What is life?

„What is life?“. That is a difficult question. Especially if you want to answer them with primary school childtren. It is a question that children ask themselves when a sibling is born, a pet dies, or a doll needs nothing to eat. People have been thinking for millennia about a question. But even the scientists of today have not found a final answer. However, even thinking about the question and its answer is worthwhile, even for elementary school children.

Aristotle defined more than 2,000 years ago: what grows, preserves itself and reproduces itself is alive. This actually applies to almost all living things. However, there are also things that can be described in this way, but are not considered as alive. Fire e.g. grows, preserves itself and continues to grow as long as it gets something combustible. Even computer viruses do that as long as they can continue to infect unprotected computers.

Characteristics of life

There is no unitary definition of „life“. Instead, science uses criteria to distinguish living from inanimate objects. The most important features of “life” (from today‘s perspective), which are also suitable as a basis for teaching, are the following:

Living creatures ... :

Grow, develop and change.

Reproduce themselves and inherit traits.

Absorb energy and transform it.

React to light, wind, heat and water

Have a figure (gestalt).

Adapt to their habitat over many generations.

Another feature, which has already been mentioned in the introduction, is the division into compartments, so delimited spaces. In the case of multi-cells, the single compartments are the individual cells, which are specialized. Thin membranes and similar structures into areas in which separate processes can happen without any disruption divide the interior of these cells. This means that compartments are also existent in unicellular organisms.