Question: a. the teacher puts a sugar cube into a container of warm water. eventually the sugar cube is no longer visible. what type of change is this and why?

physical change.

Explanation:

A physical change is defined as a change in which there is alteration in shape, size etc. No new substance gets formed in these reactions.  Example: melting of ice

A chemical change is defined as a change in which a change in chemical composition takes place. A new substance is formed in these reactions.  Example: Combustion

As the sugar cubes dissolves into a container of warm water, it only changes its state from solid to aqueous and no new substances are being formed. Thus it is a physical change.

they each offer a fresh glut of resources to the organisms that can arrive and exploit them. as individuals and new species continue to appear, they actively and passively alter the environment. competition for shared resources increases, local abiotic and biotic conditions shift, and the relative abundances of species change accordingly. the process is called ecological succession, and it is one of the earliest and most well-known concepts in ecology.