What name is given to a long term change that takes place in two species because of their close interactions with one another? give an example and explain

Coevolution is the name given to a long term change that takes place in two species because of their close interactions with one another.

Coevolution occurs when the evolution of two or more species mutually depends on each other or influences each other due to their close ecological interactions. Coevolution can create interactions such as predators and prey, parasites and hosts, mutualism and competition.

An example of coevolution is mutualistic interaction between flowering plants and associated pollinators (such as insects) which have ecological interaction and mutually depend on one another.  This species are believed to evolve together or probably came together after some time and are mutually adapted. Their interaction is as a result of coevolutionary process.  

if your own plato the answer is b. the fern transitioned from sporophyte generation to gametophyte generation.

the unequal cytoplasmic division that  results  in  one egg  and three polar bodies ensures that a fertilized  egg has  ample nutrients  forits journey  to  the uterus.