Big Idea Science

Natalie is using a three-dimensional representation to study the parts of the human heart. Isaiah is working in a laboratory to test the hypothesis that plants grow taller in green light than in white light. Which of the following best

compares their activities?

• Natalie is conducting a scientific investigation, and Isaiah is not.

• Natalie is not conducting a scientific investigation, and Isaiah is.

• Natalie is conducting an experiment, and Isaiah is conducting a field study.

• Natalie is investigating a scientific model, and Isaiah is conducting

  an experiment.

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Nicholas is conducting an investigation to determine how the number of turtles in a pond changes over several months. Which of the following would be the best way for Nicholas to organize and show his data?

• in a circle graph

• in a line graph

• in a bar graph

• in a diagram

Jacob conducted an investigation to determine the effect of acid on different types of rocks. He found that the data he collected do not support his hypothesis. Why would Jacob's hypothesis still have some value?

• It might lead to the development of new investigations.

• It demonstrates that Jacob needs more practice investigating.

• It might encourage Jacob to investigate the effect of bases instead.

• It shows that Jacob's investigation could have been better planned.

A prokaryote is a one-celled organism that does not have a nucleus. The cells of plants, animals, and other eukaryotes do have a nucleus. They also have organelles called mitochondria and chloroplasts. In the 1960s, the scientist Lynn Margulis proposed a theory about mitochondria and

chloroplasts. Her theory states that they developed from ancient prokaryotes that were taken in by larger cells. The prokaryotes lived inside the larger cells and helped them survive. For example, some of the prokaryotes made food for the cells by photosynthesis. Over time, the prokaryotes inside the cells became mitochondria and chloroplasts.

Many were skeptical of Margulis's theory when she first proposed it. Since that time, scientists have used new technologies to gather data that support the theory. The table shows some of these data.

Which of the following observations best supports Margulis's theory?

• Mitochondria and chloroplasts are similar in size, and both types of

  organelles have a single circular chromosome.

• Mitochondria, chloroplasts, prokaryotic cells, and eukaryotic cells are all less than 500 millionths of a meter in size.

• Mitochondria, chloroplasts, and prokaryotic cells are similar in size and have the same chromosome structure.

• A eukaryotic cell has many linear chromosomes, while a prokaryotic cell has a single circular chromosome.

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Isabella used litmus paper to study acids and bases. Blue litmus paper turns red when exposed to an acid. Red litmus paper turns blue when exposed to a base. Isabella tested vinegar with blue and red litmus paper. She concluded that vinegar is an acid. Which of the following most likely describes the observations that Isabella made when she tested the vinegar?

• Neither the red litmus paper nor the blue litmus paper changed color.

• The red litmus paper turned blue, and the blue litmus paper turned red.

• The blue litmus paper turned red, and the red litmus paper did not

  change color.

• The blue litmus paper did not change color, and the red litmus paper

  turned blue.

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Dr. Rodriguez conducts an investigation to test her ideas about what causes tornadoes to form. She shares the results of the investigation with other scientists, who then replicate her investigation. Which of the following best explains why

the other scientists do this?

• If they get different results, then they will know that Dr. Rodriguez's

  conclusions apply only to her region.

• If they get the same results, then they will know that Dr. Rodriguez's

  conclusions are most likely correct.

• If they conduct the same investigation, then they can publish an article in a scientific journal.

• If they conduct the same investigation, then they can share credit with Dr. Rodriguez.

There are many different fields of science, each with its own methods of investigation. In which field of science would a field study of volcanoes or other landforms most likely be conducted?

• biology

• chemistry

• geology

• physics

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Scientists often replicate experiments to verify the findings. Winch of the following is an example of replication?

• A scientist repeats another scientist's experiment on how sound waves travel.

• A scientist conducts three trials of her own experiment on the behavior of light.

• A scientist heats two different metals to compare the temperatures at which they melt.

• A scientist conducts a different experiment on heat after his first one does not support his hypothesis.

Destiny conducted an experiment to test which of four types of batteries lasts longest in a flashlight. She used four identical flashlights and placed a different type of new battery in each flashlight. She turned the flashlights on at the same time, and she recorded the time when each flashlight stopped giving off light. Destiny's data are shown.

What is the independent variable in this experiment?

• the type of battery used

• the type of flashlight used

• the total amount of time each battery lasts

• the starting time when each flashlight is turned on

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A scientist conducted an investigation to determine the relationship between algae growth and available light at increasing ocean depths. The scientist lowered a light meter into the ocean and recorded the amount of light at different depths. The scientist also collected a water sample at each depth to count the number of algae present. The table below shows the results.

Based on the information in the table, which of the following statements best describes the relationship between light and the density of the algae population?

• As the light level decreases, the density ofthe algae population decreases.

• As the light level decreases, the density of the algae population increases.

• As the density of the algae population increases, it reduces the light level.

• Light level has no effect on the density ofthe algae population.

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