Biology AQA unit 3

Osmosis

Movement of water particles across a partially permeable membrane from a region of high water concentration to a region of low water concentration

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Diffusion

Particles move from an area of high concentration to an area of low concentration

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Exchange surface adaptations for effectiveness:

1. Thin so short diffusion path 2. Large surface area so more diffusion can take place 3. Lots of blood vessels to transport molecules quickly/maintain concentration gradient 4. Ventilated (animals)

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Leaf structure

Air spaces for CO2 to diffuse into and increase surface area, stomata for gas exchange and water loss, guard cells change shape and open and close stomata, flattened shape to increase surface area, thin so short diffusion path

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Conditions that speed up evaporation/transpiration

Hot, dry, windy,sunny

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Breathing in (inhaling)

1. intercostal muscles contract 2. diaphragm contracts 3. thorax volume increases 4. pressure decreases

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Breathing out (exhaling)

1. intercostal muscles relax 2. diaphragm relaxes and becomes dome shaped 3. thorax volume decreases 4. increases pressure

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Ventilation

Movement of air into and out of the lungs

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Artificial ventilator

Pump air into lungs - expands rib cage, pumping stops - rib cage relaxes and air is pushed out of lungs

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Disadvantages of artificial ventilators

Iron lung - interferred with blood flow to lower body Start stop system - can damage/burst alveoli if they cant cope with air flow

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Iron lung

Incased patient from neck to abdomen, air pumped out of case so pressure decreases, lungs expand and air is drawn in, air pumped in, pressure increases and air is forced out

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Function of the lungs

To transfer oxygen to the blood and remove waste carbon dioxide from the blood

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Alveoli adaptations

1. Large surface area 2. moist lining to dissolve gases 3. thin walls so short diffusion path 4. good blood supply to transport molecules quickly/maintain concentration gradient

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Villi adaptations

1. increase the surface area so digested food is absorbed more quickly into the blood 2. 1 cell thick walls so short diffusion path 3. good blood supply for quick absoprtion and to maintain concentration gradient

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Root hair cell adaptations

1. "hairs" stick out into soil 2. large surface area 3. contain mitochondria for energy for active transport

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Active transport

The movement of particles from an area of low concentration to an area of high concentration against a concentration gradient. Energy from respiration is required

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Uses of active transport

Reabsoprtion of glucose from the kidneys, absorption of glucose from the gut, absorption of minerals from the soil in plants

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Phloem tubes

Made of columns of living cells with small holes in the ends to allow substances through, transport food substances from the leaves to growing regions and storage organs, transport goes in both directions

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Xylem tubes

Made of dead cells joined end to end with no end walls and a hole down the middle, carry water and minerals from root to stem and leaves in transpiration stream, transport only goes up

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Transpiration

Loss of water from the plant

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Transpiration stream

Due to transpiration there is a shortage of water in the leaf so water is drawn up from rest of plant through xylem vessels to replace it, means more water is drawn up from the roots so there is a stream of water through the plant

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Double circulatory system

1. deoxygenated blood to the lungs and oxygenated blood to the heart 2. oxygenated blood around the body and deoxygenated blood to the heart

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Arteries

Carry blood under high pressure, walls contain elastic and muscle fibres, thick walls, small lumen, no valves

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Capillaries

Carry blood really close to cells to exchange substances, permeable walls, supply food and oxygen and remove waste like carbon dioxide, one cell thick walls

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Veins

Carry blood at lower pressure, walls are thinner, larger lumen, have valves

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Red blood cell function

To carry oxygen from the lungs to all the cells in the body

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Red blood cell adaptation

1. biconcave shape to increase surface area/absorb more oxygen 2. no nucleus allowing more room for oxygen 3. contain red pigment haemoglobin to carry more oxygen

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White blood cell function

Defend against disease and infection,can change shape to ingest pathogens, produce antibodies and antitoxins, have a nucleus

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Platelet function

Help blood to clot at a wound, fragments of cells, no nucleus

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Plasma

Carries red and white blood cells, platelets, nutrients, carbon dioxide, urea, hormones, antibodies and antitoxins

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Saline function

Replaces lost volume of blood to keep red blood cells pumping around the body, patient produces new cells or has a blood transfusion

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Stents

Keep arteries open that have been blocked by fatty deposits (coronary heart disease), lowers risk of heart attack

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Disadvantages of stents

Can irritate artery and cause scar tissue meaning artery narrows again, patient has to take drugs to stop the blood clotting

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Homeostasis

Maintenance of a constant internal environment

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Six main things that need to be controlled:

1. Body temperature 2. Water content 3. Ion content 4. Blood sugar level 5. Carbon dioxide levels 6. Urea levels

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When you are too hot:

hairs lay flat, sweat is produced and evaporates from skin, blood vessels dilate so more flows near skin surface and heat is lost to the environment

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When your too cold:

Hairs stand up to create an insulating layer of air, no sweat produced, blood vessels constrict, shiver

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Kidney roles

Removal of urea from the blood, adjustment of ions in the blood, adjustment of water content of the blood

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1. Ultrafiltration

High pressure is built up which squeezes water, urea, ions and glucose out of blood and into bowmans capsule, membranes between blood vessels and bowmans capsule act like filters so proteins and blood cells arent filtered out

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2. Re-absorption

As the liquid flows along the nephron useful substances are reabsorped back into the blood - all glucose via active transport, sufficient ions via active transport, sufficient water

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3. Release of wastes

Remaining substances including urea continue out of the nephron into ureter and down to the bladder as urine

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Blood glucose levels

Blood glucose level to high and the hormone insulin is added, blood glucose level to low and hormone glucagon is added

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Waste effects:

Water (sewage and toxic chemicals), land (pesticides, herbicides, nuclear waste and houshold waste), air (smoke and gases)

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Human activities reducing land and resources available to plants and animals:

1. Building 2. Farming 3. Dumping waste 4. Quarrying for metal ores

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Carbon dioxide is sequestered in natural forms

Oceans, lakes and ponds, green plants, peat bogs

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Reasons for deforestation

For timber to use as a building material, clear more land for farming - more food and biofuels, produce paper from wood

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Major problems due to deforestation

More methane in atmosphere, more carbon dioxide in atmosphere, less carbon dioxide taken in, less biodiversity

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Biodiversity

Variety of different species in a habitat

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Consequences of global warming

Sea levels rise - flooding of low lying land, ice caps melt - sea levels rise, more extreme weather, distribution of wild animals and plants may change, biodiversity could be reduced, changes in migration patterns

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Fermentation

When bacteria or yeast break down sugars by anaerobic respiration

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Ethanol

Yeast make ethanol when they break down glucose by anaerobic respiration - glucose ----> ethanol + C02 + energy, ethanol is distilled to separate it from yeast and remaining glucose, in Brazil cars are adapted to run on ethanol and petrol (gasohol)

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Biogas

Made by anaerobic fermentation of waste materials, methane and carbon dioxide, microorganisms ferment plant and animal waste (contains carbohydrates), sewage is used on a large scale, made in a fermenter called a generator

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Biogas generators

Need to be kept at constant temperatures to keep microorganisms respiring, two types - batch and continuous, biogas cant be stored as a liquid so has to be used straight away

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Batch generators

Make biogas in small batches, manually loaded with waste which is left to digest and by products are cleared away at the end of each session

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Continuous generators

Make biogas all the time, waste is continually fed in, biogas produced at a steady rate, more suited to large scale projects

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Four factors to consider - cost

Continuous generators more expensive as waste has to be mechanically pumped in and digested material mechanically removed all the time

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Four factors to consider - convienience

Batch generators are less convenient as have to be continually loaded, emptied and cleaned

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Four factors to consider - efficiency

Gas produced most quickly at 35 degrees, generators may need to be kept insulated or warm, any leaks and gas will be lost

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Four factors to consider - position

waste will smell during activity so should be sited away from homes, best generators located fairly close to waste source

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Environmental benefits of biofuels

Greener alternative as are carbon neutral, doesnt produce significant amounts of sulfur dioxide or nitrogen oxides, methane is given off in untreated gas so burning it means its not released into the atmosphere

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Economic benefits of biofuels

Raw material is readily available and cheap, digested material is better fertiliser than dung so more crops can be grown, saves people collecting wood for fuel in developing communities, waste disposal system

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Efficiency of food production improved by - reduced number of stages in food chain

Less energy and biomass every time you move up a stage in a food chain, produce more foods by crops than by animals, some land unsuitable for growing crops, need a varied diet

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Efficiency of food production improved by - restricting energy lost by animals

intensive farming, kept close together indoors - warm and cant move about, stops them wasting energy on movement and losing energy as heat, animals grow faster on less food, cheaper for farmer and consumer

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Efficiency of food production improved by - developing new food sources - MYCOPROTEIN

Protein from fungi, used to make meat substitutes - quorn, fusarium is main source of mycoprotein, grown in fermenters using glucose syrup as food - obtained from digesting maize starch with enzymes, respires aerobically so O2, N2 and minerals added

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Preventing other microorganisms in mycoprotein

Fermenter sterilised using steam, incoming nutrients are heat sterilised and air supply filtered, mycoprotein harvested and purified

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Conflict

People think intensive farming is cruel, demand for organic meat, intensive farming leads to spread of disease, animals given antibiotics - reduces our resistance, fish stocks decreasing, warmth for animals provided by fossil fuels, food miles

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Overfishing

Less fish to eat, oceans food chains affected, some species may become extinct

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Fishing quotas

Limits on the number and size of fish that can be caught in certain areas, prevents certain species from being overfished

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Net size

Limits on the mesh size of the fishing net depending on whats being fished, reduce number of unwanted and discarded fish, means younger fish and unwanted fish can escape and breed

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Biology AQA unit 3

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