Biology B2.2 Organisms in the environment

Using This Guide:Key terms are in bold and definitions at the side. Processes or parts linking to other resources are highlighted in red and the link will be close to it in green.

Photosynthesis The process of photosynthesis can only be carried out by green plants and algae. Chlorophyll in the plants mesophyll absorbs the Sun's light energy. The equation for photosynthesis is: Carbon Dioxide + Water + ( light energy ) --> Glucose +Oxygen

Key Terms the words highlighted in bold are important and you must know the definitions for your exams. The definitions paper in the same order as they appear in the main text here.Light Energy -A form of energy plants use in photosynthesis it is turned into chemical energy.Glucose -A simple sugar needed for respiration produced through photosynthesis in plants and found in food for mammals.Variegated -(Botanical) A plant or leave that is patterned with a different colour commonly green and white.Limiting Factors -(Botanical) Factors that reduce the amount of something happening possibly photosynthesis or respiration.Mineral Ions -Metallic substances found in the soil crucial to the survival of a plant.Nitrate Ions -A substance which is needed by a plant or algae cells to make proteins, found in the soil or water.Biomass -Biological matter from living organisms the mass of these.Quantitive Sampling -Sampling which records the numbers of organisms rather than just the type. This method includes counting species in the quadrat.Transect -A line or area along which ecological measures are made.Quadrat -A square wooden or metal frame placed in an area for ecological studies.Sample size -The size of a sample in a investigation.Valid -Suitability of the investigation procedure to answer the question being asked. How reliable are they?Repeatable -A measurement is repeatable if the original experimenter repeats the investigation using the same method and equipment and obtains the same results.Reproducible -A measurement is reproducible if the investigation is repeated by another person and the same results are obtained.

Study Tip! Make sure you know the word equation for photosynthesis it often comes up in exams.

What Actually Happens? Carbon dioxide is taken in by the leaves, and water is taken up by the roots. The chlorophyll traps light energy needed for photosynthesis. This energy is used to convert the carbon dioxide and water into glucose. Oxygen is realised as a by-product. Some of the glucose is converted into insoluble starch for storage. By testing leaves for starch we can show that photosynthesis has occurred. Variegated leaves have patches of green (with chlorophyll) and patches of white (without chlorophyll) only the green patches show starch is present.

Iodine Test The iodine test sees if starch is present this is useful when proving that photosynthesis has occurred. Colourless leaves are dipped in iodine, the browny/orange solution will turn blue if starch is present. An example often used is with variegated leaves which have green and white patches only the green will turn blue.

Limiting Factors There are three main limiting factors when it comes to plants, these are conditions that put a cap on the rate of photosynthesis. The reactants are obvious choices - level of carbon dioxide and light intensity but also temperature effects the rate of photosynthesis. Therefore plants work best when they have enough light, carbon dioxide and water, and are kept at a suitable temperature. However increasing the temperature too high will denature the enzymes and the plant will die.

How plants use glucose The uses of soluble glucose- Converted into insoluble starch for storage. Used for respiration. Converted into fats and oils for storage. Used to produce cellulose which strengthens cell walls. Used to produce proteins. Plants and algae also need mineral ions and nitrate ions in order to produce proteins.

Photosynthesis in Industry Plant growers always try to create the best conditions to grow plants. They have to evaluate benefits of increasing growth to cost. Greenhouses and poly tunnels can be constructed to control conditions. It can be expensive to control the conditions so the plant grower must compare biomass inside and outside.

Organism Distribution Physical factors affecting the distribution of organisms; temperature, availability of nutrients, amount of light, availability of water, availability of oxygen and availability of carbon dioxide.

Measuring Distribution Quantitive data can be used to describe how physics features affect organism distribution. This can be along a transect or random quantitive sampling. Both methods involve using a quadrat to measure distribution. Sample size is important it needs to be representative of the overall place.We must consider if the investigations is and its results are valid, repeatable and reproducible.

Test yourself !When you can answer these five questions first time you know the topic!1 Name the solution used to test for starch.2 Give three physical factors affecting the distribution of plants.3 What is meant by the term limiting factor?4 How can you use a quadrat on a transect?5 What is meant by 'reproducible'?1) iodine solution2) three from; temperature, availability of nutrients, water, oxygen, amount of water3) factors such as light , temperature and carbon dioxide , which may prevent levels of photosynthesis increasing above a certain level4) a line is marked between two points and then the quadrat is placed a regular intervals along the line. the organisms spent are counted 5) a measurement is reproducible if the investigation can be carried out by another persona and gather the same results