"Chapter 1 The Nature of Life Science"
Chapter 1 The Nature of Life Science The Big Idea Scientists use scientific processes to study the patterns of natural events and to solve problems. Section 1 Asking about Life Key Concept Asking questions is the first step in a scientific investigation.. Starting with a Question • Asking questions is the first step in a scientific investigation. • Life science is the study of living things. • Observing the living world around you is often the best source for questions about life science. Research • Some questions can be answered by doing research. • Information for research may come from a knowledgeable person, print resources, or electronic resources such as the World Wide Web. • When conducting research, be careful to use only reliable sources of information. Observation and Experimentation • Some questions can be answered by making careful observations. • Other questions can be answered by doing an experiment. • An experiment should be carefully designed to answer a specific question. Why Ask Questions? • Life science investigations can affect you and all other living things. • Life science investigations have led to cures for diseases like polio. Life scientists continue to fight diseases like AIDS. • Life science investigations have helped to feed the world by finding better ways to produce and store food. 1 • Life scientists study environmental problems in search of solutions. • Problems like pollution and habitat loss are often the result of the misuse of natural resources. • Life science investigations can help develop plans that will reduce pollution and protect wildlife habitats. Review Tip Thinking About Your Perspective How does science affect your life? Why is it useful to learn about science? Section 2 Scientific Methods Key Concept Scientific methods are used to investigate questions and to solve problems. What are Scientific Methods? • Scientific Methods are the ways in which scientists follow steps to answer questions and solve problems. • All life scientists share a curiosity about the natural world and similar methods to investigate it. • Scientists may use the same steps in their investigations, but not always in the same order. Ask a Question • An observation may be hard to explain or out of the ordinary. • Such an observation can lead to a question. • Looking for answers may lead to more observations and more questions. Make Observations • Observations must be made with great care and attention to details. • Observations are only useful if they are accurately made and recorded. • Records of observations include measurements, tables, photographs, and written descriptions. 2 • Any information gathered through the senses is an observation. • Some typical observations include measurements of length, volume, time, speed, or temperature. • Observations can describe the color, shape, or behavior of an organism. Form a Hypothesis • After asking questions and making observations, scientists may form a hypothesis. Sometimes observations lead to several hypotheses. • A hypothesis is a possible explanation or answer to a question. • A hypothesis needs to be testable. • After forming a hypothesis, a scientist usually makes a prediction. The prediction is usually stated in an if-then format. • The prediction is used to set up an experiment to test the hypothesis. Test the Hypothesis • Scientists conduct controlled experiments to test their hypotheses. • A controlled experiment tests only one factor at a time and consists of a control group and one or more experimental groups. • A factor is anything in an experiment that can influence the experiment’s outcome. • In a controlled experiment, every factor must be kept the same except for the one factor being tested. The one factor that is tested, or changed, in an experiment is called the variable. • The group of test subjects that includes the variable is called the experimental group. The group that does not change is called the control group. The only difference between the control group and the experimental group is the variable being tested. • In addition to carefully controlled factors, a good experiment should test many individuals. When scientists test many individuals, and repeat the experiment several times, the results are more certain. Analyze the Results • After scientists finish their tests, they must analyze the results. 3 • Data are often organized into graphs or tables. This helps scientists focus on the effects of the variable being tested. Draw Conclusions • After scientists analyze the results, they can draw conclusions about whether the results support their hypotheses. • When the results do not support the original hypothesis, scientists still learn from the experiment. • A single experiment rarely answers a complex question. Each experiment builds on prior knowledge, and suggests areas of future study. Communicate Results • After scientists complete an investigation, they communicate their methods, results, and conclusions. • By communicating with written reports and oral presentations, scientists allow other scientists to repeat their work to see if the results are the same. • Sharing information may also help other scientists with their own investigations. In this way, the scientific methods help strengthen our knowledge. Review Tip Thinking about Different Perspectives Imagine that you are a detective investigating a crime. Describe the scientific methods you could use to solve your case. Section 3 Tools and Measurement Key Concept Scientists select and use tools and technology to perform tests and collect data. Technology in Science • The application of science for practical purposes is called technology. • Selecting and using technology properly is an important part of scientific work. Computers, Calculators and Binoculars • Calculators and computers are valuable tools that allow scientists to make calculations and share data. 4 • Binoculars can help you make observations from a distance. Microscopes • A compound light microscope is an instrument that magnifies small objects so that they can be seen clearly. It is a common tool in a life science laboratory. • An electron microscope uses tiny particles called electrons to produce magnified images. • Images produced by electron microscopes are extremely detailed, but organisms cannot be viewed while they are alive. • Scanning electron microscopes produce 3D images. Transmission electron microscopes produce flat images. Measurement • Making accurate measurements is an important skill in science. • The International System of Units (SI) is a global measurement system. Scientists use SI units so that their work can be shared and compared more easily. • SI units are based on the number 10 rather than parts of the body or other objects. Length and Area • Length is measured in meters (m), which can be divided by or multiplied by factors of 10. • Area is a measure of how much surface an object has. Area can be calculated from measurements such as length and width. • Area is stated in square units, such as square meters (m2) or square kilometers (km2). Volume • Volume is the measure of the size of something in three-dimensional space. • The volume of liquids is usually described in liters (L). One cubic meter (1 m3) is equal to 1,000 L. One cubic centimeter (1 cm3) is equal to 1 milliliter (1mL). • A graduated cylinder is a tool that can be used to measure the volume of a 5 liquid. • The volume of a solid is expressed in cubic meters (m3) or a factor of cubic meters, such as cubic centimeters (cm3). • Volume can be found by multiplying an object’s length by its width and its height. • You can find the volume of irregularly shaped objects by measuring the amount of liquid they displace. Review Tip Practicing Calculations Practice calculating the volume of an object. What is the volume of a box that has a length of 10 cm, a width of 20 cm, and a height of 5 cm? Mass and Weight • A measure of the amount of matter in an object is called mass. • The base unit for mass is the kilogram (kg). Smaller objects may be described in grams (g). • Mass and weight are not the same thing. The weight of an object is affected by gravity, while its mass remains constant. • A measure of the force of gravity on an object is weight. Weight is expressed in newtons (N). • The weight of an object is different on the moon than it is on Earth. • Mass can be measured with a balance. Weight is measured with a spring scale. Temperature • As it is used in daily life, temperature is a measure of how hot or cold something is. • Temperature is actually a measure of how much energy is within matter. • The SI unit for temperature is the kelvin (K), but scientists routinely use degrees Celsius (oC). 6 Section 4 Scientific Models and Knowledge Key Concept Models are used to study living things, test hypotheses, explain observations, and communicate knowledge. Types of Scientific Models • A model is a representation of an object or a system. • Models are used to study living things, test hypotheses, explain observations, and communicate knowledge. Physical Models • A physical model looks like the object it is modeling. • A plastic skeleton is a model of a human skeleton. Mathematical Models • A mathematical model uses numbers, equations, or other forms of data to make predictions. • Computers are very useful for creating and controlling mathematical models. • Mathematical models can be very complex. The more complex the model, the more carefully scientists must build the model. Conceptual Models • Conceptual models are diagrams, drawings, or verbal descriptions. • Conceptual models are used to explain how something works or how something is put together. • Conceptual models are especially useful for showing how the parts of a system affect one another. Using Scale in Models • Scale is the relationship between the measurement of a model and the actual measurement of the real object. • Measurements in a scale model are proportionally smaller or larger than the real object. • Maps and diagrams can also be drawn to scale. Such models 7 communicate more accurately than maps that are not drawn to scale. Review Tip Describing Concepts Pretend that you are teaching an elementary school student about scale models. Describe how a scale model relates to the object it represents. Benefits of Models • Models can be used to represent things that are very small or very large. • Models can be used to represent things that are very complex, or to represent things that no longer exist. Theories in Science • A theory is an explanation that ties together many related facts, observations, and tested hypotheses. • Theories are conceptual models that help organize scientific thinking. Theories help explain observations and can help predict future events. • An example of a theory is, the cell theory states that all living things are made up of cells. Laws in Science • In science, a law is a descriptive statement that reliably predicts events. • A law is a summary of many experimental results and observations. Laws are ideas that rarely change. • Unlike a theory, a law explains what will happen, not why it will happen. • An example of a scientific law is the law of gravity, which states that objects tend to fall toward the center of Earth. • There are few laws unique to life science, but there are several important theories. Building Scientific Knowledge • Scientific ideas change. Life scientists are always asking new questions, or looking at old questions in new ways. • Sometimes new results show that old conclusions were wrong. • For example, new computer models showed that the dinosaur 8 Apatosaurus could not have held its head upright, as once believed. • When a scientist proposes a new theory, other scientists examine the evidence that supports the theory. • Scientists use scientific methods to test the new theory. Sometimes the theory is accepted, sometimes it is rejected, and sometimes it is changed. • Scientific knowledge is always growing and always being refined. Section 5 Safety in Science Key Concept Following safety rules during scientific investigations will help prevent accidents and injury. The Importance of Safety Rules • Following safety rules during scientific investigations will help prevent accidents and injury. • Following directions will make your work easier, will help you get better results, and will keep you safer. Elements of Safety • Learn the meaning of safety symbols and follow their directions. This will reduce the chances that you will get hurt. • Your teacher will discuss the meanings and procedures for each of the symbols. Be certain to follow your teacher’s directions. Reading and Following Directions • Always read the instructions before starting a science experiment. If you don’t understand, ask your teacher for help. • Following directions carefully may be the single most important way to avoid accidents and injury. Neatness Counts! • Neatness is very important for safety and success in the science lab. • Always clear your work area of unnecessary objects. • Have all of the materials and equipment ready before you start. Label all chemicals carefully. 9 Using Proper Safety Equipment • Safety equipment, such as goggles, gloves, and aprons, can protect you from injury. • Make sure you follow the symbols for safety equipment, and that goggles, gloves, and aprons fit properly. • If you are using chemicals or handling animals, you must wear safety gloves. Use heat resistant gloves when handling hot objects. Proper Cleanup Procedures • After a science experiment, you should carefully clean up your work area and wash your hands. • Place caps on bottles, dispose of waste chemicals as directed, and put everything back in its proper place. • Alert your teacher if any equipment is broken or damaged. Such equipment could cause serious injury. Proper Accident Procedure • If an accident happens, the following four steps will help limit the effects of the accident: • Remain calm, and try to determine what happened. • Secure the area. Make sure you are safe and that no one else is in danger. • Tell your teacher, or call for help. Always report an accident right away, even if it seems minor. • Assist your teacher in cleaning up or giving aid. Always follow your teacher’s directions. • Know how to use all safety equipment in the classroom, and where the equipment is stored. Review Tip Practicing Questions Think of a question about controlled experiments that could be on a test. Say the question and the answer. Proper First Aid Procedures • First aid is emergency medical care for someone who has been hurt. 10 • You should not perform first aid unless you are properly trained. • The exceptions are simple treatments that should be done quickly and will not risk further injury. Review Tip Wrap - Up Think about the methods you have used to study the concepts in this chapter. Which types of Review Tips are the most helpful to you? What types of concepts do they help you study? Think about review methods you can use when you are studying. 11