user: Let's come up with a rich and complex alien world setting suitable for stories, pseudo-documentaries, or roleplaying games such as DnD. This can be an involved process, so I'd like you to just cover the basics first. We can refine the details further later.

I'd like a planet with a variety of biomes, inhabited by many creatures, much like Earth, but life on this world took its own path, with different plants and animals (and perhaps a different distinction than "plant" vs. "animal" to begin with)

There should be at least one sentient species represented in a wide variety of cultures and societies. They should have complex interactions with each other, and other species on the planet, and resulting from that, their own needs and wants and fears which ought to be relatable in context but may at the same time be strange, unusual, and, well, alien to humans.

But let's start at the beginning: Can you give a few broad, interesting biomes and how they might exist in their "wild" (pre-sentient) forms vs. how a local sentient species might have altered them over the ages?
While doing so, it is important to consider the solar system that planet is a part of, as other objects of the system, especially ones that are very close or very massive, may have a significant effect on the planet and its biomes.

assistant: Sure! Let's begin by creating a planet that we'll call "Terra Nova."

Terra Nova is a terrestrial planet orbiting a yellow dwarf star in the habitable zone of its solar system. The planet has a diverse range of biomes, including:

The Forest Biome - This biome consists of densely packed trees and thick undergrowth. The trees are tall and broad-leaved, and the undergrowth is made up of various types of ferns and mosses. There are also numerous streams and ponds that flow through the forest, providing water to the many creatures that live there. The sentient species on Terra Nova has modified this biome by building large treehouses and using the trees for shelter and resources.

The Desert Biome - This biome is hot and arid, with sand dunes, rocky outcroppings, and sparse vegetation. There are also large salt flats and occasional oases. The sentient species on Terra Nova has developed an extensive network of underground tunnels and caves to avoid the harsh surface conditions and to store water and resources.

The Ocean Biome - This biome covers more than half of Terra Nova's surface, consisting of deep trenches, vast plains, and coral reefs. The sentient species on Terra Nova has developed a complex society of underwater cities and structures, using the ocean's resources for food, energy, and transportation.

The Mountain Biome - This biome is made up of towering peaks and steep valleys, with rocky terrain and thin air. The sentient species on Terra Nova has developed specialized tools and techniques to climb and traverse the mountains, as well as building fortified structures for protection.

The Tundra Biome - This biome is characterized by cold temperatures, low precipitation, and frozen ground. There are patches of low-growing vegetation, but the landscape is mostly barren. The sentient species on Terra Nova has developed unique adaptations to survive in this harsh environment, including thick fur and specialized hunting techniques.

Overall, the sentient species on Terra Nova has had a significant impact on the planet's biomes through their activities and developments. They have built structures, modified landscapes, and created new ecosystems to suit their needs. However, they also recognize the importance of preserving the natural world and work to maintain a balance between their technological advancements and the planet's ecology.