Entering Sector 1
You have to go to the main elevator. Use the elevator that goes to sector 1. Go to the navigation booth.
As you adventure through Sector 1, you will encounter two pink lizards. Blast them with a missile to make them visible, then start blasting them with missiles and charge beams until they die.
You go through a spiral ramp. Go across the first bridge, into the navigation room. Save your game, and go on to the next two rooms. You will have to fight three shelled creatures. The best way to beat them are lethal strikes. Go through the only available door. Take a morph ball passage, to obtain a missile tank, and to go to another portion of Sector 1. Go down the stairs, into a hallway. Go to the end of that hallway. Go through the door at the end. You will be in the breeding room. Go into the next room, and Samus will feel the presence of a dark intelligence. Go back into the breeding room.
Go back to the room with stairs. Go into the other room that you can access, and have not been in yet. Go into search view mode, and blast at the zoomer with a missile. Take the morph ball passage, and back into the room with the morph ball passage. Go back to the room where you fought the shelled creatures. Locate a mouse thing in the room. Adam will unlock the door that you were not able to open before. You will go on to another navigation booth. After saving, the door to continue will be locked. You will have to use a bomb on the left wall to move on. Continue on until you reach two more pink lizards.
More Pink Lizards
You defeat them the same way you defeated the other two pink lizards.
Two robots will come out. You have to wait for them to charge up their lasers. Shoot their cannons with charge beams. When you kill one, another will pop up. You have to kill three of them in total. After you defeat the last one, you will get the diffusion beam.
You will go into a room with two fly nests. First you have to all the flies. Then, you just have to blast both of the nests with three missiles each.
Boss Battle: Fune and Nomie
First you have to wait for one of them to stick their face out of the wall or ceiling. Blast one of them in the face with a missile. When it pops out, blast its orange spots with charge beams, until it is downed. Hit the downed worm with a lethal strike. Do it all again on the other worm. Now you can use the terminal to unlock the door in the navigation booth.
Biological Test Floor
First, you have to get back to that navigation booth, and go through the door that you couldn't go through before. Go across this room. Find a morph ball passage, and go through it to deactivate the first force field. Find the second force field. Use the same morph ball passage to reach the terminal to deactivate the second force field. Find a hidden passage on a rock. Go through it (reactivate the second force field if you have to.) Now you are in the biological test floor. Go up the spiral ramp, into another room. Blast through all of the obstacles. The last one will have another shelled creature. Kill it. Go through the purple tunnel.
Boss Battle: King Kihunter
This is a pretty tough boss fight. It will begin when you spot some small brown creatures. First, kill all of his little Kihunter minions. Then five flowers will open up. You have to blast all five of them with a missile. The purple nest will fall after that, and you have to kill more Kihunter minions. Now for the final stage. Blast King Kihunter with five missiles. After that, he will turn to stone, and you will then watch a cutscene.
Are we close or not?
Adam gives you a mission to go to the Biosphere Test Area. As you go on, there will be a water room. You have to hit a lot of charge beam switches to get through it. After that, you continue exploring until you get to a room with a lot of trees.
Boss Battle: Groganshious
This boss can shift forms between a giraffe and a spider. He is simple to beat, though he takes several hits. You beat this boss by constantly shooting his orange ball. While you are shooting him, you have to dodge his purple balls that will damage you. After a few minutes he will be defeated.
Just run along to the Biosphere Test Area; there is only one way to go.