biology

plant structure

groups of similar cells work as a tissue, groups of different tissue work together as an organ, organs work together to build the organism
vascular bundle (xylem and phloem) are found in the middle of the root as it helps the root act like a anchor and allows the plant to move in the breexe
in the stem vascular bundles are located around the edge to provide strength to resist bending
in the leaf the vascular bundles form a network
xlyem cells transport water and dissolved materials from the roots to the shoots and leaves
phloem cells transport the food substances made in the leaf to all other parts of the plant

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xylem transporting water and minerals is called transpiration stream
phloem transporting sugars is called translocation
plants take up water an minerals through the roots, the roots have tiny root hairs which extend between soil particles which increase the surface area, water flows up stem and onto leaf
water leaves the plant by evaporation and diffusion from the leaves - transpiration
plants need water because it is needed to photosyntheis, when it evaporates it cools the plant, by osmosis it makes the plant strong and as the water moves through the plant it takes dissolved materials too
guard cells are on each sides of the stoma, when there is light and water the cells take up water by osmosis, expand and become turgid which causes the cells to open the stoma
if there is little water the guard cells cannot become turgid and cannot open the stoma
plants prevent water loss: waxy cuticles on the upper and lower surfaces, not mant stoma on the surfaces, plants that live in dry areas have curled leaves with the stoma inside, stoma is closed at night

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as well as glucose plants need minerals to remain healthy, the minerals make useful molecule
gardeners can add manure, compost or rotting leaves which decay slowly and release minerals, they can also add chemical fertilisers which dissolve and release minerals
nitrogen is needed to make amino acids which make proteins for growth, without them there is poor plant growth and yellow leaves
phosphorus are needed to make dna and molecules in the cell membrane, without them there is poor root growth and purple leaves
potassium is needed for enzymes in photosynthesis without it there is not enough food and energy for flowers and fruit to grow, yellow leaves with brown spots
magnesium is needed to make chlorophyll and without it yellow leaves occur
minerals are moved around by active transport because diffusion cannot occur as in the soil there is a low concentration and they are moving to a high concentration
minerals attach to a carrier protein, it changes shape by energy from respiration and the mineral cab move across the cell membrane

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plants absorb minerals and carbon made into molecules, animals eat plants and the plants molecules are inside the animals, when they die their bodies decay and it releases the elements back and the cycle continues
bacteria and fungi are the main microbes involved in decay, compost and sewage works use these microbes to help us break down waste
warm temperature speeds up decay and microbes are able to respire, grow and reproduce quicker
more oxygen there is the faster the microbes can repsire, grow and reproduce
moist conditions are needed as the microbes need water to grow and reproduce faster
detrivores (earthworms, maggots) eat small parts of dead material and realease as waste, this activity increases the surface area decomposers can act on
decomposers (bacteria, fungi) chemically break down material releasing ammonium compounds into the soil
decomposers are saprohytes, they feed by releasing enzymes onto dead animals and plants, the enzymes digest the material in a process called extracellular, the decomopsers then absorb the digested chemicals - saprotrophic feeding

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decay reduces the amount of food for people to eat, malnutriton, decayed food can lead to illness and farmers and supermarkets profits and reduces
cannings prevents entry of oxygen and decomposer microbes
cooling at 4oc slows the reproduction of decomposers
freexing at -5oc stops the reproduction of decomposers
drying means no water so decomposers do not grow or reproduce
adding salt causes water to be drawn out by osmosis and this kills them
adding sugars causes water to be drawn out by osmosis and this kills them
adding vinegar adds acid which kills decomposers

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advantages of intensive farming produces high yields per hectares and as pesticides are used less food is lost, low cost of production and fertilisers are used and no staff wages, less labour intensive as chemicals and machines do most the work
disadvantages of intensive farming is that pesticides can damage the environment, fertilisers can cause eutrophication and battery rearing animals is not humane and disease can spread quickly
pesticides are used in intesive farming: insecticides, fungicides and herbicides - use of the pesticides reduce damage to the crop, there is less competition
dioxins and organophosphates are insecticides which are harmful
battery farming impedes the animals from moving so less energy is lost through moving and the animals are not hungry

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advantages of fish farming is that there is a large captive stock that are easy to catch, it is cheap, there is less predation and their numbers can recover
disadvantages of fish farming is that diseases can spread quickly
advantages of glasshouses is that farmers can manipulate environment and grow tender crops all year roumnd, disease can be treated, pesticides and fertilisers are contained inside and don't pose as a threat to the environment and they can be produced in the uk so no food miles
advantages of hydrophonics is that plants can be grown in areas with poor soil, it gives good control of minerals, there is better use of space, water is recycled and diseases can be controlled
disadvantages of hydrophonics is that there is no support for the plant as roots are not anchored, and there is no soil to store minerals so fertilisers have to be added constantly as dissolved minerals

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farmers need to add minerals to the soil and maximise crop growth without using fertilisers or herbicides - so they use animal manure and leaf compost to add minerals and improve fibre content, they have to weed to remove competition, crop rotation and they vary their seed plantings
advantages of biological control is that no artificial chemicals are needed, there is no threat of chemicals escaping and chemicals need to be reused biological control does not usual repeat
disadvantages of biological control is that the predator may not eat the pest, eat other useful species, the predator may increase in number and become out of control, the predator may dispatch to somewhere it's not wanted and adding an organism to a food web will effect the food web

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