. Civic biology; textbook of problems, local and national, that can be solved only by civic coöperation. Biology. 286 CIVIC BIOLOGY CO O an o 1 SPECIES TIME — UNDER NATURAL CONDITIONS UNDER HUMAN CONTROL Attack by Ma7\ Adults. Lohsierlings \Na tural'Enem iesy. ^ih Fig. TOO loo. Diagram expressing Brooks's law of the extermination of a species by man as applied to tlie lobster problem The species is shown flowing along from an indefinite past nnder natural condi- tions, with minor fluctuations, hut maintaining a practically constant population, ha^^ng adjusted itself to its natural enemies hy d
. Civic biology; textbook of problems, local and national, that can be solved only by civic coöperation. Biology. 286 CIVIC BIOLOGY CO O an o 1 SPECIES TIME — UNDER NATURAL CONDITIONS UNDER HUMAN CONTROL Attack by Ma7\ Adults. Lohsierlings \Na tural'Enem iesy. ^ih Fig. TOO loo. Diagram expressing Brooks's law of the extermination of a species by man as applied to tlie lobster problem The species is shown flowing along from an indefinite past nnder natural condi- tions, with minor fluctuations, hut maintaining a practically constant population, ha^^ng adjusted itself to its natural enemies hy developing great fecundity, as seen in the wide stream of eggs and larva;, most of which are taken in the larval stage hy natural enemies. At the large arrow civilized man attacks the slender stream of adult lobsters which nature has selected to keep up the supply of eggs. This strikes the species as a "; IMan's attack is unlike that of all other enemies. Instincts of self-preservation, thickness of shell, and large size, which made the adult lobsters almost immune from attacks by other enemies, all are of no avail. Although man takes but a small number of adults, the bal- ance is disturbed, fewer eggs are produced, natural enemies crowd and tend to take a larger proportion, and the species swiftly approaches extermination. Even if man ceases his attack when the numbers have become reduced so as to render their further pursuit unprofitable, natui-al enemies may kill off the stragglers, and before we realize what has happened, the race is extinct. If we did shut off all the streams of young and adults at the jioint of the large arrow, we should have a picture of the extermination of the lobster. Under human control, if even a few adult breeders are left, man can increase the number to any desired amount; he can lift the eggs and young above the reach of natural enemies, or crowd them down, or both, and so increase the species to the limits of room or of f
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