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Biology GCSE
| Question | Answer |
|---|---|
| What are the characteristics of all living organisms? | Movement, Respiration, Sensitivity, Homeostasis, Nutrition, Excretion, Reproduce, Grow |
| What does eukaryotic mean? | Has membrane bound organelles e.g. animal cell has mitochondria, ribosomes and a nucleus |
| What does prokaryotic mean? | No membrane bound organelles eg. Bacteria |
| Both Animal and plant cells contain? | Nucleus-Controls the activity of cells Cell membrane- controls entry and exit of substances into the cell Cytoplasm-where chemical reactions take place, Mitochondria-where aerobic respiration takes place Ribosomes- Protein Synthesis |
| Plant cells only have? | Vacuole-filled with cell sap to dissolve sugars and mineral ions Chloroplasts- Carry out photosynthesis Cell Wall- protects and supports the cell, is made out of cellulose |
| Examples of different types of plants | Flowering eg. Maize Herbaceous legume eg. Peas |
| Examples of mammals and insects | Mammals- Humans Insects- Housefly, mosquito |
| What do Bacteria Cells contain? | Ribosome capsule plasmid nucleoid cell wall cell membrane cytoplasm |
| How are carbohydrates saved in animals and fungi? | As glycogen |
| How are carbohydrates saved in plants? | As starch |
| 5 Animal Kingdoms | plants animals fungi protoctists bacteria |
| Muticellular meaning? | contains many cells |
| Define a pathogen | a micro-organism which causes disease |
| Describe the Structure of a virus | they have a protein coat that surrounds DNA or RNA and they are non-living |
| Describe the structure of Bacteria | They have a cell wall, no distinct nucleus, they have a nucleoid(strands of DNA) and other plasmids |
| Describe the structure of a protoctist | The structure is variable. They can resemble both animal and plant cells. |
| Describe Structure of fungi | The cell wall is made up of chitin, contains the usual organelles, hyphae form a network called mycelium |
| Is a virus Uni or Multi cellular? | Unicellular |
| Is Bacteria Uni or Multi cellular? | Unicellular |
| Is a protocist Uni or Multi cellular? | can be either |
| Is fungi Uni or Multi cellular? | can be either |
| Is a virus Pathogenic? | Always |
| Is bacteria Pathogenic? | sometimes |
| Is a protocist Pathogenic? | sometimes |
| Is fungi Pathogenic? | sometimes |
| Give examples of viruses | HIV (causes AIDS) - Influenza - Cold virus - Measles, mumps, rubella - Tobacco mosaic virus (prevents chloroplast production - discolours leaves) |
| Give examples of bacteria | Pneumococcus (causes pneumonia) - Lactobacillus bulgaricus (used in yoghurt |
| Give examples of protoctists | Chlorella (have chloroplasts, plant-like), - Plasmodium (causes malaria) - Algae - Amoeba (more animal |
| Give examples of fungi | Mushrooms - Mucor |
| Extra detail of viruses | Can only reproduce inside another living cell - Non-living - don’t excrete, respire, move, grow etc |
| extra detail of fungi | - Uses saprotrophic nutrition |
| Define saprotrophic nutrition | The use of digestive enzymes to extracellularly break down dead matter |
| What is a cell? | Group of organelles working together to perform the same function |
| What is a tissue? | Group of cells working together to perform the same function |
| what is an organ? | Group of tissues working together to perform the same function |
| what is an organ system? | Group of organs working together to perform the same function |
| What are the main organs in plants? | Leaves - Roots - Stems - Flowers |
| What are the 7 main organ systems found in humans? | Reproductive system - Circulatory system - Digestive system - Gas exchange system - Nervous system - Excretory system - Endocrine system |
| Organs found in digestive system? | Oesophagus - Stomach - Small intestine - Large intestine |
| What is a zygote? | Single cell formed after fertilisation occurs |
| How is a 16 cell embryo formed? | By mitosis (cell division) |
| What is differentiation? | Process whereby cells become specialised e.g. nerve cells |
| What is a stem cell? | - A cell which has the potential to divide many times whilst undifferentiated (unspecialised) |
| Two types of stem cells? | Embryonic - Adult |
| What are embryonic stem cells? | Found in early stage development of embryos - Can differentiate into ANY type of cell |
| what are adult stem cells? | Found in particular tissues - e.g. bone marrow, lining of small intestine, skin - Unable to differentiate into any type of cell - e.g. stem cells in bone marrow can only differentiate into blood cells |
| what is stem cell therapy? | Use of stem cells to treat disease - e.g. bone marrow transplants |
| Describe the use of stem cell therapy in the treatment of leukaemia | Leukaemia - type of blood cancer - Chemotherapy destroys both healthy AND cancerous cells - Stem cell therapy supplies stem cells that can divide and differentiate and therefore replace cells lost in chemotherapy |
| Advantages and disadvantages of embryonic stem cell therapy | Ability to differentiate into ANY type of cell - Could be used to treat Parkinson’s disease, diabetes etc - BUT ethical issues with their use as they come from unborn foetuses |
| What elements are found in lipids? | Carbon, hydrogen, oxygen |
| Structure of a lipid? | 3 fatty acids - 1 glycerol molecule |
| what are oils? | Plant lipids - Liquids at room temperature |
| Test for lipids? | Add ethanol - Add water and shake - Positive result: milky white emulsion forms |
| Elements in proteins | Carbon, hydrogen, oxygen, nitrogen (and sometimes sulfur) |
| what are proteins made up of | Long chains of amino acids - There are 20 different amino acids |
| Examples of proteins in the body | Collagen and keratin found in skin and nails - All enzymes - Haemoglobin |
| Test for proteins | Add Biuret reagent - Positive result: purple |
| elements in carbohydrates | Carbon, hydrogen and oxygen |
| Test for glucose? | Heat with water and Benedict’s solution - Positive result: brick red |
| What are starch and glycogen made up of? | Simple sugars (e.g. glucose) joined together |
| Test for starch? | Add iodine - Positive result: turns blue/black |
| Define an enzyme | Biological catalyst - Speeds up a reaction - Without being used up |
| Define metabolism | Rate at which chemical reactions take place in the body - Metabolic reactions catalysed by enzymes |
| Key enzyme terms | Substrate - molecule an enzyme acts upon - Active site - area on an enzyme where substrate attaches - Optimum - temperature or pH at which enzyme activity rate is fastest - Denature - when enzyme changes shape so substrate no longer fits active site |
| explain the effect of high temps of enzymes | Decreases activity - Enzyme denatures and substrate can no longer fit the active site |
| explain the effect of low temps on enzymes | Lower kinetic energy - Fewer collisions between enzymes and substrates |
| Why is it important we control our internal temps? | Too high - enzymes denature - Too low - enzymes work too slowly (little kinetic energy) and can’t catalyse chemical reactions fast enough |
| explain the effect of too high or low pH on enzyme activity | Decreases activity - Enzyme denatures and substrate can no longer fit the active site |
| Define diffusion | Net movement of particles from an area of high concentration to an area of low concentration - Down a concentration gradient |
| what factors affect the rate of diffusion | Concentration gradient - Surface area to volume ratio - Diffusion distance - Temperature |
| what factors increase rate of diffusion | Steep concentration gradient - High surface area to volume ratio - Shorter diffusion distance - Higher temperature due to increased kinetic energy of particles |
| Define active transport | Net movement of particles from an area of low concentration to an area of high concentration - Requires energy from ATP |
| Examples of active transport | Root hair cells absorbing mineral ions - Movement of glucose through the lining of the small intestine |
| Define osmosis | Net movement of water - From an area of high water potential to low water potential - Through partially permeable membrane |
| What happens to a plant cell placed in a salty solution and why | Shrinks (flaccid) - Cell membrane pulls away from cell wall (plasmolysis) - Higher water potential in cell than surrounding solution - water leaves cell by osmosis |
| what happens to a plant cell placed in pure water and why | Swells (turgid) - Because higher water potential in surrounding solution compared with inside the cell so water enters the cell by osmosis - Cell wall prevents bursting |
| what happens to an animal cell placed in water and why | Bursts - Because higher water potential in surrounding solution compared with inside the cell so water enters the cell by osmosis - No cell wall so bursts |
| Examples of large surface area to volume ratios for the movement of substances | Alveoli in lungs for absorption of oxygen - Villi in small intestine for absorption of soluble products of digestion - Root hair cells for absorption of mineral ions |
| Word equation for photosynthesis | Carbon dioxide + water (+ light energy) → oxygen + glucose |
| Balanced symbol equation for photosynthesis | 6CO2 + 6H2O → 6O2 + C6H12O6 |
| What is a limiting factor? | Factor in a reaction which is in shortest supply - Lack of this factor is the reason why the rate of reaction no longer increases |
| Limiting factors of photosynthesis | - Carbon dioxide - Light intensity - Temperature - Increasing any of the above will increase the rate of photosynthesis until another factor becomes limiting |
| Why is rate of photosynthesis low in the morning? | Temperature is the limiting factor - Low temperatures inhibit enzyme activity - Carbon dioxide levels are high |
| Why is rate of photosynthesis high at midday | High temperature maximises enzyme activity - Carbon dioxide is the limiting factor as it’s in the shortest supply |
| How is the leaf adapted for its role? | Waxy cuticle - prevents evaporation of water and stops pathogen entry - Upper epidermis - transparent to allow light to enter the leaf - Palisade mesophyll - contains lots of chloroplasts for photosynthesis - Air spaces in spongy mesophyll - allow gase |
| How is the leaf adapted for its role? PT2 | Xylem - allows entry of water and mineral ions by transpiration stream - Guard cells - control opening and closure of stomata - Stomata - allow carbon dioxide to enter, oxygen and water to leave - Thin and broad (large surface area) |
| Describe an investigation to measure the effect of light intensity on photosynthesis | Use Elodea or Camboba pondweed - Oxygen bubbles produced by photosynthesis released - Count number of bubbles produced over one minute to record rate - More bubbles produced per minute = faster rate of photosynthesis |
| Describe an investigation to measure the effect of light intensity on photosynthesis PT2 | - Move a lamp different distances away from beaker to measure effect of light intensity - Improve accuracy by collecting oxygen released in test tube over longer period of time |
| Give independent variable in this investigation | Distance of lamp from pondweed |
| Give dependant variable in this investigation | Number of oxygen bubbles released per minute - OR volume of oxygen collected |
| List some control variables in this investigation | Species of pondweed used - Number of leaves on pondweed - Temperature of water - Wattage of lamp - Concentration of CO2 in water - Controlled by dissolving sodium hydrogencarbonate |
| Describe how to test leaves for starch to show photosynthesis has taken place | Remove leaf from plant - Boil beaker of water using Bunsen burner - Place leaf in boiling water for 20 seconds - Remove leaf and place into boiling tube of ethanol - Boil ethanol by placing boiling tube in beaker of very hot water |
| Describe how to test leaves for starch to show photosynthesis has taken place PT2 | - Remove leaf when colourless - Wash in cold water - Place leaf on white tile and add dilute iodine solution with a pipette - Any starch present will turn brown iodine solution blue/black |
| Why is the leaf placed in boiling water? | To denature enzymes involved in cellular processes |
| Why is the leaf placed in boiling ethanol before testing for presence of starch? | o remove green pigment (chlorophyll) in leaf - Colour change can be seen when iodine added - Removes waxy cuticle |
| What safety precautions should be taken when boiling in ethanol? | Use a water bath (do not heat with naked flame) - Ethanol is flammable - Use forceps or tongs - Protects skin |
| Explain why chloroplasts appear green | Chlorophyll absorbs red / blue light - Reflects green light |
| Explain why different colours of light affect the rate of photosynthesis | Green is reflected (not absorbed) - Results in low rate of photosynthesis - Blue & red is absorbed - Results in faster rate of photosynthesis |
| What does the plant use glucose for? | Making cellulose cell walls - Making proteins and DNA - Making starch for storage - Making sucrose for transport |
| Give the role of nitrate ions in plants | Use- Making amino acids and proteins, Making DNA, Growth Deficiency symptom- Stunted growth |
| Give the role of magnesium ions in plants | Use- Making chlorophyll Deficiency symptom-Yellow leaves |
| Why is a balanced diet important? | Helps maintain good health |
| Give the consequences of having a diet that contains too much fat | Obesity - Blockage of arteries - High blood pressure / heart disease - Diabetes |
| Why is protein good in the diet? | Helps with growth and repair of muscles found in meats, fish, egg and cheese Deficiency disease- Kwashiorkor |
| Why are carbs good in the diet? | Helps with energy store found in gluecose, lactose, sucrose and starch |
| Why are lipids good in the diet? | helps with insulation and long term energy store found in butter and cheese |
| Why is water good in the diet? | Supports chemical reactions inside cells |
| Why is fibre good in the diet? | - Prevents constipation, Helps move food through gut found in fruit and veg |
| Why is calcium good in the diet? | strong bones and teeth found in milk and cheese |
| Why is iron good in the diet? | used to make haemoglobin found in red meat deficiency disease is anemia |
| Why is vitamin A good in the diet? | Helps improve vision found in fish liver oils, butter and carrots deficiency disease is night blindness |
| why is Vitamin C good in the diet? | Sticks together cells lining the mouth found in lemons and oranges deficiency disease is scurvy |
| why is vitamin D good in the diet? | helps with strong bones found in fish liver oils, made by skin in sunlight deficiency disease is rickets |
| How do energy requirements vary with activity levels? | Age - older people need less food than young people as activity levels are lower - Pregnant women need more food, iron, and calcium to support growing baby |
| Why is food needed? | - For growth and repair of tissues - Fight disease - Supply fuel needed to release energy |
| What is digestion? | The break down of large, insoluble molecules into small, soluble ones - For absorption through the wall of the small intestine |
| What is mechanical digestion | Physical breakdown of food - e.g. teeth chew food, muscles in stomach churn food |
| What is chemical digestion? | Enzymes act as biological catalysts - Break down large, insoluble molecules into small, soluble ones |
| How does digestion start in the mouth? | Mechanical breakdown of food by teeth - Amylase released - digests starch into maltose |
| What is peristalsis? | - Contraction and relaxation of circular and longitudinal muscles which push food along the gut |
| What is the role of the stomach? | Secretes hydrochloric acid to kill pathogens - Muscular walls churn food (mechanical digestion) |
| What is the role of hydrochloric acid (HCl)? | Kills pathogens |
| What is the role of bile? | Emulsifies - breaks down large lipid droplets into small ones to increase the surface area - Neutralises hydrochloric acid |
| Where is bile made, stored, and released into? | Made - liver - Stored - gall bladder - Released into - small intestine |
| What is the role of maltase? | To digest maltose into glucose |
| What is role of amylase? | To digest starch into maltose |
| Where is amylase made? | - Salivary glands, pancreas |
| Where does amylase act? | Mouth, small intestine |
| What is the role of lipase? | To digest lipids into fatty acids and glycerol |
| Where is lipase made? | Pancreas |
| Where does lipase act? | - Small intestine |
| What is the role of protease? | To digest proteins into amino acids |
| Where is protease made? | Stomach, pancreas |
| Where does protease act? | Stomach, small intestine |
| How is the small intestine adapted for its function? | Large surface area provided by villi and microvilli - Lots of capillaries - Thin wall - short diffusion distance - Lacteals - absorption of fats |
| What is the role of the rectum? | Stores faeces |
| What is ingestion? | When food enters the mouth |
| What is absorption? | The movement of soluble food through the wall of the small intestine into the blood stream |
| What is assimilation? | When small food molecules are used to build large ones |
| What is excretion? | The removal of waste products of metabolism |
| What is egestion? | The removal of faeces from the anus |
| Describe how to investigate the energy content of food | Add water to clamped boiling tube - Record starting temperature of water - Place food sample on mounted needle and ignite using Bunsen burner - Hold burning food sample under boiling tube of water until completely burned |
| Describe how to investigate the energy content of food PT2 | Record final temperature of water - Calculate change in water temperature - Calculate the energy released by food - Repeat with different food types for comparison |
| How is the energy released by a food calculated? | Energy released (J) = mass of water (g) x rise in temperature (°C) x 4.2 |
| How is the reliability of this investigation improved? | Repeat three times - Calculate average change in temperature |
| What does a large increase in temperature indicate? | Food contains a lot of energy |
| What is the independent variable in this investigation? | Type of food being burnt |
| What is the dependent variable in this investigation? | Temperature change of water |
| What are the control variables in this investigation? | Mass of food - Mass of water - Distance of food from water |
| What is respiration? | Makes ATP - ATP used to release energy |
| What is the energy in ATP used for? | Contraction of muscles - Cell division - Building large molecules from small ones - Active transport |
| What is the equation for respiration? | Glucose + oxygen → carbon dioxide + water + (energy) |
| What is the symbol equation for respiration? | C6H12O6 + 6O2 → 6CO2 + 6H2O |
| What is aerobic respiration? | Release of energy using oxygen - Carried out by mitochondria |
| What is anaerobic respiration? | Respiration without the use of oxygen - Glucose incompletely broken down |
| Give 2 examples of anaerobic respiration | Yeast - Muscle cells during strenuous exercise |
| What is the equation for anaerobic respiration in yeast? | Glucose → ethanol + carbon dioxide (+ little energy) |
| How can the products of anaerobic respiration in yeast be used commercially? | - Ethanol - beer-making - Carbon dioxide - helps bread dough rise |
| Summary of anaerobic respiration in muscle cells: | Due to insufficient oxygen delivery to muscles e.g. when sprinting - Glucose → lactate (+ little energy) - Oxygen debt builds up |
| What is an oxygen debt? | Volume of oxygen needed to completely breakdown the lactate |
| What substance can be used to remove carbon dioxide? | Soda lime |
| Hydrogen carbonate indicator colours: | - Atmospheric carbon dioxide (0.04%) = red/orange - High levels of carbon dioxide = yellow - Low levels of carbon dioxide = purple |
| What is the role of the stomata? | Allows carbon dioxide into the leaf and oxygen out |
| What is the role of diffusion in gas exchange in plants? | Plants need oxygen for respiration and carbon dioxide for photosynthesis - These gases diffuse into the leaf through the stomata |
| What is the role of diffusion in gas exchange in plants? PT2 | Respiration produces carbon dioxide, which can be used by the leaf for photosynthesis - During the day, photosynthesis occurs much faster than respiration, so excess oxygen diffuses out of leaves into atmosphere |
| How is the leaf adapted for gas exchange? | Large surface area to absorb light and carbon dioxide - Thin and flat so short diffusion distance for carbon dioxide and oxygen - Lots of chloroplasts containing chlorophyll for photosynthesis |
| How is the internal structure of the leaf adapted for gas exchange? | Waxy cuticle reduces evaporation of water - Stomata can open to allow more carbon dioxide to diffuse in, and oxygen to diffuse out - Spongy mesophyll layer contains air spaces to allow gas exchange in and out of the mesophyll |
| When does respiration occur in plants? | Both in the day and at night |
| Describe how to investigate how gas exchange in a flowering plant changes with light intensity | Place hydrogencarbonate indicator solution into four boiling tubes - Add leaf to three tubes, no leaf in the fourth - Seal all boiling tubes with cork - Place one tube (A) with leaf in direct sunlight |
| Describe how to investigate how gas exchange in a flowering plant changes with light intensity PT2 | Cover one tube (B) with leaf with aluminium foil to prevent any light entering tube - Cover one tube (C) with leaf with thin cloth to allow some light to enter - Place tube (D) without leaf in direct sunlight (control) |
| Describe how to investigate how gas exchange in a flowering plant changes with light intensity PT3 | Leave tubes for one hour and note change in indicator colour |
| Explain the expected results of this investigation | Tube A = purple - More photosynthesis occurring than respiration - CO2 absorbed by leaf = lower levels of CO2 in tube |
| Explain the expected results of this investigation PT2 | Tube B = yellow - No photosynthesis - Respiration still occurring - CO2 produced by leaf = higher levels of CO2 in tube |
| Explain the expected results of this investigation PT3 | Tube C = orange - Rate of photosynthesis = rate of respiration - No net change in CO2 levels |
| Explain the expected results of this investigation PT4 | Tube D = orange - No leaf present - CO2 remains at atmospheric levels |
| Give control variables for this investigation | Size of leaf - Species of leaf - Volume and concentration of indicator - Temperature |
| How are the airways kept clean? | Goblet cells secrete mucus - Mucus traps the dirt/bacteria - Cilia (cells with hairlike structures) waft mucus up to mouth - Mucus is swallowed and destroyed by hydrochloric acid in stomach |
| What is ventilation? | - Movement of air into and out of the lungs |
| Describe the process of breathing in (inhalation) | - External intercostal muscles contract - Ribs move up and out - Diaphragm contracts and flattens - Volume inside thorax increases - Pressure decreases - Air is sucked into the lungs |
| Describe the process of breathing out | Internal intercostal muscles contract - Ribs move down and in - Diaphragm relaxes and become dome shaped - Volume inside thorax decreases - Pressure increases - Air is forced out of the lungs |
| Compare inhaled and exhaled air | Inhaled air contains more oxygen and less carbon dioxide than exhaled air |
| How are the alveoli adapted for gas exchange? | Large surface area - Good blood supply - Thin walls - short diffusion pathway - Moist - dissolve gases |
| Describe the effects of smoking on the body | Cilia are paralysed → build up of mucus and pathogens → smoker’s cough → bronchitis - Smoke damages alveolar walls → walls break down → decreased surface area for gas exchange → emphysema |
| Describe the effects of smoking on the body PT2 | Carcinogens → tumour growth → lung cancer - Carbon monoxide combines irreversibly with haemoglobin in red blood cells → forms carboxyhaemoglobin → less oxygen transported → reduced respiration rate |
| Why can unicellular organisms (e.g. amoeba) rely on diffusion for movement of substances into and out of the cell? | Large surface area to volume ratio - Short diffusion distance |
| Why do animals need circulatory systems? | Surface area to volume ratio is too small - Diffusion is too slow - Circulatory system needed to transport oxygen |
| What is the role of the phloem? | Transports sugars from leaves to growing regions/roots for storage i.e. Both up and down the shoot |
| Describe the structure of phloem | Sieve tubes with sieve plates in between - Companion cells contain lots of mitochondria for release of energy |
| What is the role of the xylem? | Transports mineral ions and water from roots to flowers i.e. Up the shoot only |
| Describe the structure of xylem | Hollow forming a continuous column - no cytoplasm - Lignin gives the xylem strength and support |
| How do mineral salts enter the plant? | Active transport - From an area of low concentration (soil) to an area of high concentration (in the root hair) - Requires energy |
| How is water absorbed by root hair cells? | Osmosis - From an area of high water potential (the soil) - To an area of low water potential (root hair cell) |
| Define transpiration | The loss of water vapour from the surface of the leaf (stoma) |
| Describe the transport of water in a plant | Enters root hair cell by osmosis - Water molecules are attracted to each other - Transpiration stream in xylem - Transpiration out of the stomata |
| What is the transpiration stream? | - The continuous column of water moving up the xylem from the roots to the leaves |
| What is the role of the transpiration stream? | Transports mineral ions - Keeps plant cells turgid - Cools the plant - Supplies water for the leaves for photosynthesis |
| Describe and explain how rates of transpiration may be increased | Hot - water evaporates faster - Dry - increases the concentration gradient between the leaf and the surrounding air - Windy - water is blown off the leaf increasing concentration gradient |
| Describe and explain how rates of transpiration may be decreased | Cold - water evaporates slower - Humid - small concentration gradient between the leaf and the surrounding air - Still air - water is not removed from the surface of the leaf |
| What instrument is used to measure water uptake by a plant? | - Potometer |
| Describe how to use a potometer to measure the rate of water uptake at different light intensities | Cut plant shoot underwater - Set up the apparatus and make sure it is airtight - Dry leaves of shoot - Allow single air bubble to form in capillary tube - Place lamp 10cm from leaf |
| Describe how to use a potometer to measure the rate of water uptake at different light intensities PT2 | Allow plant to adapt to conditions for 5 minutes - Record starting location of air bubble - Leave for 30 minutes - Record the end location of the air bubble - Change the light intensity |
| Describe how to use a potometer to measure the rate of water uptake at different light intensities PT3 | Calculate rate of transpiration - Repeat with lamp at different distances |
| How is the rate of transpiration calculated? | Divide distance travelled by bubble by the time period - The further the bubble travels, the greater the rate of transpiration |
| Why is the plant cut underwater? | To prevent air entering xylem |
| Why is it necessary to dry the leaves of the shoot? | - Wet leaves will reduce rate of transpiration |
| Why does the plant need to be left for 5 minutes before recording location of bubble? | Allows plant to equilibrate to new conditions - Change in transpiration rate is not instantaneous |
| What is the independent variable in this investigation? | - Distance of light from plant - i.e light intensity |
| What is the dependent variable in this investigation? | Distance moved by bubble along capillary tube |
| Give control variables for this investigation | Temperature - Air flow around plant - Supply of water to plant |
| Why is the rate of water uptake not a full representation of rate of transpiration? | Water used in photosynthesis - Water produced by respiration - Water used for cooling - Water used for support of plant stem |
| List the components of the blood | Plasma - White blood cells (phagocytes and lymphocytes) - Red blood cells - Platelets |
| What does the blood transport? | Oxygen from the lungs to other parts of the body - Carbon dioxide from other parts of the body to the lungs - Nutrients from the gut to all parts of the body - Urea from liver to kidneys |
| List substances transported in the plasma | Carbon dioxide - Urea - Glucose - Amino acids - Hormones |
| How are red blood cells adapted for their function? | Biconcave disc shape - large surface area for transport of oxygen - Haemoglobin binds to oxygen forming oxyhaemoglobin - No nucleus - more space for haemoglobin |
| How does the body prevent pathogen entry? | Skin acts as a barrier - HCl in stomach destroys pathogens - Hairs prevent entry - Platelets clot the blood at the site of a wound |
| How do white blood cells attack invading pathogens | Phagocytes engulf pathogens - Lymphocytes recognise antigens and produce antibodies which destroy pathogens - Antitoxins made |
| How do lymphocytes destroy pathogens? | Recognise antigens - Make antibodies (proteins) which destroy pathogens by: - Causing bacteria to stick together - Label pathogen so it’s easily recognisable by phagocytes - Produce antitoxins - Cause bacteria to burst |
| Explain how the body usually responds to foreign proteins | White blood cells recognise antigens - Ingest foreign proteins by phagocytosis - Antibodies produced - Memory cells produced - Provide faster response upon reinfection |
| How does a vaccine work? | Dead or weakened pathogen injected - Lymphocytes recognise antigens and produce antibodies - Memory cells made - Produce antibodies much faster next time |
| Provide some examples of vaccines and their mode of action | Dead pathogens e.g. whooping cough - Weakened pathogens e.g. TB, measles - Antigens e.g. influenza |
| What is the role of platelets? | Platelets clot the blood at the site of a wound - Soluble fibrinogen is converted to insoluble fibrin |
| Describe the movement of the blood around the body starting at the right atrium | Deoxygenated blood enters the right atrium via the vena cava - Right atrium contracts forcing blood through tricuspid valve into right ventricle - Blood enters the right ventricle and leaves via the pulmonary artery |
| Describe the movement of the blood around the body starting at the right atrium PT2 | Blood flows to the lungs and becomes oxygenated - Blood returns to the heart and enters the left atrium via the pulmonary vein - Left atrium contracts forcing blood through bicuspid valve into the left ventricle |
| Describe the movement of the blood around the body starting at the right atrium PT3 | Left ventricles contracts forcing blood into the aorta - Oxygenated blood flows around the body and oxygen is used in respiration |
| How is our heart rate increased? | - Adrenaline increases heart rate - When we exercise, muscles produce carbon dioxide - Receptors in aorta and carotid artery detect increase in carbon dioxide - Electrical impulses sent to medulla - Accelerator nerve raises heart rate |
| What is the coronary artery? | Blood vessel that supplies the heart with oxygen |
| What factors contribute to coronary heart disease? | - Heredity - High blood pressure - Diet - high levels of saturated fat and cholesterol - Smoking - Stress - Lack of exercise |
| Explain how coronary heart disease can cause death | A lot of cholesterol can block coronary artery - Less oxygenated blood to heart muscle cells - Less aerobic respiration, more anaerobic respiration - Lactic acid build up causes heart attack |
| What does single circulation mean? | Blood is pumped from the heart to the lungs and then to rest of the body |
| What does double circulation mean? | - Blood flows twice into the heart for every once around the body |
| What does the circulatory system consist of? | Heart - Arteries, veins and capillaries - Blood |
| Why is the wall of the ventricles thicker than that of the atria? | The ventricles have to pump the blood further |
| Why is the wall of the left ventricle thicker than that of the right ventricle? | Blood from the right ventricle is only pumped to the lungs - Blood from the left ventricle is pumped much further - around the whole body |
| Describe the structure of arteries | Thick muscle and elastic fibre walls - Narrow lumen - High blood pressure |
| Why are the artery walls so thick? | To withstand the high pressure of the blood flowing inside |
| Describe the structure of the veins | Thin muscle and elastic fibre walls - Large lumen - Lower blood pressure - Semi-lunar valves prevent the back flow of blood |
| Describe the structure of the capillaries | Thin walls - one cell thick - Short diffusion distance - Narrow lumen |
| Name the blood vessel that takes oxygenated blood to the kidney | Renal artery |
| Name the blood vessel that takes deoxygenated blood from the kidney | Renal vein |
| Name the blood vessel that takes oxygenated blood to the liver | Hepatic artery |
| Name the blood vessel that takes deoxygenated blood from the liver | Hepatic vein |
| Define excretion | Removal of waste products of metabolism |
| What are the waste gas products from respiration and photosynthesis? | Respiration: Carbon dioxide - Photosynthesis: Oxygen |
| How are waste gas products exported from the leaf? | Stomata allow diffusion of gases out of the leaf - From high concentration gradient to low concentration gradient |
| What substances are excreted from the body? | Urea from kidneys - Carbon dioxide from lungs - Sweat from skin - Note: faeces is NOT excreted, it is egested |
| Define osmoregulation | Control of water levels in the body |
| Explain how the structure of the blood vessels entering and leaving the glomerulus help to move glucose into the Bowman’s capsule | Vessel entering is wider than vessel leaving - Increased pressure - Causes ultrafiltration |
| What is ultrafiltration? | The filtering of small molecules from the glomerulus into the Bowman’s capsule - Glucose, ions, and urea (the glomerular filtrate) enter Bowman’s capsule - Proteins stay in blood - too large to pass through basement membrane |
| What is selective reabsorption? | Proximal convoluted tubule reabsorbs small molecules back into blood - All glucose reabsorbed (by active transport) - Some ions - Some water - No urea |
| Describe how glucose is reabsorbed back into the blood | Active transport (requires energy) - From low concentration in the nephron to a high concentration in the blood |
| How is the proximal convoluted tubule adapted for selective reabsorption of small molecules and ions? | Many mitochondria - provides energy for active transport of glucose - Large surface area - greater area for active transport proteins to be located |
| Why does the reabsorption of glucose occur in the proximal convoluted tubule? | Proteins that facilitate active transport of glucose are specific - Only found in proximal convoluted tubule |
| What is the role of the collecting duct? | Selective reabsorption of water - Passing urine to the ureter |
| What is ADH? | Hormone - Changes permeability of collecting duct |
| explain the effect of ADH on blood water levels | Osmoreceptors in hypothalamus detect water content of blood - If water content is too low: - ADH released from pituitary gland - ADH makes walls of collecting duct more permeable - More water is reabsorbed - Urine is concentrated and yellow in colour |
| What is the composition of urine? | Ions - Water - Urea |
| What is homeostasis? | - Maintenance of a constant internal environment e.g. water content, temperature |
| What is a stimulus? | Change in the environment |
| What are auxins? | What are auxins? - Plant hormones |
| What is a tropism? | The response of a plant to a directional stimulus |
| List different types of tropism | Phototropism - a plant’s response to light - Geotropism - a plant’s response to gravity |
| Describe the roots and shoots response to light | - Roots - negative phototropism - Shoots - positive phototropism |
| Describe the roots and shoots response to gravity | Roots - positive geotropism - Shoots - negative geotropism |
| What is a coleoptile? | Simple plants used to investigate tropism - Cereal seedling |
| What is a clinostat? | apparatus used to remove the effect gravity/light/water |
| Describe how a stem may bend towards the light | Auxins concentrate on the side furthest from the light - Causes cell elongation - Stem bends towards light |
| What are the sense organs in a human? | Eye - receives light energy - Ear - receives sound and kinetic energy - Muscle - receives kinetic energy - Tongue - receives chemical energy - Nose - receives chemical energy - Skin - receives kinetic and heat energy |
| What is the difference between hormonal and nervous responses? | Nervous involves electrical impulses, hormonal involves chemicals carried in the blood - Nervous response faster, hormonal slower - Nervous response short-lived, hormonal long-lived - Nervous response very localised, hormonal wide-spread |
| What is the CNS? | Brain and spinal cord - Linked to sense organs by nerves |
| What is the list of responses in a nervous response? | Stimulus - receptor - sensory neurone - CNS - motor neurone - effector - response - Involves electrical impulses and synapses |
| What is the list of responses in a reflex action? | Stimulus - receptor - sensory neurone - relay neurone - motor neurone - effector - response - Involves electrical impulses and synapses - e.g. withdrawal of finger from hot object |
| What is a synapse? | - Gap between two neurones - Neurotransmitter diffuses and binds to post-synaptic membrane |
| How is a reflex action different to a regular response? | Reflex action is faster, involuntary, and involves relay neurone |
| What is an effector? | Muscle (contracts) or a gland (secretes a hormone) |
| What is role of choroid? | - stops light being reflected inside the eye |
| What is role of cornea? | refracts light |
| What is role of lens? | refracts light |
| what is role of conjunctiva? | protects eye |
| what is role of sclera? | tough outer casing - protects eye |
| what is role of retina? | - contains photoreceptors (rods (dim light) and cones (detect colour)) which are sensitive to light |
| What is role of iris? | contains radial and circular muscles which control the size of the pupil |
| What is role of pupil? | allows light to enter the eye |
| What is role of suspensory ligament and ciliary muscles | - control the shape of the lens |
| What is role of optic nerve | - takes electrical impulses from the eye to the brain |
| What is role of blind spot | where the the optic nerve enters the eye |
| What is accommodation? | Changes that take place within the eye - Enable us to focus on objects at different distances |
| How does the eye focus on a nearby object? | Ciliary muscle contracts - Suspensory ligaments slacken - Lens fat - Light refracted strongly |
| How does the eye focus on a faraway object? | Ciliary muscle relax - Suspensory ligaments taut - Lens thin - Light refracted less strongly |
| How does the pupil constrict in bright light and why is this necessary? | Circular muscles contract - Radial muscles relax - Pupil constricts - Protects the retina from the bright light |
| How does the pupil dilate in dim light and why is this necessary? | Circular muscles relax - Radial muscles contract - Pupil dilates - Allows more light to enter the eye |
| What is the role of the skin? | Sense organ for pain, touch and pressure - Tough outer layer - Controls heat loss - Barrier - prevents entry of pathogens - Prevents water loss |
| Explain what happens when your body temperature is too high | Hair erector muscles relax - Hairs lay flat - Less insulating air trapped close to the body - Vasodilation (arterioles dilate) - Blood flows closer to skin surface - More heat radiated - Sweat evaporates and cools the body |
| Explain what happens when your body temperature is too low | Hair erector muscles contract - Hairs stand up - More insulating air trapped close to the body - Vasoconstriction (arterioles constrict) - Less blood flows to surface of skin - Less heat radiated - Shiver - contraction of muscle releases heat |
| Where is adrenaline produced? | Adrenal gland |
| What is the effect of adrenaline on the body? | Prepares the body for ‘flight or fight’ - Pupils dilate - allows more light to enter the eye - Hairs stand up on end - to appear more intimidating - Breathing rate increases - to allow more oxygen into the body |
| What is the effect of adrenaline on the body? PT2 | Heart rate increases - to deliver more oxygen around the body - Blood diverted from gut to muscles |
| How is blood sugar level decreased? | Pancreas secretes insulin - Insulin converts soluble glucose into insoluble glycogen |
| Where is testosterone made and what is its function? | Testes - Stimulate secondary sexual characteristics e.g. voice deepening, sperm production, pubic hair |
| Where is oestrogen made and what is its function? | - Ovaries - Stimulates secondary sexual characteristics e.g. hips widening, breast growth, pubic hair - Repairs uterus lining - Inhibits FSH production, stimulates LH production |
| Where is progesterone made and what is its function? | Initially corpus luteum, later in pregnancy the placenta - Maintains uterus lining |
| Where is FSH made and what is its function? | - Pituitary gland - Matures eggs in ovaries - Stimulates egg and sperm production |
| Where is LH made and what is its function? | Pituitary gland - Causes ovulation (egg release from ovary) - Stimulates sperm production |
| Summary of sexual reproduction: | - 2 parents needed to make gametes (sex cells - sperm and eggs) - Sperm and egg fuse at fertilisation - Zygote formed - Divides by mitosis to form embryo - Produces genetically varied offspring |
| Summary of asexual reproduction | - 1 parent only - No gametes - No fertilisation - Cells from parent divide by mitosis and then break away - Forms new organism which is identical to parent (clone) |
| Comparison of sexual and asexual reproduction | Sexual Reproduction Asexual Reproduction Sex cells produced Yes No Fertilisation takes place Yes No Variation in offspring Yes No Helps survival in: Changing environment Stable environment |
| How does sexual reproduction make it more likely that a species can adapt to a changing environment? | Produces genetically varied offspring by: - Random fertilisation of gametes - Mixing of alleles from both parents - Meiosis |
| What is fertilisation? | - Fusion of male (sperm) and female (egg) gamete - Zygote formed - Undergoes mitosis - Embryo formed |
| What is a zygote? | Single cell formed after fertilisation occurs |
| What is pollination? | When pollen from the anther lands on the stigma |
| What is self pollination? | When pollen from the anther lands on the stigma in the same flower |
| What is fertilisation? | When pollen fuses with the egg in the ovary |
| Describe the features of an insect pollinated flower that help it attract insects | Large petals - attract insects - Coloured petals - attract insects - Scent - makes insects push past stamen - Nectar - makes insects push past stamen - Sticky pollen grains - attach to insect |
| Describe the features of a wind pollinated flower | Exposed stamens - allow pollen grains to be easily released - Feathery stigma - catches drifting pollen grains - Small petals - allows stamens and stigmas to be exposed - Small pollen grains - easily carried by the wind |
| Describe the events that lead to seed formation | Pollen lands on stigma - Pollen tube grows down style into ovary - Male gamete (pollen) fuses with female gamete (egg) - Ovule becomes seed - Ovule wall becomes seed coat - Ovary becomes fruit |
| What is germination? | Food store in seed is used up - Radicle grows down - Plumule grows up towards light and starts photosynthesis |
| What conditions are needed for germination? | Water - to activate enzymes - Oxygen - for respiration - Warm temperature - optimum temperature for enzyme-controlled reactions |
| Describe an investigation into the factors needed for germination | Set up 4 test tubes, with each containing 15 cress seeds on cotton wool - In one test tube (A) leave cotton wool dry - In one test tube (B) add water to cotton wool to make it moist |
| Describe an investigation into the factors needed for germination PT2 | - In one test tube (C) add water to cotton wool, then add layer of oil on top - In one test tube (D) add water to cotton wool to make it moist, then place in fridge - Leave tubes A, B and C at room temperature |
| Describe an investigation into the factors needed for germination PT3 | Leave all tubes for set period of time (e.g. 5 days) - Compare results and see which tube has the greatest number of germinated seeds |
| What is the purpose of the layer of oil in test tube C? | Prevent oxygen reaching seeds |
| Which test tube would you expect to see the greatest number of seeds germinating? | B - Only tube to provide water, oxygen and warmth - All others missing at least one factor |
| Give the independent variable for this investigation | Abiotic conditions in which seeds are germinating (water, oxygen, temperature) |
| Give the dependent variable for this investigation | - Number of seeds germinating after 5 days |
| Give control variables for this investigation | Temperature of tubes A, B and C - Species of cress seeds used - Parent plant of cress seeds - Type of water used (boil first then cool) - Light intensity |
| Give examples of natural asexual reproduction in plants | Strawberry runners - Tubers |
| Describe how strawberry runners reproduce asexually | Runners = horizontal stems that grow sideways from parent plant - When runners touch the soil, plantlets grow roots - New plantlets grow and become independent from parent plant |
| Give an example of an artificial method of asexual reproduction in plants | Taking a cutting |
| Describe the process of taking a cutting | A piece of a plant’s stem is cut off - Dipped in rooting powder - Contains plant growth hormones - Transferred to soil - Grow into genetically identical plants |
| Describe the structure and function of the male reproductive system | Structure Function Penis - Passes urine out of the body from the bladder - Allows semen to enter into the vagina of a woman during sexual intercourse Testis - Contained in the scrotum - Produces sperm and testosterone |
| Describe the structure and function of the male reproductive system PT2 | Urethra- Ring of muscle in the urethra prevents mixing of urine Urethra- Exports urine or semen from the body Sex Gland - Produces semen (provides sperm cells with nutrients) Urethra |
| Describe the structure and function of the male reproductive system PT3 | Sperm Duct (Vas Deferens) - Sperm passes through the sperm duct where it mixes with fluids produced by the sex gland |
| Where is testosterone made and what is its function? | Testes - Stimulate secondary sexual characteristics e.g. voice deepening, sperm production, pubic hair |
| Describe the structure and function of the female reproductive system | Oviduct (Fallopian Tube) - Connects the ovary to the uterus - Lined with ciliated cells to push the ovum towards uterus for fertilisation Ovary - Contains female gametes (ova) which mature and develop when FSH is released |
| Describe the structure and function of the female reproductive system PT2 | Uterus - Muscular structure with a soft lining - Fertilised egg cell implanted there to develop into a foetus Cervix - Ring of muscle at lower end of uterus - Keeps foetus in place during pregnancy |
| Describe the structure and function of the female reproductive system PT3 | Urethra - Tube that passes urine out of the body Vagina - Muscular tube that the male’s penis enters during sexual intercourse |
| How long does the menstrual cycle last? | Approximately 28 days |
| On which day is the egg usually released (ovulation)? | 14 |
| What is menstruation? | Breakdown of thickened uterus lining - Occurs when egg has not been fertilised |
| How long does menstruation last? | - 5 - 7 days |
| Where is oestrogen made and what is its function? | Ovaries - Stimulates secondary sexual characteristics e.g. hips widening, breast growth, pubic hair - Causes thickening of uterus lining - Inhibits FSH production, stimulates LH production |
| Where is progesterone made and what is its function? | Initially corpus luteum, later in pregnancy the placenta - Maintains uterus lining - Inhibits release of LH and FSH |
| Where is FSH (Follicle Stimulating Hormone) made and what is its function? | Pituitary gland - Matures eggs in ovaries - Stimulates ovaries to produce oestrogen - Stimulates sperm production in males |
| Where is LH (Luteinising Hormone) made and what is its function? | Pituitary gland - Causes ovulation (egg release from ovary) - Stimulates sperm production in males |
| Explain the hormonal control of menstruation | Pituitary gland produces FSH → stimulates development of a follicle in the ovary - Egg develops inside follicle - Follicle produces oestrogen - Oestrogen causes growth and repair of uterus lining - Inhibits production of FSH |
| Explain the hormonal control of menstruation PT2 | When oestrogen reaches high enough level → stimulates release of LH from pituitary gland - LH causes ovulation (approximately day 14 of cycle) - Follicle becomes corpus luteum → starts producing progesterone - Progesterone maintains uterus lining |
| Explain the hormonal control of menstruation PT3 | If the ovum not fertilised → corpus luteum breaks down, progesterone levels drop - Causes menstruation - Uterus lining breaks down and is removed through the vagina |
| Explain the hormonal control of menstruation PT4 | If fertilisation occurs → corpus luteum continues to produce progesterone - Prevents uterus lining from breaking down and aborting pregnancy - After placenta develops, it secretes progesterone throughout pregnancy |
| Describe the changes that take place in the uterus during the menstrual cycle | Uterus lining thickens - Progesterone maintains lining - If fertilisation has not occurred, lining breaks down and is shed - If egg is fertilised, lining not broken down |
| Describe the passage of sperm in the female human | Semen (contains sperm and fluid from seminal vesicles) is ejaculated into the vagina - Sperm swim through uterus to oviduct |
| Where does fertilisation take place? | Oviduct |
| What is the function of the acrosome in the head of a sperm cell? | Contains digestive enzymes - To break through egg membrane |
| Why does a sperm cell require mitochondria? | For respiration - To provide energy for tail |
| What is the function of the sperm cell’s tail? | Allow sperm cell to move |
| Explain why avoiding sexual intercourse at certain times of the menstrual cycle may not be a reliable method of birth control | Ovulation may vary within a woman - Sperm can survive for a number of days |
| Give the different stages of development during human reproduction | Gametes - Zygote - Embryo - Foetus - Baby |
| Define gamete | A sex cell e.g. sperm or egg |
| Explain how an 8 cell embryo is formed | Sperm and egg made by meiosis - Fertilisation in oviduct - Zygote implants in uterus wall - Divides by mitosis |
| What is the role of the placenta? | Provides embryo with oxygen and nutrients from the mother’s blood - Removes urea and CO2 from embryo - Releases progesterone in late pregnancy |
| Describe how a developing foetus is supplied with nutrients | Nutrients (e.g. glucose, oxygen, amino acids) from mother’s blood - Diffuse through placenta - Placenta has large surface area and thin walls - Umbilical cord joins foetus blood supply to placenta |
| How is the placenta adapted for efficient exchange of substances? | Villi - large surface area - Good blood supply from capillaries - steep concentration gradient - Thin walls - short diffusion distance |
| What is the role of the amnion/amniotic fluid? | Protects foetus from physical impact - Acts as shock absorber |
| Where does the amniotic sac develop? | Uterus |
| What is a genome? | The entire DNA of an organism |
| What is a gene? | Section of DNA which codes for a protein |
| Where are genes found? | In chromosomes within the nucleus |
| What is the role of genes? | Control the activities of the cell - Determine which proteins are made |
| What is the structure of a nucleotide? | Sugar, phosphate, base (G, C, A or T) |
| What are the four DNA bases? | Adenine (A) - Thymine (T) - Cytosine (C) - Guanine (G) |
| Describe base pairing in DNA | Adenine (A) - Thymine (T) - Cytosine (C) - Guanine (G) |
| Describe the structure of DNA | - 2 strands - Coiled to form double helix - Strands linked by paired bases - Adenine to thymine, guanine to cytosine |
| Describe the structure of RNA | Single stranded - Contains uracil base (U) instead of thymine (T) |
| Describe base pairing in RNA | Adenine (A) - Uracil (U) - Cytosine (C) - Guanine (G) |
| How does DNA differ from RNA? | DNA RNA Sugar Deoxyribose Ribose Bases A, T, C, G A, U, C, G Double stranded vs single stranded Double stranded Single stranded Length Long Short |
| What is a codon? | 3 bases of messenger RNA (mRNA) which correspond to a specific amino acid or stop codon |
| Why is DNA described as ‘non-overlapping’ | Each codon codes for one amino acid - Codons are discrete - bases are not shared between codons |
| What is an anticodon? | 3 bases on a tRNA molecule which correspond to the codon of an mRNA molecule |
| Define polypeptide | Chain of amino acids - Polypeptide then folded to make a protein |
| What are the 2 main stages of protein synthesis? | Transcription - formation of mRNA - Translation - formation of a polypeptide |
| Where does transcription occur? | In the nucleus |
| What happens during transcription? | Occurs in nucleus - DNA unwinds in nucleus - Base pairs exposed on template strand - RNA nucleotides pair up with complementary bases of template strand - mRNA is formed and leaves nucleus - mRNA enters cytoplasm |
| Where does translation occur? | At the ribosomes |
| What happens during translation? | mRNA attaches to ribosome - mRNA has codons that act as template - mRNA codon pairs with complementary transfer RNA (tRNA) anticodon - Each tRNA is bound to a specific amino acid |
| What happens during translation? PT2 | Amino acids join to form a polypeptide - Ribosome moves along mRNA strand - tRNA is recycled - At the end of the chain a stop codon terminates translation |
| Describe the differences between transcription and translation | Transcription Translation Occurs in the nucleus Takes place at the ribosomes Uses DNA to make RNA Involves mRNA and tRNA DNA unzips, one strand copied tRNA anticodons bind to mRNA codons Produces mRNA Produces polypeptide |
| If there are 4 RNA bases (A, U, C and G), and 3 bases per codon, how many different codons is it possible to make? | 4 to the power of 3 = 64 |
| What is an allele? | Different form of the same gene which gives rise to different characteristics - e.g. B = brown eyes, b = blue eyes |
| Define homozygous | Having two copies of the same allele |
| Define heterozygous | - Having two different copies of the same allele |
| Describe genotype | The alleles an organism has |
| Define phenotype | The physical appearance of an individual |
| Define recessive | Allele only expressed if the dominant allele is not present |
| Define dominant | Allele expressed even if only one is present |
| Define codominance | If two alleles are expressed in the same phenotype |
| Define monohybrid inheritance | - Single gene responsible for phenotype |
| Define polygenic inheritance | Many genes combine to give phenotype - Most phenotypic features are a result of polygenic inheritance |
| A mother is recessive and has blonde hair (bb), and a father is heterozygous, and brown haired (Bb). Calculate the probability of their children having blonde hair. First, create a table with the information provided | Mother Father Phenotype Blonde Brown Genotype bb Bb Gametes b or b B or b |
| What is a carrier? | Someone who has a gene for a disease but does not suffer from any symptoms |
| What is a pedigree diagram? | Shows how a genetic condition is passed from generation to generation - Possible to work out which is the dominant allele - Can then work out genotype of each person/animal in the pedigree |
| What are the genotypes for males and females? | Male: XY - Female: XX |
| How is sex inherited? | X chromosome from mother - All eggs contain one X chromosome - X or Y chromosome from father - 50% of sperm cells contain one X chromosome, 50% contain one Y chromosome |
| Define haploid | Contains 1 set of chromosomes e.g. 23 in humans - Gametes are haploid |
| Define diploid | Contains 2 sets of chromosomes e.g. 46 in humans |
| Define clone | Genetically identical cell/organism |
| Give examples of when mitosis occurs | Growth, repair - Cloning - Asexual reproduction |
| Main steps of mitosis: | Prophase - Metaphase - Anaphase - Telophase |
| What is the product of one round of mitosis? | 2 genetically identical cells - Cells are diploid |
| Where does meiosis occur? | Sex organs - Meiosis produces gametes |
| What is the product of one round of meiosis? | 4 genetically varied cells - Haploid |
| Compare the features of mitosis and meiosis | Feature Mitosis Meiosis Number of cell divisions 1 2 Number of daughter cells formed 2 4 Number of chromosomes in cells formed Diploid - Haploid Type of cells formed Body cells - Sex cells (gametes) Genetic variation in cells formed None - Variation |
| How is variation within a species brought about? | Genetics (e.g. hair colour) - Environmental conditions (e.g. reduced growth due to poor diet when young) - Or a combination of both |
| How does genetic variation occur? | Random fertilisation of gametes - Mixing of alleles from both parents - Meiosis |
| What is a mutation? | - A rare, random change in the genetic material that can be inherited |
| How may gene mutations occur? | Duplication - Deletion - Substitution - Inversion |
| What effect can mutation have? | - A mutation may lead to a change in DNA - Different DNA code may lead to different amino acids forming different proteins - Therefore altering the phenotype of an individual |
| What effect can mutation have? PT2 | BUT most mutations have no effect on phenotype - In some cases they have a small effect - Only rarely do they have a significant effect |
| Explain why a mutated base sequence can lead to a different protein than the normal DNA | Different mRNA codon produced in translation - Different tRNA anticodon binds during transcription - Brings different amino acid to polypeptide |
| Explain what effect a DNA mutation could have on the functioning of the enzyme produced | Deletion or insertion - Change amino acid sequence of whole protein - Causes change in shape of active site - Substrate will no longer fit - Enzyme does not function |
| Explain what effect a DNA mutation could have on the functioning of the enzyme produced PT2 | Substitution - Some codons may code for same amino acids - Not all changes to a base change an amino acid - Only one amino acid (if any) changes in protein - Enzyme may still function |
| How is the chance of mutation increased? | Ionising radiation (gamma, x-rays, UV) - Mutagens e.g. Chemicals in tobacco |
| Define evolution | All organisms alive today, and many more which are now extinct, evolved from simple life forms which first developed more than 3.2 billion years ago |
| Describe the mechanism of Natural Selection | Variation within a species due to mutation - Individuals better adapted more likely to survive and reproduce - Alleles passed onto offspring - Repeats over many generations - Selected for alleles become more prominent in population |
| How may bacteria become resistant to antibiotics? | Some bacteria have mutations which make them more likely to survive - The bacteria reproduce and pass on these favourable alleles to future bacteria - Soon the whole population of bacteria is resistant to the antibiotic |
| What is a sample? | When you take a smaller representative part of a population |
| Define ‘environment’ | The total non-biological components of the ecosystem e.g. water, soil, air |
| Define ‘habitat’ | The place where a specific organism lives |
| Define ‘population’ | All the organisms of a particular species found in an ecosystem |
| Define ‘community’ | The population of all species found in a particular ecosystem |
| Describe how a quadrat can be used to investigate the population size of an organism in two different areas | Divide the sample areas into a grid - Place quadrat randomly using a random number generator - Count how many of the species is present - Repeat - Multiply to total area - Repeat procedure for second area |
| Define biodiversity | The variety of plant and animal species in an ecosystem |
| Describe how a quadrat can be used to investigate the distribution of organisms in their habitats and measure biodiversity | Place quadrat randomly within sampling area - Using random number generator - Count number of members of the same species within quadrat - Repeat within sampling area using same size quadrat - Repeat process in another area to compare results |
| How can the reliability of quadrat sampling results be improved? | - Randomly place quadrat - Use same sized quadrat each time - Take more samples to collect larger sample size |
| What are biotic factors? | Non-biological (non-living) factors - e.g. temperature, pH of soil, light intensity, number of daylight hours |
| Define producer | - Plants which photosynthesise to produce food |
| Define consume | Animals which eat plants or other animals |
| What is a decomposer? | Organisms which decay dead material and help to recycle nutrients |
| Define parasite | An animal which lives inside another animal, gaining food and causing harm to host animal |
| Define predator | An animal which kills and eats another animal |
| Define trophic level | Position in a food chain / web - e.g. producer, primary consumer, secondary consumer, tertiary consumer |
| What is meant by a food chain or food web? | Shows feeding relationships - By showing which organism eats which organism - Shows the flow of energy from producer to top consumer through trophic levels |
| How does chemical energy flow through food chains/webs? | By feeding |
| What do the arrows in a food chain/web represent? | Direction of energy transfer |
| What is a pyramid of numbers? | They represent the number of organisms at each trophic level, irrespective of their biomass |
| What is biomass? | The total amount of living material in an organism |
| How is biomass measured? | Organism killed - Heated to remove water - Constant dry mass measured |
| What is a pyramid of biomass? | They represent the total mass of organisms in each trophic level, irrespective of their number |
| Give the advantage and disadvantage of using a pyramid of biomass | Advantage - More accurate as organism’s size taken into account - Disadvantage - Data difficult to obtain as dry mass required |
| Describe how a quadrat can be used to estimate plant biomass in a region | Divide the sample area into a grid - Record the (dry) mass of plant using scales - Remove any animals, soil etc. - Repeat - Multiply to total area |
| Explain why only 10% of energy is transferred from one trophic level to the next | Not all of the plant is eaten (in the case of producer → primary consumer) - Some parts are indigestible (in the case of producer → primary consumer) - Some energy lost in excretory products e.g. sweat, urine |
| Explain why only 10% of energy is transferred from one trophic level to the next PT2 | Respiration leads to loss of carbon dioxide and water - Maintenance of steady body temperature (e.g. homeostasis in cows) |
| Carbon Cycle | - Carbon dioxide is absorbed by green plants in photosynthesis - Carbon used to make glucose and proteins - Plants respire releasing carbon dioxide - Plants eaten by animals and carbon becomes part of their bodies |
| Carbon Cycle Part 2 | Animals respire releasing carbon dioxide - Plants and animals die and are decomposed by microorganisms - Microorganisms respire, releasing carbon dioxide - Complete combustion of fossil fuels releases carbon dioxide |
| Nitrogen Cycle | Nitrates in the soil are absorbed by root hair cells by active transport - Nitrates used to build plant amino acids and DNA - Plants and animals die, decompose, and are converted to ammonium ions by decomposers |
| Nitrogen cycle Part 2 | Nitrifying bacteria convert ammonium ions to nitrates - Denitrifying bacteria convert nitrates to nitrogen gas |
| Nitrogen Cycle part 3 | - Nitrogen fixing bacteria are present on root nodules of beans and peas and convert nitrogen gas into nitrates which are added to the soil - Lightning and the Haber Process are other sources of nitrogen |
| Explain how nitrates are absorbed into plants | By root hair cell - Using active transport - From low concentration to high concentration - Requires energy |
| How do nitrate ions help plants grow? | Used to build amino acids and DNA |
| How does the nitrogen in a nitrate ion in the soil become the nitrogen in a protein in an animal? | - Nitrate ions absorbed by root hair cell - By active transport - Plant incorporates nitrogen into amino acids / protein - Plant eaten by animal |
| How does the nitrogen in a nitrate ion in the soil become the nitrogen in a protein in an animal? PT2 | Animal digests protein - Using protease enzymes - Amino acids assimilated into animal protein |
| Describe how ammonium ions can be converted to nitrate ions in the soil | Nitrifying bacteria - Convert ammonium ions → nitrites → nitrates |
| How is acid rain made? | Acidic impurities in crude oil (a fossil fuel) → sulfur dioxide → sulfuric acid - Nitrogen and oxygen react in car engines → nitrogen oxides → nitric acid |
| What effect does acid rain have? | Destroys limestone buildings - Kills trees - Makes ponds too acidic leading to death of fish |
| What produces carbon monoxide? | - Incomplete combustion |
| What effect does carbon monoxide have on the body? | Combines irreversibly with haemoglobin so less oxygen transported |
| What is a greenhouse gas? | Gas that traps heat by reflecting infrared radiation |
| Give examples of greenhouse gases | Methane (cows, rice paddy fields) - Water vapour - Carbon dioxide (burning fossil fuels) - Nitrous oxide (burning fossil fuels, car engines) - CFCs |
| Where do CFCs come from? | - Aerosols, fridges |
| What effect do CFCs have on the environment? | Damage ozone layer - Contribute to greenhouse effect |
| Explain how the greenhouse effect causes global warming | Sun emits energy that enters Earth’s atmosphere - Energy absorbed and re-emitted by Earth’s surface as infrared (IR) radiation - Some IR radiation reflected back out into space |
| Explain how the greenhouse effect causes global warming PT2 | Some IR radiation absorbed by greenhouse gases - Heat is trapped within Earth’s atmosphere - As greenhouse gases levels increase, Earth’s average temperature increases - Causing global warming |
| How have humans contributed to the increase in atmospheric greenhouse gases? | Carbon dioxide produced by combustion of fossil fuels - Methane produced by grazing cattle - Methane released by rice paddy fields |
| How have humans contributed to the increase in atmospheric greenhouse gases? PT2 | - Deforestation results in more CO2 in atmosphere - Less photosynthesis occurring - CFCs from fridges and aerosols released into atmosphere |
| What possible effects does an enhanced greenhouse effect have? | Global warming - Ice caps melt - Sea levels rise - Low lying land floods - Destruction of habitats - Loss of biodiversity - Extreme weather - Change in bird migration patterns |
| How can humans reduce the build up of greenhouse gases in the atmosphere? | Burn less fossil fuels - Plant more trees / reduce deforestation - Use renewable energy (e.g. wind / solar) - Reduce cattle farming and use fewer paddy fields |
| Describe the effects of leached sewage and excess fertilisers on the environment | - Eutrophication - Fertilisers and sewage are washed (leached) into rivers - Water plants grow quickly |
| Describe the effects of leached sewage and excess fertilisers on the environment PT2 | - Competition for sunlight - Plants die - Bacteria feed on the dead plants - Bacteria use up all the oxygen in respiration - Fish die as not enough oxygen |
| Define deforestation | Removal of trees and forests |
| What effect does deforestation have on the environment? | Habitats are destroyed - Soil erosion → leaching of minerals → eutrophication - Soil erosion → flooding → land slides |
| What effect does deforestation have on the environment? PT2 | Disturbance of evapotranspiration - Burning of trees/cutting down trees → releases carbon dioxide → global warming - Burning of trees/cutting down trees → less photosynthesis → less oxygen in atmosphere |
| How do glasshouses and polythene tunnels increase crop yield? | Allow natural light in during summer, can provide artificial light in winter - Provide warmer environment than outside - trap heat energy (IR radiation), reduce convection |
| How do glasshouses and polythene tunnels increase crop yield? PT2 | Can be heated electronically if it’s too cold outside - Provide humid atmosphere - reduce water loss by transpiration |
| What effect does increasing carbon dioxide and temperature have on crop yield in glasshouses? | Increasing carbon dioxide → increases rate of photosynthesis → increases yield - Increasing temperature → increased growth and photosynthesis → increases yield |
| How do fertilisers increase crop yield? | - Replace lost nitrates and minerals in the soil - Nitrates required for protein synthesis and DNA formation in plants |
| Why do farmers use pesticides? | Why do farmers use pesticides? - Kill specific pests that would otherwise damage crop - Improve yield |
| What are the advantages and disadvantages of using pesticides? | Effective at controlling pests Expensive Readily available Persistent - may decompose slowly |
| What are the advantages and disadvantages of using pesticides? PT2 | Easy to use Stored in tissues of living organisms (Bioaccumulation) Becomes more concentrated along a food chain (Biomagnification) Toxic and not specific - kill other insects |
| What is biological control? | Introduction of a predator to prey on specific pests - e.g. ladybirds introduced to prey on aphids |
| What are the advantages and disadvantages of using biological control? | Advantages Disadvantages Non-toxic Never fully removes pest Targets specific pest only Introducing alien species into an environment can have undesired results Self-sustaining Slow |
| What is the role of yeast in the production of bread? | Yeast respire using sugars - Yeast respires (aerobically at first, then anaerobically) producing carbon dioxide - Carbon dioxide makes bread rise - When baked, gas bubbles expand to give bread its texture |
| How is yoghurt made? | Heat milk to 80-90°C - To pasteurise milk (kill competing/pathogenic bacteria) - Sterilise container(s) - To prevent contamination |
| How is yoghurt made? pt2 | - Cool to approx 45°C - To prevent killing Lactobacillus bacteria when added - Bacteria added (Lactobacillus) - Leave for 6 hours at the optimum temperature (35°C) for the bacteria - Anaerobic respiration converts lactose → lactic acid |
| What is a fermenter? | Vessel containing microorganisms used for fermentation - Used to produce large quantities of product from microorganisms - e.g. insulin, penicillin |
| how is temperature controlled in a fermenter? | Temperature recorder / monitor - Cooling jacket |
| What are the suitable conditions within a fermenter? | - Nutrients - A controlled supply to feed microorganisms - pH - Kept constant at optimum level by adding acid or alkali as necessary - Air supply - Provides oxygen necessary for aerobic respiration |
| What are the suitable conditions within a fermenter? PT2 | Temperature - Respiration produces heat - Enzymes denature / microorganisms die if too hot - Maintains optimum temperature for growth and enzyme activity |
| What are the suitable conditions within a fermenter? PT3 | Agitation - Microorganisms constantly stirred - Gives more exposure to oxygen (for aerobic respiration) nutrients (for growth) and reduce temperature (to keep it at optimum level) |
| Define isolated enzyme | Enzyme removed from host microorganism |
| What is fish farming? | Lots of fish kept together in tanks/enclosures - Water quality constantly monitored to provide optimum conditions - Waste products constantly removed |
| What is fish farming Pt2 | Diet carefully controlled - Fish isolated from predators to protect them - Sorted by size to prevent bigger fish eating smaller fish of the same species - Fish with desirable characteristics selectively bred |
| Describe the advantages and disadvantages of fish farming | Farm commercialised species e.g. cod, salmon, tuna, - Advantages - can control temperature, oxygen levels, diet, kill pests, selective breeding programmes can improve the quality of the fish |
| Describe the advantages and disadvantages of fish farming Pt2 | Disadvantages - higher risk of disease as the fish are so close together, antibiotics are used to treat disease as may enter the food chain, pollution due to faeces, pesticides highly toxic to other species |
| Describe selective breeding in plants | Humans choose plants with desirable characteristics (e.g high yield, disease/pest resistance) - Cross pollinate selected plants - Plants that grow with desirable characteristics are chosen and bred - Process repeats over many generations |
| Describe selective breeding in animals | Humans choose individual animals with desirable characteristics (e.g more milk production, better quality fur) - Make them breed (or use artificial insemination) |
| Describe selective breeding in animals Pt2 | Offspring with desirable characteristics are bred - Process repeats over many generations |
| Describe how selective breeding could be used to increase milk production | Cow with high milk yield chosen - Bull with high milk yield mother chosen - Cow and bull bred - Repeat process with high milk yield offspring - Over many generations |
| Describe the differences between selective breeding and natural selection | Humans choose parents in selective breeding - Selective breeding is a faster process - No survival of the fittest with selective breeding |
| What is genetic engineering? | When genes are altered in microorganisms to code for desired products - e.g. insulin |
| What enzymes are used in genetic engineering? | Restriction enzymes - cut DNA at a specific point - Ligase - joins the cut ends of DNA back together |
| What is a vector? | Anything used to transfer biological material - e.g. a plasmid is used to transfer genes in genetic engineering - e.g. mosquito that transfers plasmodium to humans when it bites them |
| Explain how plasmids and viruses can be used as vectors in genetic modification | Plasmid: - Small circular pieces of DNA - Isolated from bacteria - Desired gene inserted into plasmid to create recombinant plasmids - Recombinant plasmids inserted back into bacteria |
| Explain how plasmids and viruses can be used as vectors in genetic modification PT2 | Virus: - Bacteriophage are a type of virus - Desired gene inserted into bacteriophage - Bacteriophage attaches to cell wall of bacteria - Injects its genetic material (DNA) - Desired gene taken up by bacterial DNA |
| Describe how large amounts of insulin can be genetically engineered | Cut out insulin gene using restriction enzyme - Cut open plasmid in bacteria using same restriction enzyme - Stick insulin gene into plasmid using DNA ligase (forming recombinant plasmid) - Plasmid is the vector - Place in fermenter |
| Give specific uses of genetically modified plants | Extend shelf life - Frost resistant - ‘Golden rice’ contains beta carotene that prevents night-blindness - Resistant to herbicides (weedkillers) |
| Give specific uses of genetically modified plants PT2 | - Modified tobacco plants produce hepatitis B antigens - potential use in manufacturing vaccines - Modified tobacco plants and soybeans produce antibodies to fight disease |
| What are the benefits of genetically modified plants? | Increased salt tolerance - More complete nutrition e.g. contains a good balance of proteins, carbohydrates, lipids, vitamins and minerals - Increased resistance to pathogens - Increased tolerance to heat and drought |
| Define transgenic | Genes from one species transplanted into different species |
| Provide an example of using transgenic animals to make human proteins | Trypsin damages liver and lungs - AAT is a human protein which stops trypsin attacking the liver and lungs - Some people don’t make enough AAT - Transgenic sheep are genetically engineered to produce AAT in their milk |
| Describe the process of micropropagation | Use small parts of plants (explants) - Place on sterile agar - Add nutrients, minerals and hormones - Keep sterile - Control humidity and light levels |
| What are the advantages of micropropagation? | Large numbers of genetically identical plants are produced quickly - All with desirable characteristics - At any time of the year |
| Define clone | Genetically identical individuals |
| Describe the process of adult cell cloning (e.g in Dolly the Sheep) | Take mature body cell of animal being cloned and remove diploid nucleus - Take egg cell from another animal of same species and remove nucleus (enucleation) - Insert adult cell nucleus into empty egg cells - Fuse with an electric shock |
| Describe the process of adult cell cloning (e.g in Dolly the Sheep) PT2 | Mitosis occurs - Embryo develops - Place embryo inside uterus of surrogate of same species |
| How can cloned transgenic animals be used to produce human proteins? | This would make it possible to produce large numbers of genetically identical animals - All containing genes for desired human protein - These animals could then make human proteins |
| What are the advantages of using embryo cloning rather than selective breeding? | Cloning is faster and produces genetically identical offspring - More offspring are produced with cloning - No need for two parents in cloning |
| When answering experimental design questions, you should always include… | hen answering experimental design questions, you should always include… - Independent variable - The variable that is being changed - Dependent variable - The variable that is being measured - Include how the dependent variable would be measured |
| When answering experimental design questions, you should always include… PT2 | Sensible time frame for taking measurements - Control variables (minimum 5) - The variables that are being kept constant - Methods of ensuring reliability |
| What is the purpose of a control? | Allows a comparison to be made - Shows what would normally happen so comparison can be made when independent variable is changed |
| Common ways of improving an investigation: | Ensure equal sizes/volumes of samples are used - Repeat the experiment at least 3 times and calculate the mean - Test a wider range of values for the independent variable |
| Common ways of improving an investigation: PT2 | Replicate experiment using different samples/species - Use larger sample size - Use random sampling method (e.g. random number generator) |
| How to make an investigation more reliable: | Repeat experiment at least three times to increase number of observations - Identify anomalous results - Calculate mean |
| How to make an investigation more accurate: | Carry out more tests within existing range - Introduce method to ensure no double counting occurs - Use a narrower range (if appropriate) |
| How to increase the validity of an investigation: | Make sure that all control variables are the same for each repeat/investigation - Collect a wide range of measurements/results |
| To ensure calculations of mean values are reliable: | - Randomly choose sample areas/fields of view to count subject of investigation - Count subject of investigation in several sample areas/fields of view - Ensure all same species used/counted |
| To ensure calculations of mean values are reliable: PT2 | - If taking samples from same organism, ensure same tissue/organ used - Count a large number of sample areas/fields of view |
| When answering ‘describe’ questions | When answering ‘describe’ questions: - Write what the data is showing e.g. trends, changes in rate, increases and decreases etc - If describing a graph, break the graph down into sections - Each section should be a describable feature |
| When answering ‘describe’ questions PT2 | e.g. constant rate from A to B, increasing rate from B to C… - Use data points provided in the question to illustrate description |
| When answering ‘explain’ questions | Say why the results have come about - Use scientific knowledge to explain any patterns and trends - Make sure explanation is specific to the question |
| When answering ‘compare’ questions: | Each statement should include both pieces of data - e.g. both A and B remained constant for 2 hours - e.g. the rate of increase of A was greater than that of B from 2 to 4 hours |
| When drawing diagrams: | nclude a title - Use a sharp pencil - Labels should be outside the diagram - Use ruled label lines - Do not cross label lines - Include a scale bar - State magnification - Do not use shading - Use at least 50% of the available space |
| When drawing graphs: | Label the x and y axis - Include units - Use sensible scale - Use at least 50% of the available space - Plot points accurately using an ‘X’ - Draw line of best fit if required |
Created by:
RoryDarling