In an investigation to determine a factor that affects the growth of rats, a student exposed 100 rats of the same age and species to identical conditions, except for the amount of living space and the amount of food each rat received. Each day the student measured and recorded the weight of each rat. State one major error that the student made in performing this

Violating 'Ceteris Paribus' {Other factors constant} assumption, as both food & space are varied (simultaneously)

Explanation:

Weight Growth is the dependent (effected) variable in this case. And, independent (causal) variables are food amount are living space respectively.

However particular independent factor's (food or living space) impact on dependent variable ie weight growth : can be determined only by - examining individual variable (food or living space) impact on weight growth. So, either of the two variables should be varied, & not both should be varied simultaneously.

This would imply depiction of each factor's clearer individual impact on the dependent factor.

answer and explanation;

volcanic rocks are igneous rocks which form from lava, molten rock which has been thrust out of a volcano onto the surface of a rocky body such as an asteroid, planet, or dwarf planet.  

plutonic rocks are igneous rocks which form from subterranean chambers of molten rock or magma. plutonic rocks make up the base of continental crust as well as oceanic crust. their slow rate of formation causes them to be coarse grained since there is plenty of time for large crystals to form before the magma solidifies into rock.

the textural difference is that plutonic rocks are more coarse grained than volcanic rocks. plutonic rocks are coarse grained while volcanic are fine grained ; glassey or fragmental. since fine and coarse are adjectives the decision as to whether a rock is fine or coarse grained is generally made on the bases of whether or not the individual crystals can be seen in most if the rock.