They are always harmful but never beneficial or neutral.

Are you referring to symbiotic relationships between organism? If so, the answer would be parasitism.

One organism, a parasite, takes advantage of another organism at the expense of the host organism.

Ex. A tick bites a dog for blood to use as food. The dog gets an uncomfortable bug bite and the dog might catch a tick borne disease.

parasitism

Explanation:

parasitism is a symbiotic relationship between 2 organisms, where one organism (the parasite), lives on/in another organism (the host), causing it some harm.

c) 50% there are four chromosomes. after crossing over, 2 of the four have been changed. that means any gamete has a 2 in 4 chance or 50% chance of receiving the mutated chromosome.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.