Presentation on theme: "Topic 2 The World of Plants"— Presentation transcript:
1 Topic 2 The World of Plants Standard Grade BiologyTopic 2 The World of Plants
2 C- Making food World of Plants is divided into: A- Introducing plants B- Growing plants (Pollination, Fertilisation, Asexual reproduction)C- Making food
3 Plants- the first link Workbook Activity Photosynthesis Respiration 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 Activityp 54 Food webs and plantsThe process by which plants do this is called:Revise Environment subtopic How It Works, terms- producer, consumer etc.Teachers notes LO- explain the dependence of food webs on photosynthesis.Interpretation- all living things get energy from food.Plants use energy from the sun to make food.Animals get their food, and their energy, by eating plants or animals which have eaten plants.Food webs therefore rely on plants to supply their energy.PhotosynthesisAll living things respire all the time to release energy from their food in a process called:Respiration
4 carbon dioxide + water glucose + oxygen Plant survivalPlants make their own food, glucose, by photosynthesis.It only happens during the daytime when there is light available.Light energycarbon dioxide + water glucose + oxygenchlorophyllRaw materialsProductsThis happens in plant cells containing the chemical chlorophyll (green-coloured) which traps the light energy.The plants have captured light energy and turned it into a store of chemical energy (glucose).SQA LODescribe the process of photosynthesis in terms of raw materials and productsInterpretation- photosynthesis combines CO2 and H2O to produce glucose (sugar) and oxygen.Chlorophyll found in the chloroplasts of plant cells is essential for photosynthesis.Chlorophyll traps the light energy from the sun.Light energy from the sun is used to combine CO2 and H2OANDState that green plants convert light energy to chemical energy using chlorophyllInterpretation- the process by which green plants make their own food is called photosynthesis.A process by which light energy is converted into chemical energy. Which takes place in theLeaves of green plantsMore on the uses for glucose shortly…
5 Is light needed for photosynthesis? Take a de-starched geranium plant (24h in dark). Cover part of a leaf with some tin foil (this prevents light getting through).Leave the plant in sunlight for a few hours.Test the leaf for starch.Common steps in expts:- leave in darkness for 24 hours- to destarch plantVariable factor tested- experimental variable tested such as light, temp, chlorophyllLeave for time- in light to allow time for plant to make starchTest for starch- show if photosynthesis has made starch.
6 Is carbon dioxide needed for photosynthesis? Take a de-starched geranium plantEnclose it in a plastic bag with a chemical that absorbs carbon dioxide. (e.g. soda lime or sodium hydroxide pellets).Leave the plant in sunlight for a couple of hours.Test the leaf for starch.
7 Is light needed for photosynthesis? Questions:Which parts of the leaf do you think will go blue- black?Why do parts that were not covered contain starch?Workbook Problem Solvingp 81 Making a starch print
8 Is carbon dioxide needed for photosynthesis? Questions:Does the leaf contain starch? Why/ why not? Has the plant carried out photosynthesis?What would be your control plant’s conditions?(Hint: a control plant should have everything it needs for photosynthesis including carbon dioxide).Workbook Problem Solvingp 76 Plants and greenhousesCO2 is converted into glucose by photosynthesis.
10 Plants’ uses of plant glucose Raw material for growth, repair and replacement of damaged partsUsed immediately to provide energy source for respirationEnergy used to turn sugars, nitrates & other nutrients into amino acids which build up proteinsTo make fats & oils (energy stored in seeds)GlucoseEnergy stored as sucrose (in fruit)Energy stored as starch (in leaves, seeds, roots and tubers)To make cellulose, the main structural material in cell wallsSQA LOState that green plants make their own food which may be stored as starch.Interpretation- green plants are able to make their own food.Green plants make food in the form of sugar.The sugar made by the plant is either used straight away or converted to starch and stored
11 Glucose molecule Workbook Activity p 70 Changes in carbohydrate SQA- Describe the fate of CO2 as structural and storage carbohydrates in plants and as energy sources.Interpretation- sugar made by plants from CO2 and H2O can be:a) Stored as starch until neededb) Used to supply energyc) Used as building material (eg cellulose in plant cell walls).Workbook Activityp 70 Changes in carbohydrate
12 Activity – Testing a plant for sugar Put a piece of raw onion in a pestle and mortar.Grind it with a little sand and 10cm3 of water.Filter the liquid into a test tubeHeat the liquid with 10 drops Benedict’s solution in a water bathWhat colour change would you expect if sugar was present?b) Write an explanation of your results.Sugar is soluble (dissolves in water).When it is converted into starch it is insoluble so can be stored.Starch can be converted (by enzymes) back into glucose when the plant needs it.REVISE Environment topic, Control and management? The CARBON CYCLE.You need to know the plant experiments in detail, explain the different steps, and results, in each one.
13 Activity -Testing a leaf for starch Dip a leaf into boiling water for about a minute (to soften it).Turn off the Bunsen burner.Put the leaf into a test-tube of ethanol (to remove chlorophyll).Stand the test-tube in a beaker of hot water for about 10 minutes.Wash the leaf in cold water.Spread the leaf out flat on a petri dish and cover it with iodine solution (tests for starch).If the leaf goes blue-black,starch is present.WhyBoil in water to soften and kill leafBoil in alcohol to remove chlorophyllRinse in water to soften leafAdd iodine, to test for starch, goes black.
14 Activity -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?
15 From little acorns do great oaks grow… 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.Where do the extra 250kg come from?Explain your answer as fully and scientifically as you can.
16 Gas Balance Respiration Photosynthesis all the time glucose + oxygen carbon dioxide (CO2) + waterPhotosynthesisdaylight onlycarbon dioxide + water glucose + oxygenDuring the day:Oxygen released by photosynthesis is greater than the amount of oxygen used up in respiration.CO2 used in photosynthesis is greater than the amount of CO2 produced by respiration.
17 Take a runner and feed it up inside the test tube. 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 hoursSourceResult?A bubble of oxygen gas should form at the top of the test tube as it photosynthesises
18 Summary of Photosynthesis Plants’ waste product- oxygen- is essential for animal life.Workbook Activityp Elodea bubbler expt
19 Quick Quiz 1 1. What does a plant need for photosynthesis? Carbon dioxide, water, chlorophyll, light.2. What does a leaf produce during photosynthesis?Oxygen, glucose3. What is chlorophyll?A green pigment which absorbs the sun’s energy4. How do the leaves obtain water?Through the roots (and xylem tubes by osmosis5. How does the plant obtain carbon dioxide?From the air (through stomata)6. List 3 uses of the glucose produced by photosynthesis?Cellulose (structural), starch (storage), energy7. Name the storage form of carbohydrate in a leaf.Starch.
20 A leaf in time Library activity Read through the file and take some short notes to summarise the life of a leafSource:
21 Leaves…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)
22 Internal structurewaxy cuticlemesophyllSQA-Describe the external features and internal structure (epidermis, mesophylls, veins) of a leaf in relation to its function in gas exchangeInterpretation- a leaf has a large surface area to allow the maximum amount of light to enter the leaf.And to expose it to as much air as possible.A leaf is thin to allow CO2 to pass quickly to the cells which carry out photosynthesis.And to allow O2 to leave the leaf as quickly as possible.Thin to allow sunlight to penetrate to all cells.Outer layer of cells on a leaf is called the epidermis.Epidermis is transparent to allow light through.Epidermis contains stomata which allow gases in and out.Top layer of the cells in a leaf is called the palisade mesophyll layerThe layer of cells below the palisade layer is called the spongy mesophyll.The spongy mesophyll cells are loosly packed with large air spaces to allow CO2 and O2to get to and from cells quickly.Leaf veins are made up of xylem and phloem within a short distance of every mesophyll cell to carryfood away from and water to, leaf cells.Collect the handout ‘Leaf structure’ and add labels/notes.
23 Outer layer- upper surface 1.waxy2.Epidermis transparent so no chlorophyll1. 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…
24 The palisade layer contains cells with lots of chloroplasts. mesophyllChloroplasts contain chlorophyll which is the chemical which absorbs the sun’s light energy.Hence this is where most photosynthesis occurs.The spongy layer (spongy mesophyll) contains rounded cells with many air spaces allowing CO2 to circulate and reach the palisade cells, while O2 leaves.
25 Workbook Activities Problem Solving Bioviewers Box 79 p Leaf surface and thicknessp67 Leaf layer cards- matchingProblem Solvingp78 How many stomata?p79 Water content and dry weight.p85 Use of cobalt choride paperBioviewers Box 79The leaf of a flowering plant
26 Outer layer- bottom surface Leaf epidermis with stomata- scanning electron microscopeSQA-State that plants take in carbon dioxide from the air through stomata which can open and closeInterpretation- stomata are tiny pores on the surface of a leaf.Carbon dioxide enters the leaf through stomata.During the day stomata are open.During the night stomata are closed.Know that water vapour is lost through stomataOn the lower surface of the leaf there are tiny pores called stomata (singular- stoma) which open and close.Stomata let CO2 diffuse in.Water vapour and oxygen (O2) move out.
27 Stomata- open Workbook 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.SQA- State that water vapour is lost through stomata.Interpretation- the tiny pores (stomata) on the surface of a leaf allow water to be lost from the leaf.Workbookp 62 Leaf surfaces
28 Stomata- closed Workbook Activity PS When there is little water the guard cells are flaccid and less curved.This closes the stomata and keeps water in the leaf. This happens at night.GUARD CELLS are only part of lower epidermis which contain chloroplastsThey control gas exchange by closing stomata in darkness, or when too much water is being lost.Workbook Activity PSp63 stomata behaviour p82 & 83 Leaf balance
29 General structure Flat leaf blade Thin Vast network of veins Stomata Has large surface areaAbsorbs as much sunlight & CO2 as possibleThinCO2, reaches inner cells easilyVast network of veinssupplies all parts of the plant with essential substancesStructural supportBioviewer slide set?Prepared microscope slides?StomataMost in lower surface of leafGas & water exchange
30 Workbook Problem Solving Leaf veinsLeaf 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 Solvingp 80 Ringing a plant
31 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.SQA LOExplain why plants need transport systemsInterpretation- water is required for photosynthesis.Food manufacture in the leaves is needed for growth and energy by the plant.Workbook Activityp 61 Food transport diagramGiant redwood trees carry water & nutrients over 100m from the soil
32 RootsRoots have specialised cells called root hair cells, which are long and thin providing a large surface area for the uptake of water and minerals.SQA LO
33 Into the root hair cellWater passes from the soil into root hairs by osmosisDEFINITIONOsmosis is the net diffusion of water across a partially permeable membrane, from a solution with a high water concentration (HWC) to one with a low water concentration (LWC).HOW DOES IT HAPPEN?The water in the soil has a weak solution of saltsThe cell sap has a more concentrated solutionWater moves from the soil into the root hair along a water concentration gradient
35 OsmosisWhen 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).This is why plants needing water ‘droop’ and become limp- WILTED
36 Functions 1. Anchoring the plant Why? So it is not blown / knocked overHow? The roots spread out over a large area to counterbalance the structures above the soil.This also helps plants find water.
37 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.Many tiny hairs branch off the main root
38 3. Absorb water Why? Water is a raw material for photosynthesis. A root hair shown under a microscopeRoot hair cellRoot hairRoot hair cells also have thin membranes to make it easier for substances to diffuse through into the plantWhy? Water is a raw material for photosynthesis.How? Root hairs increase surface area.
39 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 TissueTransports 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.SQA LOKnow the ways which water and food move in the xylem and phloemInterpretation- water and minerals are carried from the roots to the leaves.Water and minerals are carried in tubes called xylem vessels.Food is carried from the leaves to those parts of the plant which need it for growth or energyOr to areas where it is stored.Food is carried in tubes called phloem.
40 Phloem tissue Phloem tissue Carries nutrients, e.g. sugars made by photosynthesis, all 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.
41 Sugar cane Workbook Activity Leaf Veins are Vascular Bundles. Vascular bundles are composed of Xylem, Phloem and Fibres which support and protect the xylem and phloem.SQA LODescribe the structure of phloem and xylem and identify other functions of the transport systemInterpretation- xylem and phloem are usually found close together in groups called vascular bundles.In stem vascular bundles are round the outside.In root the vascular bundles are in the centre.Vascular bundles also help give the stem support.Xylem cells are dead.The walls of xylem have rings or spirals of a tough substance called lignin.Phloem cells are alive.Phloem contains two kinds of cell: sieve tubes and companion cells.The end walls of sieve tubes have pores.Workbook Activityp 72 Structure of xylem and phloem.
42 Vascular bundles Workbook Activity Vascular Bundles in sugar cane. Left: cross-sectionBelow: detail of one bundleUse celery stalk.Workbook Activityp 73 Looking at xylem
43 Xylem & phloem in stem Bioviewers Box 78 Workbook Activity The stem of a flowering plantWorkbook Activityp 60 Water transport in plants
44 Position of vascular tissue in the stem The positions are different in stems compared to roots. In a stem they are round the outside.epidermisxylemphloem
45 Position of vascular tissues in the roots epidermisxylemphloemUse busy lizzie stem, prestained.Workbook Activityp Structure stem, rootIn roots they are found in the centre.
46 What Limits photosynthesis? Light + chlorophyllIngredientsCarbon dioxide + water oxygen + glucoseFor photosynthesis to happen all the “ingredients” need to be present.If there are inadequate ingredients photosynthesis will stop or slow down.SQA LOExplain what is meant by limiting factors and describe the main factors in the process of photosynthesisInterpretation- a limiting factor is a factor that if in short supply can cut down or limit the rate of photosynthesis.The main limiting factors in photosynthesis are carbon dioxide, light, temperature and waterThe factor that is in shortest supply will be the one that limits the rate of photosynthesis and is called a “limiting factor”.
47 Factors limiting photosynthesis Low temperatureShortage of CO2Shortage of lightLack of chlorophyll Example:A plant has plenty of water, carbon dioxide and chlorophyll, but it is night.Hence, photosynthesis cannot take place due to lack of light.Light is the limiting factor.Often this sort of information is shown in a graph…
48 A Light intensity is limiting the rate of reaction A B B CO2 is limiting the rate of reactionC The difference between the lines is due to different temperatures.p 74 The effect of increasing carbon dioxidep75 The effect of increasing temperatureWorkbook Activity
49 Quick Quiz 21. How is glucose carried from the leaves to every part of the plant?Transported in phloem tubes (water in xylem)2. Give 2 structural features of a leaf that make it a good design for photosynthesis.Large surface area, thin, stomata, veins3. Why do you think that the palisade cells are near the surface of the leaf?To absorb as much sunlight as possible in chloroplasts4. Name the cells that surround the stomatal openings.Guard cells5. The spongy mesophyll cells are loosely arranged. Explain the significance of this.Large spaces between cells allow gases to diffuse quickly6. Which 3 factors limit the rate of photosynthesis?Quantity of light, carbon dioxide, temperature
50 Helping plants to growPlants 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.
52 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.QuestionsWhy do farmers want to harvest crops quickly?What do fertilisers contain to help plants grow?
53 Signs of Nutrient deficiency in plants Lack of Nitrogen causes ..Yellowing of leaves.leaves on lower parts of the plant may dieWeak stem meaning the plant cannot grow tall.
54 Lack of Potassium causes …. 1. Yellowing of leaves2. Poor fruit growth.
55 Lack of Magnesium causes leaves to turn yellow from the bottom of the plant upwards Leaf from the top of a plantLeaf from the bottom of a plant
56 Lack of Phosphorus causes …. 1. Purpling of leaves2. Poor root growth3. Small plant sizeCopy out the diagrams from p63 Co-ordinated Biology (second Edition) showing nutrient deficiency in plants
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