B4 OCR Biology Module Four Notes Higher Tier

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Module 4: It's a Green World
B4A:Who planted that there?
Structure of a plant cell
Structure of Inside a Leaf
Underlined= Name
Small font underneath= Definition
Brackets= Way in which it increases rate of photosynthesis.
Efficient Photosynthesis
Broad- large surface areas
Thin- short distance for gases to travel
Contain Chlorophyll- absorb light
Network of veins- support and transportation of sucrose/water
Internal surface area to volume ratio very large.
Further Notes
carbon dioxide/oxygen enter/exit through leaf pores

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Leaf Palisade Cell- contains many chloroplasts- traps sunlight between palisade mesophyll and spongy
B4B; Water, water everywhere.
Osmosis- a type of diffusion
The net movement of water molecules from an area of high water
concentration (dilute solution) to an area of low water concentration
(concentrated solution) across a partially-permeable membrane (allows small
molecules to pass through)and is a consequence of the random movement of
individual particles.…read more

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Transpiration/water loos from leaves- consequence of adaptations for efficient
Provides plants with water for Cooling, Photosynthesis, Support, The
Movement of Mineral Ions
How is structure of leaf adapted to reduce excessive water loss?
1)Waxy cuticle- Impermeable to water loss
2) Stoma- found mainly on lower epidermis to reduce transpiration- only a
small number on upper epidermis
How is the cellular structure of lead adapted to reduse water loss?
1) Changes in guard cell turgidity
Occurs due to changes in light intensity/ availability of water…read more

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Item B4C; Transport in Plants
XYLEM-Transports water/ dissolved minerals which are taken in by roots and moved up to leaves and shoots
where water is lost by transpiration.
PHLOEM-Transports dissolved food substances/ sugars around plant. Unlike transport of water- may be
transported up/ down stem. Can move from leaves (where its made) to tips of shoots (where growth
happens) may be sent down stem to storage organelles such as swollen roots (translocation).…read more

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The loss of water from surface of leaf by evaporation
Helps cause water to be moved up xylem vessels.
B4D; Minerals and Plants
Why do plants need minerals?
1) Nitrogen
needed to make amino acids/ proteins (for cell growth) and bases for DNA
2) Phosphorous
needed to make DNA/cell membranes and ATP (respiration and growth)
3) Potassium
this ion- essential for enzymes of respiration/photosynthesis, helps enzyme work.
4) Magnesium
this ion- used to make chlorophyll for photosynthesis.…read more

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ATP) so little active uptake.
A few ions DIFFUSE (not active transport) into roots- will stop when concentration in root is
B4E; Energy Flow
Ultimate energy source- the sun-
Plants use solar energy for photosynthesis- trap energy for rest of food chain.
Food chain- linear sequence of feeding relationships
Food web- interconnecting food chains
Pyramid of Numbers
inaccurate as for example, one oak tree does not equate to one caterpillar.…read more

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How is biomass used?
Eating it, feeding to livestock, fuel, growing the seeds
B4F- Farming
Intensive Farming;
trying to produce as much food as possible from the land, plants and animals available.…read more

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Many cases the organism used as a predator, becomes the pest
Effects food chains by removing the pest organism.
Inability to control predators once released
B4G; Decay
Factors effecting Rate of Decay
1) Temperature
As temperature increases ( up to 37) rate of decay increases as enzyme controlled reactions increase with
increased temperatures.…read more


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