How would a biological drop pod make it into the atmosphere and land safely? I have a race of aliens that use biological tools instead of technology. Their ships are living beings that can travel through space to find habitable planets. After flying over a planet they find suitable they launch their drop pods which are like plant seeds only they need to survive atmospheric entry and the landing to plant vegetation. After seeding the planet and successfully terraforming it they use the same drop pods to send themselves on their new planet.
It's very much like a more peaceful version of the Zerg swarm from Starcraft. Only the mystery is, how would the drop pods be designed for such a task?