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Science Strategies

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ACT Science*

*This is a free excerpt from our Online ACT Test Prep

Research Summary Sample Passage

Ready to apply your CSI skills to a sample research summary passage? Slap on some gloves, get out a scalpel, and proceed to investigate.

Passage

Planaria are a type of flatworm that display an amazing ability to regenerate body parts. This ability is primarily linked to a special type of cell, called a stem cell or neoblast. These cells are able to become virtually any type of cell in the worm's body. They replace old and dead cells, and also provide the new cells needed for regeneration or repair after injury. Students were asked to study the regenerative properties of planaria by slicing a planarian worm in different places.

Experiment 1

An individual flatworm should be placed in a small Petri dish. A small amount of water should be placed in the dish to prevent dehydration of the worm. The worm should be cut as shown using a scalpel. Place the head of the worm in a Petri dish labeled "head," and the tail of the worm in a Petri dish labeled "tail." Wait 2 days to look at the worms again.

Experiment 2

Use the same protocol as Experiment 1, except cut the worm vertically as shown.

Experiment 3

Use the same protocol as Experiment 1, except cut the worm vertically as shown, and only continue the cut through part of the worm.


Table 1 Experiment 1 Experiment 2 Experiment 3
Head Tail Head Tail Head Tail
Experiment day # of worms 0,5 0,5 0,5 0,5 1 whole 1 whole
2 Days Post Cutting # of worms 1 whole 1 whole 1 whole 1 whole 1 whole 1 whole

The worms in Experiments 1 and 2 look like the original worm that the students were given. The worm in Experiment 3 looked significantly different after 2 days.

Passage Breakdown

Passage Type: Biology – Zoology – Research Summary

Oh, man. Worms for dicing and an information table? Data Representation flashback and then some. We know that you read the passage in its entirety, so here are our doodles for this passage:

1. Beside intro paragraph: "neoblasts = stem cells replace missing cells"

Why? The gist of the intro paragraph is that these worms can regenerate. Pretty sweet: if Mr. Planarian loses his rear in a bike accident, he can grow it back no problemo. "Neoblast" is the first unfamiliar word in this passage, but it's also defined for you in context. You can guess that these cells must be important to the passage and questions if they are responsible for re-growing the worm's body parts, so it is a good idea to write down the definition while you read.

On a side note, research that revolves around the regeneration of body parts is crazy popular right now; it is often referred to as "regenerative medicine." You've probably heard about the controversy surrounding embryonic stem cells in the news (to use or not to use?), but you may not know that isolated stem cells from adults are showing great potential for regenerating muscle, bone, organs, and skin. Mr. Planarian has a lot more to offer than you might think.

2. Circle "neoblasts" and "stem cells," and underline "They replace old and dead cells…"

Circling the first two words is mainly a "here it is" strategy so that you know exactly where to go if you are asked about these unfamiliar terms. Since you are then told what the function of these cells is, and you think that these cells are important for Mr. Planarian to regain his bum, it would be a good idea to underline this sentence.

3. Beside Experiments: "cut worms with scalpel, wait 2 days"

Now we get to the experimental portion of the passage. It's clear that students will be cutting the worms three different ways, one each in three different experiments, and waiting 2 days for the results. The sentence you would write just summarizes the part of the protocol that isn't pictured: the tool of choice and the time to wait. You may have probably guessed by now that the sliced worms' neoblasts will be hard at work for a couple of days.

For research summary passages, always try to understand the experiments before you go on to the questions. The ACT will test you on the data, the protocol, the results, and ask about mistakes, changed protocols, or future steps. The nerve (or here, the neoblast!). This is where we arrive at the reasoning portion of the Science Reasoning Test.

4. Beside Table 1: "worms became whole"

This table sums up the results of the experiments. At this point, you can perform a little reasoning to try to figure out how ½ of a worm turned into a whole one. If you were following the passage closely, you would be able to conclude that the worms re-grew their missing parts. The worm in Experiment 3 might be confusing at this point, so we recommend you wait for the questions to figure out what went down when that worm was left to its own devices for 2 days.

Don't waste a lot of time on your first read when you run into some data or results that you don't understand. Wait until you are asked about it, which you probably will be, rather than wracking your brain beforehand and becoming overwhelmed. The confusing stuff is usually asked later in the questions, so you may even come up with a solution before you reach the question that asks about that particular result.

Now that we've marked up the passage, let's move on to the questions.

1. Which experimental tool is required for Experiments 1 through 3 to cut the worms?

  • a. Planaria
  • b. A scalpel
  • c. A Petri dish
  • d. A microscope

Easy one. The text says that a scalpel is used to cut the worms (and you wrote it down). B is the correct answer.

2. Which of the following statements is true based on the experimental results of Experiments 1 and 2?

  • a. A head piece of worm will grow a head piece if cut as in Experiment 1.
  • b. When cut in half, the planarian worm seems to know what piece of itself is missing because the piece with the head always grows a tail, and the piece with a tail always grows a head to regenerate a full worm.
  • c. The worms move a lot.
  • d. The worms cannot regenerate well at all.

This question asks you to interpret the results in Table 1 based off of the earlier images. F is not true because if this were the case, the worms generated after 2 days would not be whole worms. H may be true but is irrelevant to the question, and J is incorrect for the same reason as F. G is the correct answer. When cut in half, the worms grow the parts that they are missing, resulting in 4 worms total for the two experiments, similar to the original one worm.

3. Which of the following conclusions can be drawn from Experiments 1 and 2?

  • a. A planarian worm can be cut in half both directions, and it will still be capable of producing a new worm.
  • b. The worms move quickly and are difficult to slice.
  • c. The worms cannot produce new worms once cut.
  • d. The worms reproduce after they are cut in half.

This question closely follows the previous question. The worms are cut in both directions, horizontally in Experiment 1 and vertically in Experiment 2. They then regenerate their respective missing parts; we know this because after two days, there are 2 whole worms for each experiment. C is completely the opposite conclusion, and B is irrelevant. D may be tricky because the worms seem to "reproduce" themselves, but to "reproduce" is to actually produce a complete other whole of oneself, not fix up ½ of yourself because you were chopped in two by some high school student. A is therefore the correct answer.

4. Based on the passage, the explanation for how the worm is capable of undergoing such regenerations is:

  • a. The planarian's nerves stimulate regeneration.
  • b. The neoblasts are stimulated and undergo regeneration.
  • c. A special pheromone produced by the worms that causes regeneration.
  • d. Planaria are not mammals.

This question comes directly out of the introductory paragraph. It says that planaria are able to reproduce parts of themselves because they have many neoblasts, or stem cells. Circling helps you out again here. G is the correct answer. J is irrelevant. If you were slightly confused by F or H, thinking that they may be possible steps in the process of regeneration, you are right, they may be possible steps. However, they are not mentioned at all in the passage, and the question asks specifically for an explanation based only off of the information in the passage.

5. If you, as a human, were to have a body part removed, it would not grow back. Which of the following is a reasonable hypothesis for why this is?

  • a. Worms are special.
  • b. Worms emit a particular pheromone that helps other worms regenerate.
  • c. Humans do not have as many stem cells that promote this process.
  • d. Worms can duplicate themselves at will, unlike humans.

This question is asking you to make a logical leap from the introductory paragraph. The introductory paragraph states that planaria are able to reproduce parts of themselves because they have many neoblasts, or stem cells. Since humans cannot regenerate their fingers, the logical leap is that they do not have the necessary cells. The correct answer is C.

Though worms may be special and may emit pheromones, these ideas are not found in the passage and are therefore irrelevant. The word "duplicate" is also placed here to trick you again. Worms can replace parts of themselves with neoblasts, not make a whole other worm (duplication). Planaria reproduce sexually like many other organisms.

6. The worm from Experiment 3 looks like the image to the left. Which of the following explanations best sums up what happened in this experiment?

  • a. This was a defective worm.
  • b. The worm failed to regenerate after the cut.
  • c. The worm regenerated another head after the cut, but because the cut didn’t go all of the way down the worm, the result was a 2-headed worm.
  • d. The experiment was completed incorrectly.

The experimental results state that the worm looked different after two days. This means that initially, the worm was a normal worm (so F is not correct). If you go back and look at the experimental procedure, you can see that the cut doesn’t slice all the way through the worm. Because the partial cut was included in the protocol, the experiment was completed correctly, eliminating J. The worm did regenerate something, which eliminates G.

You know from Experiment 1 that if you cut the worm completely in half, the worm will grow the removed part. Since the base wasn’t cut, the worm grows another head to replace the two halves that are missing. H is the correct answer.

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