B3

circulatory system transports substances around the body.

heart = organ + pumps blood around body. Most of heart wall is made from muscle.

4 main chambers of heart: Left and right atria + ventricles.

1) Blood enters atria of heart. 2) Atria contract + force blood into ventricles. 3) -Ventricles contract + force blood out of heart. 4) -Valves in heart ensure blood flows in right direction.5) -Blood flows from heart to organs through arteries + returns through veins.

Main vessles of heart: Aorta, vena cava, pulmonary vein + artery.

ARTERIES - thick walls containing muscle and elastic fibres. VEINS - thinner walls - valves to prevent backflow of blood

if arteries narrow + restrict blood flow = stens used to keep them open

Organs - blood flows through narrow thin walled vessles (CAPILLARIES). Substances needed by cells in body tissues pass out of blood, substances produced by cells pass into blood through walls of capillaries

Blood = tissue - consists of fluid called plasma in which red + white blood cells and platelets are suspended.

Blood plasma transports: 1) CO2 from organs to lungs. 2) soluable products of digestion from small intestine to other organs. 3) Urea from liver to kidneys

Red blood cells transport oxygen from lungs to organs, have no nucleus, packed with red pigment (haemoglobin).

In lungs haemoglobin combine with oxygen = oxyhaemoglobin. In other organs oxyhaemoglobin splits up into haemoglobin and oxygen. 

White blood cells have a nucleus + form part of bodies defence system against microorganisms.

Platelets = small fragments of cells, no nucleus, help blood to clot at site of wound. 

Flowering plants have seperate transport systems:

-Xylem tissue - transports water + mineral ions from roots to stem + leaves.

-movement of water from roots to xylem and out of leaves = transpiration stream.

-phloem tissue - carries dissolved sugars from leaves to rest of plant, including growing regions + storage organs.

waste products that have ti be removed from body = 1) CO2 (produced by respiration + removed via lungs when breathing out. 2) urea - produced in liver by breakdown of excess amino acids + removed by kidneys in urine (temporarily stored in bladder) If water/ion content of body is wrong, too much water may move into/out of cells + damage them Water + ions enter body when eating + drinking.

Healthy kidney produces urine by: 1) filtering blood. 2) reabsorbing all sugar. 3) reabsorbing dissolved ions needed by body. 4) reabsorbing water that body needs. 5) releasing urea, excess ions + water as urine.

Kidney failure - treated by kidney dialysis machine OR kidney transplant DIALYSIS MACHINE = blood flows between patricually permeable membranes. dialysis fluid contains same conc. of useful substances as blood. ensures glucose + useful mineral ions arent lost. Urea passes out from blood into dialysis fluid. = restores conc. of dissolved substances in blood to normal levels + has to be carried out at regular intervals. TRANSPLANT - diseased kidney replaced by healthy one from donor - may be rejected by immune system unless precautions are taken.

Antigens (proteins on surface of cells) - recipents antibodies may attack antigens on donor organ - dont recognise them as part of recipent's body. prevent rejection: donor kidney with tissue type similar to recipent. OR treat with drugs to surpress immune system (immunosuppresants)

Sweating cools body. More water lost when its hot + more water taken in as frink/food to balance loss. 

Body temp - monitorred + controlled by thermoregulatory centre in brain (has receptors sensative to temp of blood flowing through brain. Also temp receptors in skin send impulses to centre + give info about skin temp. 

If core body temp too high:

1) Blood vessles supplying skin capillaries DILATE (vasodilation) so more blood flows through capillaries + more heat lost. 2) sweat glands release more sweat - cools body by evaporating.

If core body temp too low:

1) blood vessles supplying skin capillaries CONSTRICT (vasoconstirction) - reduces flow of blood through capillaries. 2) muscles shiver - contraction needs respiration which releases energy as heart - warms the body.

Blood glucose conc. of body monitorred + controlled by pancreas, pancreas produces insulin (allows glucose to move from blood into cells + converts soluable glucose into insoluable glycogen which is stored in liver)

Glucagon produced in pancreas when blood glucose levels fall - causes glycogen to be converted into glucose + released into blood.

Type 1 diabeties - disease - blood glucose conc. rises to fatally high level as pancreas doesnt produce enough insulin. 

Type 1 diabeties - controlled by careful attention to diet, exercise and injecting insulin. 

Rapid growth in human population + an increase in standard of living means more waste is produced, unless it is properly handled more pollution caused.

Waste may polute:

1) water - with sewage, fertilizer or toxic chemicals.

2) air - with smoke + gases e.g. sulfur dioxide (contributes to acid rain)

3) land - toxic chemicals e.g. pesticides + herbicide (may be washed from land into waterways.

humans reduce amount of land available for animals + plants by building,quarrying, farming + dumping waste.

Large scale deforestation in tropical areas for timber + to provide land for agriculture has:

1) increased release of CO2 into atmosphere (due to burning + activities of microorganisms)

2) reduced rate at which CO2 is reduced from atmosphere + locked up for many years as wood

deforestation leads to reduction in biodiversity. 

Deforestation has occured so:

1) crops can be grown from which biofuels (based on ethanol) can be produced

2) can be increases in cattles and in rice fields to provide more food. These organisms produce methane + has led to an increase in methane in atmosphere.

Destruction of peat bogs + other ares of peat releases CO2 into atmosphere. Peat, as well as being a fuel, improves soil quality + is used as a compost. 'Peat free' composts - important to reduce CO2 emissions.

Levels of CO2 + methane in atmosphere are increasing + contributing to global warming. An increase in earth's temp by just a few degrees celsius: 

1) may cause big changes in earth's climate 2) may cause a rise in sea level 3) may reduce biodiversity 4) may cause changes in migration patterns (e.g. birds) 5) may result in chnages of distribution of species.

CO2 can be sequestered in oceans, lakes + ponds = IMPORTANT FACTOR IN REMOVING CO2

biofuels - made from natural products by fermentation. Biogas (mainly methane) can be produced by anaerobic fermentation of a wide range of plant products/ waste material containing carbohydrates.

Ethanol-based fuels - produced by yeast by anaerobic fermentation of sugar cane juices + glucose derived from maize starch by carbohydrase. Ethanol distilled from products of fermentation + used in motor vehicle fuels.

At each stage in a food chain, less energy + less material are contained in the biomass of the organisms - means that efficiency of blood production can be improved by reducing number of stages in food chains.

Efficiency of blood production can also be improved by restricting energy loss from food + animals by limiting their movement + controlling temp of their surroundings.

Fish stocks in oceans are declining - important to maintain fish stocks at a level where breeding continues or certain species may disappear altogether in some areas.

Net size + fishing quotas play important role in conservation of fish stocks.

Fusarium (fungus) used to make mycoprotein (a protein rich food suitable for vegetarians). The fungus is grown on glucose syrup is aerobic conditions + biomass is harvested + purified.

Dissolved substances move by diffusion + active transport

Water moves across boundaries by OSMOSIS ( diffusion of water from dilute to more concentrated solutions through a particully permeable membrane that allows passage of water molecules)

Differences in conc. of solutiuons in + out of cells cause water to move into/out a cell by osmosis

Most soft drinks contain water, sugar and ions.

Sports drinks contain sugars to replace sugar used in energy release + contain water + ions to replace ones lost during sweating.

If water + ions arent replaces, the ion/water balance of the body is disturbed + cells dont work as efficiently. 

Substances are sometimes absorbed against a concentration gradient - requires energy from respiration = ACTIVE TRANSPORT - (enables cells to absorb ions from very dilute solutions)

Many organ systems are specialised for exchanging materials, the effectiveness of an exchange surface is increased by:

1) a large surface area

2) being thin (short diffusion path)

3) having an efficient blood supply (animals)

4) being ventillated (animals for gaseous exchange)

gas + solute exchange surfaces in humans + other organisms are adapted to maximize effectiveness. The size + complexity of an organism increases the difficulty of exchanging materials. 

In humans: 1) Surface area of lungs - increased by alveoli - provides very large, moist surface richly supplied with blood capillaries so gases can readily diffuse into+out of blood. 2) surface area of small intestine by villi - provide large surface area with extensive network of capillaries to absorb products of digestion by diffusion + active transport.

Lungs in thorax (upper body) - protected by ribcage + seperated from abdomen (lower body) by diaphragm.

Breathing system takes air into + out of body so oxygen from air can diffuse into blood stream + CO2 can diffuse out of bloodstream into air.

Breathing in = ribcage - out + up, diaphragm - gets flatter (OPPOSITE FOR BREATHING OUT)

VENTILATION = movement of air into + out of lungs.

in plants:

1) CO2 enters leaf by diffusion

2) most water + minteral ions absorbed by roots.

surface area of roots - increased by root hairs, surface area of leaves - increased by flattened shape + internal air spaces.

Plants have stomata to obtain CO2 from atmosphere + remove oxygen produced in photosynthesis. 

Plants lose water vapour from surface of leaves - loss of water vapour = TRANSPIRATION - more rapid in hot, dry + windy conditions - most transpiration through stomata. 

Size of stomata is controlled by guard cells which surround them.

If plants lose water faster than its replaced by roots, the stomata can close to prevent wilting.