According to scientific thought, when does one species of organisms become two species?

a.
when one population becomes extinct

b.
when populations compete for the same resources

c.
when populations become separated from one another

d.
when one population cannot interbreed with the other population

Some gamma ray bursts are hypothesized to come from mergers of neutron stars or black holes. if this hypothesis is correct, what else should we in principle be able to detect from such mergers? a. gravitiational waves b. x-ray bursts c. significant disruption of gas thousands of light-years away in the surrounding galaxy d. an "afterglow" of bright visible light, lasting for weeks

Why might a single rock layer exhibit different types of sedimentary rocks within it? view available hint(s) why might a single rock layer exhibit different types of sedimentary rocks within it? such a rock layer, termed a facies, when traced laterally represents a variety of depositional environments that formed in a sequence over time. such a rock layer, termed a facies, when traced laterally represents a single depositional environment that formed over time. such a rock layer, termed a facies, when traced vertically represents a variety of depositional environments that formed at the same time across a broad area. such a rock layer, termed a facies, when traced laterally represents a variety of depositional environments that formed at the same time across a broad area. such a rock layer, termed a facies, when traced vertically represents a variety of depositional environments that formed in a sequence over time.

Scientist: cross-sections of stalactites—calcite formations deposited on cave ceilings by seeping water—can reveal annual variations in rainfall in particular areas over hundreds and thousands of years. we often found that when—according to these cross-sections—drought occurred in a particular area, it coincided with the collapse of an ancient society in that area. i hypothesize that drought reduced agricultural productivity in these areas, thereby leaving these societies without the resources needed to handle internal stresses and external threats. which of the following, if true, would most weaken the support for the scientist's hypothesis? a. many droughts indicated in the cross-sections of stalactites do not correspond with the collapse of a society in that area. b. information from the cross-sections of stalactites alone cannot reveal the level of agricultural output in an area at a particular time. c. most of the societies that collapsed during droughts did so when internal power struggles coincided with military raids from neighboring societies. d. most of the societies that collapsed during droughts maintained large stockpiles of food and water at the time of their collapse. e. information from stalactites also suggests that the collapse of some societies coincided with periods of abnormally high rainfall.