Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Simple Model of Large Scale Organization in Evolution   A mathematical model of interacting species filling ecological niches left by
the extinction of others is introduced. Species organize themselves into genera
of all sizes. The size of a genus on average grows linearly with its age,
confirming a general relation between Age and Area proposed by Willis. The
ecology exhibits punctuated equilibrium. Analytic and numerical results show
that the probability distribution of genera sizes, genera lifetimes, and
extinction event sizes are the same power law $P(x) \sim 1/x^2$, consistent
with paleontological data.

25
The categories of this paper are: patt-sol
23
The categories of this paper are: solv-int
7
The categories of this paper are: hep-th
24
The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
3
The categories of this paper are: physics
18
The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
16
The categories of this paper are: stat
17
The categories of this paper are: q-fin
37
The categories of this paper are: supr-con
8
The categories of this paper are: hep-ex
35
The categories of this paper are: mtrl-th
2
The categories of this paper are: math
30
The categories of this paper are: q-alg
22
The categories of this paper are: chao-dyn