HI, I've read a lot of the issues people are having with the time travel, and it affecting the future. They address this within the first 30 minutes of the first episode. The daughter points out the probe that they sent back and couldn't find in the future, thus proving that they are in an alternate timelime. Thats why they knew it was safe for them to travel back there.
As for if they will travel back and forth and/or bring animals and plants to the future is pointless. They may travel back and forth for some stories who knows, but the premise is that they are going there to build their lives again, and eventually get everyone there.
I think this show has plenty of possibility, and is showing the right amount of complex story, with episodic structure for it to finally last the sci-fi curse.