Final answer:
Offspring that display the same combination of alleles as their parents are called purebred if they are homozygous, and hybrid if they are heterozygous. Organisms with identical alleles for a trait are homozygous, while organisms with two different alleles for a trait are heterozygous.
Step-by-step explanation:
The offspring that display the same combination of alleles as their parents are known as purebred if they have the same identical alleles for a trait (homozygous), or as hybrid if they have two different alleles for a trait (heterozygous). When an organism is homozygous, it has two copies of the same allele, which can be either dominant (like 'BB') or recessive (like 'bb'). Conversely, an organism is considered heterozygous when it has two different alleles for a trait (such as 'Bb'). During fertilization, each parent contributes one allele to the offspring, creating the possibility for these combinations of alleles. Therefore, the correct answer is purebred if the alleles are identical, otherwise the offspring is a hybrid.
For example, if two pea plants which are homozygous for flower color (one 'BB', and the other 'bb') are crossed, all of the F1 offspring would be 'Bb', exhibiting the dominant purple coloration, and thus would be heterozygous. This heterozygous condition is also referred to as a hybrid. Subsequent breeding of these hybrids (F1 generation) could lead to F2 offspring with different allelic combinations (YY, Yy, yy), as demonstrated by Mendel's pea plant experiments detailed in Punnett squares showing genotype ratios.