During which geologic period did plants and animals first appear in land environments?

Silurian Period

Explanation:

The Silurian is the shortest period of the Paleozoic Era. As with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by a few million years. The base of the Silurian is set at a series of major Ordovician–Silurian extinction events when up to 60% of marine genera were wiped out.

A significant evolutionary milestone during the Silurian was the diversification of jawed fish and bony fish. Multi-cellular life also began to appear on land in the form of small, bryophyte-like and vascular plants that grew beside lakes, streams, and coastlines, and terrestrial arthropods are also first found on land during the Silurian. However, terrestrial life would not greatly diversify and affect the landscape until the Devonian.

The Silurian Period.

Explanation: The Silurian Period in geologic time was the third period of the Paleozoic Era. It is a period that saw plants and animals emerge on land. It began about 443.8 million years ago and ended at about 419.2 million years ago, this means that it extended from around the close of the Ordovician Period to the beginning of the Devonian Period.

During this period, there was melting of large glacial formations, thereby causing a rise in sea levels. This was the time when coral reefs also first appeared, and also this period marked the widespread distribution of jawless fishes and fishes with jaws.