Transcript Document

9C Plants and photosynthesis
9C Plants and
photosynthesis
Green and growing
Leaves and
photosynthesis
Photosynthesis and
the environment
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9C Plants and photosynthesis
Green and growing
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9C Photosynthesis matters
Brian started with bare soil and a packet of seeds.
Now he has tomatoes for his family all summer.
The tomatoes contain lots of chemicals that were not
there at the start. Where have they come from?
What’s the role of the Sun in helping the tomatoes grow?
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9C The process of photosynthesis
Photosynthesis is a chemical
reaction that happens in the leaf.
What are the reactants?
Where do they
come from?
oxygen
REACTANT
FROM AIR
photosynthesis
glucose
PRODUCT
USED BY PLANT
water
REACTANT
FROM SOIL
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TO AIR OR
USED FOR
RESPIRATION
PRODUCT
carbon dioxide
What are the
products of the
reaction?
What happens to the
products?
sunlight
9C Where does the sugar go?
Plants make glucose by photosynthesis.
This is how they grow.
out of
of leaf
leaf
out
through stomata
stomata
through
cellulose for cell walls
oxygen
oxygen
carbon dioxide
dioxide
carbon
from the
the air
air
from
some oxygen and
glucose used in
respiration
proteins for growth and
enzymes
photosynthesis
photosynthesis
water
water
from soil
soil
from
Glucose is a sugar. But a
plant is not just sugar!
It makes lots of other
chemicals so it can grow.
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glucose
glucose
starch for storage
fats and oils for storage
Starch is one chemical that a
plant makes. A potato stores
starch. How does the starch
get there, when glucose is
made in the leaf?
9C All mixed up
Match the reactants with their products to complete
the word equations.
Respiration
oxygen + sugar
Photosynthesis
carbon dioxide + water
carbon dioxide
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carbon dioxide + water
light energy
taken in
sugar
oxygen + sugar
water
oxygen
9C Faster photosynthesis
How fast does a plant photosynthesise?
This question is very important to farmers and growers.
We can use this
apparatus to
measure the rate
of photosynthesis.
How?
oxygen collects
light source
test tube
water
pondweed (Elodea)
beaker
funnel
We might count the oxygen bubbles per minute, or collect
the gas given off in one minute and measure its volume.
What would happen if we increased the light level?
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9C Faster photosynthesis
Here are some results from the pondweed experiment.
light level
bubbles of oxygen per minute
very high
24
high
22
medium
15
low
7
very low
0
What effect does light have on the rate of photosynthesis?
What would happen if we put a layer of oil on the water?
This stops carbon dioxide from the air dissolving in the water.
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9C Photosynthesis myths?
True or false?
1. Plants
2.
3.
4.
5.
6.
Photosynthesis
Roots
Plants carry
make
look
give green
out
out
food
carbon
only
half
and
from
because
the
respiration
happens
oxygen
dioxide
photosynthesis
they
inwhen
and
work
contain
thesunlight.
light.
they
in opposite
that
the
are
chemical
takes
chlorophyll.
directions.
place
photosynthesising.
in a healthy oak tree.
TRUE! Photosynthesis
FALSE!
Without
Plants
They take
are
need
light
vital
energy,
carbon
to
produces
theall
the
dioxide
plant
reactions
glucose
but
from
roots
and
the
ofincannot
air
Chlorophyll
absorbs
the
colours
light
in
carbon
dioxide.
Oxygen
is
oxygen,
photosynthesis
and
carrywater
out
while
photosynthesis
from
respiration
cannot
thesee
soilwork.
to
breaks
–build
they’re
sugars.
them
except
green
–
we
the
green
light
produced
by
photosynthesis.
down
Oxygen
underground
to make
carbon
in the dark.
in
dioxide
photosynthesis.
and
water.
because
itisisproduced
reflected
from
the
plant.
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9C Plants and photosynthesis
Leaves and
photosynthesis
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9C Food factories
Plants are food factories! They are adapted to carry out
photosynthesis quickly. How does this help them?
Most photosynthesis happens in the leaves. Can you give
three ways in which these leaves are adapted to be food
factories?
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9C Design a food factory
Photosynthesis needs light.
You are going to design a light-catching machine.
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9C Design a food factory
Chloroplasts use light to make sugar.
Where would you put these to make the most of the light?
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9C Design a food factory
Photosynthesis needs carbon dioxide. How does this gas
get into the leaf?
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9C Design a food factory
Photosynthesis needs water. How can you get it into the
leaf?
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9C Design a food factory
If you’re a dynamite designer, you should have a
food-making factory that looks something like this:
tightly packed
palisade
cells full of
chloroplasts
spongy mesophyll
with air spaces so
gases can move
around
veins to bring water up from the
roots, and also take sugar back
down to the roots for storage
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stomata to let carbon
dioxide into the leaf
9C Quiz
1. Leaves are adapted for…
a) pollination
b) photosynthesis
c) photography.
2. Stomata are...
a) holes in a leaf that can open and close to let
gases in and out
b) the cells that carry out photosynthesis
c) small stones found in your stomach.
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9C Quiz
3. Leaves are covered with a thin waterproof layer
called the…
a) popsicle
b) cuticle
c) waxicle.
4. Leaves have a large surface area to...
a) increase the rate of reactions
b) catch the maximum amount of sunlight
c) look pretty in parks and gardens.
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9C Quiz
5. Palisade mesophyll is in the upper part of the leaf
because…
a) it needs to capture as much sunlight as possible
b) the lower areas were already full
c) it stops the upper surface from collapsing.
6. Spongy mesophyll has large air spaces between the
cells to...
a) allow veins into the leaf
b) cut down the amount of cellulose needed to build
new cell walls
c) give room for gases to move more easily.
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9C Plants and photosynthesis
Photosynthesis and
the environment
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9C Meet the energy twins
Respiration and photosynthesis are like a pair of
energy twins.
sunlight energy
oxygen
+
glucose
photosynthesis
respiration
carbon
dioxide
+
water
energy released
How do these energy twins work together to keep our
atmosphere in balance?
Where would we be without sunlight and green plants?
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9C Food, medicines, and ...
All of our food comes originally from
plants.
That’s true even if you only eat steak!
Why?
Many powerful drugs come from plants.
Aspirin first came from the bark of willow trees.
Powerful new anti-cancer drugs are made from yew trees.
Wood, hay and bamboo are used all over the world for
building.
Linen and cotton are both fabrics made from plants.
What else can we get from plants?
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9C The rainforest question
Rainforests are very complex ecosystems. Scientists
estimate that thousands of unknown species live there.
But the people living in rainforests need to live now.
They cut down the trees for building and furniture.
They grow crops on the land, but this destroys the soil.
What does deforestation do to the atmosphere?
What other problems does it cause?
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9C Rainforest answers?
Local people need
money. They need
to harvest the
forests now.
People in the rich world
cut down all of their forests
centuries ago – they can’t
tell people in the
developing world not to do
the same!
What do you think?
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Most of the money is
earned by a few rich
companies. The people
who live in the forests
get nothing – and they
lose their homes.
How many future lifesaving drugs have we
already lost from the
rainforests? How many
unknown species have
we made extinct?