Final answer:
The number of ears on a stalk of corn is not a continuous trait, unlike the other options listed which all represent examples of continuous traits that can be quantified and show a range of phenotypes.
Step-by-step explanation:
The question posed is asking which of the listed options is not a continuous trait. Continuous traits are those that can vary in degree and can be measured along a gradient. They are influenced by multiple genes (polygenic) and often show a range of phenotypes.
- Milk production in cows is a continuous trait as it can be measured and varies in quantity.
- Yield in soybean is also a continuous trait, with variations based on genetic and environmental factors.
- Growth rate of a line of turkeys is continuous, as individual turkeys can grow at different rates.
- Blood pressure is a well-known continuous trait in humans and animals, showing a range of values.
Therefore, the correct answer is E. the number of ears on a stalk of corn. While generally, corn stalks may have more than one ear, this is typically a discrete trait with a few distinct categories rather than a continuous spectrum.