B4 It’s a Green World Biology Revision

Habitats Plants need different amounts of light, water and minerals. Factors such as soil pH, temperature, light intensity and the availability of water can be measured. Samples are taken to get a picture of what the habitat is like

Measurements Quadrats (identification keys; percentage growth) Random (removes bias) Transect (how species change across landscapes) Light meters

Mark, capture and recapture Trap animals and mark in a harmless way Release and then recapture Record animals with and without marks number in 1 st sample x number in 2 nd sample number in 2 nd sample with marks

Photosynthesis Capturing energy from sunlight, used to make molecules for growth – sugars, starch, enzymes and chlorophyll. These molecules feed others in the food chain

Equation light 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 chlorophyll Glucose is made up of CHO so is a carbohydrate Photosynthesis takes place in chloroplasts. Contain chlorophyll which absorbs light and uses the energy to start photosynthesis Energy from light splits water molecules into H2 and O2 atoms. The H2 is combined with CO 2 from the air to make glucose. O2 is released as a waste product

Glucose and Starch Glucose can be converted into starch for storage or cellulose to make new cell walls. Both are polymers of glucose Glucose can also be built up into fats, proteins and chlorophyll Glucose molecules are broken down by respiration, releasing energy to power chemical reactions in cells

Storage Glucose made by photosynthesis Glucose transported from leaves together cells where is stored until it is needed for respiration. Water would move to this area unless stored as starch Insoluble starch grains

4a Who Planted that there? Plants carry out photosynthesis in leaves: Leaves are adapted by: Broad – large s.a. Thin – short diffusion distance Chlorophyll – absorb light Veins – support & transport Stomata – gas exchange Transparent epidermis Palisade contain most chloroplasts Air spaces in spongy mesophyll Large internal s.a.

Diffusion Molecules of liquids and gases move around randomly, collide with each other and spread out. They move from areas of high to low concentration Passive process To increase diffusion: Greater conc gradient Shorter distance Larger surface area

Osmosis Special type of diffusion Move water molecules in and out of cells across a partially permeable membrane Water moves from area of high concentration to area of low concentration of water molecules Drives uptake of water Lack of water - wilting

4b Water, water everywhere? Effect of osmosis on plant cells: Inelastic cell wall provides support & prevents cell bursting

4b Water, water everywhere? Osmosis – the net movement of water across a partially permeable membrane from an area of high water concentration to low as a consequence of random movement of particles Effect of osmosis on animal cells: Lysis Crenation

4c Transport in Plants Vascular bundles – arrangement of xylem & phloem XylemPhloem TranspirationTranslocation Movement of water & minerals Movement of dissolved sugar From roots to leavesFrom leaves to rest of plant Vessels – thick cellulose strengthened cell wall, dead cells so hollow lumen Vessels – column of living cells

4b Water, water everywhere? Plants use water to: Keep cool Transport minerals Photosynthesise Keep cells firm & supported Water is: Absorbed through root hair cells (large s.a.) Transported through stem Lost by evaporation/transpiration from leaves Water loss reduced by: Waxy cuticle; small number of stomata on upper surface; guard cells

4c Transport in Plants Transpiration – diffusion & evaporation of water from a leaf Rate is effected by: Light – more light increases p/s & transpiration Temperature – hotter increases p/s & transpiration Air movement – air removes water vapour from around leaves, maintaining diffusion gradient Humidity – high water vapour in air reduces diffusion gradient Potometer measures rate

Need Nitrogen! Proteins are long chains of amino acids Nitrogen needs to be combined with carbon, hydrogen and oxygen from glucose made in photosynthesis Absorbed from soil as nitrate ions Absorbed by root hair cells

What else do plants need? Magnesium to make chlorophyll Phosphates to make DNA Proteins are needed to build cells and make enzymes, so nitrates are needed in the highest quantities Fertilisers contain minerals such as phosphates and nitrates

4d Plants need minerals too Minerals are absorbed by root hairs by active transport – using energy from respiration to move substances against concentration gradient MineralPurposeDeficiency NitratesAmino acids/proteins for growth Poor growth, yellow leaves PhosphatesDNA & cell membranes, respiration & growth Poor root growth & discoloured leaves PotassiumEnzymes for respiration & photosynthesis Poor flower & fruit growth, discoloured leaves MagnesiumChlorophyllYellow leaves

Active Transport Nitrate ions are at a higher concentration inside the root cells, compared to the surrounding soil Diffusion should move ions out into soil. Plants use active transport to overcome this Cells use energy from respiration to transport molecules across the membrane

Yields The amount of product a farmer has to sell Limiting factors of photosynthesis – temperature, light intensity, carbon dioxide, water and chlorophyll Stomata may close to conserve water, but stops carbon dioxide entering the leaf

4f Farming Intensive Farming – to produce as much food as possible from the land, plants & animals available Improves energy transfer efficiency Farming MethodReduction of energy transfer Problems Pesticides: herbicide, insecticide, fungicide To competing plants & pestsPesticides bioaccumulate in food chains or harm non target organisms FertilisersEutrophication Battery farming/fish farming Limited movement Temperature control Moral/ethical – poor quality of life Spread of disease

4f Farming Alternatives to intensive farming Hydroponics – growing plants in solution without soil Organic Farming – high quality produce whilst maintaining welfare of animals & minimising environmental impact AdvantagesDisadvantages Minerals added can be carefully controlled Expensive addition of fertilisers Reduced risk of diseaseLack of support/anchorage AdvantagesDisadvantages Food uncontaminatedLess efficient – crops lost Limited soil erosionManure takes time to rot & doesn’t provide specific balance of minerals Biodiversity promotedBiological control of pests difficult to control & expensive Animal welfare

4g Decay Breakdown of complex substances into simpler ones Detritivores – feed on dead organisms or waste (detritus), form larger surface area – e.g. worms, woodlice, maggots Decomposers – feed on waste left by detritivores Saprophytes – secrete enzymes on to material then absorb digested products

4g Decay Rate effected by: 1. Temperature – microorganisms work best at 40°C, but enzymes denatured above this 2. Oxygen – needed for respiration 3. Water – grow best in moist conditions Food Preservation MethodExplanation CanningSealed to remove oxygen & prevent entry of microbes CoolingLow temperatures slow growth DryingReduces moisture needed for growth Preserving (salt/sugar)Conditions are too concentrated for survival Pickling in vinegarLow pH denatures enzymes in microbes