Angiosperms are an incredibly diverse group of plants. They have many avenues in which to specialize and speciate. Lineages of flowering plants have evolved in tandem with their pollinators by forming increasingly specialized flowers. These sets of specialized floral characteristics--including morphology, color, smell, and the presence of nectar or pollen--are considered together as the plant's pollination syndrome. Wind pollinated flowers are reduced and lack strong odors or nectar, though they contain large amounts of pollen. Bird pollinated flowers contain lots of nectar that they hide in tubular structures, often pigmented red or pink (colors that birds see well, but bees can't distinguish from greens), and lacking strong scents. Bee pollinated flowers can be a variety of colors, but tend toward blues, purples, and yellows. They tend to have sweet, fresh scents and a place for the bee to land. Moth and bat pollinated flowers are white and open at night. Some flowers have even evolved to trick flies into accidental pollination by mimicking a corpse.
They have also evolved fruits specialized for their particular seed dispersal agent. Some fruits release seeds on their own through a variety of explosive mechanisms. Others rely on wind (using wing-like structures) or water (using floats) for dispersal. Still others have coevolved with animals. Some have evolved velcro-like spines or sticky substances to attach to passing animals. Others have evolved to be eaten, some only by specific animals, and hope to survive the digestive tract or have at least some seeds escape the process.
These opportunities for specialization, as well as perhaps the influence of self-incompatibility genes and other factors, has resulted in over 350,000 species of angiosperms classified into over 400 families. However, much of angiosperm diversity can be found in a few major families. Among these are the asters (32,000), orchids (28,000), legumes (19,000), and grasses (12,000).
- Compare and contrast monocots and eudicots.
- Differentiate between monocot and eudicot flowers and leaves.
- Explain pollination strategies with regard to genetic diversity.
- Explain what is meant by the term pollination syndrome.
- Use floral characteristics to predict a plants pollinator(s).
- Describe the transition from ovary and ovule to fruit and seed.
- Use characteristics of fruits, including pericarp morphology, to identify fruit type.
- Use characteristics of fruits to predict the dispersal agent for a plant's seeds.
- Interpret a floral formula.
- Describe the characteristics used to identify each of the four largest angiosperm families.
Content by Maria Morrow, CC BY-NC