Inquiry into Life 15th Edition by Sylvia Mader ,Michael Windelspecht

Exercise 2

The Coevolution of Plants and Their Pollinators
Plants and their pollinators have adapted to one another. They have a mutualistic relationship in which each benefits-the plant uses its pollinator to ensure that cross-pollination takes place, and the pollinator uses the plant as a source of food. This mutualistic relationship came about through the process of coevolution-that is, the interdependency of the plant and the pollinator is the result of suitable changes in the structure and function of each.
Bee- and Wasp-Pollinated Flowers
There are 20,000 known species of bees that pollinate flowers. The best-known pollinators are the honeybees (Fig. 10A a ). As noted in the text, bee eyes see ultraviolet (UV) wavelengths. Therefore, bee-pollinated flowers are usually brightly colored and are predominantly blue or yellow; they are not entirely red. They may also have ultraviolet shadings called nectar guides, which highlight the portion of the flower that contains the reproductive structures. The mouthparts of bees are fused into a long tube that contains a tongue. This tube is an adaptation for sucking up nectar provided by the plant, usually at the base of the flower. Bees also collect pollen as a food.
Bee-pollinated flowers are delicately sweet and fragrant, advertising that nectar is present. The nectar guides often point to a narrow floral tube large enough for the bee's feeding apparatus but too small for other insects to reach the nectar. Bee-pollinated flowers may be irregular in shape, and are sturdy because they often have a landing platform where the bee can alight. The flower structure requires the bee to brush up against the anther and stigma as it moves toward the floral tube to feed.
One type of orchid, Ophrys , has evolved a unique adaptation. The flower resembles a female wasp, and when the male of that species attempts to copulate with the flower, the flower spring loads pollen on the wasp's head. When the frustrated wasp attempts to "copulate" with another flower, the pollen is perfectly positioned to come in contact with the stigma of the second flower.
Moth- and Butterfly-Pollinated Flowers
Both moths and butterflies have a long, thin, hollow proboscis, but they differ in other characteristics. Moths usually feed at night and have a well-developed sense of smell. The flowers they visit are visible at night, because they are lightly shaded (white, pale yellow, or pink), and they have strong, sweet perfume, which helps attract moths. Moths hover when they feed, and their flowers have deep tubes with open margins that allow the hovering moths to reach the nectar with their long proboscis.
Butterflies, in comparison, are active in the daytime and have good vision but a weak sense of smell. Their flowers have bright colors-even red, because butterflies can see the color red-but the flowers tend to be odorless. Unable to hover, butterflies need a place to land. Flowers that are visited by butterflies often have flat landing platforms (Fig. 10A b ). Composite flowers (composed of a compact head of numerous individual flowers) are especially favored by butterflies. Each flower has a long, slender floral tube, accessible to the long, thin butterfly proboscis.
Bird- and Bat-Pollinated Flowers
In North America, the most well-known bird pollinators are the hummingbirds. These small animals have good eyesight but do not have a well-developed sense of smell. Like moths, they hover when they feed. Typical flowers pollinated by hummingbirds are red, with a slender floral tube and margins that are curved back and out of the way. And although they produce copious amounts of nectar, the flowers have little odor. As a hummingbird feeds on nectar with its long, thin beak, its head comes in contact with the stamens and pistil (Fig. 10A c ).
Bats are adapted to gathering food in various ways, including feeding on the nectar and pollen of plants. Bats are nocturnal and have an acute sense of smell. Those that are pollinators also have keen vision and a long, extensible, bristly tongue. Typically, bat-pollinated flowers open only at night and are light-colored or white. They have a strong, musky smell similar to the odor that bats produce to attract one another. The flowers are generally large and sturdy and are able to hold up when a bat inserts part of its head to reach the nectar. While the bat is at the flower, its head becomes dusted with pollen (Fig. 10A d ).
Figure 10A Types of pollinators. a. A bee-pollinated flower is a color other than red. b. A butterfly-pollinated flower is often a composite, containing many individual flowers. c. Hummingbirdpollinated flowers are curved back, allowing the bird to insert its beak to reach the rich supply of nectar. d. Bat-pollinated flowers are large, sturdy flowers that can take rough treatment.
What are the potential consequences if honeybees were to go extinct?