Explique por qué se considera que la vida en la tierra debe haber comenzado con la química.

Which of these statements best describes the st. lawrence seaway? the st. lawrence seaway connects the st. lawrence river with the arctic ocean. the st. lawrence seaway provides an important trading route between the u. s. and mexico. the st. lawrence seaway provides an important trading route for the u. s, but has little value for canada. the st. lawrence seaway connects the great lakes, the st. lawrence river, and the atlantic ocean.

The eruption of a nearby volcano causes a prairie ecosystem to receive a lot less sunlight. which of these is most likely effect on the ecosystem?

Why are current extinctions of concern to enviromentalists?