Question

1. scientific claims should be questioned if
2. the data are based on samples that are very large
3. conclusions follow logically from the evidence
4. peer review was used to examine the claims made by scientists
5. the experimental results cannot be repeated by other scientists

1. a student read that liquid extracted from an aloe vera plant promotes the healing of burned tissue. she decided to investigate the effect of different concentrations of aloe vera extract on the regeneration (regrowth of lost or damaged tissue) rate in planaria. planaria are small flatworms known for their ability to regenerate.

planaria regeneration
image: cut planaria worm in two, grows new tail, grows new head
source: adapted from https://goo.gl/images/4wfcyv

the student used a sterile scalpel to cut each of 30 planaria in half. this gave her 10 heads and 10 tails for each of three experimental groups. the planaria were kept in separate petri dishes in the same amount of water and at the same temperature. group 1 received 0% aloe vera extract, group 2 received a 20% concentration of the extract, and group 3 received a 40% concentration. on days 7, 10, and 14, she recorded the amount of tissue regeneration in all three groups. she observed that the group with 20% aloe vera added regenerated more slowly than the group with 40% added.

a reasonable inference based on these results would be that

1. the application of aloe vera to earthworms would have no effect on tissue regeneration
2. if she applied 30% aloe vera to a group, it would regenerate tissue more rapidly than the 40% group
3. aloe vera affected the rate of cell division, resulting in an increased rate of regeneration
4. the control group, which received no aloe vera, did not regenerate

Explanation:

Question 1:

• Option 1: Larger samples generally improve data reliability, so this is not a reason to question.
• Option 2: Logical conclusions from evidence support scientific claims, not a reason to question.
• Option 3: Peer review is a standard validation process, not a reason to question.
• Option 4: If experimental results can't be repeated, the claim's validity is questionable as reproducibility is key in science.

• Option 1: The experiment is on planaria, not earthworms—no basis for this inference.
• Option 2: The trend shows higher concentration (40%) had faster regeneration than 20%, so 30% (between 20% and 40%) is unlikely to be faster than 40%.
• Option 3: Aloe vera affected regeneration rate (40% > 20% > 0% implied, as 20% was slower than 40% and 0% is control). Cell division is linked to regeneration, so this is a reasonable inference.
• Option 4: Planaria naturally regenerate, and the control group (0% Aloe) would still regenerate (just likely slower than Aloe - treated groups).

Answer:

1. the experimental results cannot be repeated by other scientists

Question 2: