Equal number of sham operated and age matched animals served as controls.

Aplysia is known to form mating chains with up to 20 animals, thus each animal can serve as male and female at the same time.

The infected animals can serve as the source of infection for the whole herd because they will spread the bacteria throughout the environment.

Other animals such as giraffe, kudu and hartebeest can also serve this function.

In experiments performed on dogs, each animal served as its own control.

Many other animals serve to fill spaces left at the end of lines.

The people and animals of the Everglades served as subjects for some of her earliest writings.

Such giant animals, fruits and vegetables, or replicas of famous buildings often serve as attractions themselves.

She could capture a familiar, making an animal serve her or be her eyes and ears.

So animals might have served without being self-aware.