We build on previous people's ideas and work all the time. Plagiarism refers to using someone else's work and calling it your own. You can talk about other people's work and expand using examples but you do have to show evidence of critical thinking and analysis by using more than one source to build your own argument. There's a difference between describing someone else's work and building on it.
you can totally use someone elses idea and even their study data if it is referenced. you word it like this for example (ignore the bold and italics):
To date, research on the effects of increasing temperature and ocean acidification on marine ecosystems has focused on single drivers in isolation, and there has been a particular emphasis on specific effects such as coral calcification (for overviews see Fabry et al. 2008, Przeslawski et al. 2008). Thus there is currently a disconnect between the literature examining the biodiversity – ecosystem functioning (BEF) relationship and the literature examining the effects of climate change on ocean ecosystems (Schmitz et al. 2003), as well as a general lack of studies examining interactive effects of climate change on ecosystem functioning. The latter is particularly important because the interactions between multiple stressors are difficult to predict as the resulting net effect may not be additive but, instead, may either be greater (synergistic effects) or less (antagonistic effects) than anticipated (Folt et al. 1999).As a step towards understanding the uncertainty associated with current forecasts of the ecological consequences of environmental change, here we test for interactive effects of macrofaunal species richness, temperature and atmospheric CO2 concentration on levels of nutrient release from the sediment to the water column in a model marine benthic system. An important mechanism underpinning nutrient release is the process of bioturbation, the mixing of porewater solutes and sediment particles by the movement and activities of the benthic organisms (Richter 1952). Bioturbation affects sediment permeability, breaks down chemical gradients in pore waters and subducts organic matter, thus influencing rates of remineralization and inorganic nutrient efflux (Gray 1974, Rhoads 1974, Kristensen & Blackburn 1987).
you will need to use other sources and their ideas in your essays to form your own conclusions, sometimes you will compare two contrasting ideas and give your own reasons for which one you decide is more likely.