Protozoans are single-celled organisms.

As the name suggests, chordates are a group of animals that have a notochord.

He likes to take a walk in the park at dusk.

He understands the meaning of the proverb 'Teaching is half learning', which means that teaching leads to one's own learning.

It is reported that North Korea has conducted another underground nuclear test.

He is an expert in experimental psychology.

He is spending a lot of time on experimental research.

Echinoderms are a type of marine life, many of which have star-shaped bodies.

The characteristic of annelids is that their bodies are divided into ring-shaped segments.

A tardigrade can survive in extreme environments.