Biology and Ecology
Unit 3 – Biology and Ecology
What is the biology behind invasiveness? A species can become invasive when introduced to new ecosystems and/or freed from its natural constraints. Certain qualities can give plants, animals, and insects a competitive edge over other species. Biologists recognize that “weedy” traits might indicate that a plant has the potential to become a pest. Devices and strategies for long-distance travel, such as seeds with propellers or Velcro-like casings, allow plants to invade new areas. Biological characteristics, such as the ability to harness airborne nitrogen or produce millions of seeds, allow plants to dramatically affect the environments they invade. They become “ecosystem engineers,” changing their surroundings in ways that can negatively affect other species.
In addition to invasive species’ own methods of dispersal, globalization has opened the door to rapid transit around the world. A small cluster of insect eggs clinging to the branches of an imported Christmas tree, or a seed packet ordered online can make the trip from Oregon or Central Africa to your front door in record time. What happens when these new organisms arrive in Hawai’i? Sometimes they escape into the wild. To effectively respond to these foreign invaders, scientists must investigate where they came from, how they got here, and how to keep them from spreading.
Length of Entire Unit
Activities in this unit
#1 - Weed Risk Assessment Bingo
Students learn about the weed risk assessment process and rate species’ potential “weediness” by playing a game of Bingo.
#2 - Backyard/Schoolyard Survey
Students survey their backyards or schoolyard, recording data either with field notebooks or global positioning system (GPS) units. Students learn which identifying features to look for in the field, the proper protocol for collecting specimen vouchers, and how to make plant presses.
#3 - Ecosystem Engineers I: Strawberry Guava
Students conduct a lab exploring the effect of strawberry guava bioactive compounds on lettuce seed germination and growth.
Activities 3-5 are labs exploring the same concept of ecosystem engineering by invasive species. Each lab involves different plants and strategies, but there is considerable overlap. You may want to combine them or choose the one that best fits your needs.
#4 - Ecosystem Engineers II: Ironwood
Students conduct a lab exploring the effect of ironweed needle cover on ‘a’ali’i seed germination and growth.
#5 - Ecosystem Engineers III: Nitrogen Fixers
Students design lab exercises to demonstrate how certain plants use bacteria to capture nitrogen from the air.
#6 - Wiliwili Gall Wasp Invasion
Students trace the path of the 2005 wiliwili gall wasp invasion on Maui using real-life data and Google Earth technology. They explore the concept of vectors and learn about the significance of the wiliwili tree to the dryland forest ecosystem and the native Hawaiian culture. They devise strategies for stopping the gall wasp’s spread.
10-12 class periods with extended labs.
Unit Focus Questions
1) How are unknown plants identified?
2) What is the protocol for creating a plant voucher?
3) How do scientists determine which species are invasive?
4) What is the Weed Risk Assessment and how is it used?
5) What are ecosystem engineers and how do they work?
6) How do invasive organisms travel?
7) What environmental factors influence biological invasions?
Invasive Species Module, Unit 3: Biology and Ecology
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• Discuss the “weediness” factor of non-native plants that rely on specialist pollinators. Examples include ficus trees (Ficus macrophyllaor is one species) that require fig wasps and night blooming cereus (Hylocereus undatus), or dragon fruit, that require bats or moths. As long as their pollinators do not arrive in the Islands, these plants are less likely to be invasive. But what happens when the pollinators show up? How should these plants be treated?
Resources for Further Reading
For information about the Hawai’i Weed Risk Assessment: official site: www.hpwra.org
Nitrogen Fixing and Native Hawaiian Plants: Tenbruggencate, Jan. “Nitrogen-fixing plants: Self-feeding as a bad thing,” post on Raising Islands blog: http://raisingislands.blogspot.com/2007/08/self-feeding-as-bad-thing.html
Leianuenue Bornhorst, Heidi. Growing Native Hawaiian Plants: A How-To Guide for the Gardener, Bess Press, 2005.