Here's why:

* Niche: A niche is the role an organism plays in its ecosystem, including its food sources, habitat, and interactions with other organisms.

* Competition: When two species have overlapping niches, they will compete for the same resources, such as food, shelter, or mates.

* Outcomes: Competition can have various outcomes:

* Competitive exclusion: One species may outcompete the other, leading to the exclusion of the weaker species from the niche.

* Resource partitioning: The species may evolve to use slightly different resources or specialize in different parts of the niche, minimizing competition.

* Coexistence: The species may find ways to coexist, perhaps by utilizing resources at different times or in different ways.

Examples:

* Lions and Hyenas: Both species are predators that hunt similar prey in the African savanna. They compete for food, leading to territorial fights and resource partitioning.

* Barnacles on rocks: Different species of barnacles compete for space on rocky shores. Some species may be better at attaching to specific types of rocks, leading to niche specialization.

In general, competition between species is a major factor driving evolution and shaping the diversity of life on Earth.