Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Mass-extinction: Evolution and the effects of external influences on
  unfit species   We present a new model for extinction in which species evolve in bursts or
`avalanches', during which they become on average more susceptible to
environmental stresses such as harsh climates and so are more easily rendered
extinct. Results of simulations and analytic calculations using our model show
a power-law distribution of extinction sizes which is in reasonable agreement
with fossil data. e also see a number of features qualitatively similar to
those seen in the fossil record. For example, we see frequent smaller
extinctions in the wake of a large mass extinction, which arise because there
is reduced competition for resources in the aftermath of a large extinction
event, so that species which would not normally be able to compete can get a
foothold, but only until the next cold winter or bad attack of the flu comes
along to wipe them out.

29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
23
The categories of this paper are: solv-int
0
The categories of this paper are: hep-ph
18
The categories of this paper are: econ
16
The categories of this paper are: stat
31
The categories of this paper are: ao-sci
19
The categories of this paper are: eess
34
The categories of this paper are: chem-ph
7
The categories of this paper are: hep-th
12
The categories of this paper are: nucl-th
1
The categories of this paper are: cs
13
The categories of this paper are: quant-ph
24
The categories of this paper are: dg-ga
33
The categories of this paper are: plasm-ph
35
The categories of this paper are: mtrl-th