There are four known forces that are involved in evolution:

1)mutation,

2) genetic drift

3) gene flow or migration

4) selection.

TLS Online TPP Program

#Id: 3721

#Unit 10. Ecological Principles

Gleason’s individualistic model - Competition does not cause sharp boundaries; different species do not group together due to physical variables.

TLS Online TPP Program

#Id: 3722

#Unit 10. Ecological Principles

TLS Online TPP Program

#Id: 3723

#Unit 10. Ecological Principles

Species richness - which is a count of the number of species.

TLS Online TPP Program

#Id: 3724

#Unit 10. Ecological Principles

One major problem is that this approach does not take species frequency of occurrence or relative abundance into account.

TLS Online TPP Program

#Id: 3725

#Unit 10. Ecological Principles

Berger-Parker index - Dominance indices are weighted toward the abundance of the commonest or dominant species
D_BP = N_max /N

TLS Online TPP Program

#Id: 3726

#Unit 10. Ecological Principles

More diverse communities have a lower value of D BP than less-diverse communities.