survival of the fittest

Translations
выживание сильнейшего
In the wild, it's often a case of survival of the fittest.
В дикой природе это часто вопрос выживания сильнейшего.
Definitions
A concept in evolutionary biology that suggests that individuals or groups that are better adapted to their environment are more likely to survive and reproduce, leading to the continuation of their genetic traits in future generations.