B4: It’s a Green World • Plant Structure and adaptations • Osmosis and plant support • Transpiration and reducing water loss • Plant Minerals • Pyramids of number and biomass • Farming • Decay • Carbon and Nitrogen Cycles How to use this PowerPoint: Look at each slide and try to learn the information and key words for each topic. Then try the revision questions and mark them yourself…. Easy!
B4a Plant Structure and Adaptations • Leaves are made of the epidermis and waxy cuticle, palisade layer, spongy layer veins, stomata and guard cells • Palisade cells have many chloroplasts for photosynthesis • Guard cells surround the stomata (holes in the underside of the leaf) and can open or close them to let water out and gases in • Leaves need water, carbon dioxide and light for photosynthesis Adaptations for Photosynthesis include: Broad leaves = large surface area for sun Thin leaves for gas diffusion Chlorophyll = pigment to absorb sunlight Veins to transport sucrose and water Stomata = allow gases to diffuse (oxygen and carbon dioxide both in and out) Epidermis = transparent ‘skin’ on top of leaf allowing light through Palisade layer = for photosynthesis Air spaces = gas diffusion
B4b Osmosis and Plant Support • Diffusion is the random movement of particles from a high to low concentration • Osmosis is the same as diffusion, except it only involves water • Water will move from where there is lots of water molecules (a dilute solution) to a solution that is concentrated with salt (a concentrated solution) with less water in it. • Water also travels through a semi (or partially) permeable membrane (a thin skin with tiny holes big enough for water) • We say water moves down a concentration gradient from high to low Animal cells have a concentrated cytoplasm with many salts etc- when they are in pure water, the water moves in and they burst (lysis) when put in a really concentrated solution, water moves out of the animal cell and it shrinks (crenated) Plant cells have a concentrated cytoplasm with many salts etc- when they are in pure water, the water moves in but they don’t burst as they have a cell wall (turgid) When put in a really concentrated solution, water moves out of the plant cell and the cytoplasm shrinks (flaccid then plasmolysed) Plant cells rely on this ‘turgor pressure’ to keep them upright like an inflatable chair, if you don’t water them all their cells become flaccid and the leaves go floppy- to absorb water the roots have lots of tiny root hair cells to give a bigger surface area
Plants also have phloem tubes that carry sucrose from the leaves all around the plant- this is called translocation- phloem is alive B4c Transport in Plants • Water enters through roots and root hair cells by osmosis • Water then moves into the xylem which are: dead, long, narrow and join up end to end like a drainpipe, they are also made of lignin which supports the plant and stops water leaking out • Next, the water moves up the xylem vessels and evaporate from the cells in the leaf into the air spaces, then diffuses out of the stomata at the bottom surface of the leaf- • The whole movement of water up the plant and evaporating at the leaf is called transpiration • A potometer (shown below) can be used to measure transpiration (water uptake) Cacti cut down transpiration by having sunken stomata and rolled leaves in dry places • Transpiration can be speeded up by: • Hot days = faster evaporation • More light = stomata are open more • Air movement = wind blows the water away so more evaporates (greater diffusion gradient) • Low Humidity = the drier the air, the faster evaporation Stem Root
B4d Plants Need Minerals Too • Plants need the following minerals: • Nitrate for proteins, growth and repair NO3- • Phosphate for DNA and cell membranes • Potassium for enzymes in photosynthesis • Magnesium for chlorophyll Fertilisers can be added to soil to help plants grow better NPK fertilisers contain nitrogen, phosphate and potassium Adding fertilisers can be bad as it leads to eutrophication Framers can use GPS to see where to apply fertiliser Plants absorb minerals through their roots from a low concentration in the soil to a high concentration- this needs energy as it is against the concentration gradient- this is called active transport • nitrate – poor growth and yellow leaves; • phosphate – poor root growth and discoloured leaves; • potassium – poor flower and fruit growth and discoloured leaves; • magnesium – yellow leaves.
Food chains show the direction of energy flow • The plant is always the producer as it produces food by photosynthesis • All the other organisms are consumers, the first one in the chain is the primary consumer, then the secondary and tertiary B4e Energy Flow A pyramid of numbers show how many organisms there are. They can be shaped strangely A pyramid of biomass shows the amount of biomass (the amount of living material) Biomass (living material) is a renewable fuel It can be burnt to heat water in electricity power plants Fast growing trees are grown then harvested by coppicing (cutting trees then letting them re-grow) Coppicing is carbon neutral- it doesn’t add any extra carbon dioxide into the environment Number Biomass Biomass can be used to make biogas by putting yeast and bacteria inside a digester where fermentation takes place Bioethanol can also be made by letting yeast ferment biomass- this can be used for cars in developing countries At every stage (trophic level) of the food chain or pyramid, energy is lost, this is because the animals use some energy to move around or respire. Some is also lost through egestion (poo)
B4f Farming There are many problems after using chemicals on fields: Pesticides kill animals that you don’t want to kill and affects the food chain Pesticides and herbicides can be harmful to humans and make them ill if sprayed near homes, or if they remain on fruit and vegetables Some pesticides are persistent like DDT that can build up in an animals body and cause death- we now use biodegradable pesticides that can be broken down • Intensive farming means getting the highest yield possible from your land by putting fertilisers etc onto crops • Weedkillers or herbicides kill plants, selective weedkillers only kill certain plants and don’t harm the others • Pesticides kill pests • fungicides kill fungus • insecticides kill insects like • aphids (greenfly) Biological control: using predators to kill pests + No harm to food chain, lasts for a long time, and only one type of prey harmed - Pest not completely gone, might not work, predator might leave or become a pest itself
B4g Decay • Food can be preserved by: • canning - boiling to kill microbes then sealing in air tight can • cooling/ freezing - slowing down the microbes chemical reactions • drying – deprives microbes of water so they can’t grow • Adding salt/ sugar – water moves out of the microbes by osmosis • adding vinegar – to acid for microbes’ enzymes • Biodegradable items are things that can decay like paper, bodies and poo • Micro-organisms need: water, oxygen and a suitable temperature for their enzymes in order to decay materials Making compost requires food waste e.g. potato peelings, air spaces, warm temperature and a little water Decomposers = all organisms that cause decay Detritivores = big decomposers like worms and woodlice- create a larger surface area for smaller decomposers Saprophytes = fungi that have threads called hyphae, they secrete enzymes and digest food • It is important to treat sewage as: • it might contain pathogenic (disease causing) bacteria • It contains food for bacteria to reproduce • it contains chemicals which may harm other living things • sewage is changed into sludge, methane and clean water called effluent that goes back into the sea
B4h Recycling • The Nitrogen Cycle: • Nitrogen goes into the atmosphere through denitrifying bacteria and lightning • Nitrogen is removed from the atmosphere by nitrogen fixing bacteria and nitrifying bacteria- soil bacteria and fungi convert protein and urea to ammonia • The Carbon Cycle: • carbon goes into the atmosphere through respiration, decomposers, detritivores, burning fossil fuels, volcanoes • Carbon is removed from the atmosphere by photosynthesis by plants and phytoplankton, calcium carbonate shells from sea creatures forming limestone under the sea bed Nitrogen fixing bacteria: turn nitrogen gas into nitrates e.g. rhizobium bacteria in root nodules Nitrifying bacteria: turn ammonia into nitrates e.g. nitrobacter Denitrifying bacteria: turn nitrates into nitrogen gas