Week one SSA Nature of Science

Denise and David are testing how plants respond to fertilizer. They use three plants for the experiment. The first is given a cup of Fast Grow fertilizer with no water. The second is given a teaspoon of SunLight fertilizer with a cup of water. The third plant is given no fertilizer with a cup of water. Denise and David will not be able to draw a valid conclusion from their result. Which of the following statements explains why?

• There are not enough different types of plants.

• There is no test variable (independent variable).

• Results of the experiment need to be presented in a graph.

• More than one test variable (independent variable) has been changed in the experiment.

Allison and Heather are going to conduct an experiment to see whether salt affects the growth of plants. They assemble five groups of identical plants and give the plants in each group water with a different salt concentration. What is the outcome variable (dependent variable) for their experiment?

• Salt concentration in plant tissue

• Salt concentration in plant water

• Amount of water absorbed by plants

• Average mass of plants in each group

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The graph below shows which wavelengths, in nanometers (nm), and corresponding colors of light are absorbed by the plant molecule chlorophyll a. Chlorophyll a is one of the molecules that plants use for photosynthesis. Which of the following would be an accurate analysis of the information shown?

• The least effective color of light for photosynthesis appears to be green.

• The lease effective colors of light for photosynthesis appear to be orange and red.

• The most effective wavelengths of light for photosynthesis are between 450 and 550 nm.

• The lease effective wavelengths of light for photosynthesis are between 600 and 700 nm.

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Two types of models that can be used to show details of the structures of cells are shown in the picture.

Which of the following describes a limitation of the drawing but NOT the clay model?

• It does not represent the main parts of a cell.

• It does not contain the correct number of nuclei

• It cannot represent a living cell since a true cell is three dimensional.

• It cannot represent a living cell since the cytoplasm should be in constant motion.

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A group of scientists has been asked to conduct a study on how an oil spill will affect the surrounding sea life. The scientists decide that the best way to complete the study is to create a model. Which of the following is the most likely reason that the scientists will use a model instead of creating an actual oil spill study?

• They think using a model will provide them with more accurate results.

• They can study the effects of an oil spill without harming surrounding sea life.

• They can use different species that the plants and animals found in the real ecosystem.

• They expect the oil spill in their model to have a much greater effect than an oil spill in the natural environment.

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The practice of science involves many possible areas of study. Different scientists follow the process of the scientific method using different techniques and tools. Which of the following statements is a natural conclusion why scientists use different techniques to investigate their particular field?

• Scientists use the method with which they are the most comfortable.

• Scientists must use all parts of the scientific method for conclusions to be valid.

• Techniques can only be used in certain fields of study and never overlap.

• Techniques may vary between fields of research, but the conclusions are still valid.

Until the 1500s, doctors thought diseases were caused spontaneously. Scientists began proposing that diseases were caused by seed-like entities that could be passed among people. After the invention of the microscope, doctors came to know that many diseases were actually caused by microscopic living organisms, like bacteria.

What does this suggest about the nature of scientific knowledge?

• Scientific knowledge should not be considered valid because it changes over time.

• Technology has improved enough that scientific knowledge can stop changing.

• New discoveries and evidence are more important than repeatable results.

• Scientific knowledge changes over time based on evidence.

Gregor Mendel conducted research about genetics by breeding pea plants. Although he could not actually see into cells, he deduced from his results that each of an organism’s traits is determined by two factors (alleles). Long after Mendel’s work, microscopes were improved and scientists observed that chromosomes in the nucleus occurred in matching pairs. It is now accepted that the two alleles for each trait are located on homologous chromosomes.

What does this demonstrate about science?

• Advances in science may result from new interpretations of previous work.

• Improvements in equipment and data gathering can disprove previous conclusions.

• Earlier scientists did not have the proper equipment and materials to make their conclusions.

• Much of early scientific research was faulty because the earlier scientists did not practice the same data-gathering practices as modern scientists.

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During the nineteenth century, biologists knew that South America and Africa contained similar fossils. These fossils led them to believe that a temporary land bridge between South America and Africa allowed ancient species to move between both continents. In the twentieth century, evidence showed that South America and Africa were once part of the same larger continent and that there were no land bridges between them.

How should biologists respond to the new geological finding?

• Biologists should reject the geological finding, because it is new.

• Biologists should ask physicists what to do, because physics is a more exact science.

• Biologists should reject the belief in ancient species, because there were no land bridges.

• Biologists should update the history of life, because it should include the new geological finding.

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Tracy and Eric are timing how fast marbles roll down an inclined plane. They plan to do this 5 times, and then take the average time for their results. What would be the BEST way to improve the accuracy of their data?

• Include marbles of three different colors in their investigation

• Include the average of 20 trials down the inclined plane

• Use marbles of 10 different densities

• Use toy cars instead of marbles