They breathe through their skin. Air dissolves on the mucus of their skin, so they MUST stay moist to breathe.
If worms dry out, they suffocate. As fresh air is taken in through the skin, oxygen is drawn into the worm's circulatory system, and the worm's hearts pump the oxygenated blood to the head area.
Proteins are macromolecules that are made up of the subunits that are called amino acids, there are 20 fundamental kinds of amino acids present. These varying combinations of them make different proteins needed for numerous functions.
Answer:
cells are so small because it is structural functional unit of an organism which can be only seen through microscope
Answer:
D. predicting the age of the plant
Explanation:
stems don't exactly have those powers. but they do give support by holding the plant upright. they do give defensive properties. and they do increase the amount of sun exposure (like with sunflowers). but they don't predict anything.
