Resource: Fruit Wrappers

Plants have evolved an amazing variety of adaptations to succeed in the struggle for survival. Millions of years of evolution have shaped their form and function. Many plant flowers, including the sunflower seen in the video, lure insects and birds with rewards of pollen and nectar. In exchange, these animals unknowingly carry pollen to other flowers and fertilize the eggs they contain, thus ensuring reproduction of the plant species. However, one of the most effective evolutionary adaptations of plants is seed dispersal, or the scattering of offspring far away from the parent plant. The effects are two-fold: Dispersal puts seeds in a potentially better growing environment, and it reduces the competition for resources with the parent plant.

The fruit of some plants attracts animals that in turn disperse seeds. A fruit is the ripened ovary of a plant that contains seeds. After a plant egg is fertilized, the ovary swells and becomes either fleshy, as in berries, or hard and dry, as in nuts, to protect the developing seeds. The seeds develop in the fruit until they can begin to grow.

As fruit ripen, they develop an odor and appearance that will attract animals. A plant hormone called ethylene causes ripening. For example, it turns bananas and pears from bitter and green into sweet and yellow. After an animal eats ripened fruit and it travels through the digestive system, the fruit's seeds are dispersed wherever the animal defecates.

Not all plants employ fruits to transport their seeds. Some produce seeds with hooks, barbs, and burrs on their surfaces. These "hitchhikers" may attach to an animal's hair in one field and be transported to another field miles away. Wind and water are other effective seed-dispersal agents. A single gust of wind can carry hundreds of thousands of dandelion seeds from one field to the next. Similarly, ocean currents are capable of transporting plant seeds between continents.

To learn more about the ways by which plant seeds are dispersed, check out Sock Seeds and Drift Seeds And Drift Fruits: Seeds That Ride The Ocean Currents.

• What does the color of a fruit's skin or peel signal to us or another animal?
• Besides a banana, can you think of another example from nature where the color of a plant or animal is a signal to animals that see it? What does the color signal?
• Why is it good for a plant when an animal eats its fruit?
• We know a fruit doesn't "tell" the opossum anything. What attracts the opossum to the fruit?