Pollination - The Story Behind Bees and Flowers

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Objective

SWBAT to develop and argument to explain how bees influence the probability of successful plant reproduction.

Big Idea

Effect of insect behavior on pollination.

Engage

10 minutes

To engage students in lesson I show students the TEDEd video Nature's Matchmakers on how bees help plants have "sex" (attention-getting word - could use reproduce if you'd rather but the word sex is used in the video). 

Teacher Note:  This video introduces students to new vocabulary in addition to new concepts.  It's crucial that you stop video in the following minutes to scaffold content:

  • Minute 1:25 (Figure that explains number of plant species vs pollinator species)
  • Minute 1:51 (Evolution of bees from wasps)
  • Minute 2:00 (Pollinator Networks)
  • Minute 2:20 (Specialists)
  • Minute 2:30 (Generalists)
  • Minute 3:00 (Nested Network)
  • Minute 3:45 (Modular Network)

Students are required to answer the questions below as they watch video:

1.  Most pollinator networks for which we have data are “nested.” Draw and describe how a nested plant-pollinator network looks like. Which may be the reason for nestedness to evolve?

2.  In addition to nestedness, the networks are usually “modular.” What a modular structure means and which is the advantage of a modular structure?

3.  Today, around ________ plant species receive pollination services from more than 200,000 pollinator species.

a.  1,000

b.  70,000

c.  170,000

d.  1,000,000 

 

4.  How much of our food production depends on bees?

a. 1/3

b. 1/5

c. 1/10

d. 1/20


5.  Fossil records suggest bees may have evolved from ________ that gave up hunting after they acquired a taste for nectar.

a. Ants

b. Butterflies

c. Beetles

d. Wasps


6.  Plant-pollinator networks are everywhere. Ecologists record these networks in the field by observing which pollinators visit which plants, or by analyzing ________.

a. The gut content of pollinators

b. The fingerprints left by pollinators when the visit plants

c. The DNA left by pollinators when they visit plants

d. The identity of pollen loads on the body of pollinators

 

7.  The main characteristic of the architecture of all plant-pollinator networks on Earth is ________.

a. All species have similar number of interactions

b. Most species have few interactions and few species have many interactions

c. Most species have many interactions and few species have few interactions

d. There is not a common characteristic, all networks are different.

 

Explore

20 minutes

In this section of lesson students explore pollination by completing a simulation of bee pollination. (SP2 - Developing and Using Models)

Objectives

  • Identify the plant parts involved in reproduction.
  • Identify the animal (bee) structures involved in pollination.
  • Demonstrate how pollen moves from the male stamen to the female stigma.

Materials

  • Copies of Activity Flower Diagram and Bee Diagram.
  • A small dish or container filled with talcum powder. You can also use corn starch,flour, or different colors of chalk dust.
  • Cotton swabs

Procedure

1. Give each student a photocopy of Flower Diagram. Have them study the line drawing of the flower. Ask them to identify and write down each plant part described below.

  • Female and sticky or feathery to trap pollen (the stigma)
  • Female and holds up the stigma (the style)
  • Female and contains the egg-producing ovary (the pistil)
  • Male and produces pollen grains (the anther)

2. Give each student a photocopy of Bee Diagram. Have them study the line drawing of the bee. Ask them to identify and write down the bee structure or structures that do the following:

  • collect nectar (proboscis)
  • may carry pollen (bristles, legs and baskets, head)

3. Divide the students into two groups: the pollinators (bees) and the plants. Give each member of the plant group a cotton swab and a small amount of "pollen" (talcum or other type of powder) in a container or dish. Instruct each member of the pollinator group to visit a member of the plant group and dip a finger into the pollen. At this point, ask the class to name the part of the plant that the pollinators touched (the stamen, which consists of the anther and the filament) to get the pollen on their fingers. Have them determine whether it is a male or female part. Ask the students what parts of the pollinators' "bodies" (represented by their finger) touched the stamen that could carry the pollen to the next plant. Ask what they were looking for when they got to the plant (nectar) and what appendage they used to get it (proboscis bristles).

4. Have each member of the plant group hold aloft a cotton swab. Explain that the pollinators have just visited one plant and will now move on to another plant of the same species. Instruct the pollinators to visit a different member of the plant group and rub some of the pollen they are carrying onto that plant's swab. Ask the students what part of the flower the swab represents (stigma) and whether it is a male or female part (female).

5. Have each group meet separately to discuss its specific role as a pollination partner and how it benefitted from the pollination process. Have each group select a spokesperson who will take notes and report the findings to the class.

 

Explain

5 minutes

In this section of lesson I show students a clip from the movie Wings of Life from Disneynature.  At the time that I'm writing this lesson the entire movie is being streamed on Netflix.

The objective of showing this clip is to show students in real life how the behaviors of different pollinators influence the reproductive success of different plant species.  This clip summarizes what students have learned in the previous two sections of lesson. You might want to pause it at key points and ask students what they've noticed.

 

Elaborate

10 minutes

To elaborate on what students have learned in the previous sections of lesson I show students the video below that discusses an escalating problem in the world that scientists are frantically trying to find a solution to. 

In the past decade, the US honeybee population has been decreasing at an alarming and unprecedented rate. While this is obviously bad news for honeypots everywhere, bees also help feed us in a bigger way -- by pollinating our nation's crops.

As students watch video I have students answer the following questions:

 

1.  In affected colonies ________________.

a.  There is no queen bee

b.  The food stores remain untouched

c.  There are dead bees everywhere

d.  The comb has disintegrated

 

2.  Colony collapse disorder will only affect the price of honey.

a.  True

B.  False

 

3.  When was colony collapse disorder found to affect over half the commercial hives in the United States?

a.  2006

b.  1884

c.  2001

d.  1996

 

4.  Since when have humans domesticated bees?

a.  200 years ago

b.  The early 1900's

c.  1850

d.  The 1600s

 

5.  Honeybees generate over one third of food in the United States by pollinating crops.

a.  True

b.  False

 

6.  Are there particularly important crops that you think should be protected especially from the effects of colony collapse disorder?


Evaluate

15 minutes

In this section of the lesson, students match pollinators with the plants they pollinate.  Besides the figure below I have included a printable version of the activity.  This activity is courtesy of NOVA.


Pollinator icons

INSTRUCTIONS

After you print this page out, match the pollinators shown above with the plants they pollinate (below). Note there is only one correct choice for each plant. Write your answers in the space provided.

Fuchsia
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Hardy fuchsia
Attracted to the fuchsia's bright red sepals and purple petals, this pollinator can visit hundreds of flowers each day, making it very important to the plant's reproductive cycle. Fuchsia flowers hang downward and serve as an ideal food source for this pollinator by offering great quantities of nectar.

Hint: While most pollinating insects are blind to the color red, this organism sees red objects particularly well.

Answer: ____________________________



Goldenrod
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Canada goldenrod
With its bright yellow petals, abundant nectar, and protein-rich pollen, goldenrod attracts a variety of pollinators, including one of the above. This organism is equipped with "pollen baskets" on its hind legs, and it uses the goldenrod's nectar to create a sweet, viscous liquid often prized in folk medicine as an antiseptic agent.

Hint: Farmers often utilize this easily bred organism in pollinating commercial crops such as almonds.

Answer: ____________________________



Comet Orchid
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Comet orchid
Nicknamed for its appearance, the comet orchid has a milky white flower and a long "tail" consisting of a spur that holds the flower's nectar. While scentless by day, the orchid flower becomes fragrant at night, attracting this nocturnal pollinator.

Hint: Only a very specialized pollinator can reach this flower's nectar.

Answer: ____________________________



Violet
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Common blue violet
The common blue violet has a variety of insect pollinators, but there is one other species that helps the plant procreate and even stretch beyond the insects' usual habitats.

Hint: The open "bud" pictured here is more important than you might think. What's going on here?

Answer: ____________________________



Celery
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Wild celery
Despite its name, wild celery bears little resemblance to the leafy vegetable you buy at the grocery store. In fact, while the celery we eat depends upon insects for pollination, wild celery takes an entirely different approach to reproduction: it utilizes its natural habitat to scatter its pollen.

Hint: Wild celery is a natural food source for many animals, including the canvasback diving duck.

Answer: ____________________________



Corpse Flower
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Sumatran corpse flower
Standing at up to 20 feet tall and stretching 16 feet across, the Sumatran corpse flower is easy for most pollinators to spot, but the plant's scent is what draws these organisms in. The corpse flower's "perfume" is so important in attracting pollinators that the plant will even chemically heat up to about human body temperature in order to help release its scent.

Hint: The corpse flower's perfume is said to resemble the odor of rotting flesh, hence its name.

Answer: ____________________________



Baobab
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African baobab
These sweetly scented, light-colored flowers bloom in the late afternoon and evening, just in time to attract this nocturnal pollinator. As with the fuchsia, the baobab's flowers hang downward and are shaped to fit the pollinator's facial structure.

Hint: This beakless pollinator uses its tongue to probe the flower for nectar.

Answer: ____________________________

To wrap up the lesson, students complete an Exit Slip where students are required to develop an evidence-based argument on how pollinators impact the reproductive success of plants. (SP7 - Engaging in Argument from Evidence/MS-LS1-4 - Use argument based on empirical evidence and scientific reasoning to support an explanation for how characteristic animal behaviors and specialized plant structures affect the probability of successful reproduction of animals and plants respectively/CCC - Cause and Effect.)