However, not all pension plans allow such withdrawals. Many pension plan rules do not allow in-service distributions, or withdrawals while you are still in service with the company. Some defined benefit pension plans do not allow early distributions at all. Others, such as some 401k plans, allow workers to make withdrawals at any time.
These indices not only measure species richness, but also take into account the relative abundance of species, or evenness. When measuring species diversity, species richness and evenness must always both be considered. In addition, indices provide important information about species rarity and commonness in a population. These are important and common tools used by biologists in order to understand community structure.
Biodiversity is simply the variety of life on Earth, but its importance to global ecology has made it one of the most important concepts in modern science. Because biodiversity cuts across different levels of organization it is often useful to focus on a particular type of biological diversity. 1  Species diversity is a measure of how many different species are present in a given area. Most often when people think of biodiversity they think of species diversity. Genetic diversity measures the amount of inherited genetic variability contained within a populations of species.