Common Biology Misconceptions

Watch out Biologists! These 6 common misconceptions will cost you marks

By the time we get to secondary school, most of us believe that we have left the misconceptions of childhood behind us, but quite the opposite is often true! 

For example, did you know that cavemen did not live alongside the dinosaurs, deoxygenated blood is not blue, and antibiotics will not cure your common cold? 

We’re willing to bet that you’ll find plenty of misconceptions stuck in the brains of your classmates - and probably in your own brain too! So, to avoid embarrassment and save yourself from dropping those crucial marks in exams, Save My Exams’ Biology Content Creator Naomi shares 6 myth-busting explanations in this brand new blog. 

1.  Respiration is breathing

This misconception is the bane of many a Biology teacher’s life. To save your teacher from despair, describe respiration correctly as a chemical reaction that takes place in all living cells, during which energy is released from glucose (note: it is released, never created!). Don’t forget that all living organisms do it, from bacteria to sharks to trees - and plants respire all the time, not just at night! 

2.  Evolution has a goal

It is not uncommon to read in student responses to questions about adaptation that ‘organisms adapt so that they can survive in their environment’. This shows a fundamental misunderstanding of the process of natural selection. The mutations that provide a survival advantage occur by chance, not because DNA consciously decides that growing a long, woolly coat might be useful. Don’t forget - humans did not evolve from apes, but rather share a common ancestor with them!

3.  Plants get their food from the soil

Are you part of the houseplant trend currently sweeping the nation? If so, you may have come across the idea that one way to keep your beloved plant alive is to ‘feed’ it by adding fertiliser. Given language like this, it’s not surprising that many people believe plants get their food from the soil. However, while plants do get essential nutrients such as nitrates and phosphates from the soil, they make their own food during the process of photosynthesis. Plants use light energy to fix carbon dioxide from the atmosphere and produce their own glucose.

4.  Fungi are plants

Classification errors such as this one are everywhere - from children believing that plants are not alive at all to adults believing that insects are not animals and that fungi are plants. In reality of course, plants are most definitely alive, insects are most certainly animals, and fungi actually have more in common with animals than with plants. They’re even classified in a separate kingdom all of their own. 

We no longer use characteristics such as ‘does it move?’ or ‘does it have legs?’ to classify organisms. Instead, we use information from the study of cell structure, or molecular sequence analysis from DNA or RNA. Molecular analysis has been crucial in the reclassification of whole groups of organisms, such as in the creation of the three domain system that separates the prokaryotes into two distinct groups.

5.  Correlation equals causation

This one is a classic, and can be found in all areas of science. A correlation is simply a relationship between two data sets, and can be found anywhere. There’s even a correlation that’s been found between ‘the number of people who drown per year in swimming pools [and] the number of films per year starring Nicholas Cage’. Common sense tells us here that Nicholas Cage films are unlikely to cause swimming pool drowning, or vice versa. So this data shows a correlation, but there is no causation (i.e. one event has not caused the other).

Exam questions frequently ask you to draw conclusions from data, or evaluate conclusions, and knowing that correlation does not equal a causal relationship can be handy. Note: it is a causal relationship, and not a casual relationship.

6.  Bacteria are bad

Children learn from a young age that ‘germs’ are bad for them, and we are certainly all very familiar with frequent handwashing and surface cleaning these days. (Though note that COVID-19 is caused by a virus, not a bacterium.) But what many people don’t realise is that most bacteria are harmless to humans. Bacteria are all around us, and are crucial to our health and even to our ability to consume cheese! 

The importance of the bacteria in our intestines is becoming clearer; scientists now know that a lack of diversity in our gut bacteria can be responsible for digestive disorders, obesity, and even poor mental health. We rely on bacteria for many important biotechnological processes such as the production of yoghurt and cheese, and the detoxification of sewage. And beyond this we are in fact indebted to early photosynthetic bacteria for the very oxygen in the atmosphere we breathe.

So, now you know your facts from your biological myths, feel free to make yourself popular by correcting your friends, save your teacher from distress by showing that yes, you were listening, or score yourself those crucial exam marks by avoiding that silly mistake.