1 The Desert Detective Series for High School/College: #4-The Mystery of the Desert Wildflowers Detectives solve mysteries and so do scientists. This Desert Detective Mystery will help you discover the Mystery of the Desert Wildflowers. Most of the answers can be found on the “Desert Wildflower Trail” at the west end of the garden past the gift shop. As you go through the Desert Botanical Garden, feel free to look, wonder and enjoy. Two simple rules you must follow: 1. Stay on the paths 2. Do NOT touch the plants. Good luck in your explorations! The Mystery Introduced Good Morning, Inspector! We’re glad you’re here at the Desert Botanical Garden to help us solve the mystery. Here is the problem: About two-thirds of all living organisms on Earth are plants and insects. Plants with flowers arose 100 million years ago and have lived with insects ever since. What role do flowers and insects play in each other’s lives? How do they help or harm one another? Why is pollination (pollen transfer) so important to plants and insects? Your assignment, Inspector, is to compare the many different flowers in the desert. See if you can determine how each is pollinated. Perhaps you can suggest ways both plants and insects have changed due to this relationship . Good luck with your investigations! Mystery #1—What kinds of flowers can you find? Assignment #1—Find three different flowers and sketch them. Label the sepals, petals, stamens and pistils if they are present. Note that some flowers do not have all these parts. Flower #1 Flower #2 Flower #3 2 Mystery #2— What insects (or other animal pollinators) can you find? Besides bees, be sure to look for beetles, wasps, ants, butterflies, flies, and birds. Even if you see a bee, there are hundreds of different bee species. Look carefully, but don’t touch! Assignment #2— Sketch insects below. a. Table of insects Insect #1 Insect #2 Insect #3 b. Hypothesize a benefit to the insect of flower pollination. c. Hypothesize a benefit to the plant of flower pollination. d. It has been observed in tomatoes that although flowers can self-pollinate (pollen moves from pistil to stamen within the same plant or even the same flower), bee pollinated plants have more fruits. Explain what a fruit is and how it is related to a flower. Give a hypothesis about why bee pollinated plants have more fruit. 3 e. Tomatoes will also form fruit when they are cross-pollinated (pollen is moved between flowers of different plants). If some tomato seeds are planted from selfpollinated plants and others from cross-pollinated plants, which of the offspring will show more diversity (more variation)? Explain your answer. Mystery #3—What characteristics of a flower attract each insect (or bird) pollinator? Assignment #3—Based on your observations, what characteristics of each flower attracts its pollinator? Here are some characteristics to think about: Color of the flower (Is it brightly colored to attract its pollinator?) Shape of flower (How does it match the shape of the pollinator) Is the flower close to the ground or higher up? Is there a flat landing pad? Are there patterns on the flower leading to the nectar (bulls eye, stripes)? Is there an odor or scent? Is the flower colorless and plain? Wind pollinated plants like grasses share this characteristic. Flower (name or sketch) 1. Brittlebush Pollinator observed (name or sketch) Butterfly Characteristics Flat landing pad Yellow color Bulls eye 2. 3. 4. 5. 6. 4 Mystery #4—Do pollinators stick with one kind of flower or visit many different flower types? Assignment #4—Detectives must sometimes trail the suspect. In this case, the pollinators are the suspects. List three of the pollinators you have observed. Did you find them only on one kind of flower or were they found on more than one kind of flower? a. Fill in the table below Pollinator name or sketch I observed this pollinator on: one kind of flower only more than one kind of flower 1. 2. 3. b. What advantage is there to the flower of having a specific pollinator that will only pollinate one kind of flower? c. What advantage is there to the flower of having a general pollinator that will pollinate many different kinds of flowers? d. Flowers show less variation among related plants than do leaves. What do you think happens to an offspring plant that has such different flowers that pollinators do not go to it? 5 What do you think happens to an offspring plant that has altered flowers that attract more pollinators? Teacher’s Follow Up Exercise. 1. The mystery of the Banana Yucca and the Pronuba moth The Desert Botanical Garden has a few Banana Yucca plants which are pollinated only by a small, ½ inch moth called the Pronuba moth. Each moth emerges from its underground burrow at the time of year when white, yucca flowers are in bloom. The male and female moths are attracted to the yucca flower where they mate, live a few days and die. The female has special mouth appendages to collect pollen. The female collects pollen, flies to another yucca plant, deposits the pollen on the pistil, and then drills a hole in the ovary and lays her eggs. The larva hatch and eat some of the developing seeds in the ovary leaving plenty behind for plant reproduction. The larva mature in about a month, bore a hole out of the ovary, and drop to the ground. They bury themselves in the soil and hatch as moths the next year. Unfortunately, there are not enough Banana Yucca plants in the garden to support a population of Pronuba moths and so the plant does not produce fruit. a. Why don’t the Banana Yucca plants at the Desert Botanical Garden produce fruit? b. What disadvantage is there to having a specific pollinator? c. Some habitats have been destroyed so much as to endanger certain plants. Would these rare plants be more likely to produce fruit if they 6 had a general pollinator like a honeybee or a very specific pollinator like the Pronuba moth? Explain your answer. 2. Here are some ways humans have altered the desert ecosystem. Decide how each alteration might affect native populations of insect pollinators. Human alteration Native insects will Explain your answer increase, decrease, or not change Desert is replaced by housing or farming Non-native honeybees are introduced to pollinate farm crops Weed killer is sprayed on farmer’s field and some of the surrounding land is accidentally sprayed, too Insect killer is sprayed on farmer’s field and some of the surrounding land is accidentally sprayed, too Birds learn to steal pollen nectar by slitting the flower from behind without pollinating 3. Charles Darwin found a huge orchid flower 10 inches long in Madagascar in 1862. Based on the flower’s characteristics, he postulated a huge moth must exist to pollinate it. This moth was found forty years later. a. Why is there a match between flower traits and insect characteristics? b. Does a good match between flower traits and insect characteristics benefit the plant only, insect only or both? 7 c. As new plants and insects are born, which will be the most successful? 4. Monarch butterflies migrate thousands of miles every fall from the United States to Mexico feeding on flowers along the way. But monarchs are not the only migrants. Long-nosed bats also migrate every year between the U.S. and Mexico. These migrations take a tremendous amount of energy so it is not surprising that many individuals die along the way. a. What would happen if a large land area along this migration pattern was converted from native vegetation to urban areas? b. Are bats and butterflies stopped by international boundaries between Mexico and the U.S.? Does it make sense to have a nature preserve on one side of the border and farms on the other? 5. Cross-pollination is movement from the stamen of one plant to the pistil of a second plant. Cross-pollination results in offspring which share traits from each parent plant. Domesticated plants have been shown to cross with wild relatives creating plants with traits from both. a. Are traits in wild plants stable or always changing? b. Are traits in wild insects stable or always changing? c. Does cross pollination result in more species change or less species change? d. When there is variation in a population, will some traits be more beneficial and some more harmful? Which insects and plants will survive? 8 Teachers Pre-lab for the Mystery of Desert Wildflowers This pre-lab is designed to get people thinking about the structure and function of flowers. You may also wish to have students look at dead insects. Materials: Flowers (petunias have large structures and are easy to see) Magnifying glass One-sided razor Dead bees ( available from Carolina biological) Introduction Flowers like petunia have four whorls, rings of structures. Sketch each whorl and hypothesize a function. Sketch the structure in each whorl Sepals Color # of these structures Hypothesize a function Petals Stamens Pistils Questions 1. What is the function of the flower? 9 2. Where does the fruit develop and what is its role? 3. How does pollen move from the stamens to the pisti? Introduction Bees are one of the most important pollinators in nature. See if you can identify parts of the bee body. 1. Sketch your bee and label the parts that you recognize. Hypothesize a function for these parts. 2. Rub the bee over the anther of the flower’s stamens. If pollen is being produced, see where it sticks.
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