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B1 Biology fact sheet Sense organs detect stimuli – a change in your environment Eyes contain light receptors Ears contain sound and balance receptors Nose contains smell and taste receptors Tongue contains taste receptors Skin contains touch, pressure and temperature receptors The CNS is made up of the brain, spinal cord and neurones Neurones (nerve cells) transmit information to and from CNS Sensory neurones carry impulses from receptor CNS Relay neurones connect sensory and motor neurones Motor neurones carry signals from CNS effector muscles or glands Reflex arc - stimulus receptor sensory neurone relay neurone motor neurone effector response 2 neurones are connected by a synapse, a gap across which chemicals diffuse Hormones are chemical messengers carried in the blood to activate target cells Menstrual cycle has four stages 1) DAYS 1-4 Lining of the womb breaks down – bleeding 2) DAYS 4 – 14 Lining of womb builds back up again 3) DAY 14 Egg is released 4) DAYS 14-28 Lining of the womb is maintained FSH – Follicle stimulating hormone – produced by pituitary gland - causes an egg to mature - stimulates ovaries to produce oestrogen Oestrogen - produced in ovaries - causes pituitary gland to produce LH - stops release of FSH LH – Luteinising hormone - produced by pituitary gland - stimulates releases of egg Fertility hormones can be used to either reduce or increase fertility Reducing fertility. Oestrogen used in the contraceptive pill which prevents the release of an egg by stopping release of FSH Increasing fertility. FSH taken to stimulate egg production. Eggs can then be collected for IVF. IVF – in vitro fertilisation. Eggs collected from ovaries and fertilised with a sperm in a lab. Electric shock provided to stimulate cell growth. Eggs then implanted back into uterus, in attempt to implant. Homeostasis – maintaining a constant internal environment - Ion content – taken in through food, lost through sweat, regulated by the kidneys, removed via urine - Water – taken in through food & drink, lost from body by sweat, breath & urine. On cold days sweat less & produce more urine. On hot days sweat more & produce less urine - Body temperature – controlled by brain and skin. Body temperature kept at 37oC. - Blood sugar levels – controlled by hormone insulin produced by the pancreas. Auxin is a plant hormones that control growth Auxin controls the growth of plants in respond to tropisms - Phototropism is the response to light - Geotropism is the response to gravity - Hydrotropism is the response to water Auxin is made in the tip of the shoots and the roots of a plant Shoot tips will grow towards light as more auxin is produced on the side away from the light source Shoot tips will grow away from gravity as more auxin is produced on the lower side of the shoot Roots grow towards gravity as more auxin is produced on the lower side of the shoot Roots grow towards moisture as more auxin is produced on the side near the water source - Plant hormones can be used as weed killers and rooting hormones Balanced diet contain - carbohydrates for energy - fats for storing energy - protein for growth, cell repair and replacement - fibre for regular digestive system - vitamins & minerals for a healthy body The metabolic rate is the speed at which chemical reactions happen Metabolic rate depends on - Muscle to fat ratio, more muscle needs more energy = high m.rate - Activity level, more active need more energy = high m.rate - Inherited factors Eating too much can lead to obesity Obesity can cause problems with arthritis, high blood pressure, diabetes and heart disease. Eating too little can lead to deficiency diseases Cholesterol is a fatty substance made in the liver and carried in the blood. It is needed for good health, but too much can be bad Saturated fats raise cholesterol. Polyunsaturated fats lower cholesterol Too much salt causes high blood pressure Drugs are any substance that alters your body chemistry Performance enhancers are taken by some athletes to make them better Statins are a prescribed drug given to lower heart & circulatory disease There is evidence that statins have lowered blood cholesterol and lower the risk of heart disease in diabetics, This research has been repeated by others which backed up findings and the study was done on a large sample Cannabis is an illegal drug. Scientists looked at whether cannabis smoke caused mental health problems. The results varied between test so no conclusive evidence is available. New medical drugs have to be tested thoroughly before they can be given to the general public There are 3 stages of drug testing - Drugs tested on human cells and tissue in labs - Drugs tested on live animals to see if drug works, research its toxicity and to find the best dosage - Drugs tested on humans in clinical trials. First on healthy volunteers to find optimum dose. Then drug is given to ill patients that have been split into 2 groups a) given new drug b) given a placebo (no effect tablet) and results are compared. Placebo trial are “blind” so pateints don’t know if they are getting the drug or not Thalidomide was a sleeping pill that was prescribed to pregnant women to help with morning sickness. It hadn’t been tested and affected the foetus and caused stunted growth of limbs. The drug was banned but is now used for leprosy. Tobacco smoke contain carbon monoxide which makes the blood carry less oxygen. It also contains carcinogens that cause cancer. Nicotine is the addictive part of cigarettes Alcohol reduces the activity of the nervous system – leading to impaired judgement, poor balance and coordination, lack of self control and unconsciousness Cannabis is known as a gateway drug – the effects create a desire to try harder drugs Any microorganism that causes a disease is known as a pathogen Bacteria are very small cells that damage cells and produce toxins Viruses are not cells, they contain a DNA strand surrounded by a protein coat. They replicate themselves inside another cell. The cell damage makes you feel ill. White blood cells have 3 defence mechanisms 1) WBC engulf microbes 2) WBC begin to produce antibodies to kill invading cells 3) WBC produce antitoxins to counter poisons produced by invading bacteria Immunization protects from future invasions by injecting dead or inactive microorganisms. These contain antigens which make body produce antibodies. If live microorganisms appear after injection WBC can rapidly produce antibodies to kill off pathogen. Painkiller relieve pain. They tackle the symptoms not the cause of disease Antibiotics kill the bacteria without killing body cells Viruses cannot be treated by antibiotics, only the symptoms can be treated. Bacteria can become resistance to antibiotics if they are continually exposed to the same ones, Semmelweiss cut deaths by making doctors in hospitals use antiseptics between patients. Vaccinations help to prevent diseases Desert animals are adapted to save water - large surface area compared to volume to lose more body heat - produce small amounts of concentrated urine & little sweat– conserves water - thin layer of body fat to help lose body heat - large feet spread weight across soft sand - sandy colour gives camouflage Arctic animal are adapted to reduce heat loss - small surface area compared to volume - thick layer of blubber & thick hairy coat for insulation - greasy fur sheds water - white fur for camouflage - big feet to spread weight Cacti are adapted to live in a deserts - have spines instead of leaves to reduce water loss - small surface area compared to size to reduce water loss - stores water in thick stem - have shallow extensive roots to absorb water quickly A population is a group of organisms of one species that live in a habitat Population sizes are affected by competition (space, food, water, mates), disease, predation Competition - plants - light, water, space & nutrients - animals – territory, food, water & mates Human impact can be measured using indicator species. Organisms that are sensitive to changes in their environment can be studied to see the effect of human activities Lichens can be used to monitor changes in air pollution as they are very sensitive to the levels of sulphur dioxide Mayfly larvae can be used to monitor water pollution, can’t live where not much oxygen in water Sludgeworms can be used to monitor water pollution, live where there is not oxygen in water Variation – differences between organisms of the same species - genetic – caused by inherited genes - environmental – caused by surroundings Food chains show the transfer of energy between feeding levels (trophic levels) Less energy get passed along at each stage of the food chain – energy lost through respiration, movement, heat & waste There is less biomass at each stage in the food chain Pyramids of biomass represent the food chain Materials are recycled by decay Microorganisms break down (decompose) materials and work best in warm, moist conditions with lots of O2 The carbon cycle shows the recycling of carbon in the atmosphere. Photosynthesis removes carbon from the atmosphere Respiration, burning, volcanoes all return carbon to the atmosphere Variation is the differences between species caused by - Genetics e.g. blood group - Environment e.g colour of plant leaves - Both e.g height of sunflower Most characteristics are due to a mixture of both Genetic material is contained in the nucleus of a cell. The nucleus contains 23 pairs of chromosomes Chromosomes carry genes which control the development of different characteristics A gene is a short length of a chromosome DNA is coiled up to form the arms of a chromosome Cells can reproduce to make new cells Asexual reproduction produces genetically identical cells. There is only one parent cell and the 2 offspring have identical genes to the parent Sexual reproduction produces genetically different cells. There are 2 parent organisms and genetic information is combines to produce offspring. The gametes (sperm & egg) each contain 23 chromosomes and fuse together to produce a cell with a full set of chromosomes Asexual reproduction can be used to clone plants and animals Plants can be cloned from cuttings and tissue culture - cuttings. Cutting taken from parent plant, quickly produces identical offspring - tissue culture. Few plant cells placed in growth medium with hormones, grow into new plants. Animals can be cloned using embryo transfer or adult cell cloning. - embryo transfer. Sperm from male & egg from female. Developing embryo is split to form clones before cells specialise. Cloned embryos implanted into surrogates. Offspring are all genetically identical to each other, but not the parents - adult cell cloning. The nucleus is removed from an egg cell. A set of chromosomes from the cell of another adult are inserted into the empty egg. This egg cell then grows into an embryo and is implanted into a surrogate. The offspring is genetically identical to the original adult whose chromosomes were used. Genetic engineering uses enzymes to cut and paste genes from one organism to another. Genes can be transferred into animals and plants - GM crops have been developed to be resistant to viruses and herbicides - Human insulin genes have been inserted into bacteria to produce human insulin for diabetes sufferers The theory of evolution states that life on Earth began as simple organisms that have evolved into more complex organisms over millions of years The fossil records show that organisms have evolved If organisms can’t evolved they become extinct. The 3 main reasons for extinction are - the habitat changes too quickly - a predator or disease kills them - they can’t compete with another species Darwin came up with idea of Natural Selection which states that species are well adapted to the environment that they live in. The better adapted an organism is the better its chance of survival and chance to pass on its genes Survival of the fittest.
