Self & Cross-pollination (Cambridge O Level Biology)

Self- & Cross-Pollination

• Cross-pollination occurs when the pollen from one plant is transferred to the stigma of another plant of the same species
  • This is the way most plants carry out pollination as it improves genetic variation
• Occasionally, the pollen from a flower can land on its own stigma or on the stigma of another flower on the same plant - this is known as self-pollination
• Self-pollination reduces genetic variety of the offspring as all the gametes come from the same parent (and are therefore genetically identical)
• Lack of variation in the offspring is a disadvantage if environmental conditions change, as it is less likely that any offspring will have adaptations that suit the new conditions well
  • The advantage of self-pollination is that the plant is not reliant on pollinators, so they will be able to reproduce in environments lacking pollinators
• On the other hand, cross-pollination relies completely on the presence of pollinators and this can be a problem if those pollinators are missing (e.g. the reduction in bee numbers is of great importance to humans as bees pollinate a large number of food crops)

Types of pollination diagram

Differences between self-pollination and cross-pollination