Which of the following represents a unique characteristic of many animals that, in general, distinguishes them from the members of other kingdoms?
many animals have cells with rigid cell walls.
many animals include both aquatic and terrestrial species.
many animals have organs but no tissues.
many animals have sensory organs concentrated at one end of their body.

many animals include both aquatic and terrestrial species

a "theory" a suggestion that is not 100 % accurate, or a figure. some people say its a theory because they of all the passed theory's about one subject. it depends sometimes theory might be accurate and sometimes they are.

this age may represent the age of the earth's accretion, of core formation, or of the material from which the earth formed. this dating is based on evidence from radiometric age-dating of meteorite material and is consistent with the radiometric ages of the oldest-known terrestrial and lunar samples.