I believe it is resources
Decomposers, like fungus.
Discontinuous variation <span> refer to large, conspicuous differences from the parents</span>
This is where individuals fall into a number of distinct categories, and is based on features that cannot be measured across a complete range
continious variation refer to small, indistinct differences from the normal condition.
Milk yield in cows, for example, is determined not only by their genetic make-up but is also significantly affected by environmental factors such as pasture quality and diet, weather, and the comfort of their surroundings
Genetically modified crops are genetically engineered such that a desired trait is enhanced or reproduced to appear in every offspring. Genetically engineered corn has been engineered to resist pests and herbicides; thus, we have more yield and many people especially in the low class society can afford. A disadvantage, yet is still a debate, is that genetically engineered crops such as corn, has toxic effects to internal organs such as our liver, a vital internal organ.
Speed. This is more of a physics question.