Final answer:
Plants that look alike can produce different offspring due to genetic variations and the mixing of genes through sexual reproduction, including alternation of generations and cross-pollination, just as Mendel's pea plant experiments demonstrated with various seed colors and textures across generations.
Step-by-step explanation:
How Plants Can Look the Same but Produce Different Offspring
Plants that look the same externally can produce offspring that are different due to the process of sexual reproduction. During this process, the combination of genetic material from two parents results in genetically diverse offspring. This diversity arises from the alternation of generations inherent in plant reproduction, where a diploid sporophyte stage alternates with a haploid gametophyte stage. Moreover, traits like those observed in Mendel's experiments with pea plants demonstrate that dominant and recessive genes can lead to variations in offspring, such as the eventual emergence of green peas from yellow parents through successive generations.
Furthermore, the presence of different genotypes in closely similar-looking plants can create a variety of phenotypes in the offspring, which is further diversified by cross-pollination and hybridization. For example, even when two plants display traits like yellow and round seeds, their F1 generation might be uniform, but the F2 generation can show new combinations like green round seeds or yellow wrinkled seeds, not present in the F1 or parental generations.
Thus, despite superficial similarities, internal genetic mechanisms ensure that offspring can display a mix of characteristics, some of which may not be immediately apparent in the parents but are present in their genetic material.