1. I can analyze an experiment and identify the major parts. This means that I know the difference between an independent variable, dependent variable, constant, experimental group, and control group. I can explain the scientific method and apply it. Identify a Problem or Ask a Question: The scientific method starts when you ask a question about something that you observe: How, What, When, Who, Which, Why, or Where?; And, in order for the scientific method to answer the question it must be about something that you can measure, preferably with a number. Do Background Research: look for what is already known about the topic in order to come up with an educated guess as to what is happening; Rather than starting from scratch in putting together a plan for answering your question, you want to be a savvy scientist using library and Internet research to help you find the best way to do things and insure that you don't repeat mistakes from the past. Construct a Hypothesis = A hypothesis is an educated guess about how things work: "If [I do this], then [this] will happen." You must state your hypothesis in a way that you can easily measure, and of course, your hypothesis should be constructed in a way to help you answer your original question. Your hypothesis should identify the independent variable ( if statement) and the dependent variable ( then statement) for the experiment. Conduct an Experiment = test your hypothesis by performing a controlled experiment. Your experiment tests whether your hypothesis is supported or not. It is important for your experiment to be a controlled (fair) test. You conduct a controlled test by making sure that you change only one factor at a time while keeping all other conditions the same. You should also repeat your experiments several times to make sure that the first results weren't just an accident.
Collect/Analyze Your Data: During the experiment, you collect your data/measurements so that you can analyze them to see if they support your hypothesis or not. You analyze data by organizing it into charts, graphs, or using statistics to look for patterns. Draw a Conclusion: Scientists often find that their hypothesis was not supported by the data, and in such cases they will construct a new hypothesis based on the information they learned during their experiment. This starts the entire process of the scientific method over again. Even if they find that their hypothesis was supported, they may want to test it again in a new way. A wrong hypothesis is ok because we still learn valuable information. Never change your data to support your hypothesis because communicates false information. Communicate/Publish Your Results = In a classroom experiment, you would communicate your results by presenting your data to the class or completing a lab report. In a science fair project, you would communicate your results to others in a final report and/or a display board. Professional scientists do almost exactly the same thing by publishing their final report in a scientific journal or by presenting their results on a poster or slide-show presentation at a scientific meeting. This is important so that the experiment can be repeated by other scientists to make sure that the results were accurately reported and the conclusions of the experiment were valid. It is also important so that scientists can use the knowledge gained from the experiment in order to make new hypotheses and conduct new research/experiments. Parts of An Experiment: The independent variable is the part of the experiment that is purposefully being changed. There should only be one independent variable in a controlled experiment. If you change more than one variable (factor), then the test is not valid because you cannot tell what caused the change in the results. You manipulate the independent variable (the cause) in order to determine the effect it has on the dependent variable. On a graph, the independent variable should be on the horizontal (X) axis. The dependent variable is what you measure in the experiment. There may be more than one dependent variable that are being measured because they are affected by the independent variable. On a graph, the dependent variable should be on the vertical (Y) axis. All other factors/conditions of the experiment should be kept constant (unchanged). This means that they should be the same for both the experimental group and the control group. The experimental group is the trial(s) that get the changed independent variable. This is sometimes referred to the treatment group because they get the new independent variable (example: a new medicine or drug). The control group is used for comparison so that you can tell if the independent variable had any effect on the dependent variable. You do not change the independent variable for the control group; everything should be under normal conditions. A placebo is often used in drug trials because it looks like the same as the medicine but does not contain the experimental drug. Example Experiment: A researcher wants to determine if Zyrtec is a better allergy medicine than Allegra. She gathers participants who suffer from seasonal allergies. She randomly divides the participants into three groups. Group A receives 1 dose of Allegra in the morning. Group B receives 1 dose of Zyrtec in the morning. Group C takes a pill that has no medication in it called a placebo so that they think they are still taking allergy medicine every day. Over the course of 2 weeks, the participants are exposed to the same types of allergens and are asked to record their symptoms throughout the trial. At the end of 2 weeks, all the data is collected and analyzed in order to determine which medication worked better to treat allergy symptoms. Independent Variable: Type of allergy medicine Dependent Variable: Allergy symptoms Hypothesis: If Zyrtec is a better allergy medicine than Allegra, then patients will report fewer allergy symptoms while taking Zyrtec. Constants: Duration of study (2 weeks); exposure to the same types of allergens; time of day the medicine was taken Experimental Group(s): Groups that received the different types of allergy medicine (Group A = Allegra & Group B = Zyrtec) Control Group: The group that had normal conditions (Group C = placebo)
Name Unit 1 Study Guide: Nature of Biology Test Date: 2. I can tell the difference between the experiments that disproved spontaneous generation. Spontaneous generation is an incorrect theory which stated that living things can come from nonliving things (example: rats are produced by rotting grain). Aristotle was the first person to document this theory approximately 2300 years ago. It was not disproved until the mid-1800 s. This theory may also be called abiogenesis (life from non-life). Francesco Redi performed the first spontaneous generation experiment in 1668. He placed pieces of meat in jars. Some of the jars were covered and some were left uncovered. He observed that maggots (baby flies) on the meat in the uncovered jars but no maggots on the meat in the covered jars. This meant that the flies were being produced by other flies and not by the rotting meat. Redi disproved spontaneous generation for larger (macroscopic) organisms. John Needham performed a spontaneous generation experiment in 1745. In his experiment, he boiled meat broth and then poured it into flasks. He sealed some of the flasks and left others open. His results showed that both sets of broth became cloudy because microbes (bacteria) were growing in the broth. He thought this meant that spontaneous generation did occur in microscopic organisms. However, his experimental design was flawed. He did not boil the broth long enough to kill all of the bacteria, so there were already bacteria in the broth that was poured into the flasks that he sealed. The bacteria reproduced, which is why the broth became cloudy. Lazzaro Spallanzani did not agree with Needham s conclusion, so he repeated the experiment, except he boiled the broth for almost an hour. This killed all of the microorganisms. The broth in the sealed flasks stayed clear because there were no bacteria to reproduce. The broth in the open flasks became cloudy because it became contaminated with microorganisms from the air. However, people did not believe his conclusions because he did not allow the broth in the sealed flasks to be exposed to air (which they said carried the life force ). Louis Pasteur performed the experiment that completely disproved spontaneous generation. He repeated the work of Spallanzani, but he changed the design of the flask. Instead of using the typical straightnecked flask, he heated the glass and curved the neck of the flask. He called this an S-shaped flask. These flasks were special because they allowed air to flow through the neck but the dust that carries microorganisms would get trapped in the curve of the neck. This meant that air could get to the broth but the microorganisms in the air could not. The broth in the S-shaped flasks remained clear because the microorganisms could not get into the broth to reproduce. This proved that all living organisms, even bacteria, are produced by other living organisms (biogenesis = life from life).
3. I can tell if something is living based upon the scientific criteria for life. I can identify the level of organization given examples or characteristics. I can put the levels of organization in the correct order from atom to organism. The levels of biological organization from smallest to largest are: atom molecule organelle cell tissue organ organ system organism An Atom is the smallest unit of matter. They are made of protons, neutrons, and electrons. Molecules are made of more than one atom. These could be atoms of the same element or different elements. These are sometimes referred to as compounds. Organelles are cell structures. They are made of organic molecules. Cells are the smallest unit of life. Nothing smaller than a cell is considered living. A unicellular organism performs all of the functions of life in one cell. Cells are made of organelles and a fluid called cytoplasm. Tissues are made of cells that work together to perform the same function. Organs are made of tissues that work together to perform the same function. Organ Systems are made of organs that work together to perform the same function. A complex, multicellular Organism is made of organ systems that work together to perform the functions of life. Characteristics of Life Things must meet ALL of the following criteria in order to be considered LIVING: 1) All living things are made of CELLS. 2) All living things REPRODUCE. 3) All living things EVOLVE. 4) All living things have a genetic code called DNA. 5) All living things need MATERIALS and ENERGY. 6) All living things MAINTAIN HOMEOSTASIS (stable internal conditions). 7) All living things RESPOND to changes in their environment. 8) All living things GROW and DEVELOP. While many organisms move or breathe, not ALL living things move and/or breathe. Movement and breathing are not characteristics of ALL living things. You cannot use those to determine if something is living. It must meet all 8 of the characteristics of life. 4. I can tell the difference between a virus, bacterium, and protist. A virus is not considered living because it is not a cell. It cannot perform the functions of life. A virus is made of genetic information surrounded by proteins. A virus cannot reproduce on its own because it does not have ribosomes or enzymes. It must have a host that will copy the viral genetic material (DNA or RNA) and assemble the viral proteins. When a cell is infected with a virus, it basically becomes a factory for producing more of that virus. Eventually, the cell will become so full of viral particles that the cell membrane breaks and the viruses are released. Those new viruses will then find other cells to infect. Usually, our bodies produce antibodies that will destroy an invading virus after we have been exposed to it. Vaccines work on this principle. However, sometime our immune system does not recognize the virus, even if we have had a similar virus in the past. This is because viruses do evolve due to mutations that occur while the genetic material is being copied. When the virus evolves, our immune system must re-learn how to make the antibodies to fight it. The only characteristics of life that viruses meet are that they evolve, reproduce, and contain genetic material.
Bacteria are prokaryotes (meaning that they do not have a nucleus). They are the simplest living organisms. They are always unicellular. Bacteria meet all of the characteristics of life. There are many different types of bacteria. Some are infectious and will make you (or other types of organisms) sick. Some are beneficial, such as bacteria that are decomposers. Some bacteria are autotrophs, which means they can make their own food. A protist is a unicellular eukaryote (meaning that it does have a nucleus). They live in water and are very diverse. They can be plant-like and go through photosynthesis while others are more animal-like. Some are harmful because they can cause disease or act as parasites. 5. I can tell the difference between a fungus, plant, and animal. All fungi are eukaryotes (have a nucleus). Most fungi are multicellular, but some are unicellular (yeasts). Fungi are all decomposers, which use decaying matter as food. A decomposer is a type of heterotroph (an organism that cannot make its own food). They are not plants because they do not perform photosynthesis. All plants are eukaryotes (have a nucleus). All plants are multicellular. All plants are also autotrophs, which means that they use photosynthesis to make their own food. All animals are eukaryotes (have a nucleus). All animals are multicellular. All animals are also heterotrophs, which means that they cannot make their own food.
6. I can identify the differences and between prokaryotes and eukaryotes. I can label a diagram of a prokaryotic cell and a eukaryotic cell. Prokaryotes are MUCH smaller and simpler than eukaryotes. Prokaryotes are bacteria. The genetic material (DNA) is found in the cytoplasm of a prokaryote. The DNA is arranged in one circular loop called a plasmid. Prokaryotes reproduce asexually through binary fission. Prokaryotes only have a cell wall, cell membrane, cytoplasm, ribosomes, and DNA. They may also have flagella or cilia. Prokaryotes do NOT have a nucleus (nuclear membrane, nuclear lamina, or nucleolus). Prokaryotes also do NOT have organelles surrounded by membranes such as the endoplasmic reticulum (rough or smooth), lysosomes, centrioles, vacuoles, chloroplasts, mitochondria, or Golgi apparatus. Eukaryotes include protists, fungi, plants, & animals. The genetic material (DNA) is found in the nucleus of a eukaryote. The DNA is arranged in chromosome pairs. Eukaryotes can reproduce asexually through mitosis or sexually through meiosis. Eukaryotes have a nucleus and membrane-bound organelles such as the endoplasmic reticulum (rough or smooth), lysosomes, centrioles, vacuoles, chloroplasts, mitochondria, and Golgi apparatus.