9.6 Flashcards
two ways that plants can be pollinated
wind and insect pollination
why is seed dispersal important for plant survival?
- spread out
- avoid competing for same resources
- higher chance of survival in case of natural disaster in one particular area
4 ways in which seed dispersal occurs
- wind
- animal ( internal/external)
- water
- explosions
what is light energy absorbed by
light energy is absorbed by chlorophyll - a green substance found in chloroplasts
what are the vascular bundles in a plant?
Xylem tissue delivers water from the roots to the leaf, and phloem tissue transports glucose away from the leaf.
where does gas exchange take place?
Gas exchange happens in the spongy mesophyll tissue of the leaf.
what does the spongy mesophyll permit to happen?
carbon dioxide to diffuse into the spongy mesophyll cells, and oxygen to diffuse out of it.
where doses light absorption happen?
Light absorption happens in the palisade mesophyll tissue of the leaf.
what are palisade cells packed with?
Palisade cells are column shaped and packed with many chloroplasts.
how is the arrangement of the palisade layer useful?
They are arranged closely together so that a lot of light energy can be absorbed.
features and their functions:
- large surface area
- thin
- thin waxy cuticle
- think transparent epidermis
- Large surface area = Maximise light absorption
- Thin = Short distance for carbon dioxide to diffuse into leaf cells
- Thin waxy cuticle = This protects the leaves without blocking out light
- Thin transparent epidermis = Allows light to reach the palisade cells
Three factors can limit the rate of photosynthesis:
light intensity, carbon dioxide concentration and temperature.
parts of a leaf and their function wc ue pl sl g s
waxy cuticle-prevents water from evaporating
upper epidermis-protects other cells and absorbs sun’s energy and uv rays.
palisade layer- contains lots of chlorophyll and receives lots of sunlight
spongy layer-filled with space which allows gases to circulate through
guardcells-controls water exchange
stomato-allows substances to be transported through
features of the xylem:
TRANSPIRATION
- tiny pores that allow water and minerals to pass through
- thick cell walls that provide support
- hollow on the inside
features of the phloem:
TRANSLOCATION
Sieve tubes - specialised for transport and have no nuclei.
Companion cells - since the transport of substances in the phloem requires energy. One or more companion cells attached to each sieve tube provide this energy.
what is transpiration?
the evaporation of water at the surface of the spongy mesophyll cells in leaves
how does transpiration happen?
water is absorbed by the roots and the water molecules are held together by weak forces of attraction which cause a chain of water molecules to form that travel upwards
factors that increase the rate of transpiration?
temperature (heat), wind and non humid conditions
translocation
plants make glucose and transport sucrose
difussion (doesn’t need energy-passive process)
movement from a high concentration to a ow concentration
active transport
movement from a low concentration to a high concentration
advantages and disadvantages to selective breeding?
- advantages: yield, disease resistance
- disadvantages: reduces gene pool, inbreeding can cause health problems and genetic defects, no variation in population = more ceseptable to die of same disease
3 ways of obtaining water
surface water-lakes and rivers
waste water-water used already
ground water-rocks which trap water underground
desalination
distillation to produce pure water from salt water
