Cell differentiation

Transcription

1 GCSE Biology Cells Biology 1 Cells 1. Most animal cells have a nucleus, cytoplasm, membrane, mitochondria and ribosomes. 2. Plant and algal cells also have a cell wall and often have chloroplasts and a permanent vacuole. 3. Plant and animal cells are eukaryotic cells which have a membrane, cytoplasm and a nucleus. 4. Bacterial cells are prokaryotic cells. 5. They are smaller than eukaryotic cells and have a cell wall, membrane and cytoplasm, but do not have a nucleus. 6. Their genetic material is a single loop of DNA or several small rings of DNA called plasmids in the cytoplasm. Specialised cell Function Adaptations 7. Red blood cell Carries oxygen. Large surface area. Contains haemoglobin. No nucleus to create more space. 8. White blood cell Destroys microorganisms. Irregular shape to get out of blood vessels. 9. Egg cell (ovum) Join with sperm cell and provide food for new cell formed. Large Contains lots of cytoplasm 10. Sperm cell Reach and join with egg cell. Long flagellum (tail) for swimming Enzymes of head to break into egg. 11. Nerve cell Carry nerve impulses to different parts of the body. Long Connections at each end. Carry electrical signals. 12. Muscle cell Move the body. Contain protein fibres that contract. Large numbers of mitochondria. 13. Ciliated cell Move mucus. Thin layer of tiny cilia (moving hairs). 14. Palisade cell Absorb sunlight for photosynthesis. Large surface area. Lots of chloroplasts. 15. Root hair cell Absorb water and minerals Large surface area. 16. Xylem cell Moves water through the plant. Made of dead cells. Thick, strengthened cellulose cell wall. Hollow lumen. 17. Phloem cell Moves food through the plant. Made of living cells. Connected by sieve plates to form a tube. Cell differentiation 18. Cells differentiate to form different types of cells. Animal cells differentiate at an early stage, whereas many plant cells can differentiate throughout life. 19. Differentiation is the generation of specialised cells which acquire different organelles to enable them to carry out specific functions. 20. Cells may be specialised to carry out a particular function. 21. Stem cells are unspecialised cells that can differentiate to form many different types of cells. 22. Stem cells from human embryos and adult bone marrow can be cloned and made to differentiate into different cells. 23. Stem cells may be used to treat paralysis and diabetes in the future. 24. In therapeutic cloning an embryo with the same genes as the patient is produced. Cells from this embryo will not be rejected by the patient. 25. Risks e.g. transfer of viruses, associated with the use of stem cells in medicine. 26. Stem cells from meristems in plants are used to produce clones quickly and cheaply.

2 GCSE Biology Cells Biology 1 Culturing microorganisms 27. Bacteria multiply by simple cell division (binary fission) as often as once every 20 minutes if they have enough nutrients and a suitable temperature. 28. Bacteria can be grown in a nutrient broth solution or as colonies on an agar gel plate. 29. Uncontaminated cultures of microorganisms are required for investigating the action of disinfectants and antibiotics. Microscopes 30. An electron microscope has a much higher magnification and resolution than a light microscope, so it can be used to study cells in much finer detail and show organelles. iiiiiiiiii ssssssss 31. rrrrrrrr ssssssss = mmmmmmmmmmmmmmmmmmmmmmmmmm 32. 1m = 1000mm 33. 1mm = 1000µm (micrometre) 34. 1µm = 1000nm (nanometre) 35. To get smaller x To get bigger Mitosis 37. Chromosomes are found in the nucleus. They are made of DNA. Each chromosome carries a large number of genes. 38. In body cells chromosomes are found in pairs. 39. Mitosis occurs during growth or to produce replacement cells. 40. During mitosis: copies of the genetic material separate the cell then divides once to form two genetically identical cells. 41. Mitosis forms part of the cell cycle. Diffusion 42. Substances can move into and out of cells across membranes by diffusion. 43. Diffusion is the net movement of particles from an area of high concentration from an area of low concentration down a concentration gradient. 44. Oxygen, carbon dioxide and urea passes through cell membranes by diffusion. 45. Single celled organisms have a bigger surface area to volume ratio than multicellular organisms, so transfer sufficient substances across their surface. 46. Multicellular organisms require specialised organ systems to exchange sufficient substances. Osmosis 47. Water may move across cell membranes by osmosis. 48. Osmosis is the movement of water from a dilute solution (high concentration) to a more concentrated solution (low concentration) through a partially permeable membrane. 49. An isotonic solution is one that is the same concentration as the cell. 50. Water moves in and out at the same rate in an isotonic solution. 51. A hypotonic solution has a higher concentration of water (low concentration of solutes) than the cell (low water and high solutes). 52. Water moves into the cell until it reaches equilibrium (equal concentrations). 53. A hypertonic solution has a lower concentration of water (high concentration of solutes) than the cell (high water and low solutes). 54. Water moves out of the cell until it reaches equilibrium. 55. Lysis bursting an animal cell by osmosis. 56. Crenation shrinking an animal cell by osmosis. 57. Turgid A plant cell fully inflated with water. 58. Flaccid A plant cell that is limp through a reduction of pressure inside the cell (some water lost). 59. Plasmolysed a plant cell that has lost water causing the cell membrane to be pulled away from inside the cell wall. Active transport 60. Active transport involves the movement of ions or molecules from a low concentration to a high concentration against a concentration gradient on a cell membrane. 61. Energy is required from respiration to move the substances. 62. Mineral ions can be absorbed by active transport into plant root hairs from very dilute solutions in the soil. 63. Sugar can be absorbed by active transport from the gut into the blood.

3 GCSE Biology Organisation Biology 2 Cell organisation 1. Cells are the building blocks of living organisms. 2. A tissue is a group of cells with a similar structure and function. 3. Organs are groups of tissues working together. 4. Organs are organised into organ systems. 5. An organism is made up of several organ systems. Structure Function 6. Mouth Where food enters the alimentary canal and digestion begins. 7. Salivary glands Produce saliva containing amylase. 8. Oesophagus Muscular tube which moves ingested food to the stomach. 9. Stomach Muscular organ where digestion continues. 10 Pancreas Produces digestive enzymes. 11. Liver Produces bile. 12. Gall bladder Stores bile before releasing it into the duodenum. 13. Small intestine - duodenum Where food is mixed with digestive enzymes and bile. 14. Small intestine - ileum Where digested food is absorbed into the blood and lymph. 15. Large intestine - Where water is reabsorbed. colon 16. Large intestine - Where faeces are stored. rectum 17. Large intestine - anus Where faeces leave the rectum. Food tests 18. Foods can be tested to find out which food groups they contain. 19. Starch is identified by the iodine test. Food turns black or blue if starch is present. 20. Sugars are identified by Benedict s solution. If sugar is present, the solution turns from blue to red / orange / yellow / green when heated depending on the amount of sugar. 21. Protein is identified by Biuret reagent. Food becomes purple if proteins are present. 22. Fat is identified using paper. The food is rubbed onto the paper. If, when dry, the area becomes translucent, fats are present. The digestive system 23. Enzymes are biological catalysts; they speed up a reaction without being used up. 24. Food molecules must be small and soluble in order to be absorbed into the blood. 25. Enzymes in the digestive system chemically digest food into small, soluble molecules that can be absorbed. 26. Carbohydrases break down carbohydrates into simple sugars. 27. Amylase is a carbohydrase that breaks down starch. 28. Amylase works in the mouth and small intestine. 29. Protease breaks down protein into amino acids. 30. Protease works in the stomach and small intestine. 31. Lipase breaks down lipids (fats and oils) into glycerol and fatty acids. 32. Lipase works in the small intestine. 33. The products of digestion are used to build new carbohydrates, lipids and proteins. Some glucose is used in respiration. 34. Bile is made by the liver and stored in the gall bladder. It helps in the digestion of fats by neutralising acid from the stomach and emulsifying fats. 35. Different enzymes work best at different temperatures and ph values. The heart 36. The heart is a double pump, blood passes through the heart twice on its journey around the body. 37. The right ventricle pumps blood to the lungs where gas exchange takes place. 38. The left ventricle pumps blood around the rest of the body. 39. The natural resting heart rate is controlled by a group of cells located in the right atrium that act as a pacemaker. 40. Artificial pacemakers are electrical devices used to correct irregularities in the heart rate.

4 GCSE Biology Organisation Biology 2 Coronary heart disease 41. Fatty material builds up in coronary arteries reducing blood flow to the heart muscle. 42. Stents can be used to keep the coronary arteries open. 43. Statins reduce cholesterol levels, so fatty material is deposited more slowly. 44. Faulty heart valves can be replaced with biological or mechanical ones. 45. Heart failure can be treated with a heart and lung transplant. 46. Artificial hearts can be used whilst waiting for a transplant, or to allow the heart to rest and recover. Blood 47. Blood is a tissue consisting of plasma, red blood cells, white blood cells and platelets. 48. Plasma transports dissolved chemicals and proteins around the body. 49. Red blood cells transport oxygen attached to haemoglobin. 50. White blood cells help to protect the body against infection. 51. Platelets are fragments of cells involved in blood clotting. Health issues 52. Health is the state of physical and mental wellbeing. 53. Factors such as diet, stress and life situations can have a serious effect on physical and mental health. 54. Diseases are major causes of ill health. 55. Different diseases may interact: defects in the immune system increase the chance of catching an infectious disease. Viral infections can trigger cancers. Immune reactions can trigger allergies. Physical ill-health can lead to depression and mental illness. Cancer 60. Cancers (malignant tumours) result from uncontrolled cell division. 61. Cancer cells may invade neighbouring tissues, or break off and spread to other parts of the body in the blood, where they form secondary tumours. Lifestyle and health 56. Various risk factors are linked to some noncommunicable disease. 57. These can be aspects of a person s lifestyle or substances in the person s body or environment. 58. A causal mechanism has been proven for some risk factors but not in others: The effects of diet, smoking and exercise on cardiovascular disease. Obesity as a risk factor for type 2 diabetes. The effect of alcohol on the liver and brain function. The effect of smoking on lung disease and lung cancer. The effects of smoking and alcohol on unborn babies. Carcinogens, including ionising radiation, as risk factors in cancer. 59. Many diseases are caused by the interaction of a number of factors. Plant organ system 62. Plant organs include stems, roots and leaves. 63. Organs are made up of different tissues, eg meristem tissue at growing tips. 64. The leaf is the organ of photosynthesis. 65. The roots, stem and leaves form a plant transport system. 66. Root hair cells absorb water by osmosis and mineral ions by diffusion and active transport. 67. Xylem tissue transports water and dissolved ions. The flow of water from the roots to leaves is called the transpiration stream. 68. Xylem tissue is composed of hollow tubes strengthened with lignin. 69. Phloem tissue transports dissolved sugars from the leaves to other parts of the plant. The movement of food through phloem is called translocation. 70. Phloem cells have pores in their end walls for moving of cell sap Structure Function

5 GCSE Biology Infection and response Biology 3 Communicable diseases 1. Communicable diseases are infectious diseases caused by pathogens. 2. Pathogens may be viruses, bacteria, protists or fungi. They may infect plants or animals. 3. Pathogens can be spread by direct contact, by water or by air. 4. The spread of diseases can be reduced or prevented by: simple hygiene measures destroying vectors isolation of infected individuals vaccination Bacterial disease 18. Bacterial diseases include salmonella food poisoning and the sexually transmitted disease gonorrhoea. 19. Salmonella food poisoning is spread by bacteria ingested in food or on food prepared in unhygienic conditions. 20. In the UK, poultry are vaccinated against Salmonella to control the spread. 21. Fever, abdominal cramps, vomiting and diarrhoea are caused by the bacteria and toxins that they excrete. 22. Gonorrhoea is a sexually transmitted disease with symptoms of a thick yellow or green discharge from the vagina or penis and pain when urinating. 23. It was easily treated with the antibiotic penicillin until many resistant strains appeared. 24. The spread of gonorrhoea can be controlled by antibiotic treatment and the use of a barrier method of contraception such as a condom. Viral disease 5. Viral diseases include measles and AIDS, which is caused by HIV. 6. Measles has symptoms of a fever and red skin rash. 7. It is a serious illness that can be fatal if complications arise. 8. Most young children are vaccinated against measles. 9. The measles virus is spread by inhalation of droplets from sneezes and coughs. 10. HIV initially causes a flu-like illness. 11. Unless successfully controlled with antiretroviral drugs, the virus attacks the body s immune cells. 12. Late stage HIV infection, or AIDS, occurs when the body s immune system becomes so badly damaged it can no longer deal with other infections or cancers. 13. HIV is spread by sexual contact of exchange of bodily fluids such as blood, which occurs when drug users share needles. 14. Tobacco mosaic virus (TMV) is a plant pathogen. 15. It has a distinct mosaic pattern of discolouration on the leaves, which affects the growth of the plant due to lack of photosynthesis. 16. Viruses enter cells and damage them to cause symptoms. 17. Antibiotics don t treat viruses as they cannot enter cells. Protist disease 30. Malaria is caused by a protist transmitted by mosquitos. 31. Fungal disease 25. Humans can also be infected with fungal diseases. 26. Rose black spot is a fungal disease where purple or black spots develop on leaves, which turn them yellow and makes them drop off early. 27. It affects the growth of plants as photosynthesis is reduced. 28. It is spread in the environment by wind or water. 29. It can be treated by using fungicides and /or removing and destroying the affected leaves. 32. Malaria causes recurrent episodes of fever and can be fatal. 33. Spread of malaria is controlled by preventing the vectors (mosquitos) from breeding and by using mosquito nets to avoid being bitten.

6 GCSE Biology Infection and response Biology 3 Vaccination 34. A vaccine contains a small amount of dead or inactive pathogens. These stimulate white blood cells to produce antibodies. 35. Edward Jenner made the first vaccination for smallpox, which has now been wiped out. 36. Immunity allows a person to produce specific antibodies quickly to prevent infection. 37. If a large proportion of the population is immune to a pathogen, the spread of the pathogen is very much reduced. Antibiotics 53. Antibiotics, eg penicillin, are used to kill infective bacteria inside the body. 54. Specific bacteria should be treated with specific antibiotics. 55. The emergence of strains resistant to antibiotics is of great concern. 56. Antibiotics cannot kill viral pathogens. 57. Painkillers and other medicines are used to treat the symptoms of disease but do not kill pathogens. It is difficult to kill viruses without also damaging the body s tissues. 58. Alexander Fleming discovered penicillin from the Penicillium mould. Human defence system 38. The body defends itself against the entry of pathogens. 39. Non-specific defence systems of the body are the: skin; nose; trachea and bronchi; stomach. 40. Bacteria may produce toxins that make us feel ill and damage tissues. 41. Viruses live and reproduce inside cells, causing damage. 42. The immune system tries to destroy pathogens that enter the body. 43. White blood cells help to defend against pathogens by: Phagocytosis antibody production antitoxin production. Drug development 44. Traditionally drugs were extracted from plants and microorganisms. 45. The heart drug digitalis originates from foxgloves. 46. The painkiller aspirin originates from the willow tree. 47. Most new drugs are synthesised by chemists; the starting point may still be a chemical extracted from a plant. 48. New drugs are tested for toxicity, efficacy (the ability to produce a desired result) and dose. 49. Preclinical testing in the lab, then clinical trials involving healthy volunteers and then patients. 50. Very low doses of the drug are given at the start of the clinical trial (phase 1). 51. If the drug is found to be safe, further clinical trials (phase 2 /3) to find out the optimum dose for the drug. 52. In a double blind trial, some patients are given a placebo; neither the doctors nor the patients know who has received a placebo and who has received the drug.

7 GCSE Biology Infection and response Biology 3 Monoclonal antibodies 59. Monoclonal antibodies (MAB) are produced from a single clone of cells. They are specific to one antigen, so target a specific chemical or cell in the body. 60. A lymphocyte that makes a specific antibody is combined with a tumour cell to form a hybridoma cell. This is cloned to produce many identical cells which all produce the specific antibody. 61. There are many uses for MABs: Diagnosis in pregnancy tests. In labs to measure the levels of hormones and other chemicals in the blood or to detect pathogens. In research to locate and identify specific molecules in a cell or tissue by binding them with a fluorescent dye. To treat diseases: for cancer the monoclonal antibody can be bound to a radioactive substance, a toxic drug or a chemical which stops cells growing and dividing. It delivers the substance to the cancer cells without harming other ells. 62. MABs can have more serious side effects than expected. 63. They are not as widely used as everyone hoped when they were first developed. Plant diseases 64. Plants can be infected by a range of viral, bacterial and fungal pathogens as well as by nematode worms and insects. 65. Tobacco mosaic virus affects many plants, eg tomatoes. 66. Rose black spot is a fungal disease spread by water or wind. 67. Aphids feed on the sap of plants and affect plant growth. 68. Ion deficiencies can damage plants, eg stunted growth by nitrate deficiency and chlorosis by magnesium deficiency. Detecting plant diseases 74. Plant diseases can be detected by: stunted growth spots on leaves areas of decay (rot) growths malformed stems or leaves discolouration presence of pests. 75. Identification can be made by: Using a gardening manual. Taking infected plants to a lab. testing kits that use monoclonal antibodies. Ion deficiency 69. Plants can be damaged by a range of ion deficiency conditions. 70. Nitrate deficiency causes stunted growth. 71. Nitrate is needed for protein synthesis and therefore growth. 72. Magnesium deficiency causes chlorosis (yellowing of the leaves). 73. Magnesium ions are needed to make chlorophyll. Plant defence responses 76. Plants have physical and chemical defence responses to resist the invasion of microorganisms. 77. Physical defences include: cellulose cell walls, tough waxy cuticles on leaves; layers of dead cells around stems (bark on trees) which fall off. 78. Chemical defence responses include: antibacterial chemicals and poisons to deter herbivores. 79. There are also mechanical adaptations to deter animals from eating or touching them. 80. Mechanical adaptations include: thorns and hairs to deter animals; leaves which droop or curl when touched; mimicry to trick animals.

8 GCSE Biology Bioenergetics Biology 4 Photosynthesis light 1. Carbon dioxide + water glucose + oxygen. light 2. 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 3. Photosynthesis takes place in the palisade cells in the leaf. 4. Photosynthesis is an endothermic reaction in which energy is transferred from the environment into the chloroplasts by light. Rate of photosynthesis 5. The rate of photosynthesis may be limited by: low temperature shortage of CO 2 shortage of light shortage of chlorophyll When the graph has a slope, the investigated factor is limiting. 8. When the slope levels out, another factor has started to limit photosynthesis. 9. The rate of photosynthesis can be measured by counting the number of oxygen bubbles produced by a plant in water. 10. Factors that can limit the rate of photosynthesis are called limiting factors. 11. Limiting factors are important economically in greenhouses. They help us work out the optimum conditions for growing plants. 12. Glucose produced in photosynthesis may be: used for respiration converted into starch for storage used to produce fats and oils for storage or cellulose to strengthen cell walls used to produce amino acids for protein synthesis. Respiration 13. Respiration can take place aerobically or anaerobically to transfer energy. 14. Respiration is an exothermic reaction. 15. Respiration takes place in the mitochondria. 16. Organisms need energy for chemical reactions, movement and to keep warm. Aerobic respiration 17. During aerobic respiration glucose and oxygen react to release energy. 18. Glucose + oxygen carbon dioxide + water. 19. C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O Anaerobic respiration 20. Anaerobic respiration is the incomplete oxidation of glucose so less energy is released than in aerobic respiration. 21. In muscle cells: Glucose lactic acid 22. C 6 H 12 O 6 2C 3 H 6 O In some plant and yeast cells: Glucose ethanol + carbon dioxide 24. C 6 H 12 O 6 2C 2 H 5 OH + 2CO Anaerobic respiration in yeast cells is called fermentation and has economic importance in the manufacture of bread and alcoholic drinks. Response to exercise 26. During exercise the heart and breathing rates increase and breath volume increases to supply oxygen to muscle cells faster. 27. Muscle cells can respire anaerobically if there is insufficient oxygen. This produces lactic acid and creates an oxygen debt. 28. Lactic acid can cause muscle fatigue. The cells stop contracting efficiently. 29. When exercise stops, the oxygen debt must be repaid by continuing to breathe deeply. 30. Blood transports lactic acid to the liver where it is converted back into glucose. 31. The oxygen debt is the amount of oxygen needed to oxidise lactic acid. Metabolism 32. Metabolism means all the chemical reactions happening in a living organism. 33. Metabolism includes: the conversion of glucose to starch, glycogen and cellulose the formation of lipids the formation of amino-acids and proteins respiration the breakdown of excess proteins to form urea for excretion.

9 GCSE Biology Homeostasis and response Biology only Biology 5 The brain 1. The brain controls complex behaviour. 2. The brain has billions of interconnected neurones. 3. Different areas of the brain control different functions. 4. Investigating and treating brain damage and disorders is difficult. Brain function 5. Neuroscientists have been able to map the regions of the brain to particular functions by studying patients with brain damage, electrically stimulating different parts of the brain and using MRI scans. 6. The complexity and delicacy of the brain makes investigating and treating brain disorders very difficult. 7. The cerebral cortex is the largest part of the mammal brain. 8. It is divided into four lobes, the parietal, occipital, temporal and frontal. Each has a different function. 9. It is responsible for intelligence, language, memory and consciousness. 10. The cerebellum receives information from the sensory systems, spinal cord and other parts of the brain to regulate movement. 11. The medulla oblongata is the centre for respiration and circulation. 12. It regulates breathing, heart and blood vessel function, digestion, sneezing and swallowing. The eye 13. The eye contains receptors sensitive to light and colour. 14. The cornea refracts (bends) light as it enters the eye. 15. The sclera is the front part of the cornea. It is a tough outer coat. 16. The iris is the coloured part of your eye, it contains pigments so light cannot pass through. 17. Ciliary muscles connected to the iris contract and relax to alter the size of the pupil (the hole) to change the amount of light entering the eye. 18. The lens is a transparent, bi-concave, flexible disc behind the iris which focuses light onto the retina. 19. Accommodation is the process of changing the shape of the lens to focus on near and far objects. 20. The lens is held in place by suspensory ligaments to the ciliary muscles. 21. The retina is the lining on the back of the eye. 22. The retina contains two types of photoreceptor cells: rods (sensitive to dim light and black and white) and cones (sensitive to colour). 23. The optic nerve is a bundle of sensory neurones at the back of the eye that carries electrical impulses to the brain. 24. To focus on a near object: the ciliary muscle contract, suspensory ligaments loosed and the lens becomes thicker to refract the light more strongly. 25. To focus on a distant object: the ciliary muscles relax, the suspensory ligaments are pulled tight and the lens becomes thin so it only slightly refracts the light. 26. To common defects of the eye are myopia (short sightedness) and hyperopia (long sightedness) in which rays do not focus on the retina. 27. These defects are treated with glasses which refract the light so that it focusses on the retina. 28. New technologies now include hard and soft contact lenses, laser surgery to change the shape of the cornea and replacements lenses in the eye.

10 GCSE Biology Homeostasis and response Biology only Biology 5 Maintaining water and nitrogen balance Control of body temperature 29. Body temperature is monitored and controlled by the thermoregulatory centre in the brain. It has receptors sensitive to the temperature of the blood. 30. Temperature receptors in the skin send impulses to the thermoregulatory centre. 31. If the body temperature is too high, blood vessels dilate (vasodilation) and sweat is produced from skin glands. 32. Sweat cools the body as it evaporates from the skin. 33. If the body temperature is too low, blood vessels constrict (vasoconstriction), sweating stops and skeletal muscles contract (shiver). Plant hormones 50. Hormones control and coordinate growth and responses to light and gravity in plants. 51. Auxin is a powerful growth hormone produced naturally by plants. 52. Responses to light and gravity are controlled by the unequal distribution of auxin which causes unequal growth rates in shoots and roots. 53. Auxin moves away from the light which makes that part of the shoot grow. It makes the stem grow towards the light. 54. Gibberellins are important in initiating seed germination. 55. Ethene controls cell division and ripening of fruits. 34. Water leaves the body via the lungs during exhalation. 35. Water, ions and urea are lost from the skin in sweat. 36. There is no control over water, ion or urea loss by the lungs or skin. 37. Excess water, ions and urea are removed via the kidneys in the urine. 38. If body cells lose or gain too much water by osmosis they do not function efficiently. 39. Urea is produced in the liver by the breakdown of excess amino acids. 40. In the liver, amino acids are deaminated to form ammonia. 41. Ammonia is toxic and is immediately converted to urea for safe excretion. Kidneys 42. The kidneys produce urine by filtration of the blood and selective reabsorption of useful substances. 43. All the sugar and dissolved ions needed by the body and as much water as the body needs are selectively reabsorbed. 44. Urea, excess ions and water are excreted in urine. 45. ADH is released by the pituitary gland when the blood is too concentrated. It causes more water to be reabsorbed back into the blood. 46. ADH control of water in the blood is an example of negative feedback. 47. Kidney failure can be treated by kidney transplant or by using kidney dialysis. 48. Kidney dialysis is a procedure to remove waste products and excess fluid from the blood. 49. Blood is diverted to a machine to be cleaned and pumped back into the body. Plant hormones 56. Plant hormones are used in agriculture and horticulture. 57. Auxins are used as weed killers,, as rooting powders and for promoting growth tissue culture. 58. Giberellins can be used to end seed dormancy, promote flowering and increase fruit size. 59. Ethene is used in the food industry to control the ripening of fruit during storage and transport.

11 GCSE Biology Homeostasis and response Biology 5 Homeostasis 1. Homeostasis is the regulation of internal conditions to maintain optimal conditions for enzyme action and cell function. 2. Automatic control systems involve nervous responses and chemical responses. 3. Control systems have receptors, a coordination centre and effectors. Nervous system 4. The functions of the nervous system are to detect and react to stimuli; to coordinate behaviour. 5. The structure of the central nervous system (CNS): receptors; different types of neurones, coordinator (brain or spinal cord); effectors, synapses. 6. Sensory neurones carry impulses (electrical signals) from the sense organ to the relay neurone. 7. The relay neurone carries electrical impulses in the CNS. 8. The motor neurone carries electrical impulses from the relay neurone to the muscle or gland (effector) to make it respond. 9. Neurones line up end to end throughout the CNS. 10. Synapses are the gaps between each neurone. 11. Electrical impulses cannot cross a synapse. 12. At the end of the neurone, the electrical impulse causes a chemical to be released. 13. The chemical diffuses across the synapse and triggers an electrical impulse in the next neurone. 14. Diffusion of the chemical is slower than the electrical impulse. Reflex arc 15. Some of your reactions happen without you thinking about them, e.g. moving your hand when you touch something hot. These are called reflex actions. 16. Reflex actions are automatic and rapid to protect the body from harm. 17. A stimulus is a change in the environment that can be detected by the body. 18. A receptor is a cell that detects the stimulus. 19. The effector is the area that makes the response. 20. The reflex action is a reflex arc that doesn t involve the brain, it is very fast. 21. The brain is informed after the action has happened. Human endocrine system 22. The system is composed of endocrine glands that secrete hormones into the blood to be carried to a target organ where it has an effect. 23. The pituitary is the master gland. It secretes many hormones that affect other glands. 24. Hormones are chemical messengers

12 GCSE Biology Homeostasis and response Biology 5 Control of blood glucose concentration 32. Blood glucose concentration is monitored and controlled by the pancreas. It produces insulin, which causes glucose from the blood to enter cells. 33. Glucose is converted to glycogen in liver and muscle cells for storage. 34. Glucagon is also produced by the pancreas to convert stored glycogen back into glucose when blood glucose levels fall. 35. In Type 1 diabetes the pancreas does not produce enough insulin. Glucose levels may rise too high. 36. Type 1 diabetes is usually treated with insulin injections. 37. In Type 2 diabetes the cells do not respond properly to insulin. 38. Type 2 diabetes is usually treated by diet, exercise and drugs. Obesity is a risk factor for Type 2 diabetes. 39. Hormones in human reproduction 40. During puberty hormones cause sexual characteristics to develop. 41. In females oestrogen is produced by the ovaries. Eggs mature and are released (ovulation) every 28 days. 42. In males testosterone is produced by the testes and stimulates sperm production. 43. Follicle stimulating hormone (FSH) causes the eggs in the ovary to mature (the eggs grow surrounded by cells called the follicle). 44. Luteinising hormone (LH) stimulates the release of the egg at ovulation. 45. Oestrogen and progesterone stimulate the build-up and maintenance of the uterus lining. 46. Contraception 47. Fertility can be controlled using hormonal and nonhormonal contraceptives. 48. Hormonal oral contraceptives injection implant or skin patch. 49. Non-hormonal barrier methods IUDs spermicides abstinence sterilisation surgery. Hormones for infertility 50. Infertility is when an animal or plant is unable to reproduce. 51. Women can be given a fertility drug containing FSH and LH to stimulate ovulation. 52. In IVF treatment, FSH and LH are given to stimulate many eggs to mature. These are collected and fertilised by sperm in a lab. Embryos form, and some are inserted into the woman s uterus. 53. There are many advantages and disadvantages to fertility treatment: healthy baby; multiple births; cost; stress. Negative feedback 54. Adrenaline is produced by the adrenal glands in times of stress. It increases heart rate so oxygen and glucose are supplied to the brain and muscles faster. 55. Thyroxine is produced by the thyroid gland. It stimulates the basal metabolic rate and plays an important role in physical and mental development. 56. Adrenaline and thyroxine secretions are controlled by negative feedback mechanisms.

13 GCSE Biology Inheritance, variation and evolution Biology 6 Sexual and asexual reproduction 1. Sexual reproduction involves the joining (fusion) of male and female gametes (sperm and egg) in animals and pollen and ovule cells in flowering plants. 2. This mixing of genetic information leads to variation in the offspring. 3. Only mitosis is involved. 4. Gametes are produced by meiosis. 5. Asexual reproduction involves only one parent and no fusion of gametes. 6. There is no mixing of genetic information. 7. This leads to genetically identical offspring (clones). Meiosis 8. Cells in reproductive organs divide by meiosis to form gametes. 9. When a cell divides to form gametes: copies of the genetic information are made and the cell divides twice to form four gametes, each with a single set of chromosomes. 10. All gametes are genetically different from each other. 11. Gametes join at fertilisation to restore the normal number of chromosomes. The new cell divides by mitosis, and as the embryo develops, cells differentiate. DNA and the genome 12. DNA is a polymer made up of two strands forming a double helix. 13. DNA is found in chromosomes in the nucleus of a cell. 14. A gene is a small section of DNA. 15. Each gene codes for a sequence of amino acids to form a particular protein. 16. The genome is all the genetic material of an organism. 17. The human genome has been studied and will be important for medicine in the future. Sex determination 28. Human body cells contain 23 pairs of chromosomes pairs control characteristics only. 30. The 23 rd pair carries the genes that determine sex. 31. In females the sex chromosomes are the same (XX). 32. In males the chromosomes are different (XY). Genetic inheritance 18. A gamete is the male or female sex cell which contains the genetic information. 19. Some characteristics are controlled by a single gene. Each gene may have different forms called alleles. 20. The genes present, or genotype, operate at a molecular level to develop characteristics that are expressed as a phenotype. 21. A dominant allele is expressed if only present on one chromosome. 22. A recessive allele is only expressed if present on both chromosomes. 23. If the two alleles present are the same the person is homozygous for that trait, but if the alleles are different they are heterozygous. 24. Homo means the same. Hetero means different. 25. Most characteristics are a result of multiple genes interacting. 26. Some disorders are inherited, eg polydactyly (caused by a dominant allele) and cystic fibrosis (caused by a recessive allele). 27. A Punnett square can be constructed to predict the outcome of a monohybrid cross.

14 GCSE Biology Inheritance, variation and evolution Biology 6 Genetic engineering 33. Genetic engineering involves modifying the genome of an organism to introduce a desired characteristic. 34. Genes can be cut from the chromosome of a human or other organism and transferred into the cells of other organisms. 35. Enzymes are used to cut the gene from a chromosome. 36. The gene is inserted into a vector, eg bacterial plasmid or virus. 37. The vector is used to insert gene into cell. 38. The cell then makes a new protein to produce the desired characteristic. 39. Examples of genetic engineering are: weed killer resistance soya beans; golden rice; humalin (insulin made in bacteria). 40. Concerns about GM crops, eg effect on populations of wild flowers and insects, and uncertainty about safety of eating them. Variation 41. Differences in the characteristics of individuals may be due to: genes they have inherited environmental causes a combination of genetic and environmental causes. 42. There is usually extensive genetic variation within a population of a species. 43. All variants arise from mutations. 44. Most mutations have no effect on the phenotype. 45. Some mutations influence phenotype. 46. A few mutations determine the phenotype. 47. Mutations occur continuously but it is only very rarely that a mutation leads to a new phenotype. 48. If the phenotype is suited to an environmental change, it can lead to a relatively rapid change in the species. Selective breeding 49. Selective breeding (artificial selection) is the process by which humans breed plants and animals for useful characteristics. 50. Selective breeding of food plants has produced disease or weather resistant crops, more attractive or better flavoured fruits and crops that are easier to harvest. 51. Selective breeding of animals has produced cows that produce more milk, animals that produce more, better flavoured or leaner meat. 52. Selective breeding can lead to inbreeding, where some breeds are particularly prone to disease or inherited defects. Some breeds of dogs suffer from inbred defects. Extinction 33. Extinction may be caused by: changes to the environment over geological time new predators new diseases new, more successful competitors a single catastrophic event, eg massive volcanic eruptions or collisions with asteroids. Evolution 53. Darwin s theory of evolution by natural selection states that all species evolved from simple life forms that first developed more than three billion years ago. 54. Characteristics favourable to the environment are passed on because the animal is more likely to survive and reproduce. 55. Mutations are changes in the DNA code. They may lead to more rapid evolution, although mutations resulting in a new phenotype are rare. 56. Organisms of the same species can interbreed to produce fertile offspring. Evidence for evolution 57. The theory of evolution by natural selection is now widely accepted. At the time, it contested with religious belief. 58. Fossils are the remains of organisms from many years ago, which are found in rocks. 59. Scientists can t be certain about how life began on Earth as many early forms of life were softbodied, so few traces remain. What traces there were have been destroyed by geological activity. 60. Fossils show how much, or how little, organisms have changed over time. 61. Bacteria can evolve rapidly because they reproduce at a fast rate. 62. Mutations produce new strains. Resistant strains are not killed by antibiotics, so they survive and reproduce. Resistant strains spread because people are not immune and there is no effective treatment. 63. MRSA is resistant to antibiotics.

15 GCSE Biology Inheritance, variation and evolution Biology 6 Advantages and disadvantages of sexual and asexual reproduction 64. Advantages of sexual reproduction: produces variation survival advantage if the environment changes used in selective breeding to produce organisms with desired characteristics. 65. Advantages of asexual reproduction: only one parent needed time and energy efficient as do not need to find a mate faster than sexual reproduction many identical offspring produced when conditions are favourable. 66. Some organisms can reproduce by either method, depending on conditions. 67. Some organisms reproduce by both methods depending on the circumstances. Malarial parasites reproduce asexually in the human host but sexually in the mosquito. Many fungi reproduce asexually by spores but also reproduce sexually to give variation. Many plants produce seeds sexually but also reproduce asexually by runners, such as strawberry plants, or bulb division, such as daffodils. DNA structure 77. Cloning techniques include taking cuttings, tissue culture, embryo transplants and adult cell cloning. 78. Tissue culture uses small groups of cells from part of a plant to grow identical new plants. It is important in preserving rare plant species or for nurseries. 79. Taking cuttings is an older but simpler method used by gardeners to produce many identical new plants from a parent plant. 80. Embryo transplants are splitting apart cells from a developing animal embryo before they become specialised, then transplanting the identical embryos into host mothers. 81. Adult cell cloning DNA structure 68. DNA is made up of four different nucleotides. Each nucleotide consists of a sugar, a phosphate group and one of four different bases attached to the sugar. The bases are A, C, G and T. 69. A = adenosine, C = cytosine, G = guanine, T = thymine. 70. The bases on the two strands always join together in the same pairs: C with G and T with A. 71. The DNA polymer is made up of repeating nucleotide units. 72. Proteins are synthesised on ribosomes, according to a template. Carrier molecules bring specific amino acids to add to the growing protein chain in the correct order. 73. When the protein chain is complete it folds up to form a unique shape. This unique shape enables the proteins to do their job as enzymes, hormones or forming structures in the body such as collagen. 74. Mutations occur continuously. Most do not alter the protein, or only alter it slightly so that its appearance or function is not changed. 75. A few mutations code for an altered protein with a different shape. For example an enzyme may no longer fit the substrate binding site or a structural protein may lose its strength. 76. Not all parts of DNA code for proteins. Non-coding parts of DNA can switch genes on and off, so variations in these areas of DNA may affect how genes are expressed. The theory of evolution 82. Charles Darwin published his theory of evolution by natural selection (On the Origin of Species) in It raised much controversy. 83. The theory of evolution by natural selection was only gradually accepted. 84. There were other scientists who tried to explain evolution, eg Alfred Russell Wallace and Jean-Baptiste Lamarck. 85. The work of Alfred Russel Wallace on natural selection, the theory of speciation and warning colouration in animals. 86. New species arise as a result of isolation, genetic variation, natural selection and speciation. Mendel 87. In the mid-19th century Gregor Mendel carried out breeding experiments using plants. He proposed the idea of separately inherited factors that we now call genes. 88. In the late 19th century behaviour of chromosomes during cell division was observed. 89. In the early 20th century it was observed that chromosomes and Mendel s factors behaved in similar ways, leading to the idea that the factors (genes) were located on chromosomes. 90. In the mid-20th century the structure of DNA was determined and the mechanism of gene function worked out.

16 GCSE Biology Ecology Biology 7 Classification 1. Traditionally organisms have been classified into groups depending on their structure and characteristics. 2. Classification can be described by: Kingdom; Phylum; Class; Order; Family; Genus; Species. 3. Organisms were classified into smaller and smaller groups. 4. Carl Linnaeus studied the similarities and differences between organisms to classify them. He developed the binomial system to name organisms by genus and species. 5. Today powerful microscopes are used to see internal structures. This and biochemical analysis has led to new classification systems. 6. Carl Woese developed the three domain system to classify organisms as: Archaea (primitive bacteria) Bacteria (true bacteria) Eukaryota (protists, fungi, plants and animals). Sampling 15. Quantitative data on the distribution and abundance of organisms can be obtained by: random sampling with quadrats sampling along a transect. 16. Adaptations 22. Organisms have adaptations for survival; they may be structural, behavioural or functional. 23. Extremophiles can survive in very extreme environments, such as high temperature or pressure, or in high salt concentration. Communities 7. An ecosystem is the interaction of a community of living organisms (biotic) within the non-living (abiotic) parts of their environment. 8. Organisms need a supply of materials from their surroundings and other organisms to survive and reproduce. 9. Plants compete for light, space, water and mineral ions. 10. Animals compete for food, mates and territory. 11. One species depends on others for food, shelter, pollination, seed dispersal etc. This is called interdependence. 12. A stable community is one where all the species and environmental factors are in balance so that population sizes remain fairly constant. Biotic and abiotic factors 13. Biotic factors are living factors that can affect a community: availability of food new predators arriving new disease organisms one species out-competing another so the numbers are no longer sufficient to breed. 14. Abiotic factors are non-living factors which can affect a community: light intensity temperature moisture levels soil ph and mineral content wind intensity and direction carbon dioxide levels for plants oxygen levels for aquatic animals Food chains 17. Feeding relationships can be represented by food chains. 18. A food chain begins with a producer which synthesises molecules, which is usually a green plant or alga which makes glucose by photosynthesis. 19. Producers are eaten by consumers. 20. Consumers that eat other animals are predators, and those eaten are prey. 21. In a stable community the numbers of predators and prey rise and fall in cycles. Biodiversity 24. Biodiversity is the variety of all life on Earth. 25. A great biodiversity ensures stability of ecosystems. 26. The future of the human species relies on us maintaining a good level of biodiversity. 27. Human activities can reduce biodiversity and we should try to stop this.

17 GCSE Biology Ecology Biology 7 Material recycling 28. Materials are recycled to provide the building blocks for future organisms. 29. The carbon cycle returns carbon to the atmosphere as carbon dioxide and mineral ions to the soil. Waste management 31. Rapid growth in the human population means more resources are used and more wastes are produced, which could lead to more pollution. 32. Pollution kills plants and animals which can reduce biodiversity. 33. Waste may pollute water with sewage, fertilisers or toxic chemicals. 34. Waste may pollute air with smoke and gases such as sulfur dioxide, which contributes to acid rain. 35. Waste may pollute land with toxic chemicals such as pesticides and herbicides, which may be washed from the land into water. 30. The water cycle provides fresh water for plants and animals on land before draining into the seas. Water is continuously evaporated and precipitated. Global warming 40. Levels of carbon dioxide and methane in the atmosphere are increasing and contribute to global warming. 41. Consequences of global warming include: loss of habitat when low lying areas flood changes in the distribution of species where temperature of rainfall changes changes in migration patterns. Land use and deforestation 36. Humans reduce the amount of land available for other plants and animals by building, quarrying, farming and dumping waste. 37. The destruction of peat bogs to produce compost releases carbon dioxide into the atmosphere. It destroys habitats and reduces biodiversity. 38. Large scale deforestation occurred to: provide land for cattle and rice fields to provide more food grow crops from which biofuel can be produced. 39. This destruction of large areas of trees has: increased the release of carbon dioxide by burning and microbial activity reduced the rate at which carbon dioxide is removed from the atmosphere by photosynthesis to be locked up in wood led to a reduction in biodiversity. Programmes 42. Programmes have been put in place to reduce the negative effects on ecosystems and biodiversity. breeding programmes for endangered species protection and regeneration of rare habitats, eg coral reefs, mangroves, heathland reintroduction of field margins and hedgerows in agricultural areas reduction of deforestation and carbon dioxide emissions by some governments recycling resources rather than dumping waste in landfill.

18 GCSE Biology Ecology Biology 7 Trophic levels 43. Organisms obtain food as producers, consumers or decomposers. 44. Producers are mostly plants and algae. They transfer about 1% of incident light for photosynthesis. 45. Consumers include herbivores, carnivores and omnivores. 46. Decomposers break down dead plant and animal matter. Decomposition 56. Decomposition is the process of rotting or decay. 57. Factors which affect the rate of decay of organic matter: temperature availability of oxygen availability of moisture availability of microorganisms to carry out decay ph build-up of toxic substances. 58. Compost provides gardeners and farmers with a natural fertiliser for plants and crops. 59. Anaerobic decay produces methane gas. It occurs without the presence of oxygen. 60. Biogas is a mixture of different gases produced by the anaerobic decay of organic matter. 61. Biogas generators can produce methane which can be used as a fuel. Pyramid of biomass 47. The stages in a food chain are called trophic levels. The producer is at level Level 2 is herbivores (eat plants and algae) and are called primary consumers. 49. Level 3 is carnivores that eat herbivores (secondary consumers). 50. Level 3 is carnivores that eat other carnivores (tertiary consumers). 51. Apex predators are carnivores with no predators 52. Pyramids of biomass can be constructed to represent the relative amount of biomass at each level in a food chain. 53. Trophic level 1 is at the bottom of a pyramid of biomass. 54. Only about 10% of the biomass at each trophic level is transferred to the level above. 55. They are always a pyramid shape. Impact of environmental changes 62. Environmental changes affect the distribution of species in an ecosystem. 63. These changes include: Temperature Availability of water Composition of atmospheric gases 64. These changes may be seasonal, geographic or caused by human interaction. Food security 68. Factors affecting food security include: the increasing human population changing diets in developed countries means scarce food resources are transported around the world new pests and pathogens affect farming environmental changes affect food production cost of agricultural inputs conflicts in some parts of the world over the availability of water or food. 69. New ways must be found to feed all people without endangering the ecological balance of the planet. Farming techniques 70. The efficiency of food production can be improved by restricting energy transfer from food animals. 71. Battery chickens and calves raised in pens are examples of factory farming. 72. Fish grown in cages can be fed high protein food and have restricted movement. 73. There are moral and ethical objections to some factory farming techniques. Sustainable fish 74. Fish stocks are declining and need to be maintained at levels where breeding continues or some species may disappear. 75. Net size and fishing quotas play important roles in conservation of fish stocks. Biotechnology 65. Modern biotechnology techniques enable large quantities of microorganisms to be cultured in industrially controlled vats for food or medical purposes. 66. The fungus Fusarium is useful for producing mycoprotein, a protein-rich food suitable for vegetarians. The fungus is grown on glucose syrup, in aerobic conditions, and the biomass is harvested and purified. 67. GM crops could provide more food or food with improved nutritional value, eg Golden rice.