Photosynthesis & How Plants Use Glucose
- Photosynthesis can only be carried out by green plants and algae.
- Chlorophyll in the chloroplasts absorb light energy
- CO2 is taken in by leaves, and water by roots
- Chlorophyll traps the light energyneeded for photosynthesis.
- The energy is used to conver CO2 and water into glucose.
- Oxygen is released during this process
- Some glucose is converted onto insoluble starch for storage.
- Testing leaves with iodine shows the starch in a leaf. Green patches turn blue-black.
- The glucose produced can be:
- converted into insoluble starch for storage
- Used for respiration
- Converted into fats and oils.
- Used to produce cellulose to strengthen cell walls
- Used to produce proteins
- Plant and algal cells also need mineral ions e.g. nitrate ions to produce protein.
- They are absorbed from the soil
- Algae absorb nitrate from the water they live in.
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- Lack of light slows down photosynthesis as light provides energy for the process.
- Plants shaded by trees may be limited too, even on a sunny day
- If cold enzymes don't work effectively and slow down the rate of photosynthesis
- Too little CO2 will slow down photosynthesis e.g. in a green house on a sunny day, plenty of light but not enough CO2
- Limiting factor is anything that slows down the rate of photosynthesis
- When doing photosynthesis experiments you must be aware of other limiting factors when testing one as the others need to be controlled.
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Advantages of Photosynthesis
- Plant growers control the environments for their plants to get the best results.
- They have to evaluate the benefits of increasing growth with the increased cost.
- Greenhouses and polytunnels can be constructed to grow plants in an enclosed space.
- The greenhouse heaters and lamps increases PhotoSyn but may stop if temp or light temperature is too high.
- Adding CO2 will also increase photosynthesis
- Nitrate ions can be added to soil to ensure that plants get the proteins they need.
- It can be expensive to provide a suitable temperature, light and CO2
- The grower has to compare the biomass of plants grown inddors and outdoors without these extra factors.
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Organisms In Their Environment
- Living organisms form communities. The relation between the communities is important to understand.
- The relationships may be influenced by external factors.
- Physical factors that may affect the distribution of organisms are:
- Temperature, e.g. arctic plants are small that limits number of plant eaters in that area.
- Availability of nutrients, no mineral ions means no plants grow ergo no animals can feed on the plants.
- Amount of light, few plants on forest floor as light is blocked by trees.
- Shaded plants often have broader leaves or more chlorophyll.
- Availablilty of water, no water = no growth = no plants for animals
- Availability of oxygen, most fish need high levels of oxygen dissolved in water to survive
- Availability of CO2, no CO2 = no plant growth ergo no food for animals.
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Measuring the Distribution of Organisms
- Quantative data can be used to describe how physical factors might be affecting the distribution of organisms in a particular habitat
- Quantative data can be obtained by:
- Random quantative sampling using a quadrat
- Sampling along a transect.
- A quadrat is a square frame made of metal or wood that can be subdivided into a grid.
- If several quadrats are placed randomly in a field the investigstor can count the numer of plants or animals in each quadrat.
- This can be used to estimate e.g. daisies in a whole field
- Sample size is important. ina large field enough random quadrats must be placed to be sure the sample represents the whole field.
- The estimate amount is usually given as a mean per square metre.
- Transects are not random. A line is marked between two points.
- A quadrat can be placed every 5 metres along the line and the organisms counted.
- Physical factors could also be measured at each quadrat point.
- This method supplies a lot of info about the habitat and organisms in it.
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How Valid is the Data?
- Investigations about the distribution of organisms in their environment can be very difficult
- they are done over a long period of time and not all variables can be controlled.
- Sample size is an importnat factor in order to get valid, repeatable and reproducible results.
- If the sample is too small it may not be representative.
- The larger the sample size, the more we trust we can have in the data generated in an environmental investigation.
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