BIOLOGY 4.2

charl.mallon
Mind Map by charl.mallon, updated more than 1 year ago
charl.mallon
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GCSE Biology Mind Map on BIOLOGY 4.2, created by charl.mallon on 06/03/2014.
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BIOLOGY 4.2
1 Root hairs take in water by osmosis
1.1 Root hairs give the plant a large surface area for absorbing water from the soil
1.2 There's usually a higher concentration of water in the soil than in the plant, so water is drawn in to the root hair cell by osmosis
2 TRANSPIRATION
2.1 The loss of water from a leaf as it diffuses out of the stomata by evaporation
2.2 Creates a slight shortage of water in the leaf, so more water is drawn up from the rest of the plant through the xylem vessels
2.2.1 This means more water is drawn up from the roots & there is a constant transpiration stream
2.3 Benefits of transpiration stream/provides water for
2.3.1 Keeping the plant cool
2.3.2 Provides water for photosynthesis constantly
2.3.3 Creates turgor pressure - supports plant
2.3.4 Minerals needed by the plant can be brought in from the soil along with the water
2.4 Factors that increase transpiration:
2.4.1 Increased light
2.4.1.1 Stomata close in the dark: no photosynthesis, no CO2 needed, no water escaping
2.4.2 Increased temp
2.4.2.1 Water particles have more energy to evaporate & diffuse out of the stomata
2.4.3 Increased air movement
2.4.3.1 Windy: water vapour swept away, low conc of water outside leaf = lots of diffusion
2.4.4 DECREASED humidity
2.4.4.1 Humid air has lots of water in it - not a big difference in conc in/out = less diffusion
3 Leaf adaptations for reducing water loss
3.1 Waxy cuticle covering the upper epidermis
3.1.1 Makes the upper surface of the leaf waterproof
3.2 Stomata are found on the lower surface where it is darker & cooler
3.2.1 Slow diffusion of water out of the leaf
3.3 Stomata size & number
3.3.1 The more stomata, the more water loss
3.3.1.1 Fewer & smaller on the underside, none on upper epidermis
4 Transport vessels: xylem & phloem
4.1 Deliver water and nutrients to every part of the leaf
4.2 Help support leaf's structure
4.3 Take away glucose produced by photosynthesis
4.4 XYLEM vessels
4.4.1 Made of dead cells joined end to end with no end walls between them and a hole down the middle (lumen)
4.4.2 Thick side walls made of cellulose: strong & stiff - support
4.4.3 Carry water & minerals FROM the ROOTS up the shoot TO the LEAVES in the transpiration stream
4.5 PHLOEM tubes
4.5.1 Made of columns of living cells with perforated end plates to allow stuff to flow through
4.5.2 Transport food substances made with sugars both UP and DOWN the STEM - TO growing and storage TISSUES
4.5.3 This movement of food substances around the plant is known as TRANSLOCATION
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