Convection cannot take place in solids because neither bulk current flows nor significant diffusion can take place in solids. Diffusion of heat can take place in solids, but that is called heat conduction.

As the updraft of a tornado intensifies, it creates an area of low pressure at the surface.

The male gonad, the testicle, produces sperm in the form of spermatozoa. The female gonad, the ovary, produces egg cells.

Historically, protozoa are defined as single-celled organisms with animal-like behaviors, such as motility and predation.

DNA is organized into long structures called chromosomes. During cell division these chromosomes are duplicated in the process of DNA replication, providing each cell its own complete set of chromosomes.

Earth is located about 25,000 light-years from the galactic center and 25,000 light-years away from the rim. So basically, if you were to think of the Milky Way as a big record, we would be the spot that's roughly halfway between the center and the edge.

Jupiter's moon Io is the most volcanically active body in our solar system. Active volcanoes constantly spew material onto Io's surface.

There is about 1/2 lb or 250g of table salt (NaCl) in the body of an average adult human.

Enamel is the hardest substance in the human body and contains the highest percentage of minerals, 96%, with water and organic material composing the rest. The primary mineral is hydroxyapatite, which is a crystalline calcium phosphate.

Venus is the brightest planet in Earth's dark skies. Only the moon -- which is not a planet -- is brighter. Venus outshines the other planets because it is closer and its thick cloud cover are is excellent for reflecting sunlight.