In an ecosystem. There are two types of organism. First group of organism is called the r-selected and the other is called the k-selected.

What are they?

Before an ecosystem establishes (eg. in sand dunes or in a burnt forest), the r-selected group acts as pioneer species. They have high "reproductive effort" hence their presence blooms over the new environment.

Unfortunately, the r-selected have short life span. Somehow the r-selected change their own environment and make it hostile to themselves. A paradox. Overtime, the environment transforms and the other type of organism emerges. The k-selected.

The environment that the r-selected left contains a whole lot of nutrients for the k-selected. The presence of them marks the sign of a stable environment.

the r-selected changes the environment which favors the k-selected.

Are you the k-selected or the r-selected? =)