Biology GCSE (higher combined) all topics simplified!

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scales on the axis Labelled axes Correct units Correlations + + + Dependant variable on y-axis Independent variable on x-axis + + + + 4 + + Positive correlation no correlation + + + + x X X X X Negative correlation + + + Cells Eukaryotic VS Prokaryotic Size Outer layers Cell contents Genetic material Cell division Eukaryotic cells Mitochondria Cytoplasm Eukaryotic (has nucleus) 5 μm 100 μm (bigger) Cell membrane- surrounded by cell wall o Nucleus Mitochondria Cytoplasm Chloroplasts Ribosomes These are animal/plant cells DNA in nucleus Mitosis Cell membrane 0. Prokaryotic (no nucleus) 0.2 μm - 2.0 μm (smaller) Cell membrane- surrounded by cell wall material No nucleus No mitochondria Cytoplasm No chloroplasts Ribosomes DNA loops are found in the cytoplasm Additional DNA is found as plasmids (small rings of DNA) Binary fission Nucleus-contains genetic Ribosomes Chloroplasts Cell membrane These are bacterial cells DNA loop in cytoplasm Vacuole Plasmid O 00 Mitochondria Nucleus Prokaryotic cells A group of archaea are also prokaryotic cells. These are microorganisms that are similar in size/structure but are genetically different Ribosomes Cell membrane Cell wall Cytoplasm Cell wall No nucleus Functions Function nucleus cytoplasm ribosomes cell membrane mitochondria cell wall-plant only vacuole- plant only chloroplasts-plant only Microscopy Light microscopes: Definition Electron microscopes were invented before light microscopes holds genetic information/material and controls what happens in the cell chemical reactions happen proteins are made holds the cell together and controls what goes in and out reactions for aerobic respiration take place → releases energy made of cellulose → strengthens the cell contains cell sap and provides storage photosynthesis occurs → chloroplasts contain a pigment called chlorophyll that absorbs light needed to photosynthesis Electron microscopes: uses light and lenses to form an image and magnify it you can see individual cells large subcellular structures uses electrons to form an image and magnify it higher magnification better resolution can see smaller things in more detail understand subcellular structures better size of image size of object magnification Chromosomes and the cell cycle Chromosomes Found in nucleus Coiled up lengths of DNA molecules → carry genes In pairs Cell cycle A series of stages that cells divide to produce new cells Before a cell divides, it does 3 things: 1. Grows/gets bigger 2. Increases amount of subcellular structures Duplicates DNA 3. Mitosis The stage of the cell cycle where the cell divides STAGE Interphase Prophase Metaphase Anaphase Telophase Cytokinesis What happens DNA duplicates DNA in both original, and copies, condense Chromosomes align in the middle of the cell One set of chromosomes are pulled to each end of the cell Membranes form around the chromosomes at each end Cytoplasm and cell membranes divide → 2 cells are formed, they are identical to each other to the parent cell *Mitosis allows multicellular organisms to grow or replace cells that have been damaged* WAY TO REMEMBER THE PHASES IN ORDER: Idiot, Pass Me Another Tequila (then cytokinesis) Cell differentiation Differentiation: the process in which a cell changes to become specialised for its job 5 types of specialised cells: Sperm cell Reproduction- needs to get male DNA to female DNA Long tail and streamlined → helps to swim towards the egg Lots of mitochondria provide energy Nerve cell Rapid signalling- needs to carry electrical signals from one part of the body to another Long →→→ to cover a large distance Branched forms a network of connections Xylem and phloem Transporting- substances in plant ● Xylem → hollow so substances can flow through Phloem →→ few subcellular structures so substances can flow through Muscle cell Contraction Long → space to contract Lots of mitochondria → provide energy Root hair cell Absorbing-water and minerals Large surface area due to long hairs that go into the soil → absorbing water/mineral ions from soil From: Stem cells Undifferentiated cells → divide to produce more stem cells and can differentiate into many other types of cells Adult stem cells Embryos Plant meristem Uses in medicine: stem cells could produce: nerve cells to treat paralysis/spinal injuries insulin-producing cells to treat diabetes bone marrow can replace faulty blood cells Can become: Blood cells Any kind of human cell → sperm, nerve, blood, white blood, muscle, skin Any kind of plant cell → root hair, guard In therapeutic cloning, an embryo could be made with the same genes as the patient- then the stem cells used wouldn't be rejected by the patient RISK: *stem cells from the lab could get a virus, which could get transferred to the patient* Uses in plants: Produces clones of plants quickly and cheaply This may done to grow more plants of a rare species, or to clone crops with desired features Transport in cells Diffusion- particles spread from an area of high concentration → low concentration Only very small molecules (oxygen, glucose) can diffuse through a cell membrane 3 factors increase the rate of diffusion across a cell membrane: high concentration gradient (loads of particles on one side and hardly on the other) high temperature large surface area Osmosis The movement of water molecules across a partially permeable membrane from a region of higher water concentration → lower water concentration Partially permeable membrane- A membrane that can only have small molecules of water and certain solutes passing through, but larger molecules can't get through When exposed to very concentrated solutions, both animal and plant cells have low water concentration and shrink However in pure/diluted solutions, animal cells usually burst as osmosis has occurred, plant cells just swell with high water concentration Active transport The movement of substances from a more dilute solution to a higher concentration. Unlike diffusion and osmosis, it requires energy from respiration It allows: Mineral ions (for plant growth) to be absorbed from the soil into the root hair cells Glucose (for cell respiration) to be absorbed into the bloodstream from the gut Exchanging substances Surface area to volume ratio: In a single celled organism, enough substances can pass across the outer surface to meet the needs of the organism. This means it has a large surface area: to volume ratio However, in a multicellular organism, many cells are too far away from the outer surface. Substances cannot get in and out of the cell this way. Instead, exchange surfaces and transport systems are needed. This means it has a smaller surface area: to volume ratio Exchange surfaces Usually have these things: large surface area (lots can diffuse at the same time) thin membrane (short diffusion distance) efficient blood supply (in animals) breathing (gas exchange- in animals) Organs adapted for exchange Leaves: gas exchange flat shape stomata lets gases in and out Gills: gas exchange in fish (oxygen and carbon dioxide move between water and blood) Gas exchange takes place in the gills Water passes through the mouth and over the gills, each gill has lamellae. The lamellae is where: oxygen diffuses into the blood carbon dioxide diffuses into the water Lamellae are adapted because: they have a thin surface layer of cells lots of capillaries Small intestine: absorption of food molecules from the gut to blood Alveoli in lungs: ● single layer of surface cells covered in villi capillary network air moves in and out thin walls capillary network Cell organisation Cells- basic building blocks of all living organisms Tissue- a group of similar cells that work together Organ- a group of different tissues that work together Organ system- a group of organs working together to create a system This is in order from smallest to largest Enzymes Enzymes catalyse (speed up) chemical reactions. Each enzyme only catalyses (speeds up the chemical reaction) in one specific reaction because of the unique shape of its active site ● High temperatures and high and low pHs change the shape of the active site → the enzyme will no longer work enzymes are made up of long chains of amino acids Temperature and pH: If an enzyme gets too hot/pH gets too low bonds break active site changes shape substrate no longer fits ● The enzyme is now denatured All enzymes have an optimum temperature and pH that they work best at. This means optimising the rate of reaction that occurs when using the enzyme catalyst denatured: bonds holding the enzyme together are disrupted → it loses its structure Enzyme shapes: chemical reactions usually involve things being split apart or joined together every enzyme has an active site with a unique shape for an enzyme to work, the substrate has to fit perfectly. If it does not match the active site, then it won't be catalysed ENZYME B SUBS ☺- Ⓡ ENZYME-SUBSTRATE COMPLEX Digestion and enzymes Bile SUBSTRATE Starch, proteins and fats are too big to pass through the walls of the digestive system. Enzymes come and turn bigger molecules into smaller molecules that can be absorbed into the bloodstream LOCK AND KEY MODEL Digestive enzymes: Amylase breaks down carbohydrates into simple sugar. It is made in the salivary glands, pancreas and small intestine Protease breaks down amino acids. It is made in the stomach, pancreas and small intestine Lipase breaks down fatty acids and glycerol. It is made in the pancreas and small intestine Liver bile: bile is an alkaline substance that breaks down fat into fatty acids and helps with the digestion of fat in the small intestine. It is made by the liver and stored in the gallbladder Pancreas. -the hydrochloric acid in the stomach is too acidic for enzymes to work properly, therefore the bile neutralises the stomach acid Mouth ENZYME-PRODUCT COMPLEX -bile emulsifies fats → turns it into tiny droplets to give it a bigger surface area for the lipase to work. This speeds up digestion Small intestine PRODUCTS Oesophagus Stomach Large intestine The digestive system as a whole How the digestive system works (this is in order btw): the mouth: breaks down food physically by chewing salivary glands: helps to make the food more liquidy. Also contains salivary amylase → helps break down carbohydrates stomach: produces hydrochloric acid → kills bacteria and regulates pH for protease contracts muscular walls to mix the food villi: increase surface area of the small intestine → digested food can be absorbed quickly small intestine: produces enzymes to complete digestion. Digested food is absorbed into the bloodstream pancreas: produces enzymes and releases them into small intestine liver: bile is produced. This neutralises stomach acid and emulsified fats gallbladder: bile is stored before released into small intestine large intestine: excess water is absorbed from food rectum: poop is stored before it leaves through the bum Food tests lodine test: to detect starch -add a few drops of iodine on the food sample -if colour changes to blue/black then starch is present Potato Peeled Add iodine Benedict's test: to detect sugars (glucose) -add water to the food sample (in the test tube) -add the same amount of benedict's solution -gently shake it -place test tube into hot water for a few minutes -if colour changes to orange/brown then sugar is present Biuret test: to detect proteins ● add water to food sample (in test tube) add equal amounts of potassium hydroxide and copper sulphate gently shake it if colour changes to purple proteins are present Emulsion test: to detect fats add ethanol to the food sample (in test tube) gently shake it a cloudy emulsion is left is lipids are present HAZARDS wear safety goggles iodine solution is an irritant copper sulphate is an irritant potassium hydroxide is corrosive ethanol is flammable avoid contact with skin and eyes The Lungs Left lung Bronchus (bronchi: plural) Trachea (windpipe) Right lung Alveoli (surrounded by capillary network) Function of lungs: the lungs take in oxygen from the air and transfers it into the bloodstream so it can reach all the parts of the body the lungs consist of trachea, bronchi, alveoli and the capillary network Air enters and leaves respiratory system through the nose and mouth trachea: tube that connects mouth/nose to lungs bronchus: tube allowing air to pass into lungs→ divides into bronchi alveoli: moves oxygen and carbon dioxide (CO2) molecules into and out of the bloodstream Gas exchange: 1. the hearts pumps blood to the lungs where it gains oxygen 2. blood returns to the heart and is pumped around the body where it delivers carbon dioxide air passes through lungs (trachea) 3. 4. cartilage prevents the trachea from collapsing during inhalation trachea splits into bronchi, then bronchioles 5. 6. bronchiole are like branches that end in little air sacs called alveoli 7. alveoli are where gases diffuse in and out of the bloodstream 8. red blood cells carry oxygen around the body from the lungs Alveolus Gases diffuse between the alveolus and blood Air goes in and out The heart pulmonary 2 artery V semi- vena cava, right atrium lunar valves: valvé tendons (cords) right ventricle 0₂ CO₂ The blood goes to the rest of the body aorta pulmonary vein left atrium atrio- ventricular valves left ventricle Blood coming from the rest of the body (lots of CO₂) The circulatory system is made up of the heart (an organ), blood vessels, and blood. Humans have a double circulatory system 1: heart (right ventricle) → lungs → heart 2: heart (left ventricle) → rest of body →→ heart Coronary arteries supply the heart muscle with oxygenated blood 'Pacemaker' cells in the right atrium wall control the resting heart rate. This is done by sending electrical impulses across the heart to trigger contractions. An artificial one (electrical device put under the skin) can control the heartbeat if the natural pacemaker doesn't work Venta carva Aorta Pulmonary artery Pulmonary veins Right atrium Right ventricle Left atrium Left ventricle *left ventricle is thicker than right ventricle* Types of blood vessels Arteries: ● ● Definition transports deoxygenated blood from the body transports oxygenated blood from left ventricle to the body transports deoxygenated blood from right ventricle to lungs transports deoxygenated blood from lungs to left atrium receives blood low in oxygen and pushes it into right ventricle pumps blood low in oxygen to lungs where it can gain more oxygen pushes oxygen rich blood to left ventricle pushes oxygenated blood which is distributed throughout the tire body elastic layers carries blood away from heart small diameter thick muscle and elastic layers → blood moves at a high pressure branches to smaller arterioles lumen thick muscle Capillaries: Veins: carries blood close to body cells to exchange substances thin permeable walls → allows substances to diffuse in and out easily smallest diameter Rate of blood flow volume of blood/time taken carries blood back to the heart valves inside stop blood flowing backwards thinner walls than arteries →→ lower blood pressure large diameter Blood components Component Red blood cells Platelets White blood cells Plasma Function Carry oxygen around the body Defend against infection Helps blood clots to heal a cut Carries everything in the blood Description No nucleus (more space for oxygen) Dimpled shape →→ big surface area (lots of oxygen can be absorbed Contains haemoglobin (binds to oxygen) Nucleus Antitoxins Antibodies Fragments of cells Amino acids Glucose Antibodies White blood cells Red blood cells Platelets Carbon dioxide Proteins hormones Coronary Heart disease Cardiovascular diseases → diseases in the heart or blood vessels Normal coronary arteries are clear and open Someone with coronary heart disease will have restricted blood flow- causing a lack of oxygen to the heart muscle (may cause an attack). This is because of fatty deposit blocking up the artery Treatments of Cardiovascular diseases Treatment Statins (tablets to be taken) Stent (tube put in coronary artery) Heart transplant Artificial heart Replacement heart valves (biological or mechanical) ● 2 types of diseases: Advantages Reduces the amount of cholesterol in the blood → slows down fatty being built up Keeps coronary arteries open for a long time Recovery time is quick Can treat heart failure Donor hearts work better than artificial ones Can be used while waiting for a donor heart or while heart is healing Human cost: Can treat severe valve damage (stiff valves that won't open properly or leaky valves) Faulty heart valves stop blood circulating effectively Non communicable: A disease/illness that cannot be caught/spread Financial cost: Health -the state of physical and mental wellbeing Diseases can cause bad health, however these 3 things can also affect it: Diet Stress Life situation (access to health care) Cost of non-communicable diseases Disadvantages Needs to be taken long term Can have negative side effects Might forget to take them Takes a while to start working Communicable: A disease/illness that can be spread from person to person or between animals and people. This could be caught through coughing, sneezing, sexual contact, shaking hands, etc. Viruses include: COVID-19, colds, flu, influenza, HIV, salmonella, measles Millions of deaths Poor quality of life ● Shorter life span Surgery can cause bleeding and infection. Artificial devices can lead to blood clots in blood vessels Surgery can cause bleeding and infection Donor hearts can be rejected by the immune system Diseases include: cancer, diabetes, heart attacks, dementia/alzheimers, asthma Research and treatment Surgery can cause bleeding and infection Artificial devices can lead to blood clots in blood vessels Surgery can cause bleeding and infection Artificial devices can lead to blood clots in blood vessels Donor valves can be rejected by the immune system Those with diseases may not be able to work which can affect family finances and the countries economy Risk factors for non-communicable diseases Risk factors →→ things that are linked to an increase in the likelihood hood that a person will develop a certain disease during their lifetime Lack of exercise and unhealthy (high in fat) - diet is linked to cardiovascular disease Obesity is linked to type 2 diabetes and cancer of the bowel, liver and kidneys Drinking too much alcohol can cause liver disease and affect brain function Smoking can cause cardiovascular disease, lung disease, lung cancer, bowel cancer, stomach cancer, and cervical cancer 5. Exposure to radiation can cause cancer 1. 2. 3. 4. Cancer A normal cell changes → uncontrolled growth and division → tumour (mass of cells) Then it could become benign or malignant Benign tumours: Not harmful Non-cancerous Slower growth Won't invade other cells Good chance of being healed from treatment Malignant tumours: Tissue Can be very harmful/fatal Healthy tissue is invaded Tumour cells travel in blood the blood, causing secondary tumours elsewhere in the body Multiplies faster than the immune system can handle Cancer is not only affected by lifestyle, but also genetic factors- some people inherit faulty genes to make them more susceptible Plant tissues (refer to diagram in book- page 16) Epidermal Palisade mesophyll Spongy mesophyll Xylem Phloem Meristem tissue definition It is a single layer of cells that covers the leaves, flowers, roots and stems of plants. It forms a boundary between the plant and the external environment through a waxy coating to reduce water loss. Cells in the upper layer are transparent to let light through Most photosynthesis happens (lots of chloroplasts) Air spaces to allow the diffusion of gases Carries water in the transpiration stream Transports the nutrients needed for the optimal development of the plant Found at the tips of shoots and roots The cells can differentiate into many types of cell so the plant can grow Disease *Leaves are also organs. Together with the roots and stem, they form an organ system that transports substances around the plant* Malaria Xylem Phloem ● Hollow tubes made of dead cells Liglin for strength Water and mineral ions From roots →→stem and leaves Living cells Small pores in the end walls let cell sap through Nutrients (mainly dissolved sugars) are moved from leaves to the rest of the plant Nutrients can either be used immediately or stored Translocation →→ the process in which nutrients are moved through the phloem tubes Transpiration The loss of water from a plant Water evaporates and diffuses out of the plant, this causes more water to be drawn into the plant from the roots Things that increase the rate of transpiration: Warm temperatures (provides more energy) High light intensity (stomata open when it's light) Good air flow Low humidity Fewer water molecules surround the leaves (so there's a higher water concentration inside the leaf than outside) Rose black spot Guard cells They are adapted for gas exchange and controlling the water loss within a leaf When the plant has lots of water: Turgid (swollen with water) guard cells Stoma open Water vapour escapes Gases diffuse in and out (eg. CO2 for photosynthesis) When the plant is short of water or it's dark: Flaccid (deflated/weak) guard cells Stoma closed Diseases (communicable) Pathogens: microorganisms that cause diseases which spread between organisms Pathogen How its spread Fungus Protist -Water -Wind Mosquito bites Symptoms -Purple/black spots on leaves which can turn yellow and drop off the plant -Reduced growth -Sweats/chills (fever) -Difficulty breathing -Feeling confused -Yellow skin prevention/treatment -Removing and destroying infected leaves -Fungicides -Mosquito nets -Stop mosquitoes breeding Salmonella/food Bacteria poisoning Gonorrhea Measles HIV Tobacco mosaic Bacteria Virus Virus ● Virus Eating contaminated food Sexual contact Airborne droplets (coughs and sneezes) Sexual contact Blood donation Direct contact between plants Rose black spot Defence systems against pathogens -Shaking -Can be fatal (death) 3 ways white blood cells attack pathogens: -Fever -Stomach cramps -Vomiting -Diarrhoea -Pain when peeing -Yellow/green discharge from vagina/penis -Fever -Red skin rash (itchy) -Heavy cold symptoms -Sensitive to light -Can be fatal (death) -Initially flu-like -Damaged immune system Tobacco mosaic virus -Mosaic pattern on leaves (reduces photosynthesis and growth) -Poultry needs vaccinating -Unhygienic food preparation -Drinks lots of fluids over the next 24 hours -Condoms -Antibiotics -Vaccination of children -Condoms -Avoid sharing needles -Antiretroviral treatment 1. Skin → acts as a barrier and releases antimicrobial chemicals to kill pathogens 2. Nose hairs and mucus trap particles containing pathogens 3. Trachea and bronchi → mucus traps pathogens, cilia directs mucus up to throat so that it can be swallowed 4. Stomach → hydrochloric acid kills pathogens -Burn infected plants (do not put them in compost heap or soil!) Phagocytosis- pathogens get engulfed and digested by the white blood cells Producing antibodies- pathogens have antigens, the antibodies are specific to the pathogen produced, they attack all copies of the pathogen in the body Producing antitoxins- these counteract toxins produced by invading bacteria Vaccination: Vaccinating a large proportion of the population greatly reduces the spread of pathogens so that even people who are not vaccinated are unlikely to catch the disease Drugs Vaccination involves introducing small quantities of dead or inactive forms of a pathogen into the body to stimulate the white blood cells to produce antibodies If the same pathogen re-enters the body the white blood cells respond quickly to produce the correct antibodies, preventing infection It's hard to develop drugs that destroy viruses because they live and reproduce inside cells Painkillers treat the symptoms but don't kill the pathogens Drug Penicillin (first antibiotic made) Digitalis Aspirin Type Antibiotic Heart drug Painkiller Alexander Fleming discovered Penicillin! Preclinical testing: Drug testing New drugs are trialled to check they are safe and effective Nowadays, drugs are often created in a lab, but the process could still start with a chemical extracted from a plant Clinical trials: Tests on human cells and tissues (grown in the lab) Tests on living animals Source 1. Toxicity →→ how harmful 2. Efficacy → whether it works and produces the effect you're looking for 3. Dosage →→ how much should be given, and how often Penicillium mould Foxgloves Willow Healthy volunteers → dosage gradually increases from a very low initial dose Unwell patients → finding optimum dose Peer review Carbon dioxide + water →glucose + oxygen 6CO2 + CH₂O → C6H12O6 + 60₂ Placebos → inactive versions of the drug. Volunteers are split into groups, some receive the drug and others receive the placebo. It is important they do not know which they are taking. This is called a blind trial. Sometimes, a double-blind trial is carried out where the doctor giving the patient the drug is also unaware. Results from the groups are compared to ensure that the drug is having an effect and that any changes are not due to the experimental trial process Photosynthesis An endothermic reaction in which energy is transferred to chloroplasts from the environment by light 4 uses of glucose in plants: ● ● ● Respiration → energy is transferred from glucose Strengthening cell walls →glucose is converted into cellulose Protein synthesis → glucose and nitrate ions are used to make amino acids, which are then made into proteins Energy storage →→ glucose is turned into lipids or insoluble starch to store energy Rate of photosynthesis An increase in any of these 4 factors tends to increase the rate Light intensity 1. 2. Temperature 3. CO2 concentration 4. Amount of chlorophyll Any of these factors can become the limiting factor Inverse square law: Links light intensity with distance from a light source Doubling the distance means the light intensity is 4x less Greenhouses You can control the limiting factors in a greenhouse to maximise the rate of photosynthesis, but this costs money Ventilation Shade Heaters Lamps Respiration The process of transferring energy from glucose It's an exothermic reaction The energy is transferred for all living things 1. To contract muscles for movement 2. To keep warm (mammals and birds) 3. To build larger molecules from smaller ones Aerobic respiration: Uses oxygen It's the most efficient type of respiration Glucose + oxygen → carbon dioxide + water Anaerobic respiration: Respiration without oxygen Transfers much less energy than aerobic respiration because the glucose isn't fully oxidised In muscle cells: Glucose lactic acid In plant and yeast cells: Glucose ethanol + carbon dioxide In yeast cells it's called fermentation. This is process used to make bread and alcoholic drinks Metabolism The sum of all the reactions that happen in a single cell or the body They use energy from respiration to make new molecules eg: Effects of exercise on the body Exercise ↓ More energy needed ↓ More aerobic respiration needed ↓ More oxygen needed 3 things to increase oxygen getting to your muscles: Heart rate Glucose and nitrate ions combine to make amino acids, then made into proteins Lipids broken down into glycerol and fatty acids Glucose molecules joined together to make carbohydrates Long periods of exercise cause muscle fatigue- the muscles get tired and stop contracting efficiently Oxygen debt The amount of extra oxygen needed to react with built-up lactic acid and remove it from cells During intense exercise, not enough oxygen is supplied to the muscles so: 1. Anaerobic respiration takes place in the muscles 2. 3. Oxygen debt created 4. Heart rate and breathing rate stay high after exercise to repay oxygen debt Breathing rate Breath volume The liver also helps to deal with lactic acid by converting it to glucose eyes Homeostasis the regulation of internal conditions ears Receptor tongue nose Lactic acid builds up in muscles skin Conditions that need regulating: body temperature blood glucose level water content carbon dioxide levels Function light sound/change in position taste smell touch/pain/temperature/pressure All control systems include: ● receptors → detect environment changes coordination centres → receive and process information from receptors effectors → to trigger a response to counteract the change and restore optimal conditions The nervous system neurones: cells that carry information as electrical impulses in the nervous system the nervous system: means that humans can react to their surroundings and coordinate their behaviour stimulus → receptor → sensory neurone →→ CNS →→ motor neurone → effector → response So Rumplestiltskin said, come Mulan, end Regina. CNS: CENTRAL NERVOUS SYSTEM consists of the brain and spinal cord. It is connected to the body by sensory neurones and motor neurones *effectors can be muscles which respond to impulses by contracting, or they can be glands which give hormones* Synapses synapse the gap between two neurons the electrical impulse reaches the synapse and chemicals called neurotransmitters are released- they diffuse across the gap Reflexes rapid, automatic responses to certain stimuli that don't involve the conscious part of the brain. They can reduce the chance of injury here is how it happens: 1. stimulation of pain receptors 2. impulses travel along the sensory neurone 3. impulses are passed to relay neurone 4. impulses travel along motor neurone 5. muscle contracts and reaction takes place Types of reflexes reflex blinking sneezing knee jerk salivating why protects anything getting in eyes stops anything getting up nose/clears nose important for balance neutralise some acids and soften food heat withdrawal Speed of the reflex can be calculated using speed distance / time The Endocrine system made up of glands that let out chemicals (hormones) directly into the bloodstream, which carries them to the target organs pancreas- produces insulin testes (male)- produces testosterone Thyroid hormones: produces thyroxine regulates metabolism deficiency causes weight gain Adrenal glands: produces adrenaline 'fight or flight' ● increased heart/breathing rate ● blood diverted to the muscles ● repository rate increases. increased amount of glucose in blood sweaty/cold Ovaries: produce several hormones so you don't get burnt Hormones the effects of hormones are slower than nerves but last longer Testes: produce testosterone pituitary gland (in the brain)- stimulates other glands thyroid gland (in the neck)- produces thyroxine Pancreas: produces insulin adrenal gland- produces adrenaline ovaries (in female)- produces oestrogen Oestrogen: regulates menstrual cycle Progesterone: thickens uterus wall and prevents contractions until a baby is born helps the development of male secondary sexual characteristics controls the conversion from glucose to glycogen increases metabolic rate deficiency causes diabetes where the glucose level is unregulated Pituitary gland: produces several hormones controls reabsorption of water from the blood into the kidneys controls many hormones In females: Follicle stimulating hormone (FSH): causes the follicle in the ovary to develop and let out oestrogen Luteinising follicle (LH): works with FSH to cause ovulation Control of glucose 5 steps to reduce blood glucose: 1. blood with too much glucose 2. pancreas detects high glucose → produces insulin 3. insulin causes glucose to move into cells 4. insulin makes the liver turn glucose into glycogen (stored in liver and muscles) 5. blood glucose reduced 5 steps to increase blood glucose: Diabetes blood with not enough glucose glucagon released by pancreas not enough glucose but glucagon as well glucagon makes liver turn glycogen → glucose (released from liver) blood glucose increased Type 1: -pancreas fails to produce enough/any insulin -uncontrolled high glucose levels -treated with insulin injections Type 2: -the body cells no longer respond to insulin produced by pancreas -carbohydrate controlled diet (helps to improve/treat) -regular exercise (helps to improve/treat) -obesity → risk factor Adrenaline and thyroxine: adrenaline is released in response to fear or stress → increase in heart rate → increases supply of oxygen and glucose to muscles and brain → readies body for 'fight or flight' thyroxine regulates the metabolic rate → important for protein (growth and development) Puberty and sex hormones puberty →→ when the body starts releasing sex hormones (trigger the development of secondary sexual characteristics) secondary sexual characteristics: facial hair, boobs, voice deepens In males → main reproductive hormone is testosterone (stimulates sperm production) In females → main reproductive hormone is oestrogen The Menstrual cycle Stage 1: lining of uterus breaks down and menstruation starts Stage 2: uterus lining builds up into thick layer of blood vessels ready to receive a fertilised egg Stage 3: egg develops and is released from ovary- ovulation Stage 4: wall is maintained- if there is no fertilised egg, the lining breaks down and the cycle repeats FSH (follicle stimulating hormone) → causes egg to mature in an ovary Oestrogen causes the lining of the uterus to thicken LH (luteinising hormone) stimulates ovulation Progesterone maintains the uterus lining *At the beginning of the cycle there is lots of oestrogen being produced, by the end the hormones being released are progesterone* Contraception Hormonal methods: contraceptive pills → contains hormones that prevent FSH being made and stop eggs maturing ★ contraceptive implant → releases progesterone to continuously stop maturation and release of an egg injections/patches →→ releases progesterone (works the same way as implant but doesn't last as long) IUD (intrauterine device) → inserted into uterus to prevent eggs implanting (may also release hormones) ★ Non-hormonal methods: ★ condoms → physically prevent sperm from reaching the egg ★ sterilisation → a permanent surgical procedure to stop a male/female being fertile spermicides →kill sperm stop having sexual intercourse completely ★ The pill: combined or progesterone only stops FSH being made stops the ovaries from maturing eggs Effects: ܀ ܀ ܀ moods weight blood pressure risk of blood clots Advantages: prevents unwanted pregnancies lowers risk of ovarian cancer Increasing fertility women who can't get pregnant may be given a fertility drug containing FSH and LH. She may chose to try IVF (in-vitro fertilisation) ★ the women is given FSH and LH to stimulate several eggs to mature ★the eggs are collected from the woman's ovaries these are fertilised in a lab using the man's sperm the fertilised eggs are grown into embryos ★ once the embryos are tiny balls of cells- 1-2 of them are put into the woman's uterus Disadvantages: emotionally and mentally stressful low success rate can lead to multiple births which can be dangerous for both the mother and the babies Inheritance, variation and evolution sexual reproduction: in animals (fusion of egg and sperm) in plants (fusion of egg and pollen in ovules) 2 parents meiosis and mitosis cell division Offspring has a mix of both parent's genes Due to the mixing of genetic information, sexual reproduction leads to varied offspring Asexual reproduction: 1 parent only involves mitosis no mixing of genes characteristics are passed on genetically identical offspring (like a clone → Jango Fett and Boba Fett) Genetic material DNA- the chemical a cell's genetic material is made from DNA is a polymer → made up of 2 strands coiled into a double helix chromosomes- molecules of DNA that normally come in pairs. humans have 23 pairs the 23rd pair carries genes that determine the sex genes- a small sections of DNA found on a chromosome- each gene codes for a particular sequence of amino acids which are put together to make a specific protein 20 amino acids → 100 possible proteins genomes- an organism's entire set of genetic material the entire human genome has been worked out → ★ genes linked to diseases can be identified, this helps us understand inherited diseases to develop effective treatments * tiny differences in people's genomes can be studied, this helps us trace the migration patterns of past human populations Meiosis produces cells with half the normal amount of chromosomes 1. the cell duplicates its genetic information 2. the cell divides and each new cell has one copy of each chromosome 3. both cells divide again to make 4 gametes 4. each gamete only has a single set of chromosomes *all the gametes produced by meiosis are genetically different* More about gametes gametes- sex cells (egg or sperm) they are formed by meiosis in the reproductive organs gamete + gamete = offspring the fertilised cell divides by meiosis many times to form an embryo. The normal number of chromosomes are restored Genetic terms allele dominant recessive homozygous heterozygous genotype phenotype dominant example: the allele for brown eyes is dominant, meaning you only need one copy of this allele to have brown eyes recessive example: a type of allele that when present on its own- will not affect the individual. For example, the allele for blue eyes is recessive, therefore to have blue eyes you need to have two copies of the 'blue eye' allele. a version of a gene if the alleles of a gene are different, one will always be expressed (the dominant gene) an allele that is only expressed when there is 2 copies both organism's alleles for a trait are the same an organism's alleles for a trait are different an organism's combination of alleles the characteristics an organism has Punnett square diagrams At fertilisation an egg has an equal chance of fusing with a Y-sperm or an X-sperm. The result is shown using a Punnett square: Y is male and X is female Male X Y X XX XY Female X XX XY this is a punnett square for a genetic cross between a pea plant homozygous for round peas and a pea plant homozygous for wrinkly peas the ratio of male to female offspring is 1:1 Inherited disorders diseases caused by certain alleles that are inherited from the parents Polydactyly a genetic disorder where a baby's born with extra fingers or toes- caused by a dominant allele Cystic fibrosis a genetic disorder of the cell membranes- caused by recessive allele Cystic fibrosis is an inherited condition in which the lungs and digestive system can become clogged with mucus. It can cause problems with breathing and digestion from a young age. Over many years, the lungs become increasingly damaged and may eventually stop working properly. Embryonic screening Against: For: screening is expensive people may want to screen their embryos so they can pick the most 'desirable' one it implies that people with genetic disorders are 'undesirable' ● will help people stop suffering treating disorders costs the government a lot of money there are laws to stop it going to far Genetic modification in crops pest resistance frost resistance herbicide (weed killer) resistance drought resistance disease resistance longer shelf life Variation and evolution differences in the genes individuals inherit cause variation within the population. the variation is usually extensive mutations cause these differences in genes, mutations occur continuously. very rarely a mutation will lead to a new phenotype. If the new phenotype is suited to an environmental change it can lead to a relatively rapid change in the species. environmental variation: differences in the conditions of the environment which causes variation eg. leaf colour genetic and environmental variation: characteristics caused by genetics and the environment eg. plant height Natural selection Charles Darwin came up with the theory of evolution by natural selection: all of today's species have evolved from simple life forms that first started to develop over 3 billion years ago the theory is now widely accepted as scientists have found that characteristics are passed to offspring in genes species show wide variation → limited resources mean organisms are in competition → organisms with the most suitable characteristics for the environment are most likely to survive → these organisms are most likely to breed → the beneficial characteristics are passed on and gradually become more common in the population 2 populations of a species can evolve in different ways if they change so much that they can no longer breed with one another to produce fertile offspring, then they have to become separate species examples of natural selection: ● giraffes → evolved to have long necks to eat leaves that other giraffes can't reach peacocks → more colourful/bright feathers to attract the females (ideal for reproduction) examples of selective breeding: unusual/rare flowers ● dogs with a gentle nature animals that produce more meat/milk disease resistance in food crops selective breeding can lead to 'inbreeding' where some breeds are particularly prone to disease or inherited defects genetic information is carried in the nucleus of the gametes (sex cells). This is passed on from generation to generation NATURAL SELECTION VS SELECTIVE BREEDING Natural selection is caused by environmental factors that limit survival and reproduction, such as harsh environments or competition for mates. Selective breeding is also known as artificial selection. Artificial selection is done by human intervention. genetic engineering: transfers a gene directly responsible for a desirable trait examples: genes for producing insulin for people genes for better crops and nicer fruit genes for resistance to insects, diseases, and herbicides (weed killer) NATURAL SELECTION VS GENETIC ENGINEERING Selective breeding makes use of existing, naturally present gene variants in a species and the natural process of breeding. Genetic engineering involves a direct change to an organism's genome in the lab. Fossils and antibiotic resistance fossils are remains of organisms from many thousands of years ago there are 3 ways they form: 1. gradual replacement by minerals → it slows decaying parts 2. casts and impressions → footprints and burrows 3. preservation → places where conditions prevent decay (amber glaciers) fossils show how much or how little organisms have changed as life developed, however there is uncertainty to how life began as the fossil record is still incomplete. many early life forms were soft-bodied and decayed away completely some fossils have been destroyed by geological activity fossil formation: mineralisation →→ fossils are compressed in sediment and as it decays, its slowly replaced by minerals imprints in mud → animal walks through mud and the footprint solidifies amber glaciers →→ insects land in tree sap which covers the insect and hardens to amber, preserving it frozen in ice →→→ the animal dies and is covered in ice, therefore preserving it Antibiotic resistance bacteria can evolve quickly because they reproduce rapidly 1. random mutations can lead to resistance to an antibiotic 2. resistant bacteria survive the antibiotic and reproduce 3. populations of the resistant bacteria increase and spread easily → this is because people aren't immune and there isn't effective treatment developing new antibiotics is costly and slow →→ this process takes so long we couldn't keep up with the new variants and strains (think Covid-19) 3 ways to reduce the rate of development of antibiotic-resistant strains: not prescribing antibiotics for non-serious/viral infections reducing the use of antibiotics in agriculture patients should take the full course of antibiotics to kill the bacteria Classification and extinction the Linnaean system: developed by Carl Linnaus → it organises organisms by their characteristics and structures into these groups: 1. Dominion 2. Kingdom 3. Phylum 4. Class 5. Order 6. Family 7. Genus 8. Species (D) Kidnapping Pedro Causes Oscar Feeling Glad Sometimes Binomial naming system: Genus Species Developments in Classification better microscopes show → internal structures of organisms improved chemical analysis → understanding of biochemical processes new models →→ Carl Woese- 3 domain system bacteria archaea eukaryota true bacteria type of prokaryotic cell (found in extreme places) protists, fungi, plants and animals Evolutionary trees shows how scientists think different species are related to each other data source for living species are identified through current classification data extinct species are identified through fossil data Extinction Extinction- when no individuals of a species remain this may be due to: ● ● Ecology environmental changes new predators new diseases competition natural disasters (volcanoes) population community stable community ecosystem adaptation interdependence all the organisms of one species living in a habitat populations of different species living in a habitat all species and factors are in balance → population rate is constant interaction of communities and the areas of their environment that are non-living A feature that enables an organism to survive in the conditions of its normal habitat each species in a community depending on other species for things (pollination, food, shelter, seed dispersal) Factors affecting communities both biotic (living) and abiotic (non-living) factors can affect organisms in the community moisture level new predators food availability oxygen level (for aquatic animals) light intensity Ju wind intensity/direction temperature new pathogens CO2 level for plants soil pH and mineral content light ● ● space minerals water food mates territory 3 types of adaptation: 1. structural a white coat helps camouflage against the snow 2. behavioural → some birds migrate to warmer climates in winter 3. functional → some animals lower their metabolism and hibernate over winter Extremophiles-organisms that are adapted to live in extreme conditions, such as high temperature, high pressure or high salt concentration Food chains producer → primary consumer → secondary consumer producers: a plant that makes glucose by photosynthesis. All food chains start with a producer primary consumers: an animal that eats producers and may be eaten by secondary consumers secondary consumers: an animal that eats primary consumers and many be eaten by tertiary consumers predator: a consumer that kills and eats other animals (prey) biomass: the mass of a livin material energy stored in the biomass is transferred along food chains and used by other organisms to build biomass Predator-prey cycles in a stable community the numbers of predators and prey rise and fall in cycles prey population increases → predator population increases → prey population increases → predator population increases Biodiversity the variety of different species on Earth, or within an ecosystem high biodiversity leads to: reduced independence of one species on another for things like food, shelter, and the maintenance of the physical environment this leads to stable ecosystems for humans to survive, it's important that a good level of biodiversity is maintained human actions are reducing biodiversity- we have only recently began to take measures to prevent this Recycling materials materials are cycled through abiotic and biotic parts of an ecosystem photosynthesis, absorption from soil materials in environment → materials in organisms waste, death and decay materials decay because they are broken down by microorganisms. Decay puts materials like mineral ions back into the soil The Water Cycle the trees and plants transpire, and condensation forms in the clouds. Then it precipitates and the water falls into sea/rivers and evaporates. The cycle repeats this provides fresh water for plants and animals The Carbon Cycle carbon compounds are found in plants and animals animals respire, making CO2 in the air- allowing photosynthesis to occur plant and animal products are made, burning also releases carbon dioxide (fossil fuels) when thee animals/plants die, carbon compounds in the soil get decayed by microorganisms Global warming the earth is gradually heating up because of increasing levels of greenhouse gases consequences of this may include: ● rising sea levels (flooding) change in distribution of some organisms decrease in biodiversity (extinction) radiation is trapped in the atmosphere from methane and carbon dioxide Land use and distribution humans use land for things such as building, quarrying, farming and dump wastes →→less land for other organisms peat bogs have a carbon store and is a habitat for different species → loss of habitat (reduced biodiversity) → peat sold as compost and fuel → decay and burning releases CO2 into the atmosphere Deforestation cutting down of forests it has been done in many tropical areas to: clear land → rice fields and farming cattle grow crops →→ biofuels Maintaining ecosystems pollution increasing human population and standard of living →→ more resources used quicker and more waste produced → more pollution → more plants/animals killed (less biodiversity) 1. 2. sewage, fertilisers, and toxic chemicals (pesticides) from farming and industry get washed into water smoke and acidic gases are released into the atmosphere and pollute the air 3. toxic chemicals (from farming) and waste gets dumped in landfill sites and pollute land Ways to protect ecosystems 1. breeding programs → endangered species are bred in captivity 2. habitat restoration → rare habitats such as mangroves, heathland and coral reefs are protected 3. hedgerows and field margins →→ reintroduced around fields where a single type of crop is grown 4. government regulations →→ reduces deforestation and Co2 emissions 5. recycling →→ reduces amount of waste going to landfills