In each level there is one heart tank that will make your life-bar longer.

Chill Penguin: go on top of the cave and use Fire Wave (from Flame Mammoth) on the igloos. The heart will be on the last igloo.

Flame Mammoth: after defeating Chill Penguin, you will be able to walk on the floor using the Ice Shotgun weapon. After destroying the miners, go underneath the platforms and walk to the heart by freezing the lava.

Boomerang Kuwanger: after scaling the outside wall, go to the top and use the Boomerang Cutter (from Boomerang Kuwanger) to grab the heart.

Sting Chameleon: before entering the cave, slide down the hole and use the upgraded boots to break through the wall and dash to the far right to obtain the heart.

Spark Mandrill: after you get overwelmed with the robots on the ground and ceiling, look for a ladder going down. Climb up the wall at that spot (not on the ladder) and use Boomerang Cutter to grab the heart.

Storm Eagle: at the top of the escalator platforms, dash to the very left to get the heart.

Armored Armadillo: the second big 'plower' can be destoryed by the use of Fire Wave. Go forward you see an upward tunnel. Climb it and you will see the heart.

Launch Octopus: ride the third air jet to the top of the boat. Destoy the boat and let it sink. Go down with the boat and walk to the right. Enter the room and destroy the long snake. Then move to the right and get the heart.