The somewhat-predictable series of changes to ecosystems over time is called
(community development / ecological succession / population ecology /
symbiosis development). the first species to colonize barren areas are called
(pioneer / primary / secondary / tolerant) species, and may include lichens and
some grasses.

Ecological succession and pioneer species.

Explanation:

The ecological succession may be defined as the change in the species community with respect to the time. Two main types of succession are primary succession and secondary succession.

The species that occupies the first in the succession is pioneer species. The grasses, lichens can acts as the pioneer species in the primary succession. Secondary succession is faster than primary succession.

Thus, the answer is ecological succession and pioneer species.

the answer is b.) hydrogen bonds between bases.