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"Invasive species"-they may not sound very threatening, but these invaders, large and small, have devastating effects on wildlife.

Invasive species are among the leading threats to native wildlife. Approximately 42 percent of threatened or endangered species are at risk due to invasive species.

Human health and economies are also at risk from invasive species. The impacts of invasive species on our natural ecosystems and economy cost billions of dollars each year. Many of our commercial, agricultural, and recreational activities depend on healthy native ecosystems.

What Makes a Species "Invasive"?

An invasive species can be any kind of living organism-an amphibian (like the cane toad), plant, insect, fish, fungus, bacteria, or even an organism's seeds or eggs-that is not native to an ecosystem and causes harm. They can harm the environment, the economy, or even human health. Species that grow and reproduce quickly, and spread aggressively, with potential to cause harm, are given the label "invasive."

An invasive species does not have to come from another country. For example, lake trout are native to the Great Lakes, but are considered to be an invasive species in Yellowstone Lake in Wyoming because they compete with native cutthroat trout for habitat.

How Invasive Species Spread

Invasive species are primarily spread by human activities, often unintentionally. People, and the goods we use, travel around the world very quickly, and they often carry uninvited species with them. Ships can carry aquatic organisms in theirballast water, while smaller boats may carry them on their propellers. Insects can get into wood, shipping palettes, and crates that are shipped around the world. Some ornamental plants can escape into the wild and become invasive. And some invasive species are intentionally or accidentally released pets. For example, Burmese pythons are becoming a big problem in the Everglades.

In addition, higher average temperatures and changes in rain and snow patterns caused by climate change will enable some invasive plant species-such as garlic mustard, kudzu, and purple loosestrife-to move into new areas. Insect pest infestations will be more severe as pests such as mountain pine beetle are able to take advantage of drought-weakened plants.

Threats to Native Wildlife

Invasive species cause harm to wildlife in many ways. When a new and aggressive species is introduced into an ecosystem, it may not have any natural predators or controls. It can breed and spread quickly, taking over an area. Native wildlife may not have evolved defenses against the invader, or they may not be able to compete with a species that has no predators.

The direct threats of invasive species include preying on native species, outcompeting native species for food or other resources, causing or carrying disease, and preventing native species from reproducing or killing a native species' young.

There are indirect threats of invasive species as well. Invasive species can change the food web in an ecosystem by destroying or replacing native food sources. The invasive species may provide little to no food value for wildlife. Invasive species can also alter the abundance or diversity of species that are important habitat for native wildlife. Aggressive plant species like kudzu can quickly replace a diverse ecosystem with a monoculture of just kudzu. Additionally, some invasive species are capable of changing the conditions in an ecosystem, such as changing soil chemistry or the intensity of wildfires.

Examples of Invasive Species

Cogongrass is an Asian plant that arrived in the United States as seeds in packing material. It is now spreading through the Southeast, displacing native plants. It provides no food value for native wildlife, and increases the threat of wildfire as it burns hotter and faster than native grasses.

Feral pigs will eat almost anything, including native birds. They compete with native wildlife for food sources such as acorns. Feral pigs spread diseases, such as brucellosis, to people and livestock. E. coli from their feces was implicated in the E. coli contamination of baby spinach in 2006.

European green crabs found their way into the San Francisco Bay area in 1989. They outcompete native species for food and habitat and eat huge quantities of native shellfish, threatening commercial fisheries.

Dutch elm disease (caused by the fungus Ophiostoma ulmi) is transmitted to trees by elm bark beetles. Since 1930, the disease has spread from Ohio through most of the country, killing over half of the elm trees in the northern United States.

Water hyacinth is a beautiful aquatic plant, introduced to the U.S. from South America as an ornamental. In the wild, it forms dense mats, reducing sunlight for submerged plants and aquatic organisms, crowding out native aquatic plants, and clogging waterways and intake pipes.

Curbing the Spread

One way to curb the spread of invasive species is to plant native plants and remove any invasive plants in your garden. There are many good native plant alternatives to common exotic ornamental plants. In addition, learn to identify invasive species in your area, and report any sightings to your county extension agent or local land manager.

Regularly clean your boots, gear, boat, tires, and any other equipment you use outdoors to remove insects and plant parts that may spread invasive species to new places. When camping, buy firewood near your campsite (within 30 miles) instead of bringing your own from home, and leave any extra for the next campers. Invertebrates and plants can easily hitch a ride on firewood you haul to or from a campsite-you could inadvertently introduce an invasive to a new area.

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Invasive Species | National Wildlife Federation

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Invasive species are among the leading threats to native wildlife. Learn about how they spread and how they threaten native wildlife in the United States.

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Succession - body, water, process, life, plants, form, energy, animals, primary

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The changes that take place during any form of succession depend on a variety of environmental factors, such as the amount of moisture, temperature, and wind. One possible scenario for primary succession might begin with the appearance of simple plants, such as lichens and mosses.

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In September 2011, a wildfire burned over 32,000 acres in Bastrop county. Almost all of Bastrop State Park was affected by the fire. The image shows part of the park a few days after the fire.

How do you think the area has changed since 2011? How do you think it might change in the next 10 years? The next 100 years? Record your ideas in your notebook.

Interested in learning more? Click the image for more about Bastrop State Park and its recovery from the 2011 fire.

Image courtesy of Ryan Depew, National Fire Protection Agency.

Ecological Succession
Watch the video about ecological succession, and record important information on the Ecological Succession Two-Column Notes handout. You can download a copy of the Ecological Succession Two-Column Notes handout in the View Related Resources section below.

Video retrieved from https://www.youtube.com/watch?v=V49IovRSJDs

Primary succession occurs where no life previously existed. It occurs in an area with no soil. Examples of primary succession include areas where

lava has hardened and formed new rock,

new sand dunes have formed, or

bare rock has been exposed after a glacier has retreated or melted.

Because soil must be formed before most plants can grow, it takes much longer for organisms to appear during primary succession than secondary succession. Some of the first organisms to appear during primary succession, the pioneer species, include lichen, algae, fungi, and mosses. These organisms can help break down rock and form soil.

Secondary succession occurs in an area where soil already exists and life previously occurred. Because there is already soil and because some organisms may survive a disturbance, life generally returns much faster during secondary succession.

Secondary succession follows some sort of disturbance to the env ironment. In the Engage images and the Explore video, secondary succession was observed after a wildfire. Fire is not the only disturbance that can result in secondary succession. What other natural events or human activities could result in secondary succession? Record your ideas on the Ecological Succession Two-Column Notes handout.

How are animals affected by succession?

Primary succession occurs in an area where there was previously no life, so there are very few or no animals in an area when primary succession begins.

Secondary succession occurs after a disturbance in an area with plant and animal life. In addition to destroying the plant community, a disturbance may kill many animals in the area. Animals that survive may move to new areas to find shelter, water, and food.
Return of wildlife
As plant species appear during succession, wildlife will follow. Insects appear early in succession with the first plant species, such as grasses. As succession continues, small herbivores and omnivores appear, followed by larger predators.

Find links to more information about ecological succession in the View Related Resources section at the bottom of the page.

Match each ecological succession vocabulary term with the correct description. Record the terms and descriptions in your science notebook.

To retake the quiz, reload the page and then select "No" when the "Resume Quiz" dialog box appears.

Students observed a garden plot over one school year and recorded their observations in a garden journal. Instead of planting seeds, the students left this garden alone to observe what happened over time. The picture shows the garden plot near the end of the school year.

The interactive activity below shows a selection of observations recorded in a garden journal throughout the school year. Use your knowledge of ecological succession to sequence the garden journal observations.

How might the garden change if the area remains undisturbed for a long period of time? Describe your ideas and/or draw a sketch in your science notebook.

Use the interactive Venn diagram to compare primary succession and secondary succession. After you place each descriptor, click "Submit" to check your answer.

To retake the quiz, reload the page and then select "No" when the "Resume Quiz" dialog box appears.

This resource is a compilation of text, videos, and other elements to create a scaffolded 5E learning experience for students. This is meant for Tier I instruction under the Response to Intervention (RtI) model for science TEKS (7)(10)(C). In this lesson, students will observe and describe the process of ecological succession.

Be sure to check for prerequisite knowledge and skills as well as differentiation needs by reviewing the entire resource and the related items before assigning it to or working through it with your students.
This resource can be used for instruction in a variety of ways.

Use with a single computer and projector; this resource can be delivered in a traditional classroom.

Use with a combination of individual student computers and teacher computer and projector (in either a computer lab or other 1:1 environment).

Assign the resource to students as work to do outside of the school day as part of a flipped lesson to allow application, practice, and additional support during the school day.

Use with students as tutorials.

Share with parents to inform them about what their child is learning in school.

Use with students who are unable to participate in the traditional classroom environment.

Engage
Students view a picture of Bastrop State Park taken a few days after the wildfire in September 2011. Students think about how the area may have changed since 2011 and how it may change in the future. Students record their ideas in their notebook. A link to the Texas Parks and Wildlife website is provided for students who are interested in learning more about the impact of the wild fire on Bastrop State Park. Encourage interested students to research the Bastrop County Complex Fire further online.

Explore

This activity is no longer working. We hope to have it available in the future. Students explore an interactive activity that models primary and secondary succession. The first tab of the interactive activity provides background information, including simple descriptions of primary and secondary succession. The second tab of the activity models primary succession. Students can increase or decrease the temperature and amount of rainfall to determine how these factors affect the rate of succession. The third tab of the activity models secondary succession after a forest fire. Students should observe secondary succession occurs at a much faster rate than primary succession. The last tab of the activity is a quiz. Students sequence the appearance of vegetation in primary succession and then in secondary succession. After completing the interactive activity, students answer three questions about ecological succession in their science notebook.

Please note that although the term "climax community" is often used to describe relatively stable conditions, that term is no longer used by many ecologists because scientists have come to realize that flux and change are always happening. Although equilibrium is not achieved, "climax community" still remains a useful term when describing ecological succussion.

Explain
Students learn more about ecological succession and compare primary and secondary succession. Students complete Ecological Succession Two-Column Notes while viewing a short video and reading about ecological succession. Students then match ecological succession vocabulary terms with their definitions. Related videos are provided to help students' understanding of ecological succession.

Elaborate
Students apply what they have learned to an example of succession in a microhabitat. Students sequence observations from a garden journals in an interactive activity. After sequencing the observations, students describe in their notebook how they expect the area to change if the garden remains undisturbed.

Evaluate

Students complete a Venn diagram comparing primary and secondary succession in an interactive activity. A key is provided below.

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A Tier 1 life science instructional resource for Grade 7