Tomatoes, peppers, eggplant, beans, and peas are nearly completely self-pollinated. The flowers of these plants are arranged so that the flowers are pollinated by the natural growth process of the flower shedding pollen from the male to female parts. These plants all produce separate male and female flowers and bees are necessary to transfer pollen from one to the other. If bees fail to pollenize these flowers, the fruit will start to develop but shrivel and fall off. If bees pollenize the flowers only sparingly, the fruit may develop but be misshapen or poorly filled.
Many questions also arise regarding cross-pollination of plants in the garden.
For all practical purposes, this does NOT happen. Each of these crops has different chromosome numbers which means they will not cross with one another even if you tried. Cucumbers cross only with other cucumbers, etc. In addition, you would not see the result of any cross until you planted the seed from a fruit produced this year and grew out the resultant fruit in the next generation next year. Remember self-pollenized crops do not cross with anything else.