Add higher life-forms before anything competitive can evolve.

Not when higher life-forms are the very thing the invaders desire.

Planets where the mutation rate was big enough to create higher life-forms, leaving the fossils Horis showed us earlier.

One great mystery is why sexual reproduction became dominant for higher life-forms.

No life-forms higher than deep sea algae remain on a world that, to judge by the artifacts left behind, had an advanced civilization.

The "high powers" are the highest known life-forms.

There is only one area in which higher life-forms are present in great enough concentration to register despite the interference.

"The artifact appears to know when a higher life-form wishes to penetrate the field."

Appetite exists in all higher life-forms, and serves to regulate adequate energy intake to maintain metabolic needs.

I'm not getting communications from any higher life-forms.