Before We Leave

This is one of the easier scenarios. There are no space whales to worry about. The main objective of the game is reached when you've collected 100 of each type of plant on your initial island. Play the game as normal, expanding out. Each planet will have one or two (two initially, then down to one per planet) ancient ruins to explore after colonizing an island. Upon exploration, the ruin will transform into one of the 5 farms you'll need to grow. Connect it to your road system, work it, build more on the island, then trade it back up the chain to your initial island. If you can grow it on your initial island, great, but if not, rely on the spaceship trade networks.

Two tips:
1) For spaceship trades, be sure to set the desired amount at the destination (Planet 1, Island 1) at 101+. I set mine at 110 to be safe. This will ensure that trade spaceships will continually run that planet from the satellite planets to your home planet.

2) On your initial island, draw out some road and build 5 warehouses. When you discover a seed, set one of those warehouses to that plant and nothing else. Also, hit and select the goods tab. Select that plant/seed with and then set a minimum reserve for trade and at 100+. This will ensure that folks won't eat that plant. You have to have 100 of each plant at once.

Spam farms to keep your people fed otherwise. You may find other types of seeds that aren't in your objectives list. I found something like a "moon orchard" fruit that was just a buffed orchard. It didn't count in any way.

With no whales, there's nothing to worry about. I had two Sphinxes and a few gremlins in my game, but nothing too disastrous. Just takes a while for the goods to move through your trade network.

Edit: I started another game of Seed Hunter to go for the "Warm at Heart" achievement and this time I have space whales. Could be a case of YMMV, or, maybe there's a way of toggling space whales for scenarios. Hopefully someone can comment to confirm.