The Receiver level in Darwinia is where the souls of the Darwinians fall back down to the ground, to be collected by giant towers that send the souls to the Pattern Buffer for reincarnation. Because of this purpose, the Receiver level is considered holy ground to the Darwinians. You have two primary objectives here, first to man enough receiver towers with Darwinians to collect 50 souls per minute and second, to enable the Biosphere Trunk Port for the souls to be sent through.
Start this level of Darwinia by clearing the first island where the Yard Trunk Port is built upon. Capture the Incubator as soon as possible so you can begin to amass some Darwinians. From here you can move to the nearby island with receiver towers via the Radar Dish. Go here next, and clear up the area of the virus infection while again collecting all the souls you can. You can start sending your Darwinians through the Radar Dish to assist in the fight and start manning the towers to collect souls.
Once you have these two islands under your control, create some Armor and load them up with Darwinians. Make sure you bring at least 20 Darwinians and 2 Turrets to the central island where the Soul Destroyers are, and set them up near each other, close enough to the Spiders and Soul Destroyers here to fire upon them, but not close enough that they can kill your Darwinians before they can man the turret.
Once this central island is clear, you can capture the Biosphere Trunk Port before heading to the last two islands to capture more receiver towers. I suggest taking the island with the Army Ant infestation first, sending in an army of Darwinians with deployed Armor turrets in order to not only capture the receivers, but the Trunk Port to the Pattern Buffer, giving you a second route of attack when you begin that level. Just keep clearing the infestation and manning more towers until the objective marks as completed and you are free to move on to the Pattern Buffer.