GCSE REVISION GUIDE!! Aesthetic | Summaries | Visual Learners

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across the gap - these chemicals set of another electrical signal in the next neurone. Reflexes: -automatic responses to a stimulus that don't involve the conscious part of the brain in order to prevent injury or harm. Reflex arc: Passage of information in a reflex - from receptor to effector. Effector (contracts) -sensory neurone K STINGI -receptor -motorne This creates a reflex arc Endocrine system Hormones: -they are chemical molecules released directly into the bloodstream where they are transported to target organs (particular cells in particular organs). -they control things that need constant adjustment. -produced in endocrine glands, these glands make up the endocrine system. -have long lasting affects. Endocrine glands: Pituitary gland "master gland": produce hormones that regulate body conditions. - the hormones produced by the pituitary gland also direct other glands to release hormones. Thyroid: - produce thyroxine ~ which regulates the rate of metabolism, heart rate, and temperature. Adrenal gland: - produces adrenaline ~ prepares the body for the "fight and flight" response. Pancreas: - produces insulin ~ regulates the blood glucose level. Ovaries (only females): produce oestrogen involved in the menstrual cycle. Testes: produce testosterone~ controls puberty and sperm production. Nerves - fast action - act for a short amount of time -act on a precise area BRAIN ENDOCRINE SYSTEM Pituitary gland Thymus Thyroid Ovaries Hormones - slow action - act for a long amount of time - act in a general way Pineal gland Hypothalamus a Pancreas Adrenal glands Testes Controlling blood glucose Insulin and glucagon: -eating foods that contain lots of carbohydrates puts glucose into the blood from the gut. - metabolism of cells removes glucose from the blood. -exercise removes glucose from the blood. -excess glucose can be stored as glycogen in the liver and in the muscles. -level of glucose must be kept steady so changes are monitored and controlled by the pancreas which use the hormones insulin and glucagon in a negative feedback cycle. High levels of glucose: 1. Insulin gets secreted from the pancreas to the blood. 2. The glucose moves from the blood into the liver and muscle cells. 3. Insulin makes the liver turn glucose into glycogen. 4. This reduces the glucose level in the blood. Low levels of glucose: 1. Glucagon gets secreted from the pancreas into the blood. 2. Glucagon moves into the liver where it converts into glucose. 3. The glucose gets released into the blood. 4. This increases the glucose levels in the blood. Type 1 Diabetes: -pancreas produces little or no insulin so this means glucose levels can rise in the blood to the point it can kill them. How to control the glucose in the blood stream: Insulin therapy: ~ involves injecting insulin throughout the day usually at mealtimes. This means the glucose is removed once the food has been digested. ~ amount of insulin injected depends on the persons diet and how active they are. Limiting the intake of food with carbohydrates: ~causes the blood glucose to rise rapidly. Regular Exercise: - helps remove excess glucose from the blood. Type 2 Diabetes: -person becomes resistant to their own insulin - so they produce insulin but their cells don't respond to it. This causes the blood glucose levels to rise to a dangerous level. -risk factor to type 2 diabetes is obesity. How can it be controlled: -carbohydrate controlled diet. -regular exercise. 5 = Menstrual Cycle and Puberty Hormones sexual characteristics -at puberty your body starts producing sex hormones that trigger secondary sexual characteristics. Men: -reproductive hormone is testosterone. -produced by the testes. -stimulates sperm production. Women: -main reproductive hormone is oestrogen. -produced by the ovaries. -this hormone is also involved in the menstrual cycle. Menstrual cycle: Stage 1: -menstruation starts from day 1 to day 4. -lining of the uterus breaks down. Stage 2: -the uterus lining builds up again from day 4 to day 14. -the uterus lining builds up as a thic spongy layer full of blood vessels, ready for an egg. Stage 3: -egg develops and is released at day 14 ~ called ovulation. Stage 4: -the wall is maintained for another 14days till day 28. -if no fertilised egg has landed on the uterus wall by day 28 the spongy lining breaks down and the whole cycle repeats. Hormones control the menstrual cycle: Follicle-stimulating hormone: -produced in the pituitary gland -causes an egg to mature in the ovaries in a structure called a follicle. -stimulates the ovaries to produce oestrogen. Oestrogen: -produced in the ovaries. -causes the lining in the uterus to grow. -stimulates the release of luteinising hormone and inhibits release of FSH. Luteinising hormone: -produced by the pituitary gland. -stimulates the release of an egg at day 14 (ovulation). Progesterone: -produced in the ovaries. - maintains the lining of the uterus during the second half of the cycle. -when the level of progesterone falls the lining of the uterus breaks down. -inhibits the release of LH and FSH. Adrenaline and Throxine Adrenaline: -hormone that is released by the adrenal gland (just above the kidneys). -its released as a response to stressful or scary situations - when the brain detects fear its sends nervous impulses to the adrenal glands which respond by secreting adrenaline. -gets the body ready for "fight or flight" by triggering mechanisms that increase the supply of oxygen and glucose to the cells in the brain and muscles e.g heart rate increases. Thyroxine: -produced by the thyroid gland in the neck. -regulates the basal metabolic rate. -stimulates protein synthesis for growth and development. -thyroxine is released in response to thyroid stimulating hormone which is released from the pituitary gland. Mutations Mutation: -a random change in an organisms DNA which can sometimes be inherited. -mutations can happen continuously or spontaneously e.g when the chromosomes aren't replicated properly. -chances of mutations can increase if exposed to certain substances or types of radiation. -mutations change sequence of the DNA base in the gene and produces a genetic variant (different form of the gene). -mutations have little or no effect on the protein and will change it to a small extent that the appearance or function is not affected. -however some can affect a protein and the mutation will code for an altered protein and changes its shape which could affects its function e,g enzyme active site is changed. Meiosis Gametes: -have one copy of each chromosome so when the gametes fuse they get the right amount of chromosomes. -to make gametes cells divide by meiosis. This process involves 2 cell divisions and happens in the reproductive organs - ovaries and testes. Meiosis: 1.before the cell divides it duplicates its genetic information and forms 2 armed chromosomes and then arrange themselves in pairs. 2.first division - chromosomes line up in the centre of the cell and are pulled apart so each new cell has one copy of each chromosome. Some of the fathers and some of the mothers chromosomes go into each cell. 3.second division - the chromosomes line up again in the centre and are pulled apart. 4. You get 4 gametes with a single set of chromosomes. Each gamete is genetically different because the chromosomes get shuffled during meiosis and each gamete gets half of them randomly. X & Y Chromosomes Genetic diagrams: Punnet square - xx represents the female gametes and xy represents the male gametes. female gametes X (eggs) XX XX XY XY male gametes (sperm) possible combinations of gametes... ...two males (XY) and tvo females (XX). Genetic diagrams Characteristics are controlled by genes: - the genes you inherit controls what characteristics you develop as different genes control different characteristics. - some characteristics are controlled by one gene but most characteristics are controlled by several genes interacting. - genes exist in different versions called alleles. - there are 2 types of alleles. - homozygous, is when an organism has 2 alleles of a particular gene that are the same. - heterozygous, is when an organism has 2 alleles of a particular gene that are different. - if 2 alleles are different only one can determine the characteristic, this allele is the dominant allele and the other one is recessive. - for an organism to have a recessive characteristics both alleles must be recessive but to have a dominant characteristic it can either be one dominant allele and one recessive or both dominant alleles. - genotype is the combination of alleles you have. - - phenotype is the characteristics you have. Gregor Mendel: - he noted how characteristics in plants were passed on from one generation to the next, this became the foundation of modern genetics. - he carried this experiment on pea plants - one tall and one dwarf (pair 1) and two tall (pair 2) he breaded them together and looked at their offspring and noted it down. Mendel's conclusions: - characteristics were determined by hereditary units. - hereditary units are passed on to offspring unchanged from both parents - one unit from each parent. - hereditary units can be dominant or recessive. Selective breeding Selective breeding: -when humans artificially select the plants or animals they are going to breed so that the particular characteristics remain in the population. -organisms which are selectively bred to develop features that are useful or attractive e.g disease- resistant crops or dogs with good temperament. Process of selective breeding: -select an animal or plant from your existing stock which have characteristics you like. -breed them with each other. -select the best offspring and breed them together. -continue this process over several generations so the desirable traits get stronger. Eventually all offspring will have the same characteristics. -selective breeding is popular in agriculture as farmers use this to improve yields. Disadvantages of selective breeding: -reduces the gene pool in a population, this is because people breed the best animal or plant which are closely related known as inbreeding. -inbreeding causes health problems as the organism can inherit genetic defects e.g pugs have breathing problem. -there would be a big problem if a new disease appears as there isn't much variation in the population so if one gets affected all the others will too. Genetic Engineering Genetic engineering: - transfer of a gene responsible for a desirable characteristic from one organisms genome to another organism so that it also has the desired characteristic. Process of genetic engineering: -useful gene is isolated from one organisms genome using enzymes and is then inserted to a vector. -the vector is a virus or a bacterial plasmid, depending on the type of organism that the gene is being transferred to. -when the vector is introduced to the target organism the useful gene gets inserted into its cell. scientists use genetic engineering for lots of things: -bacteria has been genetically modified to produce insulin for people with diabetes. -GM crops have had their genes modified e.g to improve the size of their fruit etc. Advantages to GM crops: -characteristics for GM crops can increase yield and make more food. -people living in nations where there is a lack of nutrients in their diet GM crops could be engineered to contain nutrients that are missing. -GM crops are being grown in places and there are no problems. Disadvantages to GM crops: -growing GM crops will affect the number of wild flowers that live in and around the crops and reduces farmland biodiversity. -some people say it is not safe and are concerned that we don't fully understand the effects of eating them may have on human health. -transplanted genes may get out into the natural environment. Fossils Fossils: -remains of organisms from thousand of years ago and can be found in rocks and give us evidence that organisms lived years ago. Fossils tell us how much or how little and organism has changed over time. Fossils for in rocks by: Gradual replacement by minerals -teeth, shells and bones don't decay easily and can last a long time when buried. -they eventually get replaced by minerals as they decay and form rock like substances shaped like the original hard parts. -surrounding sediment turn into rock as well but the fossils stay distinct inside the rock and eventually someone digs it up. Casts and Impressions -fossils form when an organism is buried in soft material like clay. Clay hardens over time and the organism decays leaving a cast a itself. E.g animal burrows or plant roots. -footprints can be pressed into these materials leaving an impression when it hardens. Preservations -in amber and tar pits there is no oxygen or moisture so decay microbes cant survive. -in glaciers its too cold for decay microbes to work. -peat bogs are too acidic for decay microbes. -this means organisms can be preserved. Speciation Speciation: -is the development of a new species -it happens when populations of the same species become so different that they can no longer be interbred to produce fertile species. Isolation and natural selection: -isolation is when populations of species are separated -isolation can happen due to a physical barrier e.g floods -conditions of either side of the barrier may be different e.g different climate. Therefore different characteristics will become more common in each population due to natural selection. -each population shows genetic variation because they have a wide range of alleles, however individuals with characteristics that make them better adapted to their environment have a high survival rate and so breed more successfully. -so alleles that control beneficial characteristics are more likely to be passed on to the next generation. -eventually individuals from different populations will have changed so much that they wont be able to breed and produce fertile offspring. -the 2 groups become separate species. Abiotic resistant bacteria Antibiotic resistant: -bacterias can mutate this leads to changes in characteristics. -this can result in an antibiotic-resistant strains forming as the gene for antibiotic resistance become more common in the population. -as bacteria reproduce rapidly they can evolve quickly. -for the bacterium it is an advantage as they are able to survive antibiotics and can live longer, this increases the population size. -antibiotic resistant bacteria is a problem for people as the person infected with these bacteria have no effective treatment. This means infections easily spread between people. -MRSA is a common superbug that is hard to get rid off. Antibiotic resistance is becoming more common: -due to the overuse and inappropriate use of antibiotics e.g doctors may prescribe them for non- serious conditions or infections caused by viruses. -more antibiotics used = bigger the problem of antibiotic resistance. -some people don't take the full course of antibiotics the doctors gave them which can increase the risk of antibiotic resistant bacteria forming so it is important to take the full corse as it makes sure all the bacteria is destroyed and that there is non left to mutate and develop antibiotic resistant strains. -in farming antibiotics are given to animals to prevent them becoming ill and to make them grow faster. This leads to the development of antibiotic resistant bacteria in animals which spread to humans. Classification Classification: -organising living organisms into groups. -"Linnaean system" is classifying organisms into groups based on their characteristics and structures and are divided into kingdoms. The kingdoms are subdivided into smaller groups - phylum, class, order, family,genus and species. Classifications system change over time: -as biochemical processes developed inside organisms and technology improved, scientists put forward a new model of classification. -Carl Woese proposed the three domain system using evidence gathered from new chemical analysis techniques e.g RNA sequence analysis. -in the three domain system organisms are split into 3 groups called domains - archaea ( primitive bacteria and are found in extreme places) bacteria (true bacteria) eukaryota ( range of organisms including fungi plants animals and protists). Binomial system: -organisms have a 2 part latin name - first part refers to the genus the organism belongs to - second part refers to the species. Evolutionary trees: -show how scientists think different species are related to each other. -show common ancestors and relationships between species. -scientists analyse classification data and fossil records to work out the evolutionary relationship. recent ancestor distant ancestor Whale Dolphin Whales and dolphins have a recent common ancestor so are closely related. They're both more distantly related to sharks. Shark Competition Population - all the organisms of one species living in a habitat. Community - the population of different species living in a habitat. Abiotic factors - non-living factors of the environment e.g temperature Biotic factors - living factors of the environment.g food. Ecosystem - interaction of a community of living organisms with non-living parts of their environment. Competition: -organisms need things from the environment and other organisms in order to survive and reproduce. -plants need light, space, water and mineral ions. -animals need shelter, food, water and mates. Organisms compete with other species for the same resources. Changes in the environment: -species depend on each other for things e.g food. -interdependence of all living things in an ecosystem means that any major change in the ecosystem can have negative effects. -stable communities are when all the species and the environmental factors are in balance so the population size is constant. Abiotic factors: -moisture level -light intensity -temperature -carbon dioxide level -wind intensity -oxygen level -soil pH and mineral content -different organisms are adapted to different abiotic conditions. Changes in abiotic conditions: -decrease in light intensity temperature or cabon dioxide level could decrease the rate of photosynthesis in plants and could affect plant growth and cause decrease in population size. -decrease in mineral content of the soil could cause nutrient deficiencies and affect plant growth and cause decrease in population size. Biotic factors: -new predators -competition -new pathogens -availability of food Changes in biotic factors: -this can affect size of populations in a community. -new predator could cause a decrease in prey. Using Quadrats Quadrats: -used to find the distribution of an organism. -measure how common an organism is in 2 sample areas and compare them. -this method is quantitive data about distribution. Quadrat practical: -a quadrat is a square frame enclosing a known area. 1.place a 1m^2 quadrat on the ground at a random point within the first sample area. 2.count all the organisms within it. 3.repeat steps 1 and 2 as many times as you can. 4.work out the mean number of organisms per quadrat within the first sample area. 5.repeat steps 1 and 2 but in the second sample area. 6.compare the two means. Population size: Work out the mean number of organisms per m^2 then multiply by the total area. EXAMPLE Students used a quadrat with an area of 0.5 m² to randomly sample daisies on an open field. The students found a mean of 10.5 daisies per quadrat. The field had an area of 800 m². Estimate the population of daisies on the field. 1) Work out the mean number of organisms per m². 2) Then multiply the mean by the total area (in m²) of the habitat. 1 + 0.5 = 2 2 x 10.5 = 21 daisies per m² 800 x 21 16 800 daisies on the open field Environmental change -environmental change causes the distribution of organisms to change. Temperature: -distribution of bird species can change due to the rise in temperature. Availability of Water: -distribution of some animals and plant species in the tropics changes between wet and dry seasons. Composition of atmospheric gases: -distribution of some species change in areas with air pollution. Water cycle: -water is constantly recycled. 1. Energy from the sun makes water evaporate from the land and sea, turning it into water vapour. Water also evaporates from plants (transpiration). 2. Warm water vapour is carried upwards as warm air rises and cools as it hets higher up and forms clouds. 3. Water falls from the clouds as precipitation (rain) onto land and provides fresh water for plants and animals. 4. It then drains into the sea and the process starts again. Carbon cycle: 1. Co2 is removed from the atmosphere by green plants and algae during photosynthesis. 2. When plants and algae respire carbon is returned to the atmosphere as co2. 3. When plants and algae are eaten by animals, carbon becomes fats and proteins in their bodies and the carbon moves through the food chain. 4. When animals respire carbon is returned into the atmosphere as co2. 5. When plants and animals die other organisms feed on them and when these organisms respire co2 is returned to the atmosphere. 6. Animals produce waste that is broken down by detritus feeders and micro-organisms 7. Combustion of wood and fossil fuels releases co2. 8 carbon is being cycled from the air though the food chain and eventually back into the air. Biodiversity and Waste management Biodiversity: -is the variety of different species of organisms on earth within an ecosystem. -biodiversity is important because it makes sure ecosystems are stable. -for humans to survive biodiversity is important. -waste production and global warming reduces biodiversity. Rising population: -population is rising due to advancement in medicine and farming which has reduced the number of people dying from disease and hunger. Increasing demands on the environment: -increasing population puts pressure o the environment as we take the resources needed to survive. -people around the world are demanding higher standard of living so that means more raw materials and energy is needed. -raw materials are being used up quicker that they are being replaced so if we keep this going we will eventually run out. Producing more waste: -water Sewage and toxic chemicals from industry can pollute lakes rivers and oceans affecting plants and animals. The chemicals used on land can be washed into the water affecting plants and animals living in it. -land We use toxic chemicals for farming and bury nuclear waste underground and dump household waste in landfill. -air Smoke and acidic gases released into the atmosphere can pollute the air. Global warming: -gases in the atmosphere act as an insulating layer and absorbs most energy that would normally be radiated out into space this increases the temperature. -this keeps the energy in and keeps us from getting cold. -gases that keep energy in are called greenhouse gases and the levels of co2 and methane are rising this causes global warming which is a type of climate change. Consequences of global warming: -sea levels rise -changes in species distribution -changes in migration patterns -reduction in biodiversity Ecosystems and biodiversity Programmes have been set up to minimise damage by human activities: Breeding programmes -set up to help endangered animals from being extinct -where animals are held in captivity to make sure the species survives if it dies out in the wild. -these individuals can be released into the wild to boost or re-establish the population. Habitat protection: -protects and regenerates rare habitats e.g mangroves -protecting habitats means protecting the species that live there. Preventing global warming; -government has introduced regulations and programmes to reduce the level of deforestation taking place and the amount of co2 being released into the atmosphere. Reducing waste: -people are encouraged to recycle and reduce the amount of waste going into landfill. -this can reduce the amount of land cleared for landfill leaving ecosystems in place.