In the family WhatsApp group, a video is going around saying that drinking water with lemon "cures any infection." Do you believe it? Before sharing it, a scientist would ask herself several questions: Who is saying this? What evidence do they give? What do other sources say?
Primary and secondary sources
If you want to know what the Curiosity rover has discovered on Mars, you can read the original data that NASA sent or watch a YouTube video that summarizes it with animations. How are these two ways of getting information different?
Written, audiovisual, oral, and internet sources
Besides being primary or secondary, sources can be written (books, magazines), audiovisual (documentaries, videos), direct (observing for yourself or doing an experiment), oral (people who tell you what they know), and from the internet.
Oral and community sources are worth a lot: your grandmother, a traditional healer or midwife, or a farmer who knows her milpa all hold knowledge that has been passed down for generations. We listen to them with respect and, like any other source, we compare them with other sources: do other people or books confirm the same thing? Has it been checked with evidence?
Practice★☆☆Not started
Look at the diagram: it distinguishes primary sources from secondary sources, but the four examples marked with "?" are waiting to be classified. Explain the difference…
Look at the diagram: it distinguishes primary sources from secondary sources, but the four examples marked with "?" are waiting to be classified. Explain the difference between a primary source and a secondary source, and classify the four examples from the diagram: a research paper in which a team describes its own experiment, a textbook, a popular science video, and an encyclopedia entry.
Explain what it means for a source of information to be reliable, and give two examples of reliable sources and two of unreliable sources for doing a science project.
Explain what it means for a source of information to be reliable, and give two examples of reliable sources and two of unreliable sources for doing a science project.
When a lab develops an effective vaccine after months of testing, it does not start manufacturing it the next day: first it sends its work to other scientists so they can look for flaws. Why does science need this collective review?
Practice★☆☆Not started
Scientific teams publish their results in journals and present them at conferences. Give two reasons why communicating results is an essential part of the scientific…
Scientific teams publish their results in journals and present them at conferences. Give two reasons why communicating results is an essential part of the scientific method.
Before being published, scientific papers undergo peer review. Explain what this process consists of and what assurances it provides to the rest of the scientific…
Before being published, scientific papers undergo peer review. Explain what this process consists of and what assurances it provides to the rest of the scientific community.
Choose a male or female scientist (for example, Margarita Salas or Severo Ochoa) and briefly summarise their contribution, an obstacle they had to overcome, and why it…
Choose a male or female scientist (for example, Margarita Salas or Severo Ochoa) and briefly summarise their contribution, an obstacle they had to overcome, and why it is important for people from all backgrounds to participate in science.
A trustworthy source is one you can rely on because its information is true, verifiable, and comes from people or institutions with knowledge. How can you tell whether a source is trustworthy?
Reliable sources: scientific journals, universities (UNAM, IPN), the Secretaría de Salud (Ministry of Health), the WHO, textbooks. Unreliable sources: unsigned WhatsApp chain messages, websites that sell "miracle" products, anonymous posts on social media.
Practice★★☆Not started
A video circulating on social media claims that drinking lemon water "cures any infection". Write at least three questions you should ask yourself to check if the…
A video circulating on social media claims that drinking lemon water "cures any infection". Write at least three questions you should ask yourself to check if the information is reliable, and name two sources where you could verify it.
A soft drinks company funds a study concluding that sugar does not contribute to obesity. Reason why this funding requires the study to be examined more carefully, and…
A soft drinks company funds a study concluding that sugar does not contribute to obesity. Reason why this funding requires the study to be examined more carefully, and name three things you would check regarding its design and who paid for it.
On the internet, bracelets are advertised that promise to "align your quantum energy" and cure pain without explaining how they work or presenting evidence. How can you tell these products apart from genuine medical treatments?
Fake news (disinformation) works in a similar way: it appeals to emotions, says "share it before they delete it," cites no sources, and arrives through chain messages. Before forwarding it, look for the news on the Secretaría de Salud website, at a university, or in an outlet with fact-checking.
Practice★★★Not started
An advertisement sells a bracelet that "rebalances the body's energy" and is "endorsed by thousands of satisfied users". Identify at least three signs of pseudoscience…
An advertisement sells a bracelet that "rebalances the body's energy" and is "endorsed by thousands of satisfied users". Identify at least three signs of pseudoscience in this message and explain what evidence you would demand before believing its effects.
Sources for classifying living things: kingdoms and keys
Mexico is one of the countries with the most species in the world: jaguars, axolotls, nopales (prickly pear cacti), fungi, bacteria… No one can study them all without some order. How do scientists agree on how to group and identify them?
All living things carry out the life processes: they get nutrition, interact with their environment, and reproduce. A rock or a screw does none of that: they are inert matter. Based on how they get nutrition, how many cells they have, and how they reproduce, scientists group living things into large groups called kingdoms.
Kingdom
Main features
Examples from Mexico
Monera
Bacteria; a single cell with no nucleus
Pulque bacteria, Escherichia coli
Protists
One cell with a nucleus (or simple algae); live in water
Amoebas, microscopic algae
Fungi
Absorb their food; do not photosynthesize
Huitlacoche, yeasts, mushrooms
Plants
Make their own food using light (photosynthesis); do not move from place to place
Corn, nopal, maguey
Animals
Are multicellular; get their food from other living things and most can move
Axolotl, jaguar, monarch butterfly
To find out which species an organism belongs to, an identification key (dichotomous key) is used. It is a list of paired options: at each step you choose the one that describes your organism and it takes you to the next step, until you reach a name. Field guides and catalogs from institutions like CONABIO are secondary sources that include these keys. Use them with respect: observe without harming organisms or taking them away.
Practice★★★Not started
You have found that lentils germinated while listening to classical music and others germinated in silence grow practically the same. Write the conclusions section of…
You have found that lentils germinated while listening to classical music and others germinated in silence grow practically the same. Write the conclusions section of your report (4-6 lines): what you were testing, what results you obtained, whether the hypothesis is supported, and what limitations your experiment has.
Back to the beginning: the lemon water video cites no studies, has no medical authorship, and promises magic cures: it is fake news that you should neither believe nor share. Check it with the Secretaría de Salud or with a doctor.
Summary
Let's practice! 3 medium exercises in this section