A gas was produced.

A solid was produced.

The salinity of the reactants was high.

The temperature of the reactants was low.

The area was once covered by water.

Volcanic activity once occurred in the area.

A catastrophic event once occurred in the area.

Erosion turned most of the limestone in the area into sand.

Heat from the asteroid caused massive fires that reduced the food supply.

Dense clouds formed following the collision, causing a global drop in temperature.

Land masses were altered by the collision, reducing the space where dinosaurs could roam for food.

Glaciers melted rapidly from heat produced by the asteroid, causing floods that destroyed dinosaurs' habitats.

Muscle cells use more energy than skin cells.

Muscle cells have fewer proteins than skin cells.

Muscle cells have a smaller nucleus than skin cells.

Muscle cells have more excess water than skin cells.

Both are contagious diseases.

Both infect host organisms.

Both reproduce using host cells.

Both break down food using oxygen.