dinosaurs’ decline may have been more subtle

lovethee History

The cause of the dinosaurs’ decline may have been more subtle. ln 1977, Animatronic Dinosaur costume Robert Bakker explored the biological consequences of the slower building of mountains and shrinking of seas that.marked the latest Cretaceous. New species often form from part of an existing population when it is cut off in an isolated valley or a continent. No longer breeding with the main population, the new population is free to evolve into its own species. The more such isolated pockets are created, the more quickly new species develop. The opposite happens when isolated highland valleys disappear and isolated continents become connected -species formation slows down. New links between previously separated continents also allow once separated faunas to intermix. This may increase the rate of species extinction, as new competition causes some species to lose out. Walking Dinosaur Costume Such interchanges can also spread diseases to unprotected species, and the ensuing epidemics can drastically reduce their populations. ‘fhe decimation of Native Americans was an example of such competition and disease-although in this case cuhural instead of species differences were the key ingredients. If a species’ population is so reduced, it is even more r,rrlnerable to competitirre pressures. Especially if a genetic “bottleneck” occurs-that is, the population is reduced to only a dozen or so individuals, making the species’ genetic diversit-v too low for reproductive success.2s If this happens, Realistic Dinosaur Costume the species may survive the initial crisis only to fail to reestablish itself in the long term. If species formation rates decline below the rate of species extinction, and this continues for long enough, then extinction of the entire group is mathematically assured.