Many species of orchids are known as epiphytes. these are organisms which grow upon or are attached to other plants. epiphytic orchids use trees or shrubs for physical support, and do not or harm the trees or shrubs in any way.
what type of relationship does an epiphytic orchid have with its host plant?
commensalistic
mutualistic
competitive
parasitic

The orchid derives the benefit of physical support from the tree, while the tree receives neither benefit nor harm. This is an example of a COMMENSALISTIC relationship.

not necessarily. higher fitness requires the organism to be reproductive successful. for example, an organism at age 10 with 15 offspring is much more fit than an organism at age 15 with only 5 offspring.

propane is burned to provide the heat in many cooking grills. the chemical reaction for this process is shown in the equation below.

c3h8 + 5o2 ? 3 co2 + 4h2o + energy

what are the products in this chemical reaction?

3co2 + 4h2o + energy