Final answer:
The F1 hybrid between sand oats and durum wheat would have 42 chromosomes and would likely be sterile due to the unpaired chromosomes that result in difficulties during meiotic cell division, inhibiting the formation of viable gametes.
Step-by-step explanation:
The student has asked how many chromosomes the F1 hybrid between sand oats and durum wheat would have, and whether they would be fertile or sterile. Sand oats, with a somatic chromosome number of 14, and durum wheat, with a somatic chromosome number of 28, both have the basic chromosome number x of 7. Therefore, the F1 hybrid would have the combined somatic chromosome number of its parents, which would be 14 (from sand oats) + 28 (from durum wheat) = 42 chromosomes. Since each species has a different number of chromosome sets (sand oats are diploid, and durum wheat is tetraploid), their hybrid would likely be sterile due to the difficulties in pairing chromosomes during meiosis.
In general, when polyploidy occurs, a biological mechanism might double the chromosome number to restore fertility. This is what led to the formation of species such as emmer wheat and bread wheat in agricultural history. But initially, F1 hybrids like the one between sand oats and durum wheat are typically sterile because they contain unpaired chromosomes, which hampers the formation of viable gametes necessary for reproduction. The sterility of hybrids is often a barrier to gene flow between species with differing chromosome numbers.