Directorate: Curriculum FET SUBJECT and GRADE TERM 1 TOPIC AIMS OF LESSON RESOURCES Life Sciences Grade 10 Week 1 Orientation to Life Sciences At the end of this lesson you should be able to know the following: • What Life Sciences is • The nature of science and • how science works Paper based resources Digital resources Refer to: • Your textbook section on how science works INTRODUCTION • • • Click on link below to watch a Telematics video on the scientific method: https://bit.ly/2nJnBel Life Sciences is the study of living things from molecular level to their interactions with one another and the environment Life is characterized by changes over billions of years Living systems exhibit levels of organization from molecules to biomes CONCEPTS AND SKILLS The nature of science: • Science involves contested knowledge, and non-dogmatic inferences based on evidence and peer review. How does science work? Science is based on: • fundamental knowledge built on scientific evidence and verified findings (articles that are published in journals or at conferences: peer review); • observing; • investigating; • making measurements and understanding the importance of scaling; • collecting and presenting data in the form of drawings, written descriptions, tables and graphs; • understanding the limitations of scientific evidence; • identifying patterns and relationships in data; • communicating findings; and • taking societal aspects of scientific evidence into account. Know the meaning of instructional verbs in test and examination questions e.g. Instructional verb Name Differentiate Tabulate Describe Explain Compare Meaning Give the name of something Use differences to qualify between two or more categories Draw a table and indicate the answers as direct pairs. State in sentences the main points of a process Give your answer in a cause-effect or statement and reason sequence Give similarities and differences between concepts Examples of scientific skills: Answer the following questions: (a) Relationship between structure and function: Question 1: • Different structures (cells, tissues, organs and systems) perform specific functions e.g. the epidermal cells of a leaf allow gaseous exchange to occur in a leaf. These cells are bean-shaped and contain chloroplasts. 1. An investigation was carried out to study the effect of light intensity on the rate of water loss from the leaves of a plant. • (b) Biological drawings: You will be expected to make drawings of your observations and interpretations in Life Sciences. • Use the following basic guidelines when you make drawings: • Do all drawings in pencil and label them in blue or black ink. • Drawings must be an appropriate size so that all labelled parts are clearly visible • Label lines must be drawn with a ruler and they must not cross each other • Label lines must point to the exact labelled part • A drawing must have an appropriate heading • Apparatus X (shown in the diagram below) was used to measure the rate of water loss from the leaves at several light intensities. At each light intensity, the apparatus was left for 15 minutes before starting measurements. The water loss was recorded in the dark and at four different light intensities. (c) Presentation of data Scientific data can be presented in various ways e.g. in the form of a table or a graph. Tables: • Tables are used to record the results of an investigation • A table must have an appropriate heading • A table is divided into rows and columns • Each column and row may have its own heading with units if applicable. • Rows run from left to right across the table. • Columns are the vertical blocks of a table. • The independent variable is normally in the lefthand column • The dependent variable is normally in the righthand column Number of children born with sickle cell disease in some regions in a particular year REGION NUMBER OF CHILDREN BORN WITH SICKLE CELL DISEASE Democratic Republic of 39 746 Congo USA 90 128 Nigeria 91 011 1.1 Formulate a hypothesis for this investigation. The results of this investigation are shown in the table below. 1.2 State the dependent variable in the above investigation. 1.3 Draw a line graph to represent the results in the investigation 1.4 Describe ONE way in which the reliability of the results obtained at each light intensity could have been improved. Question 2 2. A scientist knew that as one moves to higher altitudes (height above sea-level), the air has less oxygen. She therefore wanted to investigate the relationship between altitude and the number of red blood corpuscles in a person's blood. Types of graphs: • Line graphs show the relationship between two types of information where the independent variable is continuous. Line graphs are useful in showing trends over time and are often used for biological data. 2.1 Formulate a hypothesis for the scientist’s investigation. 2.2 State the dependent variable. 2.3 State the independent variable. Question 3 3. An investigation was done to determine the effect of temperature on the growth of grapevines in South Africa. The table below shows the data on the mass of grapes produced by the vines at different temperatures. Study the results in the table and then answer the questions that follow: • Bar graphs show different categories of data and are used when the independent variable is not a set of continuous numbers or continuous groups (discontinuous data). They are best used to compare values across categories. Temperature (ºC) Mass of grapes produced (kg) 10 15 20 25 30 0,5 1,0 1,5 2,5 2,0 3.1 Name the dependent variable for this investigation. 3.2 Name the independent variable for this investigation. 3.3 Use the data given to explain the relationship between temperature and the mass of grapes produced. 3.4 Draw a bar graph to represent the results of this investigation. • Histograms have connected bars displaying continuous data. They are used when the values of the independent variables are continuous but fit into categories or groups that follow on after each other. Question 4 4. A group of learners noticed that some areas of the sports fields were covered in standing water, some areas were damp but not saturated; while other areas appeared to be relatively dry. Puzzled by this observation, they set out to investigate why this was so. When the areas had dried out, they took soil samples from the different areas (A, B and C) and performed an experiment. The results of their investigation are shown in the table. Soil samples A B C 50 g 50 g 50 g Volume of water added 100 ml 100 ml 100 ml Volume of water retained 30 ml 82 ml 59 ml Mass of soil sample 4.1 Formulate a possible hypothesis for the above investigation. 4.2 What logical deduction could be made from the results of their investigation with respect to the different soil samples (A, B and C) found on their sports fields? 4.3 State THREE ways in which the validity of this investigation could be increased. • Pie charts are circular charts used to compare parts of the whole. They are divided into sectors that are equal in size to the quantity represented. They are used for discontinuous data. Formulating a hypothesis: A hypothesis is an attempt to explain some event or observation using whatever information is currently available. It is a testable statement that may be accepted or rejected. A hypothesis must: • • • • have two variables (dependent and independent variables); state the relationship between the two variables; be testable; and state the independent variable first (cause) and then the dependent variable (effect). Study the following example of a hypothesis question: A scientist conducted an investigation to determine the effect of sulphur dioxide on the growth of young roots of bean seeds. He took three gas jars and placed a germinating bean seed in each jar. A different number of sulphur dioxide bubbles were passed through each jar. Each jar was sealed with a cover glass. The increase in length of each young root was measured after 5 days. Formulate a hypothesis for the above investigation. If germinating bean seeds are exposed to sulphur dioxide the growth of the roots of beans will slow down ✓✓ OR If germinating bean seeds are exposed to sulphur dioxide the growth of the roots of beans will increase✓✓ OR If germinating bean seeds are exposed to sulphur dioxide there will be no growth of the roots of beans✓✓ Identify variables: • Controlled / fixed variable – refers to the factor/s that should be kept constant so that the results of an investigation can be considered valid. • Independent variable – refers to the factor that is being investigated. This factor is usually manipulated by the investigator either at the start of or during the course of the investigation. The independent variable appears on the X-axis of a graph. • Dependent variable – refers to the effect of the independent variable. This effect is usually measured in some way and appears on the Y-axis of a graph What is reliability? • The idea behind reliability is that any significant results of an investigation must be more than a once-off finding and be repeatable. • Other researchers must be able to perform exactly the same experiment, under the same conditions, and generate the same results. • This would reinforce the findings of the experiment and ensure that the wider scientific community accepts the hypothesis. • If you are asked how the reliability of an investigation could have been improved, the following answers apply: Repeat the investigation OR Increase the sample size. What is validity? • Validity questions show how the experiment/investigation was carried out. It is important to be sure that all the factors/variables have been controlled/ fixed except the variable/factor being tested. • In questions which require you to suggest some factors that might have decreased the validity of an investigation, your answers should centre on the criticism of the scientific process; for example, some factors/variables that were not fixed/controlled when carrying out the investigation. Common errors made by learners in examinations: • Unable to answer questions based on scientific investigations • Unable to make appropriate drawings and draw appropriate graphs ACTIVITIES/ASSESSMENT • Complete the questions given in this lesson CONSOLIDATION • Work through the questions and activities on the scientific method using past examination papers • Reflect on your learning and understanding of this topic and assess your progress VALUES By studying this section, you will develop scientific skills and ways of thinking scientifically that will enable you to see the flaws in pseudo-science in popular media. You will also develop an ability to critically evaluate and debate scientific issues and processes.
