presentation about Making food

Plants- the first linkPlants are the link between the energy in the sun being converted into a form which animals can eat and get the energy to survive… Workbook Activity p 54 Food webs

Topic 2 The World of Plants

Standard Grade Biology

World of Plants is divided into:

A- Introducing plants

B- Growing plants (Pollination,

Fertilisation, Asexual reproduction)

C- Making food

Plants- the first link

Plants are the link between the energy in the sun being converted into a form which animals can eat and get the energy to survive…

Workbook Activity

p 54 Food webs and plants

The process by which plants do this is called:

Photosynthesis

All living things respire all the time to release

energy from their food in a process called:

Respiration

The plants have captured light energy and turned it into a store of chemical energy (glucose).

Is light needed for

photosynthesis?

1. Take a de-starched geranium plant (24h in dark)

2. Cover part of a leaf with some tin foil (this prevents

light getting through)

3. Leave the plant in sunlight for a few hours

4. Test the leaf for starch

Is carbon dioxide needed for

photosynthesis?

1. Take a de-starched

geranium plant

2. Enclose it in a plastic bag

with a chemical that

absorbs carbon dioxide

(e.g soda lime or sodium

hydroxide pellets)

3. Leave the plant in

sunlight for a couple of

hours

4. Test the leaf for starch

1 Which parts of the leaf do you think will go blue-

black?

2 Why do parts that were not covered contain starch?

Is light needed for photosynthesis?

Workbook Problem Solving

p 81 Making a starch print

Is carbon dioxide needed for

photosynthesis?

Questions:

1 Does the leaf contain starch? Why/ why not?

2 Has the plant carried out photosynthesis?

3 What would be your control plant’s conditions?

(Hint: a control plant should have everything it needs for

photosynthesis including carbon dioxide)

Workbook Problem Solving

p 76 Plants and greenhouses

CO 2 is converted into glucose by photosynthesis.

Mans’ uses of plant glucose

Plants’ uses of plant glucose

Glucose

Used immediately to provide energy source for respiration

Energy used to turn sugars, nitrates &

other nutrients into amino acids which build up proteins

To make cellulose, the main structural material in cell

starch (in leaves,

seeds, roots and

Glucose molecule

Workbook Activity

p 70 Changes in carbohydrate

Activity

– Testing a plant for sugar

1. Put a piece of raw onion in a pestle and mortar

2. Grind it with a little sand and 10cm3 of water

3. Filter the liquid into a test tube

4. Heat the liquid with 10 drops Benedict’s solution in

a water bath

a) What colour change would you expect if sugar

was present?

b) Write an explanation of your results.

You need to know the plant experiments in detail,

explain the different steps, and results, in each one

-Testing a leaf for starch

1. Dip a leaf into boiling water for

about a minute (to soften it).

2. Turn off the Bunsen burner

3. Put the leaf into a test-tube of

ethanol (to remove chlorophyll).

4. Stand the test-tube in a beaker of

hot water for about 10 minutes

5. Wash the leaf in cold water

6. Spread the leaf out flat on a petri

dish and cover it with iodine

solution (tests for starch).

7. If the leaf goes blue-black,

starch is present

-Testing a leaf for chlorophyll

Repeat the starch test

but this time use a

variegated leaf from a

geranium plant

Variegated means that a

plant has coloured and

white parts on its leaves

Do the green parts

contain chlorophyll? Do

the white bits? Which do

you think will test

positive for starch?

From little acorns do

great oaks grow…

 Where do the extra 250kg come from?

 Explain your answer as fully and scientifically as you can

A tree is planted in a meadow

After 20 years it has grown into a big tree,

weighing 250kg more than when it was planted

Gas Balance

During the day:

Oxygen released by photosynthesis is greater than

the amount of oxygen used up in respiration.

CO 2 used in photosynthesis is greater than the

amount of CO2 produced by respiration

glucose + oxygen  carbon dioxide (CO 2 ) + water

carbon dioxide + water  glucose + oxygen

all the time

daylight only

Fill a jar with water

Fill a test tube with water too

and cover the top as you

place it upside down inside

the jar

Take a runner and feed it up

inside the test tube

Leave in direct sunlight for a

few hours

Result?

A bubble of oxygen gas should

form at the top of the test tube as it photosynthesises

Summary of Photosynthesis

Workbook Activity

p 64-65 Elodea bubbler expt

Plants’ waste product-

oxygen- is essential

for animal life.

Quick Quiz 1

1 What does a plant need for photosynthesis?

2 What does a leaf produce during photosynthesis?

3 What is chlorophyll?

4 How do the leaves obtain water?

5 How does the plant obtain carbon dioxide?

6 List 3 uses of the glucose produced by

photosynthesis?

7 Name the storage form of carbohydrate in a leaf

Carbon dioxide, water, chlorophyll, light

Oxygen, glucose

A green pigment which absorbs the sun’s energyThrough the roots (and xylem tubes by osmosisFrom the air (through stomata)

Cellulose (structural), starch (storage), energyStarch

A leaf in time

Library activity

Source: http://www.life.uiuc.edu/plantbio/102/links.html

Read through the file and

take some short notes to

summarise the life of a leaf

http://www.portlandpress.com/pp/books/online/leaf/alit_eng.pdf

Leaves are the organs of

photosynthesis and make all the food for a plant

We will look at:

 Outer layers (top & bottom)

 Inner structure including veins (its transport

system)

Internal structure

Collect the handout ‘Leaf structure’ and add labels/notes

mesophyll

waxy cuticle

Outer layer- upper surface

1 The waxy cuticle is a waterproof layer which cuts

down water loss by evaporation.

2 The upper cells of the leaf make up the epidermis They are transparent so light passes straight through

them into the next layer of cells…

1.waxy

2.

The palisade

layer contains

cells with lots of

chloroplasts

The spongy layer (spongy

mesophyll) contains rounded cells

with many air spaces allowing CO2

to circulate and reach the palisade cells, while O2 leaves

Workbook Activities

p 66-67 Leaf surface and thickness

p67 Leaf layer cards- matching

Problem Solving

p78 How many stomata?

p79 Water content and dry weight

p85 Use of cobalt choride paper

The leaf of a flowering plant

Outer layer- bottom surface

Leaf epidermis with stomata- scanning electron microscope

On the lower surface of the

leaf there are tiny pores

called stomata (singular-

stoma) which open and

close.

Stomata let CO 2 diffuse in.

Water vapour and oxygen (O2) move

out

Stomata- open

Stomata have guard cells surrounding

them to control their opening & closing

When there is

plenty of water

(daytime) the

guard cells are

turgid and curved.

This opens the stomata and water

can escape.

Workbook

p 62 Leaf surfaces

Stomata- closed

When there is

little water the

guard cells are

flaccid and less curved.

This closes the

General structure

Vast network of veins

supplies all parts of the plant

with essential substances

Structural support

Flat leaf blade

Has large surface area

Absorbs as much sunlight

& CO2 as possible

Thin

CO2, reaches inner cells easily

Stomata

Most in lower surface

of leafGas & water exchange

Leaf veins

Leaf veins (and roots and stems) contain the xylem and

phloem tubes in vascular bundles.

They run throughout the plant, transporting various

substances up and down them

Workbook Problem Solving

p 80 Ringing a plant

Transport systems used for?

Plants need to allow:

 Gases to get in and out of

the leaves

 Water and nutrients to

move into the plant from the

soil

 Glucose made in

photosynthesis to be carried

to the rest of the plant

Giant redwood trees carry water & nutrients over 100m from the soil

Workbook Activity

p 61 Food transport diagram

 Roots have specialised cells called root hair

cells, which are long and thin providing a large

surface area for the uptake of water and minerals

Into the root hair cell

HOW DOES IT HAPPEN?

 The water in the soil has a weak solution of salts

 The cell sap has a more concentrated solution

 Water moves from the soil into the root hair

along a water concentration gradient

Water passes from the soil into

root hairs by osmosis

O

 When water moves into a plant cell by osmosis it

increases the pressure inside the cell

 The cell walls are sufficiently strong to withstand the pressure

 It is this pressure which keeps the cells rigid

(maintains their turgor) and provides support

Transpiration is the evaporation of

water from the leaves of a plant

The transpiration stream is the

movement of water up the xylem

(roots-stem-leaves)

Why? So it is not blown / knocked over

How? The roots spread out over a large area

to counterbalance the structures above the soil

This also helps plants find water

Functions 1 Anchoring the

plant

Many tiny hairs branch off the main root

2 Absorb essential nutrients

Why? To take up substances to survive

How? Roots have tiny hairs on their surface which increases their surface area to maximise absorption

A root hair shown

under a microscope

Root hair cell

Root hair

3 Absorb water

Why? Water is a raw material for photosynthesis

How? Root hairs increase surface area

Transport in Flowering Plants

In flowering plants there are separate transport

systems for water and nutrients

Substances are transported in vascular bundles

made up of the xylem and the phloem.

Xylem Tissue

Transports water and

minerals upwards from the roots to the stem and

leaves.

The Xylem is made of dead cells joined into hollow tubes They have thick strong walls made of lignin which give the plant support

round the plant.

The sugars are

transported all round

the plant especially to

growing regions and

the storage organs

Phloem cells are alive and are made of 2 types of cells; sieve tubes and companion cells

Sieve cell end walls have holes (pores) in them Companion cells contain the cell nuclei

Sugar cane

Vascular bundles

are composed of

Xylem, Phloem and

and protect the

xylem and phloem

Leaf Veins are Vascular Bundles.

Workbook Activity

p 72 Structure of xylem and phloem

Vascular bundles

Workbook Activity

p 73 Looking at xylem

Vascular Bundles in sugar cane

Left: section

cross-Below: detail of one bundle

Xylem & phloem in stem

Workbook Activity

p 60 Water transport in plants

Bioviewers Box

78

The stem of a flowering plant

Position of vascular tissue in the

stem

epidermis

xylem phloemThe positions are different in stems compared to

roots In a stem they are round the outside.

Position of vascular tissues in the

p 68-69 Structure stem, root

In roots they are found

in the centre.

What Limits photosynthesis?

 For photosynthesis to happen all the “ingredients” need to be present

If there are inadequate ingredients photosynthesis will stop or slow down

Light + chlorophyll

Ingredients Carbon dioxide + water oxygen + glucose

 The factor that is in shortest supply will be the one that limits the rate of photosynthesis and is called a

“limiting factor”.

Factors limiting photosynthesis

Light is the limiting factor.

Often this sort of information is shown in a graph…

B CO2 is limiting the rate of

reaction

C The difference between the

lines is due to different

temperatures

p 74 The effect of increasing carbon dioxidep75 The effect of increasing temperature

Workbook Activity

Quick Quiz 2

2 Give 2 structural features of a leaf that make it a

good design for photosynthesis

3 Why do you think that the palisade cells are near

the surface of the leaf?

4 Name the cells that surround the stomatal openings

5 The spongy mesophyll cells are loosely arranged Explain the significance of this

6 Which 3 factors limit the rate of photosynthesis?

1 How is glucose carried from the leaves to every

part of the plant?

Transported in phloem tubes (water in xylem)Large surface area, thin, stomata, veins

To absorb as much sunlight as possible in chloroplasts

Guard cellsLarge spaces between cells allow gases to diffuse quickly

Quantity of light, carbon dioxide, temperature

Helping plants to grow

 Plants need mineral salts from the soil for healthy growth In nature, plants die, decompose and

mineral salts return to the ground

 When crops are harvested, the plants are removed, there is no decomposition, and the quality of the soil decreases as less nutrients become available

 Manufactured fertilisers are added to the soil to

replace those that are lost This enables healthy crops to grow quickly, but at a cost to the farmer

Questions

1. Why do farmers want to harvest crops quickly?

2. What do fertilisers contain to help plants grow?

Signs of Nutrient deficiency in

plants

Lack of Nitrogen

causes

1 Yellowing of leaves.

2 leaves on lower parts of the plant may die

3 Weak stem meaning the plant cannot grow tall.

Lack of Potassium causes …

1

Yellowing

of leaves

2 Poor fruit growth.

Lack of Magnesium causes leaves to turn

yellow from the bottom of the plant

of a plant

Lack of Phosphorus causes …

1 Purpling of leaves

2 Poor root growth

3 Small plant size

Copy out the diagrams from p63 Co-ordinated

Biology (second Edition) showing nutrient deficiency

in plants

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