Investigating the effects of environmental pollution is a significant aspect of Biology Topics.
Define the Life Span. What Is The Life span of Living Organisms?
All the living things start their life when they are born as babies or hatched from eggs (as animals do), or grow from seeds, etc. (as plants do). These living things (animals and plants) grow into adults, remain alive for a certain time and finally die. No living thing remains alive forever (except GOD!). Different kinds of living things remain alive for different durations of time. The time period for which a living thing remains alive is called its life-span. All the living things have a definite life-span. For example, man has an average life-span of 60 to 70 years. This means that the average duration of life of man on this earth is 60 to 70 years.
Different living things have different life-spans. For example, the life-span of some insects seen during rainy season is of only a few hours whereas the life-span of a tortoise is more than 100 years. Just as in the case of animals, different types of plants have different life-spans. But most of the large trees have longer life-spans than animals. Thus, a yet another characteristic of living things is that they ultimately die. On the other hand, non-living things do not have a definite life-span. Non-living things live for ever. For example, a rock is a non-living thing which does not have a definite life-span. It exists forever.
The Case of a Seed
In general, a living thing may show all the characteristics that we have discussed. This, however, is not always true. Sometimes, a living thing may not show all the general characteristics of living things. It may show only a few of them. This point will become more clear from the following example.
Let us take the case of seeds, say wheat seeds (or wheat grains). Now, wheat seeds (or any other seeds) are living things but they do not show most of the characteristics of living things. For example, wheat seeds do not require food, they do not grow (wheat seeds can remain as such in a shop for months and months), they cannot move on their own, they do not excrete and do not reproduce. The wheat seeds, however, respire. So, the only characteristic of living things shown by wheat seeds is respiration. The fact that wheat seeds undergo respiration can be shown as follows :
Let us put our hand deep inside a gunny bag full of wheat grains. We will find that it is somewhat warm inside. This means that some heat is being produced inside the gunny bag full of wheat. Actually, the wheat grains or wheat seeds respire and give out some heat energy during respiration. It is this heat produced by the respiration of wheat seeds which makes our hand feel warm when put inside the bag full of wheat. Thus, respiration is a life process which takes place in dry, stored seeds even when other usual life processes are not observed. So, we can say that seeds are a living thing because they undergo respiration. If, however, we sow a seed in the soil and water the soil, then the seed shows growth and turns into a new plant.
Before we end this discussion on the characteristics of living things, we are giving below the differences between living and non-living things in the form of a table.
Differences between Living Things and Non-Living Things
| Living things | Non-living things |
| 1. Living things need food, air and water. | 1. Non-living things do not need food, air or water. |
| 2. Living things grow. | 2. Non-living things do not grow. |
| 3. Living things can move on their own. | 3. Non-living things cannot move on their own. |
| 4. Living things respond to stimuli (changes around them). They are sensitive. | 4. Non-living things do not respond to stimuli. They are not sensitive. |
| 5. Living things reproduce themselves. | 5. Non-living things do not reproduce. |
| 6. Living things respire. They release energy from food. | 6. Non-living things do not respire. |
| 7. Living things excrete. They get rid of waste materials from their body. | 7. Non-living things do not excrete. |
| 8. Living things have a definite life-span after which they die. | 8. Non-living things exist for ever. |