Answer:
Answer is A. allow them to control all the variables involved.
Explanation:
Modelling in ecology means the use of constructed mathematical models for understanding of ecological processes and to predict or know how real it is for ecosystem to change.
Ecological modelling is useful in defining problems more precisely and clarity of concepts.
The guinea pig and the raccoon are both members of :
The eukarya domain, the kingdom of animals, the chordates and the mammal class.
After the level of class (Mammalia), they start to belong to different groups.
The guinea pig belongs to rodents and the raccoon belongs to the carnivores.
"Viruses straddle the definition of life. They lie somewhere between supra molecular complexes and very simple biological entities. Viruses contain some of the structures and exhibit some of the activities that are common to organic life, but they are missing many of the others. In general, viruses are entirely composed of a single strand of genetic information encased within a protein capsule. Viruses lack most of the internal structure and machinery which characterize 'life', including the biosynthetic machinery that is necessary for reproduction. In order for a virus to replicate it must infect a suitable host cell".
From The Bacteriophage T4 Virus
Boundary between two air masses of different temperatures and/or humidity levels
