It could also lead to infections. Therefore, smokers cough to rid themselves of these foreign objects. Bronchitis: Tar irritates bronchi and bronchioles. More mucus is produced, which can’t be removed due to the damaged cilia. This causes chronic bronchitis. Coronary Heart Disease: Carbon monoxide irreversibly binds to haemoglobin, stopping oxygen binding to it, so reducing the amount of oxygen the blood can carry. To make up for this heart rate increases, leading to higher blood pressure. High blood pressure damages artery walls, making blood clots more likely, increasing the risk of coronary heart disease, or heart attacks. Cancer: Tobacco smoke contains carcinogens. Investigating the effect of exercise on breathing rate: Sit still for 5 minute. Count the number of breaths in one minute. Do 4 minutes of exercise. As soon as you stop, start counging the number of breaths in one minute. Repeat and find average. Use other people as well. Breathing rate increases after exercise since your muscles respire more during exercise, so more oxygen is need and more carbon dioxide needs to be removed. Investigating the release of carbon dioxide in breath: Put the same volume of limewater in 2 boiling tubes. Set up the experiment as shown. Breathe in and out several times with your mouth around the mouthpiece. As you breathe in, air from the room is drawn in through boiling tube A. This air contains very little carbon dioxide, so limewater remains colourless. When you breathe out, the air you exhale bubbles through the limewater in boiling tube B. Since it turns cloudy, it proves that carbon dioxide was produced during respiration. Since the limewater in boiling tube A stays clear, you know the carbon dioxide from the exhaled air was from respiration, since it was inhaled through boiling tube A. Transport: Unicellular organisms don’t require a transport system since their nutrients and gases can diffuse into them, since there is a short diffusion distance. Multicellular organisms require a transport system since without one, direct diffusion would be too slow, and they wouldn’t get enough nutrients or gases. Transport systems allow the substances to move to and from individual cells quickly. Transport in plants: Plants have two systems transporting stuff to every part of the plant: The xylem carries water and mineral salts from the roots up the shoot to the leaves in the transpiration stream. The phloem transports sugars, such as sucrose, and amino acids from the leaves to every other part in the plant. This movement of food substances is translocation. Root hair cells absorb water: The cells on plant roots grow into long hairs, which stick out into the soil. There are millions of these, giving the plant a high surface for water absorption. There is a higher concentration of water in the soil, so it is drawn in by osmosis. Transpiration: Transpiration is caused by the evaporation and diffusion of water from a plant’s surface, usually the leaves. This causes a slight shortage of water in the leaf, so more water is drawn up through the xylem vessels. This means more water is drawn up through the roots, causing a constant transpiration stream. Transpiration is an effect of how leaves are adapted for photosynthesis. Since they have stomata, there is more water in the plant than outside, so it escapes via diffusion. Factors affecting transpiration: ο· Brighter light, higher transpiration rate since stomata close in dark and plants can’t photosynthesise. Stomata are closed, no water can escape. ο· Warmer, faster transpiration. When warm, water particles have more energy to evaporate or diffuse out of the stomata. ο· Faster wind speed, faster transpiration. If wind speed is low, water vapour hangs around the leaf, so the concentration gradient is small. If wind speed is high, little water particles around leaf, so higher concentration gradient, so faster diffusion of water. ο· Lower humidity, faster transpiration. If humid, lots of water around leaf, small concentration gradient. If dry air, almost no water particles around leaf, high concentration gradient, fast diffusion. Investigating how environmental factors affect transpiration rate, POTOMETER: Cut a shoot underwater, to prevent loss of air from xylem, at a slant, to increase surface area. Assemble the potometer in water. Remove apparatus from water, keep end of capillary tube in beaker of water. Check apparatus is water and airtight. Dry leaves, leave shoot to acclimatise and shut the tap. Remove end of capillary tube from beaker until one air bubble forms. Record starting position of air bubble. Leave for an hour, measure final position of bubble. You can change the conditions around the plant: ο· Light intensity – lamp to increase, put in cupboard to decrease ο· Temperature – change temperature of surroundings ο· Humidity – increase by spraying water in a bag and surrounding the plant with said bag ο· Wind – to increase, use a fan. The further the bubble moves, the faster the transpiration rate, since more water is being taken up by the xylem to replace the water lost via transpiration. Transport in Humans: Blood is made of: ο· Plasma ο· Platelets ο· Red Blood Cells ο· White Blood Cells Plasma: Pale yellow liquid. Carries everything that needs to be transported around the body, such as blood cells, platelets, carbon dioxide, urea, hormones, heat, digested food products. Red Blood Cells: They transport oxygen from the lungs to all the cells in the body. Adaptations: ο· Biconcave shape gives it large surface area for absorption and release of oxygen ο· Contain haemoglobin, allows it to carry lots of oxygen. ο· No nucleus, frees up space for more haemoglobin. White Blood Cells: Pathogens cause disease and can kill you if allowed to reproduce rapidly. The immune system and white blood cells, phagocytes and lymphocytes, stop this. Phagocytes: They detect foreign objects and engulf and digest them. They aren’t specific and will attack anything that isn’t meant to be there. Lymphocytes: Every pathogen has antigens on its surface. When lymphocytes find a foreign antigen, it starts to produce antibodies, which are proteins. These antibodies lock on to the invading pathogens and mark them. The antibodies produced are specific to that antigen. Then, antibodies are produced rapidly and mark all other pathogens of that kind. Memory cells are also produced. These stay in the body and remember a specific antigen. If the same pathogen re-enters the body, this memory cell can reproduce the antigen very quickly. Therefore, you are immune to diseases if you already had it. This is how vaccinations work. Vaccinations: Vaccines are dead/inactive pathogen that are injected into the body. Your lymphocytes then produce the antigen required to combat this pathogen and store it in a memory cell. This means that if the active version of the pathogen infects your body, the lymphocytes already know what antigen to produce, and can produce it very quickly. Blood Clotting: When a blood vessel is damaged, the platelets clump together to plug up the damaged area. This is blood clotting and stops you losing too much blood and prevents other bacteria entering the wound and causing an infection. The platelets are held together by a mesh of fibrin. The clot also requires clotting factors. Blood vessels: There are 3 different types of blood vessels: ο· Arteries ο· Capillaries ο· Veins. Arteries: Blood flowing away from the heart runs through this. Therefore, the artery walls are strong and elastic to withstand the high pressure. The elastic fibres allow the arteries to expand. The walls are thick compared to the lumen. The largest artery in the body is the aorta. Capillaries: Arteries branch into capillaries, which are tiny. They carry the blood very closely to every cell to exchange substances. They have permeable walls, so substances can diffuse, such as waste products, like CO2. They supply food and oxygen. Their walls are 1 cell thick, reducing the diffusion distance. Veins: Capillaries eventually join up to form veins. The blood is at a low pressure, since it is travelling to the heart, so the walls don’t need to be thick, like arteries. Bigger lumen to help blood flow. Have valves to keep blood flowing in the right direction. Largest vein is the vena cava. The Heart: 1. Right atrium receives deoxygenated blood through vena cava 2. Deoxygenated blood moves to right ventricle, which pumps it to the lungs via the pulmonary artery. 3. Left atrium receives oxy blood from lungs, via pulmonary vein. 4. Oxygenated blood moves to left ventricle, which pumps it to the whole body via the aorta The left ventricle has much thicker wall than the right, since it pumps blood to the whole body, whereas the right only pumps to the lungs. Therefore, the blood is under higher pressure in the left ventricle. The valves prevent the backflow of blood. Exercise increase heart rate, muscles need more energy, so respire more. To respire more, you need more oxygen and less carbon dioxide, so the blood is pumped around faster to give oxygen faster. You can investigate this by measuring pulse before and after exercise. This all done by: ο· Exercise increases the carbon dioxide level in the blood ο· This is detected by receptors in the aorta and carotid artery ο· The receptors send signals to the brain ο· The brain sends signals to the heart, telling it to contract more frequently and with more force. Adrenaline can also affect heart rate: If an organism is threated, the adrenal glands release adrenaline. This binds to specific receptors in the heart and causes the cardiac muscle to contract more frequently and with more force, so heart rate increases and pumps more blood. This increase oxygen supply to muscles, readying the body for action. Circulation system: Arteries carry oxygenated blood, except the pulmonary artery. Veins carry deoxygenated blood, except the pulmonary vein. Pulmonary = lungs Hepatic = liver Renal = kidneys Factors leading to coronary heart disease: Coronary heart disease is when the coronary arteries, that supply blood to the heart muscle, get blocked by layers of fatty material. This causes arteries to become narrow, so blood flow is restricted and there is a lack of oxygen to the heart muscle, leading to a heart attack. Risk factors: ο· High saturated fat – fatty deposits form inside arteries ο· Smoking – increase blood pressure, causing damage to inside of coronary arteries. Also, cigarette smoke causes damage that makes it more likely for fatty deposits to form. ο· Inactive – high blood pressure damages artery lining, making it more likely for fatty deposits to form. Excretion in Humans: Kidneys: Kidneys remove urea, which is produced in the liver from excess amino acids from the blood. Adjusts ion/salt levels in the blood. Adjusts the water content of the blood. This is all done by filtering stuff out of the blood under high pressure, then reabsorbing the useful stuff. The product of all this is urine. Ultrafiltration: 1. Blood from the renal artery flows through the glomerulus, which is a bundle of capillaries at the start of the nephron. 2. High pressure is built up, which squeezes out water, urea, ions and glucose out of the blood and into the Bowman’s capsule. 3. Membranes between the blood vessels in the glomerulus and the Bowman’s capsule act like filters, so big molecules, like proteins, aren’t lost. The filtered liquid in the Bowman’s capsule is known as glomerular filtrate. Reabsorption and release of wastes: 1. As the filtrate flows through the nephron, useful substances are reabsorbed. 2. All glucose is reabsorbed from the proximal convoluted tubule via active transport. 3. Sufficient ions are reabsorbed, excess ions aren’t. 4. Sufficient water is reabsorbed from the collecting duct via osmosis. 5. The remaining substances form urine, which continues out of the nephron, through the ureter, into the bladder, where it is stored until it is released through the urethra. Osmoregulation: The kidneys also adjust the body’s water content: 1. Water is taken in via food and drink and lost via sweating, breathing and excretion. 2. The kidney can balance out the body’s water content by using a hormone called ADH. 3. ADH makes the collecting ducts of nephrons more permeable, so more water is reabsorbed. 4. If the body is low on water, lots of ADH is released, so more water is reabsorbed. Lung: The lung excretes carbon dioxide as a waste product of aerobic respiration during exhalation. Skin: The skin excretes excess water and salts through the sweat glands on the skin producing sweat. This can also act as evaporative cooling. Co-ordination and response: Organisms can respond to changes in their external environment to increase their chances of survival. They can also respond to changes in their internal environment, to ensure conditions are always right for their metabolism. A change in environment is called a stimulus. Receptors detect stimuli and effectors bring about a response to the stimuli. Effectors could be muscle cells or cells found in glands, they could trigger a muscle to contract and secrete hormones. Central Nervous System (CNS): The nervous system consists of all the neurones in your body, sensory neurones, relay neurones and motor neurones. The CNS consists of the brain and spinal cord ONLY. When receptors detect a stimulus, they send electrical impulses along sensory neurons to the CNS. The CNS sends electrical impulse to an effector, via motor neurones. The effector responds. The CNS coordinates the response. Coordinated responses always require a stimulus, receptor and effector. These are very rapid responses since the electrical impulses are very quick. Synapses: The connection between two neurones is a synapse. The nerve impulse reaches the synapse and triggers a release of neurotransmitters, which diffuse across the gap. When the neurotransmitters reach the next neurone, they trigger a new electrical signal. Reflexes are automatic responses to certain stimuli, to remove your body from danger and stopping it getting damaged. The reflex arc: 1. In a reflex arc, the neurones go through the spinal cord, an unconscious part of the body. 2. When a stimulus is detected, an impulse is sent along a sensory neurone to the CNS. 3. In the CNS, the sensory neurone passes on to a relay neurone, which relays to a motor neurone. 4. The impulse travels along the motor neurone to the effector. These responses are very fast and don’t wait for you to realise what is happening. One example of this is when your finger goes near a hot object or when a cat sees a predator. The Eye: Conjunctiva Lubricates and protects surface of eye Sclera Tough outer layer, protects eye Cornea Refracts light into eye. Transparent, no blood vessels. Oxygen diffuses in from outer surface. Iris Controls diameter of pupil and how much light in the eye Pupil Hole in the middle Lens Focuses light onto retina Retina Light sensitive. Covered in rods and cones, which are light receptors. Optic nerve Carries impulses from receptors to brain Rods More sensitive in dim light. Can’t sense colour Cones Sensitive to colour. Not good in dim light. Fovea Lots of cones here. The Iris Reflex: Very bright light can damage the retina, so there is a reflex to protect it. Light receptors detect the light intensity and send a message through the optic nerve, along a sensory neurone, to the brain. The message continues to a relay neurone, then a motor neurone, which tells the circular muscle to either contract or relax. There is also a reflex when focusing on near and distant objects: Distant Objects: 1. Ciliary muscles relax 2. Suspensory ligaments pull tight 3. Lens becomes thin 4. Refracts light less Near Objects: 1. Ciliary muscles contract 2. Suspensory ligament slackens 3. Lens becomes fat 4. Light refracts more Longsighted people can’t focus on near objects, since lens doesn’t bend light enough, so glasses are used to refract the light more. Short sighted people can’t focus on distant objects, since the lens bends the light too much, so glasses are used to refract the light less. Hormones: Hormone Adrenaline Source Adrenal glands Pancreas Role Readies body for ‘fight or flight’ Insulin Helps control blood sugar level Testosterone Testes Main male sex hormone Progesterone Ovaries Supports pregnancy Oestrogen Ovaries Main female sex hormone ADH Pituitary Controls water gland content FSH Pituitary Female sex gland hormone LH Pituitary Female sex gland hormone. Effects Increase heart rate, blood flow to muscles, blood sugar level Stimulates liver to turn glucose into glycogen for storage Promote male secondary sexual characteristics Maintains lining of the uterus Controls menstrual cycle, promotes female secondary sexual characteristics Increase permeability of collecting ducts Causes egg to mature in ovary. Stimulates ovaries to produce oestrogen Stimulates release of egg from ovary. Differences between hormones and nerves: Hormones Nerves Slower Very fast Act for long time Act for very short time Act in a general area Act in a precise area. Homeostasis: Homeostasis is the maintenance of a constant internal environment. Homeostasis balances water content and body temperature. Water content: Water is taken in by food and drink and lost by sweating, breathing and weeing. We can look at urine to see whether you are losing lots of water. On a hot day or during exercise, you sweat a lot. You produce less urine, but it is more concentrated, so darker colour. You lose more water in your breath since you breathe faster. On a cold day or when you’re not exercising, you don’t sweat. You produce more urine, which will be paler since it is more dilute. Body Temperature: All enzymes work best at a certain optimum temperature, usually 37C, so your body tries to keep it at this temperature. A part of the brain is constantly receiving messages from temperature receptors in the skin that provide information about skin temperature. It is also sensitive to the blood temperature in the brain. Based on the signals, your CNS can activate necessary effectors to maintain this body temperature. The skin helps to maintain body temperature. When you’re too hot: 1. Lots of sweat produced 2. Evaporates, transfer energy from skin to environment, cooling you down. This is evaporative cooling. 3. Blood vessels wide, this is vasodilation. Allows more blood to flow near surface, so can transfer more energy to surroundings When you’re too cold: 1. Little sweat is produced 2. Blood vessels near surface constrict, this is vasoconstriction. Less blood flows near surface, less energy lost to surroundings 3. Shiver, increases rate of respiration, transfers more energy to warm body. 4. Hairs stand on end to trap insulating layer of air. Coordination and response in plants: Plants can also increase their chances of survival by responding to changes in their environment. They can sense the direction of light and grow towards it to maximise light absorption for photosynthesis. They can sense gravity, so their roots and shoot grow in the right direction. Climbing plants have a sense of touch so they can climb and reach sunlight. Plants can produce toxins to avoid being eaten. Plants can produce certain proteins that stop the environment killing them. Auxins: Auxins are growth hormones that control growth at the tips of the roots and shoots. They move through the plant dissolved in water. It is produced in the tips and diffuses backwards to promote cell elongation, which occurs just behind the tips. Auxins promotes growth in the shoot but inhibits growth in the root. Auxins are involved in phototropism and geotropism. Shoots are positively phototropic: This means they grow towards the light. 1. When a shoot tip is exposed to light, the auxin accumulates on the shaded side. 2. This makes the cells grow faster on the shaded side. 3. This makes the shoot bend toward the light. Shoots are negatively geotropic: This means they grow in the opposite direction of gravity. 1. When a shoot grows sideways, gravity forces the auxin on the lower side. 2. This causes the lower side to grow faster. 3. So, the plant bends upwards. Roots are positively geotropic: 1. A root growing on its side will have auxin on its lower side 2. In a root, the auxin inhibits growth, so the cells on the top grow more than the bottom, so the root bends downwards. Roots are negatively phototropic: 1. If root is exposed to light, auxin accumulates on shaded side. 2. Auxin inhibits cell elongation here, so side with light grows more than shaded. This means the light bends away from the light. Reproduction and Inheritance: The nucleus of a cell contains all the genetic material in the form of chromosomes. Chromosomes are long lengths of DNA coiled up. A gene is a short section of DNA. Human cells are diploid, so they have 2 copies of each chromosome, arranged in pairs. There are 46 chromosomes in a human cell nucleus. The diploid number for a human is 46. Genes: DNA is a long list of instructions of how to make an organism and make it work. All the DNA of an organisms is its genome. Each gene in a DNA molecule is a chemical instruction that codes for a protein. Proteins control most processes in the body and determine inherited characteristics. There can be different versions of the same gene, which give different versions of a characteristic. The different versions of the same gene are called alleles. DNA: A DNA molecule has two strands coiled together in a double helix. The two strands are held together by bases: ο· Adenine (A) ο· Cytosine (C) ο· Thymine (T) ο· Guanine (G) The bases are paired into A-T and C-G. This is complementary base pairing. Protein Synthesis: Proteins are made of chains of amino acids. Each protein has a number and order of amino acids. Amino acid chains fold to give each protein a unique shape, so each protein has a different function. Each gene codes for a protein. The order of bases in a gene decides the order of amino acids. Each amino acid is coded by 3 bases. This is a codon. Some codons code for the same amino acid. Some regions of DNA don’t code for any amino acids but are still used in protein synthesis. Proteins are made in two stages: ο· Transcription ο· Translation Transcription: Proteins are made in the cytoplasm by ribosomes. DNA is in the nucleus and can’t move out of it, since it is big. To get the information from the DNA out, mRNA is used. mRNA is also made up by a sequence of bases, but it is shorter, a single strand and uses uracil (U) instead of thymine (T). RNA polymerase is the enzyme that joins the base sequence to make mRNA. 1. RNA polymerase binds to a noncoding region of DNA in front of a gene 2. The DNA strands unzip and the enzyme move along one of the strands 3. It uses the bases in the gene as a template to make mRNA. Base pairing between DNA and RNA ensures that mRNA is complementary to the DNA’s bases. 4. Once made, the mRNA moves out of the nucleus and joins with a ribosome. If the DNA had the base ATAGC, then the mRNA would have UAUCG. This is because of the complementary base pairing and uracil (U) is used instead of thymine (T). Translation: 1. Amino acids are brought to the ribosome by tRNA 2. The order that the amino acids are brought matches the order of codons. 3. Part of the tRNA structure is called an anticodon, it is complementary to the codon for the amino acid. This pairing ensures that the amino acids are brought in the correct order. 4. The amino acids are joined by the ribosome, making a protein. Asexual reproduction and mitosis: A cell can make a new cell by dividing in two. Both cells are genetically identical, they both contain the same genetic information. This is called mitosis. Organisms that use mitosis to reproduce are said to asexually reproduce. Asexual reproduction involves only one parent. The offspring have identical genes to the parent – so there’s no variation between parent and offspring. Mitosis is when a cell reproduces itself by splitting to form two cells with identical sets of chromosomes. If a diploid cell divides by mitosis, you get two diploid cells. 1. DNA is spread out in long strings 2. If the cell gets a signal to divide, it needs to duplicate its DNA, so there is a copy for each new cell. The DNA forms X-Shaped chromosomes. Each arm is an exact duplicate of the other. 3. The chromosomes line up at the centre of the cell and cell fibres pull them apart. The two arms go to opposite ends of the cell. 4. Membranes form around each sets of chromosomes. These become the nuclei of the two cells. 5. Finally, the cytoplasm divides. You now have two new cells containing the same DNA – genetically identical. Sexual Reproduction: Sexual reproduction is where genetic information from two organisms (father and mother) is combined to produce offspring which are genetically different to either parent. Both parents produce gametes, father=sperm cell, mother=egg cell. The gametes are haploid, so they have half the chromosomes in a normal cell. In a human, the haploid number is 23. Fertilisation: The male gamete fuses with the female gamete to form a zygote, which is a fertilised egg. The zygote ends up with a full set of chromosomes, 1 half each from each gamete. The zygote undergoes mitosis and develops into an embryo. It has a mixture of chromosomes, so inherits features from both embryos. There is random fertilisation, making genetic variation in offspring. Meiosis: Meiosis is also cell division but doesn’t produce identical cells. It only happens in the reproductive organs, ovaries and testes. Meiosis produces four haploid cells with different chromosomes. 1. Before it starts to divide, it duplicates its DNA. One arm of each X-shaped chromosome is the same as the other. 2. In the first division, the chromosomes line up. They are then pulled apart, so each new cell only has one copy of each chromosome. Some of the father’s chromosomes and some of the mother’s chromosomes go into each new cell. 3. Each new cell has a mixture of the mother’s and father’s chromosomes. This creates genetic variation. 4. In the second division, the chromosomes line up again and the arms are pulled apart. 5. This creates 4 haploid gametes, each gamete only has one set of chromosomes, not the normal two. 6. All the gametes are genetically different. Sexual Reproduction in Plants: Pollination: Pollination is the transfer of pollen from an anther to a stigma, so that male gametes can fertilise the female gametes. Cross pollination is when pollen is transferred from the anther of one plant to stigma of another. Plants that cross pollinate rely on insects or wind. Insect Pollination: 1. They have brightly coloured petals to attract insects. Also, scented flowers and nectaries. 2. Plants produce big, sticky pollen grains that stick to insects as they go from plant to plant. 3. The stigma is also sticky, so any pollen picked up by insects on other plants will stick to the stigma. Wind Pollination: 1. Dull petals on plant, no need for insects. No nectaries or strong scents 2. Lots of small and light pollen grains, so can easily be carried by wind. 3. Long filaments hang anthers outside flower, so lots of pollen gets blown away. 4. Large feathery stigma outside flower to catch pollen. Fertilisation in plants: 1. Pollen grain lands on stigma 2. Pollen tube grows out of pollen grain and down through style to ovary and into ovule 3. Nucleus from male gamete moves down and fuses with female gamete. 4. The fertilised female gamete forms a seed. The ovary develops into a fruit around the seed. Germination: A seed will lie dormant until all the conditions are right: ο· Water – to activate enzymes that break down food reserves in seed ο· Oxygen – for respiration ο· Suitable temperature – for enzymes inside seed to work. Germinating seeds get their energy from food stores, until they can produce their own food: 1. developed seed contains any embryo and store of food reserves, wrapped in a hard seed coat, to protect it. 2. When germination begins, it gets glucose from the food store, transferring the energy it needs to grow. 3. Once the plant has grown enough to produce green leaves, it can get its own food via photosynthesis Investigating the conditions needed for germination: Boiled water contains no oxygen. Put cotton wool at the bottom of four boiling tubes. Put 10 seeds at the top of each cotton wool. Set up the boiling tubes as above. Leave tubes for a few days. and observe what happens. There should only be germination in Tube 1., since all conditions are needed for germination. Asexual reproduction in plants: Plants can reproduce asexually using natural methods, or we can make them reproduce asexually using artificial methods. Natural Method: 1. The plant sends out runners, which are fast growing stems that grow out sideways, just above the ground. 2. The runners grow roots at various points and new plants start to grow 3. The new plants are clones, so there is no genetic variation. Artificial Method: You can use cuttings to grow genetically identical copies of a plant. Gardeners take cuttings from parent plants that they wish to be cloned. These plants can be produced quickly and cheaply. Human Reproduction: Male Reproductive system makes sperm cells: Sperm mixes with a liquid to make semen, which is ejaculated into a vagina during sexual intercourse. Female Reproductive System makes ova/eggs: One ovum is produced every 28 days form one of the ovaries. It then passes through the Fallopian tube, where it might meet sperm during sexual intercourse. If it isn’t fertilised, the ovum will break up and pass out of the vagina. If it is fertilised, the ovum begins to divide. The new cells will travel down to the Fallopian tube to the uterus and attach itself to the endometrium. A fertilised ovum will develop into an embryo. Sexual characteristics: During puberty, your body starts to release sex hormones, testosterone in mean and oestrogen in women. These trigger secondary sexual characteristics: Oestrogen: ο· Extra hair on underarms and pubic area ο· Widen hips ο· Breast development ο· Release of ovum and start of periods Testosterone: ο· Extra hair on face and body ο· Develop muscles ο· Penis and testicles enlarge ο· Sperm production ο· Voice deepening Menstrual Cycle: Stage 1 - menstruation starts, uterus breaks down for four days. Stage 2 - uterus lining builds up again, from day 4 to 14, into thick spongy layer, full of blood vessels, ready to receive fertlised egg. Stage 4 - wall is maintained until day 28. If no fertilised egg, spongy lining breaks down and starts all over again. Stage 3 - Egg develops and is released from ovary at day 14. This is ovulation. The menstrual cycle is controlled by four hormones: FSH (Follicle Stimulating Hormone) Oestrogen LH (luteinising hormone) Progesterone 1. 2. 3. 1. 2. 3. 4. 1. 2. Produced in pituitary gland Causes egg to mature in ovaries in a follicle Stimulates ovaries to produce oestrogen Produced in ovaries Causes uterus lining to grow Inhibits release of FSH Stimulates release of LH Produced in pituitary gland Stimulates release of egg at day 14. This is ovulation 1. Produced in ovaries, then by remains of follicle after ovulation 2. Maintains uterus lining during second half of cycle. When not enough progesterone, lining breaks down. 3. Inhibits release of LH and FSH Development of embryo during pregnancy: Once an ovum is fertilised, it develops into an embryo and implants itself in the uterus. Once the embryo is implanted, the placenta develops. This allows the blood of the embryo and mother to get very close to allow the exchange of substances, such as food oxygen and waste. Also, the amnion membrane forms, surrounding the embryo and is full of amniotic fluid, which protects the embryo against knocks. This eventually develops into a foetus. Alleles and Inheritance: Some characteristics are controlled by a single gene; however, most are controlled by several genes interacting. Most of the time, you have two copies of each gene, or two alleles. If the alleles are different, you have instructions for two different versions of the same allele, but you only show one version. The version that is shown is said to be dominant, the other recessive The recessive characteristic is shown if both alleles are recessive. Some characteristics are caused by codominant alleles. Neither allele is recessive, so you show characteristics from both alleles. Genetic diagrams: Family Pedigrees: Family pedigrees require you to deduce what each person’s alleles are from whether they are sufferers or carriers of a disease. If someone is a carrier, then the disease is recessive, and they must have the allele for the disease, but also an allele not for the disease. Sufferers will have both alleles if recessive, one or both if dominant. Neither carriers nor sufferers won’t have any of the alleles linked to the disease. Sex Determination: The 23rd pair of chromosomes is labelled XX or XY. Males have XY. Females have XX. There is an equal chance of having a boy or a girl. All eggs have an X chromosome, but a sperm can have either X or Y, so the sex of offspring depends on the sperm. Genetic Variation: All animals are slightly different due to their genes being slightly different. Most variation is caused by a mixture of genetic and environmental factors. Almost every aspect of life is affected by our environment. Factors not affected by environment: ο· Eye colour ο· Hair colour ο· Inherited disorders ο· Blood group Environment can affect many other characteristics, such as: ο· Weight ο· Height ο· Health Some characteristics are affected by both genes and environment: ο· Intelligence ο· Sporting ability Huntington’s Disease: Disorder of nervous system. Caused by dominant allele. Shows up when patient is around 30-40 years old, when they have already had kids. Cystic Fibrosis: Disorder of cell membranes. Causes lungs to produce sticky mucus, makes breathing difficult and absorption of food difficult. Caused by recessive allele. Sickle-cell Anaemia: Both alleles influence phenotype. Red blood cells become sickle-shaped, since they contain an abnormal amount of haemoglobin. Common in Africa. 1 allele will give the trait, 2 gives the disease. Haemophilia: Part of sex chromosomes, on the X chromosome. Men only need 1 to have it, since they only have 1 X chromosome. Women need both to have it, since they have 2 X chromosomes. Environmental variation in plants: Environmental variation in plants is much greater, since they are strongly affected by sunlight, moisture level, temperature, mineral content, carbon dioxide level, oxygen level. Plants could grow twice as big or twice as fast depending on environment. The organism in the environment: Habitat – where an organism lives Population – all the organisms of one species in a habitat Community – all the different species of a habitat Ecosystem – All organisms living in area and all non-living conditions. Biodiversity –variety of different species of organisms on Earth, or within ecosystem. High biodiversity is important since it ensures ecosystems are stable since species depend on each for shelter and food. Many human actions are reducing biodiversity. The environment can also affect habitats. changes caused by abiotic and biotic factors. Abiotic factors: ο· Environmental– temperature, light intensity, moisture, soil pH. ο· Toxic chemicals Biotic factors: ο· Availability of food ο· Number of predators ο· Competition Investigating population size using quadrats: Place quadrat on ground at a random area within first sample area, using a random number generator. Count the number of the organisms you are investigating. Repeat steps 1 and 2 many times, then find the average. Repeat the whole process in a new sample area. Compare the two averages. You can then estimate the population size by multiplying the mean per m2 by the total area in m2. Investigating the distribution of organisms and measuring biodiversity using quadrats: Mark a line across your area, e.g. hedge to middle of field. Place quadrats next to each and count number of organism. You could record other data, such as average height of the plant, or temperature, or light intensity. Repeat the process, counting for a different organism, and find an average number of organisms. Food Chains: Food chains always start with a producer, which is something that makes its own food using energy from the Sun. Producers are eaten by primary consumers. Primary consumers are eaten by secondary consumers. Secondary consumers are eaten by tertiary consumers. Each stage is called a trophic level: Food Webs: Food webs show how food chains are linked. There are many different species in an environment, so there are many different possible food chains. A food web shows all of them. All the species are independent, meaning if one species changes, all the others are affected. An arrow points at the organism eating it. Pyramid of number: Pyramids of number show the number of an organism at one stage of a food chain. The producer is at the bottom, the tertiary consumer is at the top. They aren’t always pyramid shaped, since 1 fox can feed 5000 fleas. Pyramid of Biomass: A pyramid of biomass shows the mass of living material at that stage of the food chain. Biomass pyramids are almost always pyramid shaped. Pyramids of energy transfer: Pyramids of energy show the energy transferred to each trophic level in a food chain. They are always pyramid shaped, since no energy can be gained, only lost: 1. Energy from Sun is source of energy for producers 2. Plants uses this energy to make food during photosynthesis. 3. Only 90% of the energy is passed on to the next trophic level due to many reasons. 4. Some parts, such as bones or roots, aren’t eaten, so energy isn’t taken in. Some parts are indigestible, so pass through as faeces. 5. A lot of energy is used in respiration. 6. Most energy is eventually transferred to surroundings as heat. 7. Only 10% becomes biomass. The Carbon Cycle: Material are constantly recycled. Carbon passes through living organisms and other things, like air and rocks. 1. Carbon is used by plants in carbon dioxide during photosynthesis. 2. Eating passes carbon in the plant to animals 3. Respiration releases carbon dioxide back to the air 4. Plants and animals eventually die and decompose via microorganisms known as decomposers. These decomposers release carbon dioxide into the air via respiration. 5. Some plants and animal products are burnt, which produces carbon dioxide. 6. Decomposition returns nutrients to the soil. Food Production – Crop Plants: You can increase crop yield by making the optimal conditions for photosynthesis. You can do this by putting them in glasshouses, or polythene tunnels. These: ο· Keep plants enclosed, safe from pests and diseases ο· Help farmers control water supplied ο· Allow farmers to supply artificial light after the Sun sets ο· Trap the sun’s heat to keep the plants warm. ο· Allow farmers to increase carbon dioxide level You can also use fertilisers to ensure the crops have enough minerals, such as nitrogen, potassium and phosphorous. You can also use pest control sprays to get rid of any chance of your crop being eaten. Pesticides are a form of pest control. They are poisonous to humans, so must be used carefully with food. Some pesticides also harm other wildlife. Biological control is an alternative to using pesticides. It means using other organisms to reduce the numbers of pests by encouraging wild organisms or adding new ones. The organisms added could be predators to the pest, or diseasecausing to the pest. Biological control can have a longer-lasting effect and be less harmful to wildlife.
