B1-3 Long Answer Ideas

Transcription

1 B1-3 Long Answer Ideas Use the collection of points for each question to help check that you have covered the key points when answering questions for revision. Use it as a ticklist to check over the questions when you are Revising. Key words are in italics Contents: 1. Inherited and Environmental 2. Sex Chromosomes 3. Genetic Diseases 4. Genetic Screening 5. Stem Cells 6. Natural Immunity 7. Vaccination 8. Testing for Safety 9. Antibiotic Resistance 10. Blood Vessels 11. Heart Disease 12. Homeostasis 13. ADH 14. Extinction 15. Food Chains 16. Cycling Nitrogen 17. Theories of Evolution 18. Natural Selection 19. Biodiversity 20. Sustainability

2 Describe the difference between an inherited and environmental characteristic and describe how genetic information is stored and passed on. Inherited Factors which are determined by the genetic make up of an organism, (e.g. eye colour) Environmental Determined by the interaction with the environment (e.g. scars) These two factors can interact (e.g. weight) Storage Genetic information is stored in the DNA, which make up the chromosomes, found in the nucleus of a cell. 46 (23 pairs) of chromosomes in body cells apart from sex cells which have 23. Passed On In sex cells sperm and egg, fuse in fertilisation Using a diagram and explanation explain why the chances of a baby being born a boy are 50%. X X X XX XX Y XY XY Mother has sex chromosomes XX Father has sex chromosomes XY Four possible outcomes: XX (x2) Girl XY (x2) Boy Therefore 50/50 chance. The sex-determining gene on the Y chromosome triggers the development of testes, and that in the absence of a Y chromosome ovaries develop Describe the similarities and differences between Huntington s Disease and Cystic Fibrosis. Similarities - Both are genetic diseases, passed on from parent to child. - Both caused by a faulty allele of a single gene Differences - Huntington s is caused by a dominant allele whilst Cystic fibrosis (CF) is caused by a recessive allele. -Huntington s is late onset, CF affects from birth - Huntington s affects nervous system whilst CF affects respiratory and digestive system. - Can be a carrier of CF but not of Huntington s disease. What are the uses of genetic screening and what are the implications of this on the stakeholders? Uses: - testing embryos for embryo selection (preimplantation genetic diagnosis) - predictive testing for genetic diseases - testing an individual before prescribing drugs Implications: - risk of miscarriage as a result of cell sampling for the genetic test - using results that may not be accurate, including false positives and false negatives - whether or not to have children at all - whether or not a pregnancy should be terminated - whether other members of the family should be informed - Information for insurance companies - Information could get into the wrong hands - Employers could genetically screen for those likely to get an illness leading to discrimination.

3 What are stem cells and how do they enable us to clone living organisms? Why is this useful? Stem Cells: Embryonic Stem Cells unspecialised cells that can develop into any type of cell. Adult Stem Cells unspecialised cells that can develop into many, but not all, types of cell. Cloning Process - Egg cell removed from female organism - Nucleus removed from egg cell - Nucleus taken from adult body cell which is to be cloned. - Inserted into the unfertilised empty egg cell - Cells divide to form cloned embryo. Uses: -Embryos could be used as a source of embryonic stem cells. - Stem cells can be used to treat diseases as they are unspecialised. - Could be used to clone endangered animals/ stock animals/ sport animals Describe how white blood cells protect the body from infection and how immunity naturally arises. White Blood Cells: Destroy micro-organisms by engulfing and digesting them or by producing antibodies. Natural Immunity The invading pathogen enters the body. On the surface it has antigens. The white blood cells can use this to recognise that it is an invader to the body. The white blood cells produce antibodies which will bind to the antigens if they match up. The particular antibody is specific to that particular antigen. Once the body has made the antibody to recognise a particular microorganism, memory cells can make that antibody again very quickly, therefore protecting against that particular microorganism in the future (natural immunity) Explain how vaccines protect you from infection. Why is it important that lots of people are vaccinated? Vaccines contain a safe form of a disease causing micro-organism. This is either a weakened or small sample, a dead sample, or part of the microorganism. The white blood cells produce the antibodies to destroy the invading microorganism. The memory cells can then make antibodies again very quickly to protect against further attacks if you encounter the pathogen later on in life. Herd immunity means that it is unlikely that a person with a disease would come into contact with an unvaccinated person. This limits the spread of the disease and makes it easier to contain any outbreaks. Describe how drugs and vaccines are tested for safety and explain the different forms of drug trials. Vaccines and drugs are never completely risk free, individuals can have varying side effects. Genetic differences mean people react differently. Testing for Safety Animals and Human Cells Safety and Effectiveness Healthy volunteers Safety People with the illness Safety and Effectiveness Drug Trials Open Label Both patient and doctor know Blind Only the doctor knows Double Blind Doctor and patient don t know

4 How can resistance come about in bacterial populations and what can we do to minimise the chances of this occurring? Using antibiotics against bacteria and fungi can sometimes lead to resistant populations e.g. MRSA Random mutations in the genes will sometimes lead to varieties which are less affected by antimicrobials. When a surface or illness is treated these will survive and have the space and resources to multiply. Over time the number of resistant microbes will increase until they cause a significant problem To minimise the risk always complete the recommended course of antimicrobials as prescribed by the doctor, even if you start to feel better. Only use the suitable medicine e.g. not using antibiotics against a viral infection. Explain how the arteries, veins and capillaries are suited to their function. Arteries Blood coming from the heart, so under high pressure. Therefore thick outer walls and thick layers of muscle and elastic fibres Veins Going back to the heart so under much lower pressure than arteries. Therefore thin walls and thin layers of muscle and elastic fibres. Valves to prevent the blood from flowing the incorrect way. Capillaries Needed for gaseous exchange, food and oxygen into the cell, carbon dioxide the other way. Thin walls, one cell thick, to enable efficient transfer. Thin lumen brings red blood cells close to body cells. How could you determine if someone is at risk of heart problems? Why is homeostasis important for the body? How does negative feedback work? Measure blood pressure: Measures pressure of blood on artery wall. Consists of two numbers; -the higher number when heart contracts - the lower number when heart relaxes Fatty deposits in coronary arteries can produce a heart attack Genetic factors Lifestyle factors: - Poor Diet - Stress - Cigarette smoking - Misuse of drugs (ecstasy, alcohol, cannabis) Homeostasis is important as it maintains a constant internal body environment allowing all the processes vital for life to occur. (e.g. water balance and cell contents concentration) Control System Receptor Detects change in environment Processing Centre Receives information and co-ordinates responses automatically Effector Produces the response Negative feedback When there is a change from the steady state a negative feedback between the effector and receptor reverses any change. Example: Balancing water with kidneys

5 Explain the role of ADH in maintaining constant water levels in the body. How can ADH levels be affected? The kidneys balance water levels by producing dilute or concentrated urine as a response to concentration of blood plasma, which is affected by external temperature, exercise level and intake of fluids and salt The concentration of urine is controlled by a hormone called ADH. ADH is released into the bloodstream by the pituitary gland When water levels low, ADH released, kidneys reabsorb more water, therefore producing concentrated urine. When water levels high, ADH not released as much, kidneys release water to bladder, urine becomes dilute. Alcohol Suppresses ADH production Ecstasy Increases ADH production What is a species and how can they become extinct? Species: A group of organisms that can breed together to produce fertile offspring. Extinction: When there are no remaining living organisms of a species A change in the environment may cause a species to become extinct, for example, if: - the environmental conditions change beyond its ability to adapt - a new species that is a competitor, predator or disease organism of that species is introduced - another species (animal, plant or microorganism) in its food web becomes extinct Describe how energy is passed through a food chain and why the length of a food chain is limited. Energy Transfer All energy in a food chain originates from the Sun. Plants absorb a small percentage of the Sun s energy for the process of photosynthesis This energy is transferred through a food chain when organisms are eaten. Dead organisms and waste materials are fed on by decay organisms (decomposers and detritivores) to recycle nutrients Limited Length Energy is lost at each stage through: -Heat -Uneaten parts -Waste products Describe how nitrogen can be moved around the nitrogen cycle. Nitrogen is cycled through the environment in a number of different ways: - Nitrogen in the air (N2) is fixed to form nitrogen compounds, such as nitrates, by bacteria and also by lighting. - Nitrogen compounds are converted into proteins by both plants and animals. - Nitrogen compounds are transferred through the food chain by organisms consuming each other. - The death and decay of plants and animals results in the release of nitrates into the soil by decomposing bacteria. - Plants can take up these nitrates from the soil. -Denitrifying bacteria also release Nitrogen (N2) back into the air. Microorganisms are extremely important in ensuring the cycling of nitrogen in the environment.

6 Describe why Darwin s theory of evolution is a better scientific theory than that of Lamarck. Darwin: Darwin's theory of natural selection. Genetic variation leads to differences between members of the same population. Some will become better adapted to their environment and will be able to outcompete other animals and therefore be more likely to breed. This will lead to their characteristics becoming more common in individuals in future generations. Lamarck: Lamarck believed that organisms could change their physical features in their lifetime and that this would be passed onto their offspring. Why better: Darwin s idea fits in with advances in the understanding of genetics. No evidence or mechanism for Lamarck's acquired characteristics Explain how the theory of natural selection could lead to changes in a population of animals. Natural Selection: Darwin's theory of natural selection. Genetic variation leads to differences between members of the same population. Genetic variation is caused by random mutations in the genetic information. These happen all the time, though will rarely confer an advantage upon an individual. Some will become better adapted to their environment and will be able to outcompete other animals and therefore be more likely to breed. This will lead to their characteristics becoming more common in individuals in future generations. Evidence has been found in the fossil record, and from analysis of similarities and differences of organisms. Explain what is meant by the term biodiversity and say why it is important to maintain it. What is sustainability and how can it be improved? Biodiversity: Biodiversity refers to the variety of life on Earth. This includes: - The number of different species - The range of different types of organism e.g. plants, animals and microorganisms - The genetic variation within species. Importance to maintain: The development of future medicines and food crops. Ensure the conservation of future species Stability of ecosystems Ensure supplies of clean water and other ecosystem services Sustainability Meeting the needs of people today without damaging the Earth for future generations. Improving Sustainability Using less packaging Considering the materials used in packaging Using less energy in production Utilising waste products Not having large scale monoculture farming Even if products are biodegradable we should still minimise their use as there is still energy used in their transport and production and in oxygen deficient landfill sites decomposition time are extremely long.