Transcript
Biology Practical Notes Module 1: Our Local Ecosystem 1.1) Process and analyse information obtained from a variety of sampling studies to justify the use of different sampling techniques to make population estimates when total counts cannot be performed. Type Method Advantage Disadvantage Transect Good for environmental (terrain/vegetation) changes Observes the type of vegetation and their height. Controlled Variables: - Length of String - Intervals (e.g. a knot at every 1m). 1. Randomly select an area that you want to observe. 2. Using string, tie a knot into an even interval through the area. 3. As you walk along the transect, record the organisms and plants (including their height) that are touching the string. 4. Use a key to identify each organism. When observing changes, transect are also useful to show what Abiotic factors cause these changes e.g. sunlight, temperature, moisture, vegetation and water levels). Useful when the area is too large to do a direct investigation. You only record the organisms that are found across the transect. Therefore, the results may not be accurate so many transects need to be made. Quadrat Useful when organisms are immobile (don’t move/slow) Observes the types and number of species that are found within the frame. The number is either counted or an estimated percentage is made. Controlled Variables: - Size of Quadrat - Shape of Quadrat 1. Place the frame (square/rectangle etc.) is randomly chosen areas within the study site. 2. Record the number of organisms(s) found within the quadrat. 3. Calculate the average number of the organisms(s). 4. Multiply this number by the total area of the site in order to get the organisms(s) abundance in the area. The number of an organism found within the quadrat can be calculated using this formula: Useful for estimating the population of stationary organisms, plants and animals. It is a more specific way of estimating the population of a species than using transects. You only record the organisms that are found within the quadrat. It does not make it an accurate estimate of the entire study site. Type Method Advantages Disadvantages Capture – Recapture Useful when determining the abundance of mobile (moving) animals. Observes the number of animals through a period of time. Controlled Variables: - Number of times collected (once) - Organism tagged - Amount recaptured - Amount tagged 1. Capture a sample of the population of a species(e.g. 10 animals) 2. Tag the sample of the population (e.g. microchip, rings) 3. Release the sample of population back into the wild. 4. Wait for a period of time. 5. Recapture a sample of the population of the same species. 6. Count the number of tagged animals in the second sample. 7. Estimate the total population by using this formula: It is the main method that is used to estimate the distribution of mobile (moving) populations. Knowledge about the biology of the organisms and some idea of their range and mobility is needed. Daily and seasonal changes in the population will affect your method. If you are not aware of the changes, you may carry out the method at a time when the population has migrated. Can be dangerous to individuals or have an impact on them in some way. Tagging the sample can be expensive and labour (physically) intensive. It requires ongoing monitoring and vital data collection. Example of a Transect Example of a Quadrat Observation of an Onion Cell Under a Light Microscope Prac 1.2) Perform a first-hand investigation to gather first-hand information using a light microscope to observe cells in plants and animals and identify the nucleus, cytoplasm, cell wall, chloroplast and vacuoles. Practical – Pg. 71 – Observing Cells Using a Light Microscope Aim: To observe a plant cell under the light microscope. Method: Steps: 1. Remove the outer papery skin of the onion . 2. Peel off one layer of the onion and place the layer on a white tile, with the shiny side facing up. 3. Using forceps - pull away a small section of its shiny outer skin. 4. Place the section on a cover slide . 5. Add a drop of iodine to stain the section and then cover it with a cover slip . 6. Soak up any excess iodine with a piece of paper towelling. 7. Observe the section under the microscope. Results: Chemical Substances Prac 2.1) Plan, choose equipment or resources and perform a first-hand investigation to gather information and use available evidence to identify the following substances in tissues: Prac 2.4 – Pg 86 – Chemical Substances Found in Tissues Aim: To identify the availability of glucose, starch, lipids, proteins, chloride ions and lignin in tissues. Method: Chemical Compound Test Indication Glucose Tes Tape (pink at the end) Paper changes from pink to purple. Benedict solution (blue)/water bark Changes colour to bright orange. Starch Iodine solution (light brown) Changes to dark blue/black Lipids Brown paper bag Goes translucent Proteins Biuret test (light blue) Changes colour to lilac/purple Chloride ions Silver Nitrate solution White precipitate created Lignin Toluidine blue solution/phlorglucinol and HCL Lignin will stain blue. WARNING: Careful when using Silver Nitrate. Wear an apron as it can stain clothing. Results: Chemical Compound Test Using: Amount Indication Glucose Tes tape 1 Strip End of paper changed from pink to purple. Benedict Solution 3-5 drops in warm water bark Changed colour from blue to bright orange in 2 minutes. Starch Iodine Solution One drop Instantly turns black from cloudy white. Proteins Biuret test 3-5 drops Changed colour from light blue to lilac (purple) in a few minutes. Lipids Brown paper bag 1 piece Turned translucent instantaneously. Chloride ions Silver Nitrate solution 3-5 drops Formed a white precipitate instantly. Lignin Phlorglucinol and Hydrochloric acid 3-5 drops The end of the match stick turned bright pink instantaneously. Glucose Proteins Starch Chloride Ions Lipids Lignin
