Mendel used several contrasting characters in his pea plant experiments. List any four such contrasting characters and explain why pea plants were a good choice for his experiments.

Four contrasting characters Mendel studied in pea plants: 

1. Stem Height: Tall vs. Dwarf 

2. Seed Shape: Round vs. Wrinkled 

3. Seed Color: Yellow vs. Green 

4. Pod Shape: Inflated vs. Constricted 

5. Pod Color: Green vs. Yellow 

6. Flower Color: Purple vs. White 

7. Flower Position: Axial vs. Terminal Reasons why pea plants were a good choice for Mendel's experiments: 

1. Easily Cultivated: Pea plants are easy to grow and maintain in a garden setting. 

2. Short Life Cycle: They have a relatively short generation time, allowing Mendel to observe multiple generations in a reasonable period. 

3. Self-pollinating: Pea plants naturally self-pollinate, which allowed Mendel to obtain pure-breeding lines (homozygous for specific traits) easily. 

4. Cross-pollination Possible: They can also be easily cross-pollinated artificially by hand, enabling controlled crosses between different parental plants. 

5. Distinct Contrasting Traits: Pea plants exhibit several easily observable and distinct contrasting traits (e.g., tall vs. dwarf, round vs. wrinkled seeds) that were not blended in hybrids. 

6. Large Number of Offspring: Each cross produced a large number of seeds, providing statistically significant data for analysis.