BiologyBiologyJust an introduction or summery – whatever way you look at itI don’t know what is needed and not needed but it covers most things

ContentsContents

PLANT PROCESSESPLANT PROCESSES

Leaf structurePhotosynthesis

Limiting Factors

Uses of GlucosePlants and Water

Osmosis

Osmosis in Different CellsTranspirationPlant Growth and Fertilisers

Plant Senses and their Commercial Uses

Response to Water

Response to Gravity

Response to Light

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The Leaf StructureThe Leaf StructureBack to Contents

The LeafThe LeafBack to Contents

Leaves and Leaves and PhotosynthesisPhotosynthesis

A leaf has an upper and lower epidermis covered with a waxy cuticle

The spongy mesophyll and palisade cells contain chloroplasts

Guard cells surround the stomata Leaves are adapted for efficient photosynthesis by having

a large surface area, being thin and having veins Photosynthesis occurs mainly in the leaves Water enters the root hairs by osmosis Carbon dioxide enters and oxygen leaves by diffusion

through stomata The leaf is very efficient in photosynthesising because it

has a large internal surface area, internal air spaces and many chloroplasts in the palisade layer

There are three main limiting factors that affect the rate of photosynthesis. They are:◦ Light◦ Carbon dioxide◦ Temperature

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Limiting FactorsLimiting Factors

45°C

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Uses of GlucoseUses of GlucoseSome glucose is used in respiration to

obtain energyOther uses include converting it to:

◦ Insoluble starch stored in the roots, particularly in the winter. In this form it does not cause too much water to move into the cells by osmosis, as it doesn’t contribute to the concentration inside the cells

◦ Cellulose, needed for cell walls◦ Lipids and oils are formed from glucose

and stored in seeds◦ Glucose can also be combined with other

substances, such as nitrates obtained from the oil and turned into proteins

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Plants and WaterPlants and Water Plant cells are supported by their cell walls and turgor

pressure in the cell sap Water enters the root hairs by osmosis Osmosis is the movement of water from a high

concentration to a low concentration through semi-permeable membrane

A semi-permeable membrane only allows the movement of small molecules

Water moves both in and out of the root to try to even the concentrations. Therefore we use the net movement of water

Osmosis is a type of diffusion A plant must balance its water uptake and water loss Water is needed for photosynthesis, cooling and

transport A leaf is adapted to reduce water loss Leaves lose water because a leaf is adapted for

photosynthesis

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OsmosisOsmosis Root hairs take in water by

osmosis Water moves along the cells

of the root and up the xylem to the leaf

All the time the water is moving to areas of lower water concentration

Osmosis makes plant cells swell up

The water moves into the plant cell vacuole and pushes against the cell wall making it turgid

It is useful as it gives the stem support

When there is little water the cells become flaccid as water has moved out of the cell

If a lot of water leaves the cell, the cytoplasm started to peel away from the cell wall which is called plasmolysis

The cell will behave differently in an animal cell because there is no cell wall to prevent the cell from bursting (haemolysis)

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Osmosis in Different Osmosis in Different CellsCells

In a

Pla

nt

In a

n A

nim

al

NormalToo Much Water Too Little Water

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TranspirationTranspiration Water loss from a plant is called transpiration The water evaporates and exits the leaves by diffusion Water travels from the roots, through the stem to the leaves in

xylem cells Dissolved food travels downwards in phloem cells The rate of transpiration is speeded up by a higher

temperature, more wind, a low humidity and more light More light will increase the transpiration rate because the

stomata will be open A higher temperature will increase the transpiration rate by

increasing the diffusion rate A low humidity will allow more water vapour to diffuse out of

the leaves Xylem cells are dead because they have extra lignin

thickening The flow of water up the xylem to the leaves is called the

transpiration stream The transpiration stream also draws minerals into the plant as

well as water As water is lost, the transpiration stream replaces it so there is

a constant flow

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Fertilisers and Plant Fertilisers and Plant GrowthGrowth Plants need minerals in fertilisers such as nitrates,

phosphates, potassium and magnesium compounds Minerals are needed only in small quantities Nitrates are needed to make proteins for growth Phosphates are needed for root growth Potassium is needed for flower formation Magnesium is needed to make chlorophyll If minerals are missing from the soil water, the plant

shows that it is mineral-deficient Minerals are taken up from the soil water by active

transport Minerals are taken up against a concentration

gradient Active transport uses energy An NPK fertiliser contains nitrogen (N), phosphorus

(P) and potassium (K)

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Plant Senses and Commercial Plant Senses and Commercial UsesUses

Plant Senses Commercial Uses

Plants respond to their surroundings to give them a better chance of survival

Plant responses are called tropisms and are controlled by a hormone

Plants respond to light, gravity and water

Remember: unequal distribution of auxin speeds up growth in shoots and slows down growth in roots

1. Growing Cuttings◦ Rooting powder contains synthetic

auxins◦ A cutting is taken from a plant and

dipped in this powder. This stimulates the roots to grow quickly and enables gardeners to grow lots of exact copies of a particular plant

2. Killing Weeds◦ Synthetic auxins are used as

selective weed-killers◦ They only affect the broad-leaved

weeds; narrow-leaved grasses and cereals are not affected

◦ They kill the weed by making the weed grow to quickly

3. Seedless Fruits◦ Synthetic auxins are sprayed on

unpollinated flowers◦ Fruits form without fertilisation and

thus form without pips

4. Early Ripening◦ Plant hormones can also be used to

ripen fruit in transport

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Responses to Water and Responses to Water and GravityGravity

Response to Water Response to Gravity

A plant’s response to water is called hydrotropism

Roots always grow to a certain extent towards water, even if it means ignoring the pull of gravity and growing sideways

An uneven amount of moisture will cause more auxin to appear on the side with more water

This inhibits the growth of cells on this side

The root cells on the outside will grow quicker and will bend towards the moisture

A plant’s response to gravity is called geotropism

Even if you plant a seed the wrong way up, the shoot always grows up, away from gravity and the root grows down towards gravity

If a plant is put on its side, auxin gathers on the lower half of the shoot and root

Auxin slows down the growth of root cells, so the root curves downwards

Auxin speeds up the growth of the shoot cells so the shoot curves up

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Response to LightResponse to LightA plant’s response to light is called phototropismPlants need light for photosynthesis and thus grow

towards the lightNormally light shines from above. Auxin is spread

evenly and the shoot grows upwards If light comes from one side, auxin accumulates

down the shaded side. Auxin makes these cells grow faster

The result is that the shoot bends towards the light

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BIOMASS, FARMING BIOMASS, FARMING AND DECAYAND DECAY

BiomassPyramid of Numbers

Pyramid of BiomassIntensive Farming and Organic Farming

Pesticides

Fertilisers

EutrophicationDecay and Food PreservationRecycling of CarbonRecycling of Nitrogen

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BiomassBiomass Energy enters food chains in photosynthesis Plants are producers because they produce food Animals are consumers A pyramid of numbers show the number of

organisms in each link (trophic level) in a food chain

A pyramid of biomass shows the mass of living material in each link (trophic level) in a food chain

Energy is transferred along a food chain or food web

Some energy is transferred into less useful forms such as hear or body waste

Biomass fuels are wood (by burning), alcohol (by fermentation) and biogas (from decay)

Biomass fuels are renewable, produce less pollution and are energy self-reliant

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Pyramids of NumbersPyramids of NumbersA pyramid of numbers tells us how

many organisms are involved at each stage in the food chain

At each trophic level the number of organisms get less

However, sometimes a pyramid of numbers doesn’t look like a pyramid at all because it doesn’t take into account the size of the organisms◦E.g. There are many fleas on a single fox

which would make the pyramid ‘top heavy’

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Pyramids of BiomassPyramids of BiomassA biomass pyramid takes into

account the size of an organism at each level unlike the pyramid of numbers

It looks at the mass of the organismYou can take the information from

the pyramid of numbers and multiply it by the organism’s mass which will achieve the pyramid shape again

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Intensive and Organic Intensive and Organic FarmingFarming Intensive farming uses pesticides (insecticide and

fungicide) to kill pests and herbicides to kill weeds Intensive farming produces more food but also

causes problems such as pesticides accumulation in food chains

Fish farming, glasshouses, hydroponics and battery farming are all examples of intensive farming

Organic farming does not use artificial fertilisers, herbicides or pesticides

Organic farming uses animal manure, crop rotation, hand-weeding and biological control of pests

Intensive farming improves the efficiency of energy transfer in food chains

Hydroponics gives better control of fertilisers and diseases

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Intensive FarmingIntensive Farming

Intensive farming can produce more food because it is designed to provide more food for the given land

Many people regard intensive farming of animals as cruel

In order to produce more food from the land, fertilisers and pesticides are needed

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PesticidesPesticidesPesticides are used to kill insects

that damage cropsThey also kill harmless insects, then

insect-eating birds have a shortage of food

The pesticides can get washed into rivers and lake which can then get into our food chains

This was the case in the 60s when a pesticide, DDT, got into the food chain and threatened populations of animals

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FertilisersFertilisersPlants need nutrients from the soil

to growArtificial fertilisers are used to

replace the nutrients in the soil because there isn’t enough because of intensive farming

Fertilisers enable farmers to crop more crops in a smaller space.

Less countryside will be lost for farming but eutrophication is caused because of fertilisers

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EutrophicationEutrophication If too much fertiliser is used and it rains, it

goes into rivers and lakesThe water plants grow quicker as a result

of this and they quickly cover the surface of the water

There is then more competition for light and some plants die

Microbes break down the dead plants and use the oxygen for respiration

The amount of oxygen in the water is then reduced and animals die through suffocation

Untreated sewage can also cause eutrophication

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Organic FarmingOrganic FarmingPeople need to limit their needsIntensive farming produces quality food

and enough to supply people’s needs in Europe but has its problems – alternative is organic farming

Organic farming produces less food per area of land but is kinder to the environment

Organic farming uses manure as a fertiliser and has land for wild plants and animals to flourish.

Biological control of pests are also used where animals eat the pests, it’s not as effective but it isn’t harmful

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Decay and Food Decay and Food PreservationPreservation Decomposers such as fungi and bacteria cause

decay Decay breaks down sewage and compost Decay is affected by temperature and the

amount of oxygen and water Detritivores are animals that feed on dead and

decaying material Earthworms, maggots and woodlice are

Detritivores Saprophytes are plants that live on dead and

decaying material Food can be preserved by stopping or reducing

decay Food preservation methods include canning,

freezing, drying and adding salt, sugar or vinegar

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Recycling of Nitrogen and Recycling of Nitrogen and CarbonCarbon When plants and animals die, their chemicals, such as

nitrogen and carbon, are recycled Plants remove carbon fro the air by photosynthesis Respiration and the burning of fossil fuels releases carbon

in the form of carbon dioxide Carbon is recycled through marine shells, limestone and

eventual weathering There is 78% nitrogen in the atmosphere but it is

unreactive Plants take in nitrogen as nitrates Dead bodies decay, releasing nitrates Decomposers convert proteins and urea into ammonia Ammonia is converted into nitrates by nitrifying bacteria Some nitrates are converted into nitrogen by denitrifying

bacteria Nitrogen-fixing bacteria in the soil and root nodules fix

atmospheric nitrogen (This is further explained on the next few slides...)

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THE CARBON THE CARBON CYCLECYCLE

Feeding

Decomposers

Death but no decay

Death and Decay

Photosynthesis

Burning and Combustion

Respiration

The atmosphere

Fossil Fuels

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THE CARBON CYCLE IN THE CARBON CYCLE IN DETAILDETAIL

Added Notes:Decomposition

•Decomposers are bacteria and fungi which break down dead material•They help recycle carbon into the atmosphere and recycle nutrients into the soil•Plants use this nutrients dissolved in water during photosynthesis.•Animals eat plants, and both animals and plants die, making the cycle start from the beginning again•Decomposition happens everywhere in nature, in compost heaps and even sewage works•The perfect conditions are:

• Warm• Moist• Plenty of oxygen

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THE NITROGEN CYCLETHE NITROGEN CYCLE

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THE NITROGEN CYCLETHE NITROGEN CYCLEBack to Contents

THE NITROGEN CYCLETHE NITROGEN CYCLEADDED NOTESADDED NOTES

•The atmosphere contains 78% nitrogen gas•Nitrogen is needed to make protein•Plants and animals cannot use nitrogen as a gas – it has to be converted into nitrates•Animals get protein by eating plants which plants make from nitrates•It is a continuous cycle•There are four ways that nitrogen is converted into nitrates and only two ways that nitrogen is taken out of the soil•There are three different types of bacteria involved in this cycle:

• Nitrifying bacteria• Nitrogen-fixing bacteria• Denitrifying bacteria

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Key/ Scientific WordsKey/ Scientific Words

PhotosynthesisRespirationCombustionCarbonFossil fuelsDecomposers/

decompositionNutrientsWarmthMoistureOxygen

LighteningNitratesNitrogenNitrogen-fixing bacteriaRoot nodulesProteinDetritivoresDecomposersNitrifying bacteriaLeachingDenitrifying bacteria

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More Key/ Scientific More Key/ Scientific Words...Words...

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