Fresh water is most dense at a temperature of about __________.

The rapid decline in the populations of top predator species such as cod, marlin, swordfish, and halibut severely impacts marine ecosystems because _________.

Tropical cyclones form over the ocean and not continents because of the greater source of ____________ heat from the ocean than from continents.

Controls of climate include __________.

In the atmosphere up to an altitude of about 80 km, oxygen (O2) makes up about __________ % and nitrogen (N2) comprises about _________% of the gases by volume.

Coral atolls ____________.

Earth is unique among the planets of the solar system because ____________.

Piloted and unpiloted submersible vehicles of the 21st century include all except for __________.

The amount of waste that an ecosystem can assimilate (via decomposition by bacteria, fungi, and invertebrates) without damaging ecosystem functions or building up waste products to levels that may cause unwanted or harmful impacts on living organisms (including humans) is called the ___________.

The Vikings were forced back across the North Atlantic from their occupation of North America by __________.