Why can it be difficult to define the boundaries of an ecosystem?

Compare and contrast cladistics and phylogeny. what are their advantages and disadvantages? which is the most useful in understanding how an organism developed into its current form? which concept most strongly supports your opinion about the origin of any given organism?

Advances in technology have enabled scientists and researchers to better study the evolutionary relationships between species

Why do we perceive objects as retaining their brightness under different lighting levels?