b4 revision


distribution of organisms

habitat- where plants or animals live COMMUNITY- all animals and plants living in the garden

POPULATION-the number of particular plant or species in a community

NATURAL ECOSYSTEMS- such as a native woodland or lake, contains large amounts of biodiversity. ARTIFICIAL ECOSYSTEMS- such as fish farms have low biodiversity

The distripution of organisms can be mapped using a transect line.

In artificial ecosystems have humans delibertly protecting one species and would remove any other organsim which competes with it and lower the yield

-A transect line can show zonation- which is caused by abiotic factors (non biological) e.g trampling near a foot path and exposure on sea shore

An ecosytem is a self supporting due to exchange of gases during photosynthesis and respiration. Only thing which isnt self supporting is the light from the sun

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population size

How do you make measuring more accurate?-by having a bigger quadrat and more samples

What does the capture recapture method assume?

-there are no deaths or reproduction or immigration or emigration

-marking doesnt affect survival and identical samples are used

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the chemistry of photosynthesis



-respiration-realsing energy

-converted into cellulose to make cell walls -coverted into proteins for growth and repair

-converted into starch fats and oil for storage

-starch is used for storage as its insolouble and doesnt move out of storage areas, unlike glucose it does not affect water concentration of cells and cause osmosis


-water is split up by light energy releasing oxygen gas and hydrogen ions

-co2 gas combines with hydrogen ions producing glucose and water

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historical understanding of photosynthesis

-GREEK scientists believed plants took up minerals from the soil to grow and gain mass

-Van HELOMONT-concluded from his experiment when he grew a willow tree that plant growth is not only due to soil-it must depend on something else as the soils mass did not grow

PRIESTLY-plants produce oxygen

Modern experiments discovered-light energy splits water,not co2. The water is split into hydrogen ions and oxygen gas. Isotopes are different forms of the same element

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The rate of photosynthesis


-more co2 -more light -higher temp which increases enzyme action

-plants respire at all times by taking in oxygen and releasing co2. Where as during photosynthesis they release oxygen and take in co2

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leaf strucuture


-outer eperdemis lacks chloroplast so is transparent- meaning no barriers to stop light from getting in

-upper paliside layer contains most of leafs chloroplasts so they recieve the most light

-spongy mesophyll cells are loosely spaced so that diffusion between of gases between cells and the outside atmosphere can take place

-the arrangement of mesophyll creates a large surface area to large amounts of gas enter and exit cells

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leafs adaptations for photosynthesis

-large surface area to get as much light as posible

-thin so gases diffuse in and out easily

-chlorophyll so they can get light from a broad range of the spectrum

-vascular bundles for support and transport of materials

guard cells which control the opening of stomata and regulate the flow of  c02 and oxygen

-by hvaing carotene to maximise use of suns energy and abosrbing light from different wave lengths

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-net movement of particles in a gas or liquid from an ear of high concentration to an area of low concentration, resulting from random moving particles

-duffusion is how co2 and whater and oxygen enter and leave the cells throught the cell membrane


-large surface area -specialised opening called the stomata -gaps between spongy mesophyll cells


-a shorter distance for the molecules to travel -greater surface area for molecules to diffuse into

-steep concentration gradient

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-type of diffusion which depends on a parially permable membrane which allows the passage of water molecules but not large molecules such as glucose

-movement of water from  HIGH concentration (dilute soloution) and a low concentration (concenrated solution)

-osmosis is the consequence of water molecules moving randomly

-knowing concentrations of water inside and outside the cell will help you predict the net movement

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water in cells

-water puts pressure on the cell wall which is rigid and not elastic. TURGOR pressure supports the cell and sstops it from collapsing. When water loss is great the plant looses this turgor pressure and begins to wilt

-when a plant cell looses water it becomes shrivelled and plasmolysed and is then called flacid

-animal cells do not have a cellwall which means when too much water enters they burst and when too much water leaves an animal cell its shrinks and becomes scalloped shaped

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xylem and pholem cells

phloem- carries food xylem-carries water

xylem- carries water from roots to leaves

phloem carries food substances such as sugar up and down stems to growing and storage tissues via the process translocation

xylem carries minerals and water froom roots too the leaves via transpirtation

XYLEM cells are called vessels and are dead cells which lack cyptoplasm. Their cellulose walls are very thick and give great strength and support

PHOEM- arrange in columns and are living cells

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-evaportation and diffusion of water. This loss of water helps to create a continuous flow of water from roots to leaves via xylem

-root hairs have a large surface area to increase the amount of water they can take up

trasnpirtation insures plants have water for- cooling, photosynthesis, support due to turgor pressure and transport of materials

WATER LOSS IS STOPPED BY- a waxy cuticle covering outer eperdemis cells and stomatas on shaded lower parts of leaves

PLANT CELLS ARE ADAPTED FOR EFFICIENT PHOTOSYNTHESIS by-stomata open for entry of gases and spongy mesphyll cells which help gases to diffuse and dissolve in quick

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transpiration part 2

THE RATE OF TRANSPIRATION CAN BE INCREASED BY -increase in light intensity which results in stomata being more open -increase in temp which icreases evaporation of water -incese in air movement which blows water vapor away -decreases in humidity which allows water to evaporate

guard cells decrease amount of water loss by being able to manipulate the size of the stomatas opening and having fewer stomata

HOW DO GUARD CELLS OPEN STOMATA- they contain chloroplasts so photosynthesi happens and produces sugars increasing turgor pressure and making cells swell, making guard cells curve and open stomata

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use of minerals

-nitrates which make proteins through ammino acids for growth and repair

-phosphates to make dna and genetic code, also for cell membrane and respirtation

-potassium which help speed up enzyme action in photosynthesis and respiration

-magnesium which make chlorophyll essential for photosynthesis

-lack of nitrates- yellow leaves and poor growth

lack of phosphates-poor root growth and discoloured leaves

lack of potassium-poor flower growth and discoloured leaves

lack of magnesium-yellow leaves

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minerals uptake

-present in soil at low concentrations

-transported by active transport and not osmois or diffusion

-transported by the root hair cells containing high amounts of minerals-this equires energy from respirtation as it goes up an area of concentration

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DETRITIVORES- earth worms and maggots and wood lice

increase rate of decay by feeding of detritus and increase surface area of the substances for further microbiotic break down

rate of decay is increased by amount of water and oxygen and temp

-higher temps increase respiration where as if its too hot it will denature enzymes

-increasing amount of water allows material to be digested and absorbed and increases growth and reproduction of bacteria

SAPROPHYTE- e.g fungus creates enzymes to digest food outside the cell and reabsorb the simple soluble substances this is called extraceullar digestion

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food preseevation

CANNING-foods are heated to kill bacteria and placed sealed in a vaccum to prevent oxygen and bactera entering

COOLING- allows bacteria growth and reproduction to slow down

-drying removes water so bacteria cant feed or grow

-vinegar puts acidic conditons which kills bacteria

-salt and sugar- kills it as the high osmotic concentration will remove water from them

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disads of adding pesticides e.g herbicides- enter and accumlate food chains causing a lethal dose to predators -harm non pest -some take a long time to break down

ORGANIC FARMING- doesnt use pesticides or fertilisers it uses manure and crop rotation t0 avoid soil pest and also nitrogen fixing plants and varying typs of seeds planting times to reduce amount of pests. However its more expensive and crops are small ut people believe it tastes better and is healtheir

BIOLOGICAL CONVERTER- Usinng living organisms to control pests but they damage plants and eventually kill other members of food chains as population increaseso much

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hydrophonics and intensive farming

intensive- uses artificial fertilisers which increase crop yield however concerns about animal cruelty askept in a small area and affects of chemicals on soils

hydroponics- growing plants without soil and using aerated water which contains minerals and done in gree  houses. They have better control over mineral levels and disease

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