Download B4: It’s a Green World

B4: It’s a Green World
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b.
c.
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h.
Plant Structure and adaptations
Osmosis and plant support
Transpiration and reducing water loss
Plant Minerals
Pyramids of number and biomass
Farming
Decay
Carbon and Nitrogen Cycles
How to use this PowerPoint:
Look at each slide and try to learn the information and key words for each
topic. Then try the revision questions and mark them yourself…. Easy!
B4a Plant Structure and Adaptations
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Leaves are made of the epidermis
and waxy cuticle, palisade layer,
spongy layer veins, stomata and
guard cells
Palisade cells have many
chloroplasts for photosynthesis
Guard cells surround the stomata
(holes in the underside of the leaf)
and can open or close them to let
water out and gases in
Leaves need water, carbon dioxide
and light for photosynthesis
Adaptations for Photosynthesis include:
Broad leaves = large surface area for sun
Thin leaves for gas diffusion
Chlorophyll = pigment to absorb sunlight
Veins to transport sucrose and water
Stomata = allow gases to diffuse (oxygen and carbon dioxide both in
and out)
Epidermis = transparent ‘skin’ on top of leaf allowing light through
Palisade layer = for photosynthesis
Air spaces = gas diffusion
Test your knowledge of
leaf structure- click the
mouse for the answers
Answers
B4b Osmosis and Plant Support
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Diffusion is the random movement of particles from a high to low concentration
Osmosis is the same as diffusion, except it only involves water
Water will move from where there is lots of water molecules (a dilute solution) to a solution that is
concentrated with salt (a concentrated solution) with less water in it.
Water also travels through a semi (or partially) permeable membrane (a thin skin with tiny holes big
enough for water)
We say water moves down a concentration gradient from high to low
Animal cells have a concentrated cytoplasm
with many salts etc- when they are in pure
water, the water moves in and they burst (lysis)
when put in a really concentrated solution,
water moves out of the animal cell and it
shrinks (crenated)
Plant cells rely on this ‘turgor pressure’ to keep them
upright like an inflatable chair, if you don’t water them
all their cells become flaccid and the leaves go floppyto absorb water the roots have lots of tiny root hair cells
to give a bigger surface area
Plant cells have a concentrated cytoplasm with
many salts etc- when they are in pure water,
the water moves in but they don’t burst as they
have a cell wall (turgid) When put in a really
concentrated solution, water moves out of the
plant cell and the cytoplasm shrinks (flaccid
then plasmolysed)
Answers
Plants also have phloem
tubes that carry sucrose from
the leaves all around the
plant- this is called
translocation- phloem is alive
Cacti cut down transpiration
by having sunken stomata and
rolled leaves in dry places
B4c Transport in Plants
• Water enters through roots and root hair cells by osmosis
• Water then moves into the xylem which are: dead, long, narrow and join
up end to end like a drainpipe, they are also made of lignin which supports
the plant and stops water leaking out
• Next, the water moves up the xylem vessels and evaporate from the
cells in the leaf into the air spaces, then diffuses out of the stomata at the
bottom surface of the leaf• The whole movement of water up the plant and evaporating at the leaf is
called transpiration
• A potometer (shown below) can be used to measure transpiration (water
uptake)
Transpiration can be speeded up by:
1. Hot days = faster evaporation
Stem
2. More light = stomata are open
more
3. Air movement = wind blows the
water away so more evaporates
(greater diffusion gradient)
Root
4. Low Humidity = the drier the air,
the faster evaporation
Answers
B4d Plants Need Minerals Too
• Plants need the following minerals:
• Nitrate for proteins, growth and repair NO3• Phosphate for DNA and cell membranes
• Potassium for enzymes in photosynthesis
• Magnesium for chlorophyll
Fertilisers can be added to soil
to help plants grow better
NPK fertilisers contain
nitrogen, phosphate and
potassium
Adding fertilisers can be bad
as it leads to eutrophication
Framers can use GPS to see
where to apply fertiliser
• nitrate – poor growth and yellow leaves;
• phosphate – poor root growth and
discoloured leaves;
• potassium – poor flower and fruit growth
and discoloured leaves;
• magnesium – yellow leaves.
Plants absorb minerals through
their roots from a low
concentration in the soil to a
high concentration- this needs
energy as it is against the
concentration gradient- this is
called active transport
Answers
• Food chains show the direction of energy flow
• The plant is always the producer as it produces
food by photosynthesis
• All the other organisms are consumers, the first
one in the chain is the primary consumer, then
the secondary and tertiary
Biomass (living material) is a renewable fuel
B4e Energy Flow
A pyramid of numbers show how
many organisms there are. They
can be shaped strangely
A pyramid of biomass shows the
amount of biomass (the amount
of living material)
It can be burnt to heat water in electricity power plants
Fast growing trees are grown then harvested by coppicing
(cutting trees then letting them re-grow)
Coppicing is carbon neutral- it doesn’t add any extra
carbon dioxide into the environment
Number
Biomass can be used to make biogas by
putting yeast and bacteria inside a
digester where fermentation takes place
Bioethanol can also be made by letting
yeast ferment biomass- this can be used
for cars in developing countries
Biomass
At every stage (trophic level)
of the food chain or pyramid,
energy is lost, this is
because the animals use
some energy to move
around or respire. Some is
also lost through egestion
(poo)
Answers
B4f Farming
• Intensive farming means getting the highest yield
possible from your land by putting fertilisers etc
onto crops
•Weedkillers or herbicides kill plants, selective
weedkillers only kill certain plants and don’t harm
the others
•Pesticides kill pests
• fungicides kill fungus
• insecticides kill insects like
aphids (greenfly)
Crops in
glasshouses
Hydroponics
There are many problems after using
chemicals on fields:
Pesticides kill animals that you don’t want to
kill and affects the food chain
Pesticides and herbicides can be harmful to
humans and make them ill if sprayed near
homes, or if they remain on fruit and
vegetables
Some pesticides are persistent like DDT that
can build up in an animals body and cause
death- we now use biodegradable pesticides
that can be broken down
Grower can control temperature, light and reduce
the problem of pests and weeds
Same as glasshouses but grows plants without soil,
plants grown in nutrient solution- can be grown in
desert
Battery Farming
Keeping animals in small spaces indoors so no
energy is wasted- some people think its cruel
Fish Farming
Fish kept in cages in lochs, food, pesticides and
faeces can drop to bottom causing pollution
Organic Farming
Use nitrogen fixing bacteria, crop rotation and weed
by hand, but less crops so more expensive to buy
Biological control: using
predators to kill pests
+ No harm to food chain, lasts
for a long time, and only one
type of prey harmed
- Pest not completely gone,
might not work, predator might
leave or become a pest itself
Answers
Answers
B4g Decay
• Biodegradable items are things that can
decay like paper, bodies and poo
• Micro-organisms need: water, oxygen
and a suitable temperature for their
enzymes in order to decay materials
Making compost
requires food
waste e.g.
potato peelings,
air spaces, warm
temperature and
a little water
It is important to treat sewage as:
• it might contain pathogenic (disease causing) bacteria
•It contains food for bacteria to reproduce
• it contains chemicals which may harm other living things
• sewage is changed into sludge, methane and clean water
called effluent that goes back into the sea
Food can be preserved by:
• canning - boiling to kill microbes
then sealing in air tight can
• cooling/ freezing - slowing down
the microbes chemical reactions
• drying – deprives microbes of
water so they can’t grow
•Adding salt/ sugar – water moves
out of the microbes by osmosis
• adding vinegar – to acid for
microbes’ enzymes
Decomposers = all organisms
that cause decay
Detritivores = big decomposers
like worms and woodlice- create
a larger surface area for smaller
decomposers
Saprophytes = fungi that have
threads called hyphae, they
secrete enzymes and digest food
The Carbon Cycle:
B4h Recycling
• carbon goes into the atmosphere through
respiration, decomposers, detritivores,
burning fossil fuels, volcanoes
• Carbon is removed from the atmosphere
by photosynthesis by plants and
phytoplankton, calcium carbonate shells
from sea creatures forming limestone
under the sea bed
The Nitrogen Cycle:
• Nitrogen goes into the atmosphere through
denitrifying bacteria and lightning
• Nitrogen is removed from the atmosphere by
nitrogen fixing bacteria and nitrifying bacteriasoil bacteria and fungi convert protein and urea
to ammonia
Nitrogen fixing bacteria: turn nitrogen gas into
nitrates e.g. rhizobium bacteria in root nodules
Nitrifying bacteria: turn ammonia into nitrates e.g.
nitrobacter
Denitrifying bacteria: turn nitrates into nitrogen gas