2.3 Classification: order or confusion?
Classification is used to bring some order to scientific knowledge, but as with all human constructions, there are debates and contentious issues surrounding the topic. For example, the concept of whether something is living or not is central to the study of biology. It may seem obvious to us, but it’s much more complicated than you might think. Children learn about the criteria for ‘living’ and ‘dead’ through experience as well as formal learning, and the criteria they use to identify living things change as they develop their conceptual frameworks. Children under six are unlikely to have any concept of ‘living’. At first, children associate ‘living’ with something being active in any way. In the next stage, living is associated with movement. Around the age of nine to eleven years, children start to view living things as those organisms that move by themselves. You will explore this in the next activity.
Activity 7 Living, non-living or dead?
1. What are the seven characteristics of living things? Explain how each applies to a plant.
Answer
| M | - movement: this may be obvious movement or internal movement of substances such as sap. |
| R | - respiration: the process of releasing energy from food, not to be confused with breathing. Like all living things, plants need to respire. |
| S | - sensitivity: detecting changes in the environment. Plants respond to light, gravity, and some respond to touch (e.g. the venus flytrap). |
| G | - growth: this is not just growing bigger, but also includes the replacing of cells that die, and the repair of wounds. |
| R | - reproduction: passing on of genetic information to new individuals. Plants produce seeds (sexual reproduction), or reproduce vegetatively (asexual reproduction) with the new individuals being identical to the parent plant. |
| E | - excretion: the process of getting rid of metabolic waste products. Oxygen is a plant waste product, released during photosynthesis. |
| N | - nutrition: all living things need nutrients to make new material and drive the living processes. Plants take in nutrients and the energy needed to drive these processes. Plants also take in micronutrients, usually dissolved in the water taken in by the roots. |
2. Look at the list of objects in Table 4. Classify them as ‘living’, ‘non-living’, ‘once lived (dead)’ or as ‘other’. Note your classifications in the table along with any potential causes of confusion for primary-aged children, and outline any misconceptions you think they might have.
Compared to children, you will have a more sophisticated view of the definition of ‘living’, and you may start off thinking that this question is very straightforward. However, the examples in the list may get you thinking and questioning your decisions. For example, children seeing a lump of coal are unlikely to classify this as ‘once lived’, but if you know how coal is made, you may be less sure. Although coal is made from things that once lived and have undergone tremendous pressure and heat over time, coal as a substance has not ‘once lived’. This is an example of how a little bit of knowledge can actually confuse matters.
| Object: | Living / non-living / once lived (dead) / other: |
| Fire | |
| Tree | |
| Mushroom | |
| Seed | |
| Bird’s egg | |
| Milk | |
| Egyptian mummy | |
| Bottle cork | |
| Ammonite fossil | |
| Virus |
Answer
| Object: | Classification: | Notes: |
| Fire | non-living | Children may classify it as living because it moves. |
| Tree | living | Plants are often not classified as living by children, because they are not obviously active and moving. |
| Mushroom | living | Even when children categorise plants as living, fungi such as mushrooms may not be included. (If the mushroom has just been picked and is still respiring it’s still living. When it stops respiring, it’s dead.) |
| Seed | living | Whether a seed is living or dead is hard to tell until they are planted or tested to see if they are respiring. Seeds start off as living – if they didn’t, the world would be in deep trouble! |
| Bird’s egg | living | Like the plant seed, it can be hard to tell if the egg is dead or alive. If it’s been bought from the supermarket, it has probably never been alive because it will not have been fertilised. The embryo in an egg that has been fertilised will die if not kept warm though. Like seeds, fertilised eggs start off as living. |
| Milk | non-living | This is an animal product, produced by a living thing, but not in itself alive or once alive. |
| Egyptian mummy | once lived | Of course, the movies would have you believe that they can still get up and about! |
| Bottle cork | non-living | This is an interesting one, because it conflates material from a once living thing that has been crafted into an object. Would you say a wooden table once lived? The material it is made from came from a tree that once lived, but tables and bottle corks have not once lived. So, the bottle cork was part of a living tree once, but as an object it was never alive. To add to the conundrum, much like hair, cork bark is made of dead cells. |
| Ammonite fossil | non-living | This is another interesting one that leads to arguments. To classify it, you need to have a clear idea of what a fossil is. An ammonite was a living thing, but any traces of the living cells have long gone and been replaced with rock. Essentially, the fossil ammonite is a mould made of rock. |
| Virus | other – viruses cannot be clearly placed in any of these categories | They meet some of the biological requirements for being defined as living, but not all of them. This shows that imposing such definitions on the world is not as simple as we would like to think. Human constructions of ‘living’ are philosophical as well as biological, and where to draw the line is the source of much debate. |