Crosses of pure-breeding lines can result in progeny phenotypes that don't appear to follow mendel's rules. explanations for this include:
a) no definitively dominant or recessive allele
b) more than two alleles exist
c) multiple genes involved
d) gene-environment interactions

b) More than two alleles exist

Explanation:

There are cases where more than two alleles determine a character in the population. This type of inheritance is called multiple alleles (or polyalelia). Classical examples of polyalelia are hair color determination in rabbits and blood groups of the ABO system in humans.  

In the attached figure we can see another example of polyalelia where a flower is self-fertilized generating different phenotypes in its offspring.

answer: national resource conservation services

national resource conservation services is the us. based approach that provides technical and financial assistance for natural resource management. nrcs society in conservation of resources by involving in activities like farmland protection, flood prevention, watershed protection, urban conservation, conserves economic and environmental conditions. it conducts soil surveys and implements the policy of natural resources management on the society.

producers: apple trees, potatoes, carrots, grains, acorns, cabbage, grass, corn, lettuce

consumers: deer, mice, rabbits, chickens, squirrels, horses, worms, cows

predators: eagles, frogs, wolves, owls