Theory

[jman]

Is it at all possible for a planet to evolve where most of the surface is covered by tropics and very little temperate regions?

[vh]

if you mean the evolution of organisms on the planet, inheritance, variation, and competition is needed for evolution, so as long as the tropical environment satisfies that, i guess so

[jman]

I meant tropical regions as climate and landforms

[vh]

animals evolve in tropical regions of earth too

[smjjames]

If the planet had very little axial tilt (and isn't tidally locked to it's sun), seasons as we know them would be nonexistent, and if it were warm enough, then yes much of it would be tropical climate.

Of course though, if the orbit (or the gas giant parent, if that's the case) was elliptical enough but not TOO elliptical, that could create something like seasonal variation.

[jman]

Wouldn't factors such as wind patterns and ocean currents affect the climate as well?

[smjjames]

Yeah it would, mountains as well. I mean that if the climate is warm enough (like say, during the Jurassic period), then there would be a good deal of tropical climate, but it won't be the only climate or biome.

[jman]

Could the planet also evolve with thick clouds such as venus but maintain habitable?

[Darvince]

thick clouds are more of a localized event. like during the jurassic, with weak jetstreams and such, a hemisphere probably would've gone from like 5% cloudcover during the night to something like 70% cloudcover during the stormy afternoon

[AFFA]

Some possibilities. Disclaimer: I am not a scientist and have no idea what I'm talking about.

Rapidly rotating planet with low axial tilt

The low axial tilt reduces seasonal variation. The rapid rotation helps stabilize the axis (assuming there isn't a large moon to do so) and reduces the day-night temperature difference.

Slowly rotating planet with a dense atmosphere and superrotating jet

I'm not sure if anyone has figured out why Venus and Titan have a superrotating upper atmosphere, but a long day-night cycle seems to be part of the cause. Titan's "day" is about 16 Earth days, so anything rotating this slow or slower might have this feature. It tends to spread heat out very effectively so most of the planet could be a jungle. Surface winds probably wouldn't be much higher, all else being equal.

Huge ocean with islands, reasonable axial tilt

If the oceans are mostly open from pole to pole, this would probably even out temperatures on the whole planet. Deserts, tundras, etc tend to occur in the middle of large land masses. A planet of smaller islands (although I'm not sure how that might form) would have a more mild climate and could have "jungles" on all the islands that aren't very close to the poles.

Moon of gas giant with low obliquity and eccentricity

In this case, the hot spot that would normally occur on the side of the moon facing the gas giant is mitigated by the daily eclipses.

To get a "day" of 24 hours or less, it's tricky to set up a situation where tidal heating isn't a problem (hints: >Jupiter mass giant, moon smaller and denser than Earth, no resonance with other moons). So either the gas giant is a little further from the star and the moon is very tectonically active or the day-night cycle is long and the day-night temperature difference may be rather high (but several things can mitigate this, such as a thick atmosphere or if the day gets long enough to cause superrotation in the upper atmosphere, etc).

If the moon has a long "day," it might not have a strong magnetic field. In that case, the magnetic field of the gas giant is very important as one that is either too weak or too strong could result in the moon losing its atmosphere very rapidly (but most of that loss might go into orbit around the gas giant and end up hitting the moon again, depending).

Moon of a gas giant with a high moon-giant obliquity

This situation doesn't end up with even heating across the whole moon, but the equator can be only a few degrees warmer than the poles. There will be a large "hot spot" on the side of the moon that faces the gas giant which will be significantly warmer. I don't think anyone knows what that would do. It would probably depend heavily on the orbital period "day" length.