Not really a cheat sheet It's more of my last minute revision brain dump and remembering of stuff There are loads of typos and mistakes, I wrote ~15,000 characters in 2 hours The content itself should be factual You might find it useful for a few things Not covered is the heart, kidney Also didn't have time to do topic 9 (ecosystems) but I like that so I remember it anyway :) ## Core Practicals ### Investigate the rate of respiration in living organisms Boiling tube containing soda lime, cotton wool plug, capillary tube and bung. Firstly heat the boiling tubes at different temperatures from 30 to 40 degrees at regular intervals, maximum 40. Cotton wool is used to protect organisms and the person, soda lime is corrosive and absorbs the carbon dioxide produced by respiration. Place the maggots inside the tube, on top of the wool which is above the soda lime, and bung it. Copy this with a control tube without maggots. Move this into a water bath for 5 minutes to adjust to the temperature. Then add coloured liquid to a beaker, and bring this to the end of the capillary tube so the liquid begins being sucked up by the maggots. Mark the position on the tube and wait 5 minutes. After this mark the value and measure the distance. Repeat at regular temperature intervals ### Investigate the relationship between organisms and their environment using fieldwork techniques including quadrats and belt transects Using this is a systematic sampling method along an area. Measuring tape from one area to another, place a quadrat on the value 0m. Count the population of a species and record in a table. Progress further at regular intervals and repeat. Draw a bar chart to show the data obtained. ## Topic 6: Plant Structures and their Functions The xylem has a lignified dead cells surrounding it to transport water and dissolved minerals one-way (usually up) the plant. ## Living cells in the phloem use energy to transport water and minerals up and down the plant, and also sucrose. ## Water and mineral ions are transported through the plant by a transpiration stream, from root hair cells which absorb water from the soil by osmosis to the stomata on the underside of leaves. These control gas exchange and amount of water lost. The size of the stomata is changed by neighbouring guard cells, which can become rigid or flaccid. The stomata opens (at day) when the guard cells are rigid and close when the guard cells become flaccid. They are found on the lower surface area of the leaf, and oxygen, water vapour and carbon dioxide diffuse into and out of the leaf for photosynthesis. A continuous column of water is therefore pulled up the stem in the transpiration stream by evaporation from the leaves. ## Photosynthesis produces glucose in plants which is converted to sucrose. It is then transferred around the plant in phloem vessels and destination cells can convert it back into glucose for respiration. This also happens for other things like amino acids. Co2 + h2o -> glucose + oxygen ## A leaf has a waxy cuticle to stop water escaping via the epidermis. To reduce water loss there are less stomata on the top of the leaf. They have a large surface area which allows them to do more photosynthesis. **Top of leaf** - Cuticle for protection and reduce water loss - Epidermis: thin and transparent to allow light to reach palisade cells - Palisade mesophyll: absorb light, increasing rate of photosynthesis, large amounts of chloroplasts. packed tightly - Spongy mesophyll: air spaces allow gases to diffuse - Lower epidermis, guard cells, stoma allow gas exchange to be regulated - Cuticle for protection **Bottom of leaf** Carbon dioxide moves in at the same time oxygen goes out (due to lower concentrations of the gases - diffusion). Cells in the leaf are loosely packed to control water vapour. ## - Temperature increases transpiration as evaporation and diffusion happen faster at higher temperatures. - Humidity decreases rate of transpiration as diffusion will slow down if the leaf is surrounded by moisture - Light intensity increases rate of transpiration as the stomata will open wider to allow more CO2 for photosynthesis - Wind speed will increase rate of transpiration as the water vapour is removed more rapidly increasing rate of diffusion ## Phototropism: response to light. Sunlight breaks down auxins, bending the plant to the light source. Plants grow towards the light. Roots have a negative phototropism as they grow away from the light. Gravitropism: response to gravity. Roots have a positive gravitropism while the rest of the shoots have a negative gravitropism. ## Plant hormones can be used to have a desired effect. - Auxins stimulate cell elongation which can be beneficial. Some weedkillers can contain high levels of auxins which result in the plant growing rapidly but cannot support this growth, killing the plant. Plant cuttings can be stimulated with auxins to promote growth. - Gibberellins are also used for growth and development of plants. They can be used to increase fruit size and make plants flower more quickly. They can also make seeds germinate earlier as they stop seeds being dormant. As a result of their ability to quickly make fruits grow, they are used to grow seedless fruits like grapes. - Ethene can be used to ripen fruit during storage and transport, bananas are ripened in shops and are picked green. bananas also release ethene naturally, causing other plants to ripen earlier. ## Topic 7: Animal Coordination, Control and Homeostasis The endocrine system controls loads of stuff like metabolic rate, energy levels, reproduction and stuff with hormones. - The pituitary gland is the 'master gland' at the base of the brain which secretes hormones to control body condition like blood water levels. - The thyroid gland produces thyroxine and is located in the neck and are responsible for metabolic rate - The pancreas produces insulin which controls blood glucose levels. It increases the conversion of glucose into glycogen for storage and targets the liver. - The ovaries in women produce oestrogen which does stuff to the menstrual cycle - The testes in boys produce testosterone which do stuff to sperm and increases in puberty ## - The adrenal glands secrete adrenaline which prepares the body for 'fight or flight'. It targets many organs by increasing the breathing rate, heart rate, increases blood flow to muscles. - It stimulates the liver to change glycogen into glucose, increasing blood sugar levels. - It makes the heart beat harder and faster. (Especially before an exam) ## Thyroxine controls the metabolic rate and is an example of negative feedback. When there are low levels of thyroxine, TRH is produced in the hypothalamus, which causes the pituitary gland to release TSH. As a result of this, the TSH acts on the thyroid to produce more thyroxine. When thyroxine levels return to normal, the release of TRH is inhibited and I so the production of TSH > TSH means thyroid stimulating hormone ## The menstrual cycle has 4 hormones involved. In order: - FSH causes the maturation of the egg in the ovary. (follicle-stimulating hormone) - Oestrogen is made from the corpus luteum in the ovaries (cells from when the egg was released) and stimulates the reparation and thickening of the uterus lining. Day 7-14. Stops FSH. - LH (luteinizing hormone) stimulates the release of the egg. It is only around day 14. - Progesterone maintains the uterus lining from days 14-28. It is also produced from the corpus luteum and inhibits FSH and LH (negative feedback). - If the egg is not fertilised the corpus luteum dies and progesterone levels drop and the uterus lining breaks down ## Hormonal contraception can prevent pregnancy as 'the pill' contains small doses of oestrogen and/or progesterone (taken daily) inhibit the production of FSH which stops the egg developing. Low levels of oestrogen stimulate the release of an egg while high levels stop FSH. If the levels remain high, as with the pill, egg development will stop and no chance of a baby. Other pills like the morning after pill can reduce the amount of progesterone, inhibiting its release, and therefore results in the uterus lining breaking down. ## Barrier methods of contraception can also be used to prevent pregnancy. These are things like condoms which physically prevent sperm meeting with the egg. As a result, no fertilisation can happen. However there is a chance that they may rip or tear. Spermicide can be added to physical barriers like condoms to kill any potential sperm but this can cause an allergic reaction. ## Hormones are used in Assisted Reproductive Technology (ART) to help achieve pregnancy. These fertility drugs may contain FSH and LH which stimulates eggs to mature and to be released. It also increases the chance of twins or triplets as it could cause multiple eggs to be released. ART also includes IVF and clomifene. IVF collects eggs from the mother and combined with the father's sperm in a dish, and then re-implanted in the woman. Clomifene is a drug blocks oestrogen's negative feedback on LH. Therefore when this drug is removed, more LH is released at once, simulating the LH surge before ovulation. > hormones travel in the bloodstream ## Homeostasis is the maintaining of a constant internal environment in the body, controlled by the nervous system and hormones. They are all automatically controlled by the signals given by the receptor, move to a control centre and the effector creates the response. Thermoregulation is controlled by the hypothalamus. When a chnage is detected, if it is too hot, sweat glands in the dermis release more sweat onto the epidermis. As this sweat evaporates, heat energy is transferred into the surroundings. On the contrary shivering happens if we are too cold, which results in the rapid contraction of muscles, which require respiration, releasing heat. Erector muscles also trap an insulating layer of air in the hairs. > If a constant internal temperature is not maintained at around 37 degrees then enzymes will denature and cannot catalyse reactions. The amount of blood flowing in the capillaries is changed by also vasodilation and vasoconstriction. When it is too cold, capillaries vasoconstrict, making the arterioles narrower. As a result, blood flow is decreased, and physical distance from the bloodstream to the environment is decreased, resulting in little heat being lost. Conversely, when it is too hot, arterioles get wider from vasodilation, making blood flow increase and increases heat loss too, cooling the body. These are all controlled by nerve impulses from the hypothalamus. ## Osmoregulation is the control of water and mineral ions like salt in the blood. If the concentration of water in and out of the cell are similar, there is no overall change. If the water concentration on the outside is larger, then water enters via osmosis. Too much and the cells can burst. (Hypotonic) If there is to little water on the outside, the cells may shrivel and lose water. Cells won't function if there is not a good balance of water. If there is too much salt, this can uncontrollably cause cells to shrivel as it is good at absorbing water. ## Insulin in the pancreas controls blood glucose concentration. Glucose is needed for respiration. If there is a high concentration of blood glucose, the pancreas secretes the insulin hormone, causing glucose to move from the blood into cells. In liver cells this glucose is stored as glycogen for use later on, resulting in decreased amounts of glucose. Glycogen is insoluble, whereas glucose is soluble and will disturb osmotic balance (hypertonic like salt). When the concentration of blood glucose is low, glucagon is secreted. This makes glycogen convert into glucose, increasing the amounts of glucose available. ## Type 1 diabetes happens when your body cannot produce enough insulin to control blood glucose. This will result in uncontrolled high blood glucose levels. It is controlled by injecting insulin to simulate the pancreas's work. Exercise can lower blood glucose levels due to muscles respiring more, or by taking foods with low blood sugar effects. Type 2 diabetes is when the cells in a person no longer responds to insulin. It can be controlled by exercise and eating less carbohydrates. These are digested into glucose, which would raise blood glucose levels. fat people are more likely to have type2 diabetis. waist:hip >0.85 in women and >1 in men. BMI = mass / (height)^2^ ## **kidney stuff here** ## Topic 8: Exchange and Transport in Animals Exchange surfaces are needed to move substances in and out of a cell quickly by diffusion. A simple, small, unicellular organism has a high surface area:volume ratio, so nutrients, water and substances can pass quickly through its membrane and circulate in the body of the organism. Hoverver, the surface area:volume ratio of a multicellular, large organism is small, so transport systems specialised in the movement of particles is needed, on top of specialised exchange surfaces. Exchange surfaces are: - thin for a short diffusion distance - have a large area (long and thin, flat or folded) Transport systems often: - have vessels which transport substances around parts of the organism - are close to cells, reducing diffusion time and distance like exchange surfaces. The circulatory system in humans is pumped by the heart whereas the phloem and xylem in plants is not pumped. ## Gas exchange in humans occurs in the lungs, in the alveoli. When air is inhaled, this oxygenated air is added into the alveoli and diffuses into the bloodstream across the exchange surface of the alveoli. The capillary curves around the alveoli, maximising the contact with the air pocket, allowing for CO~2~ to diffuse into the alveoli and O~2~ to go in to the bloodstream. - Large surface area - Thin walls - Moist walls - Permeable walls - Extensive blood supply - Large diffusion gradient ## Fick's law describes the relationship between the rate of diffusion and the factors that affect it. $\text{Rate of diffusion} \propto \frac{\text{surface area} \times \text{concentration difference}}{\text{thickness of membrane}}$ ## Cellular respiration occurs continuously in living cells to release energy metabolic processes, including aerobic and anaerobic respiration. It is exothermic. Aerobic respiration needs oxygen and releases large amount of energy in cells by the breakdown of glucose with oxygen, producing carbon dioxide and water. Most aerobic respiration reactions occur in mitochondria. (19x more energy released than below) Anaerobic respiration does not need oxygen but results in a relatively small amount of energy being released. It converts glucose straight into lactic acid. this lactic acid needs to be oxidised to carbon dioxide and water later. This is known as oxygen debt which needs to be repaid after the exercise has stopped. > It also happens in plants and yeast, glucose -> ethanol + CO~2~ ## Calculate heart rate, stroke volume and cardiac output, using the equation cardiac output = stroke volume × heart rate ## ## Topic 9: Ecosystems and Material Cycles I really can't be bothered. nitrifying bacteria. nitrogen fixing bacteria. > Written with [StackEdit](https://stackedit.io/).