To separate evidence from political recommendations, sort each statement into what was measured, what it is explained by, and what someone thinks should be done. Only the first two are the job of the biology. The third involves choices the data alone cannot settle.
It is the final skill in human influence on ecosystems and relies on the habit of assessing evidence for a habitat change.
What are the three kinds of statement?
- Evidence: a measurement or observation. It can be checked. Example: “The mean nitrate level was 14 mg/dm³ downstream.”
- Interpretation: an explanation or inference from the evidence. Example: “The high nitrate is probably from fertiliser runoff.”
- Recommendation or value judgement: what someone thinks should happen, often including words like should, must or ought. Example: “Fertiliser use near rivers must be stopped.”
Interpretation can be strong or weak depending on the supporting evidence. A recommendation is a different kind of claim, because it depends on what people value and what is practical, not only on the data.
How do you handle a recommendation in an answer?
State what the science supports, then say what the recommendation adds. For example: “The data show lower oxygen downstream, which is consistent with nutrient runoff. Whether to restrict fertiliser is a decision that also depends on cost and farming needs.”
This keeps your answer accurate without taking a political side.
Worked example
Invented passage for practice. “Dissolved oxygen downstream of the farm was 2.5 mg/dm³ compared with 8.0 mg/dm³ upstream. The farm’s fertiliser runoff is the reason the fish have gone. The council should ban fertiliser use within 100 m of the stream.”
Question: Identify the evidence, the interpretation and the recommendation, then say what the data support.
Step 1, evidence: “Dissolved oxygen downstream … was 2.5 … compared with 8.0 … upstream.” It is a measurement.
Step 2, interpretation: “The farm’s fertiliser runoff is the reason the fish have gone.” It explains the result, but the passage gives no data on fish numbers or fertiliser.
Step 3, recommendation: “The council should ban fertiliser use within 100 m.” This is a decision about what to do. It uses words like should and depends on more than the data.
Step 4, what the data support: they support a lower oxygen level downstream. A link to fertiliser is plausible, but the passage does not measure fertiliser or fish, so the interpretation needs further evidence. The recommendation is outside what the data can settle.
The mistake to watch for
A common error is to treat a recommendation as a scientific conclusion.
Mistaken answer: “The data prove that fertiliser must be banned.”
The data do not prove a policy. They show a measured difference. Whether to ban a substance depends on values, costs and other options too.
The correction is to write what the data show, what they suggest and what is a separate decision.
Check yourself
Try these first, then open each answer.
1. Classify: “Sewage discharge has caused the decline in fish in the river.”
Show answer
Interpretation. It explains a decline by a cause. It goes beyond the measurements unless other evidence supports the link.
2. Classify: “The mean number of fish per net fell from 40 to 30.”
Show answer
Evidence. It is a measurement that can be checked.
3. A student writes: “The data show that the government must protect the mangroves.” Rewrite it so that it keeps the science and separates the recommendation.
Show answer
“The data show that mangrove saplings fell by about 36%. Whether and how to protect the area is a decision that depends on values and costs as well as this evidence.”
Where this leads next
Bring all five skills together in the human influence on ecosystems practice set. If you want to revisit the method for weighing options, comparing conservation options using specified ecological criteria sets out how criteria keep judgement tied to biology. The same habit applies to biology data and investigations.
Some students understand the difference but still drift into opinion when a question feels important. A teacher reading your answers in online one-to-one Biology tuition can point to the exact sentence where that happens.