6th grade science chestnut.” complete questions that

6th Grade Science

Day 1 Complete “Bye bye birdie?” Day 2 Read and annotate “Worldwide Loss of Bees a Growing Concern” and “The American Chestnut.” Complete questions that follow. Day 3 Complete “Is Chocolate for the birds?” Day 4 Complete “Do Insects prefer local of foreign foods?” Day 5 Read and annotate “The Origin of Species.” Complete the questions that follow.

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Data Nuggets developed by Michigan State University fellows in the NSF BEACON and GK-12 programs

1

Bye bye birdie? Part I

Featured scientist: Richard Holmes from the Hubbard Brook Experimental Forest

Research Background: The Hubbard Brook Experimental Forest is an area where scientists have collected ecological data for many years. It is located in the White Mountains of New Hampshire, and data collected in this forest helps uncover trends that happen over long periods of time. It is important to collect data on ecosystems over time because these patterns could be missed with shorter experiments. Each spring, Hubbard Brook comes alive with the arrival of migratory birds. Many migrate from the tropics to take advantage of the abundant insects and the long summer days of northern areas, which are beneficial when raising young. Avian ecologists are scientists who study the ecology of birds. They have been keeping records on the birds that live in the experimental forest for over 40 years. These data are important because they represent one of the longest bird studies ever conducted! Richard is an avian ecologist who began this study early in his career as a scientist. He was interested in how bird populations were responding to long-term environmental changes in Hubbard Brook. Every summer since 1969, Richard has taken his team of trained scientists, students, and technicians into the field to count the number of birds that are in the forest and identify which species are present. Richard’s team monitors Male Black-throated Blue Warbler feeding nestlings. Nests of this species are built typically less

than one meter above ground in a shrub such as hobblebush. Photo by N. Rodenhouse.

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populations of over 30 different bird species. They wake up every morning before the sun rises and travel to the far reaches of the forest. They listen for, look for, identify, and count all the birds they find. The team has been trained to be able to identify the birds by sight, but also by their calls. Team members are even able to identify how far away a bird is by hearing its call! The scientists record the number of birds observed in four different study areas, each of which are 10 hectare in size — roughly the same size as 19 football fields. Each of the four study areas contains data collection points that are arranged along transects that run east to west through the valley. Transects are parallel routes along which the measurements are taken. Each transect is approximately 500 meters from the next. At certain points on each transect, an observer stands and records all birds seen or heard during a ten-minute interval, and estimates the distance the birds are from the observer. The entire valley is covered three times a season. By looking at bird abundance data, Richard and his colleagues can identify trends that reveal how avian populations change over time. Scientific Question: How has the total number of birds at the Hubbard Brook Experimental Forest changed over time? Scientific Data: Use the data below to answer the scientific question

YearTotal number of birds counted / study area Year

Total number of birds counted / study area

1969 158 1993 941970 163 1994 841971 212 1995 721972 214 1996 931973 192 1997 871974 161 1998 721975 201 1999 851976 194 2000 891977 187 2001 911978 149 2002 711979 147 2003 891980 131 2004 761981 117 2005 961982 124 2006 1081983 118 2007 1001984 89 2008 921985 116 2009 1061986 91 2010 1081987 85 2011 951988 113 2012 1051989 101 2013 1201990 133 2014 1131991 120 2015 1141992 130

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What data will you graph to answer the question? Independent variable:

Dependent variable:

Draw your graph below: Identify any changes, trends, or differences you see in your graph. Draw arrows pointing out what you see, and write one sentence describing what you see next to each arrow.

Interpret the data: Make a claim that answers the scientific question.

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What evidence was used to write your claim? Reference specific parts of the tables or graph. Explain your reasoning and why the evidence supports your claim. Connect the data back to what you learned about long-term datasets and what they can tell us about bird populations.

Worldwide Loss of Bees a Growing Concern

Worldwide Loss of Bees a Growing Concernby Alissa Fleck

When we think of bees, we think of pesky, buzzing insects that sting us and ruin outdoor gatherings. We might wonder: how badly can we possibly need bees? The truth is, bees are an incredibly important part of our ecosystem on Earth-no matter how annoying they may be to humans. Unfortunately, bees have been disappearing around the world for some time now, and their mass disappearance continues to present new problems around the planet.

According to Reuters news source, scientific researchers have been trying desperately for the past 15 years to understand why honeybees around the world are dying off at frighteningly high rates. Over 1 million bee colonies disappear every year, never to return, Reuters reporters noted in 2012.

Kevin Hackett, the national program leader for the bee and pollination program at the U.S. Department of Agriculture (USDA), called the massive honeybee disappearance "the biggest general threat to our food supply."

How could something so small be so important to us as humans? Bees are used to pollinate many crops, for instance a large portion of California's almond crop, which relies heavily on bee pollination. Bees are also essential for the pollination of apple and citrus fruit crops. Without the pollination by bees, these plants are unable to reproduce and may die off.

The mass deaths of honeybees have been linked to something known as Colony Collapse Disorder (CCD)-a mysterious loss of bee colonies with many potential causes-as well as a variety of pesticides, parasites and disease, all of which hurt bee populations. Other possible causes include land development and changes in agricultural practices around the world.

There are numerous kinds and species of bees, and honeybees are not the only ones disappearing in large quantities. Bumblebees can be added to the list of pollinators whose widespread disappearance

ReadWorks.org · © 2013 ReadWorks®, Inc. All rights reserved.

Worldwide Loss of Bees a Growing Concern

worries scientists. While the dangers of losing bees, such as the damage to our food supplies, have long been known, researchers are uncovering even more distressing information about the loss of these ecologically crucial insects.

According to researchers who published their findings in the Proceedings of the National Academy of Sciences in 2013, the disappearance of bumblebees offers new cause for concern: certain plants are having difficulties reproducing with the loss of their bumblebee pollinators, and are at higher risk for extinction.

Two scientists, who conducted research on the impact of bumblebee loss on plant reproduction, found that when a particular species of bumblebee was removed from the pool of pollinators, other bees did not completely take over the pollinating duties. Instead, with less competition from the bees which had been removed from the pool, the remaining bumblebees flew between many different plants and were less likely to be faithful to one kind of plant.

The researchers noted this experiment had damaging effects. For instance, the larkspur, a purple wildflower, requires pollination from its own species-other larkspurs-to survive. The researchers found with fewer bumblebees, the remaining bees were "less faithful" to a particular plant, meaning the larkspur was unable to survive as it would have before the loss of bumblebees.

This particular study highlights the importance of bees to the continuation of, not just our food supply, but also all biodiversity, as the effects of this study do not end with the larkspur plant alone, but point to a much larger issue. The larkspur is just one example of this issue.

In 2012, the USDA and Environmental Protection Agency (EPA) released a joint statement discussing the issue of bee loss, and the search for a solution to the cycle of problems caused by bees dying off.

The organizations concluded: "No single silver bullet will solve the problems affecting honey bees and other pollinators."

In terms of solutions, the organizations proposed: "Habitat enhancement...targeted pesticide use, improved colony management techniques and improved disease and pest resistant stocks of bees are collectively needed to improve the health of honey bee colonies."

"It is imperative that we increase honey bee survival both to make beekeeping profitable," the statement noted, "but more importantly to meet the demands of U.S. agriculture for pollination and thus ensure of [sic] food security."


The American Chestnut

The American Chestnutby ReadWorks

You've probably never seen an American chestnut tree-at least, not one that's fully grown. But only one hundred years ago, this enormous tree covered the eastern coast of the United States. People constructed buildings from its smooth, glowing wood. They ate nuts from the trees every fall and winter. Now the American chestnut has practically disappeared. Scientists are working hard to find a way to save it-but time is running out.

The American chestnut, Castanea dentata, stands tall at almost 100 feet with a trunk diameter of 10 feet. Its wood is hard and naturally resistant to termites and other pests, making it ideal for buildings and furniture. It is a deciduous tree-throughout the seasons the leaves change color from green to orange, yellow and red, making the mountains look as though they are on fire and, eventually, they fall.

When chestnuts were common in the United States, they could be found all the way from the northern tip of Maine to the warm, southern foothills of Mississippi. In some states, like Pennsylvania, 30% of the hardwood forests were of chestnut trees. The total number of chestnut trees in North America was ReadWorks.org · © 2013 ReadWorks®, Inc. All rights reserved.


estimated to be at least one billion! Now there are only a few thousand surviving. Scientists are careful to protect them, in the hope that, within these trees' genes, is the secret to saving the species.

What caused the decline of the American chestnut? It all began when travel between continents increased in the past hundreds of years. For thousands of years the chestnut trees in North America were isolated. But as modes of transportation improved, people began to trade with other continents more often.

Though the North American chestnuts had been isolated, they weren't the only chestnut trees in the world. There were also European chestnut trees and Asian chestnut trees. Though these trees are all part of the same species, their genes are quite different. This is because they evolved in different habitats, interacting with different species. Even trees within the same habitat have genes that are a tiny bit different.

Over time, a process called natural selection occurred. In each habitat, trees faced changes in their environment. The trees that were able to adapt to these changes and survive had different genes from the trees that died off. Over thousands of years, this made the species noticeably different. Asian chestnuts co-evolved with a fungus called Cryphonectria parasitica. Both Japanese and Chinese chestnut trees are usually able to resist the fungus and are not killed by the infection. But the American chestnut trees had not been previously exposed to this fungus and were especially vulnerable. It is thought that the fungus, commonly known as the chestnut blight, was accidentally brought to the United States around 1900. In 1904, the first American chestnut tree sick with the blight was spotted in the Bronx, a borough of New York City.

The fungus enters the tree through cuts and grows beneath the bark, eventually killing the tree. The first symptom of the fungus is a small orange-brown area on the tree bark which then spreads and grows. These spots, called cankers, split the bark of the tree and gradually kill it.

Before the American chestnut disappeared, it made up 25% of all of the hardwood forests in the Appalachians, the main mountain range in the eastern United States. The disappearance of the chestnut tree had several negative consequences for the people in this region. Previously, their houses had been built out of chestnut wood. They had relied on the trees for nuts. They had sold the lumber from the trees to make money to support themselves and their families.

Pockets of the American chestnut still survive in the Northwestern United States, where the climate is too cold for the fungus to survive. On the East Coast, chestnut trees still sprout, but they typically die while they are still very young and before they have a chance to produce nuts.

The last large group of surviving chestnut trees is in West Salem, Wisconsin. About 2,500 trees exist there, the descendants of trees planted generations ago by a settler named Martin Hicks. For most of the twentieth century, these trees escaped the blight. But in 1987, scientists found the fungus among them, as well.

Scientists are now working hard to save the American chestnut, but it is a long and arduous process. Surviving chestnut trees are rare and must be protected from exposure to the fungus. In 2008, government officials in Ohio announced they had found an adult chestnut tree in a marsh. Though the officials had known about the tree for seven years, they waited to announce its existence because they wanted to protect it. The exact location of the tree remains a secret for its own protection from the fungus.



Scientists are trying different approaches to save the American chestnut. Researchers at the American Chestnut Foundation, an organization in western North Carolina, have been cross-breeding the American chestnut with the Chinese chestnut. The goal is to create a tree that has all the characteristics of the American chestnut, but keeps the Chinese chestnut tree's resistance to the blight. Because the Chinese chestnut co-evolved with the fungus, it is not killed by the fungus.

Other scientists are attempting to modify the American chestnut genes to make them resistant to the fungus. Researchers at the State University of New York College of Environmental Science and Forestry have inserted genes from wheat into the American chestnut genes. These genes help (the gene) create an enzyme (a complex protein) that kills the fungus. However, genetic modification is highly controversial. Trees that have been genetically modified need approval from the government before they can be planted in the wild. The scientists doing genetic modification defend their work. They point out that there are around 45,000 genes in the chestnut tree, and the researchers are adding one-to-three additional genes.

But whether the genetically modified trees can be grown in the wild comes down to whether government regulators think those added genes are dangerous. Right now, these trees are only permitted to be planted in specific areas where there is no danger of spreading pollen to other, non-genetically modified trees. From 2006 to 2012, the researchers planted hundreds of genetically modified chestnut trees in Syracuse. They also planted over 150 trees in other New York locations. Each tree begins as a group of cells grown in a Petri dish. It takes two years before those cells are large enough to have a seedling that can be planted in the ground.

Ultimately, these researchers want to repopulate the hardwood forests of the eastern United States with the American chestnut tree. Chestnuts aren't the only trees from ancient American forests that have nearly disappeared. Elms have fallen prey to Dutch elm disease, a fungus that devastated native elms in both Europe and America (in spite of the fungus's name, it actually originated in Asia, not the Netherlands). The disease was introduced to the United States from Europe in 1930. The disease spread unusually rapidly due to the European elm bark beetle, which spreads the fungus as it feeds on the twigs and bark of elm trees. The white pine tree, native to northeastern United States, was attacked by another fungus called "blister rust." The first sighting of blister rust occurred in New York in 1906, just two years after the first documentation of the chestnut blight.

Collaborations between scientists, government and preservationists may be able to save all of these trees and bring back healthy American forests.


Threatened Species - Paired Text QuestionsWorldwide Loss of Bees a Growing Concern · The American Chestnut

Name: ___________________________________ Date: _______________

Use the article "Worldwide Loss of Bees a Growing Concern" to answer questions 1 to 3.

1. Colony Collapse Disorder, pesticides, and land development are all possible causes

of the disappearance of bees. What is one effect of the disappearance of bees?

2. What are three solutions that the USDA and EPA have proposed to help improve the

health of honey bee colonies?

3. What is the main idea of this text? Support your conclusion with evidence from the

text.



Use the article "The American Chestnut" to answer questions 4 to 6.

4. What caused the decline of the American chestnut?

5. How are scientists attempting to save the American chestnut? Describe two

approaches they are taking.

6. What is the main idea of this text? Support your conclusion with evidence from the

text.



Use the articles "Worldwide Loss of Bees a Growing Concern" and "The American Chestnut" to answer questions 7 to 8.

7. Explain whether the main ideas of these two articles are related. Use evidence from

both texts to support your answer.

8. Understanding the causes and effects of the disappearance of a species can help

people find ways to protect that species. Use evidence from both texts to support this

statement.


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Figure 1: Undergraduate researchers Dan and Gabe checking on the 610 plants in the experiment. The experiment ran for three years, from 2011 to 2013.

Figure 2: Every year, Elizabeth measured the proportion of leaf area removed by herbivores on each of the experimental plants.

Do insects prefer local or foreign foods?

Featured scientist: Elizabeth Schultheis from Michigan State University

Research Background: Insects that feed on plants, called herbivores, can have big effects on how plants grow. Herbivory can change the size and shape of plants, the number of flowers and seeds, and even which plant species can survive in a habitat. A plant with leaves eaten by insect herbivores will likely do worse than a plant that is not eaten. Plants that naturally grow in an area without human interference are called native plants. When a plant is moved by humans to a new area and lives and grows outside of its natural range, it is called an exotic plant. Sometimes exotic plants become invasive, meaning they grow large and fast, take over habitats, and push out native species. What determines if an exotic species will become invasive? Scientists are very interested in this question. Understanding what makes a species become invasive could help control invasions already underway and prevent new ones in the future. Because herbivory affects how big and fast a plant can grow, local herbivores may determine if an exotic plant thrives in its new habitat and becomes invasive. Elizabeth, a plant biologist, is fascinated by invasive species and wanted to know why they are able to grow bigger and faster than native and other exotic species. One possibility, she thought, is that invasive species are not recognized by the local insect herbivores as good food sources and thus get less damage from the insects. Escaping herbivory could allow invasive species to grow more and may explain how they become invasive.

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To test this hypothesis, Elizabeth planted 25 native, 25 exotic, and 11 invasive species in a field in Michigan. This field was already full of many plants and had many insect herbivores. The experimental plants grew from 2011 to 2013. Each year, Elizabeth measured herbivory on 10 individuals of each of the 61 species, for a total of 610 plants. To measure herbivory, she looked at the leaves on each plant and determined how much of each leaf was eaten by herbivores. She then compared the area that was eaten to the total area of the leaf and calculated the proportion leaf area eaten by herbivores. Elizabeth predicted that invasive species would have a lower proportion of leaf area eaten compared to native and noninvasive exotic plants. Let’s look at one leaf to see how Elizabeth collected herbivory data. Here is an example of a leaf from an invasive plant:

Observe the shape of the leaf. Does it appear some of the leaf area is missing and has been eaten by herbivores? Estimate how many grid cells the leaf covers and how many grid cells are missing from the leaf. Each grid cell represents 1 square centimeter (cm).

Area of leaf eaten by herbivores =

Total area of leaf =

Proportion leaf area eaten by herbivores = area of leaf eaten / total area of leaf = Scientific Question: How does insect herbivore damage compare for native, exotic, and invasive plant species? What is the hypothesis? Find the hypothesis in the Research Background and underline it. A hypothesis is a proposed explanation for an observation, which can then be tested with experimentation or other types of studies.

1 cm

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Draw Your Predictions: On the three leaves below, draw your predictions for the amount of herbivory on the three plant types. Use one color to fill in areas that the herbivores have eaten. Use another color to fill in the rest of the leaf. Remember to fill in the legend to show which colors you used. Scientific Data: Scientific Data: Use the data below to answer the scientific question:

What data will you graph to answer the question? Independent variables:

Dependent variable:

Plant Type 2011 2012 2013

native 0.046 0.037 0.046

exotic 0.075 0.063 0.057

invasive 0.168 0.087 0.078

Year of Data CollectionAverage Proportion Leaf Area Eaten by Herbivores

= eaten by herbivores

= leaf remaining

native exotic invasive

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Below is a graph of the data: Identify any changes, trends, or differences you see in your graph. Draw arrows pointing out what you see, and write one sentence describing what you see next to each arrow.

Interpret the data: Make a claim that answers the scientific question. What evidence was used to write your claim? Reference specific parts of the table or graph.

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Explain your reasoning and why the evidence supports your claim. Connect the data back to what you learned about the effects of herbivory on plant performance. Did the data support Elizabeth’s hypothesis? Use evidence to explain why or why not. If you feel the data were inconclusive, explain why. Your next steps as a scientist: Science is an ongoing process. What new question(s) should be investigated to build on Elizabeth’s research? What future data should be collected to answer your question(s)?

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Is chocolate for the birds?

Featured scientist: Skye Greenler from Colorado College Research Background: About 9,000 years ago humans invented agriculture as a way to grow enough food for people to eat. Today, agriculture happens all over the globe and takes up 40% of Earth’s land surface. To make space for our food, humans must clear large areas of land, creating a disturbance, or drastic change, to the habitat. This disturbance removes the native plants already there, including trees, small flowering plants, and grasses. Many types of animals including mammals, birds, and insects need these native plants for food or shelter and will now find it difficult to live in the area. For example, a woodpecker bird cannot live somewhere that has no trees because they live and find their food in the trees. However, some agriculture might help some animals because they can use the crops being grown for the food and shelter they need to survive. One example is the cacao tree, which grows in the rainforests of South America. Humans use the seeds of this plant to make chocolate, so it is a very important crop! Cacao trees need very little light. They grow best in a unique habitat called the forest understory, which is composed of the shorter trees and bushes under the large trees found in rainforests. To get a lot of cacao seeds for chocolate, farmers need to have large rainforest trees above their cacao trees for shade. In many ways, cacao farms resemble a native rainforest. Many native plant species grow there and there are still taller tree species. However, these farms are different in important ways from a native rainforest. For example, there are

Skye out in the field counting birds along one of her four transects.

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Cacao Rainforest

Total Bird Count

106

116Rainforest

Cacao

many more short understory trees in the farm than there are in native rainforests. Also, there are fewer small flowering plants on the ground because humans that work on cacao farms trample them as they walk around the farm. Skye is a biologist who wanted to know whether rainforest birds use the forest when they are disturbed by adding cacao farms. Skye predicted she would see many fewer birds in the cacao farms, compared to the rainforest. To measure bird abundance, she simply counted birds in each habitat. To do this she chose one rainforest and one cacao farm and set up two transects in each. Transects are parallel lines along which the measurements are taken. She spent four days counting birds along each transect, for a total of eight days in each habitat. She had to get up really early and count birds between 6:00 and 9:00 in the morning because that’s when they are most active. Scientific Question 1: What is the effect of Table 1: Bird Observation Data cacao farms on bird abundance? Scientific Data 1: Use the data from Table 1 to answer scientific question 1: The image on the left shows a typical cacao farm with some taller trees remaining to provide

shade for the cacao. The image on the right shows an undisturbed rainforest. In the rainforest, all the taller trees and small flowering plants remain.

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What data will you use to answer question 1? Independent variable:

Dependent variable: Interpret the data: Make a claim that answers scientific question 1 – What is the effect of cacao farms on bird abundance? What evidence was used to write your claim? Reference specific parts of the table or graph. Explain your reasoning and why the evidence supports your claim. Connect the data back to what you learned about how agriculture may act as a disturbance. Skye’s next steps: Skye was shocked to see so many birds in cacao farms! She decided to take a closer look at her data. Skye wanted to know how the types of birds she saw in the cacao farms compared to the types of birds she saw in the rainforest. She predicted that cacao farms would have different types of birds than the undisturbed rainforest. She thought the bird types would differ because each habitat has different types of food available for birds to eat and different types of plants for birds to live in. Skye broke her abundance data down to look more closely at four groupings of birds:

1. Toucans (Eat: large insects and fruit from large trees, Live: holes in large trees) 2. Hummingbirds (Eat: nectar from flowers, Live: tree branches and leaves) 3. Wrens (Eat: small insects, Live: small shrubs on the forest floor) 4. Flycatchers (Eat: small insects, Live: tree branches and leaves)

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Scientific Question 2: What is the effect of cacao farms on the abundance of different bird types? What is the hypothesis? Find the hypothesis in Skye’s next steps (above) and underline it. A hypothesis is a proposed explanation for an observation, which can then be tested with experimentation. Scientific Data 2: Use the data from Table 2 to answer scientific question 2:

Table 2. Bird Observation Data by Bird Type

Date Habitat Toucans Hummingbirds Wrens Flycatchers

3/16/13 Cacao 0 0 0 11

3/22/13 Cacao 1 2 0 7

3/25/13 Cacao 0 3 0 10

4/4/13 Cacao 0 7 1 5

4/8/13 Cacao 0 7 0 9

4/12/13 Cacao 0 6 0 9

4/18/13 Cacao 0 6 0 6

4/25/13 Cacao 0 7 2 7

3/14/13 Rainforest 1 3 2 2

3/14/13 Rainforest 2 4 10 8

3/21/13 Rainforest 2 2 9 3

3/26/13 Rainforest 2 4 7 4

4/6/13 Rainforest 2 1 8 3

4/9/13 Rainforest 2 3 8 6

4/20/13 Rainforest 3 2 8 5

4/22/13 Rainforest 0 0 0 0

Toucans Hummingbirds Wrens Flycatchers

1 38 3 64

14 19 52 31

Total Count (abundance)

Cacao

Rainforest

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What data will you graph to answer question 2? Independent variable:

Dependent variable:

Below is a graph of the data: Identify any changes, trends, or differences you see in your graph. Draw arrows pointing out what you see, and write one sentence describing what you see next to each arrow.

Interpret the data: Make a claim that answers scientific question 2 – What is the effect of cacao farms on the abundance of different bird types?

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What evidence was used to write your claim? Reference specific parts of the table or graph. Explain your reasoning and why the evidence supports your claim. Connect the data back to what you learned about diet and living preferences of the different types of birds. Did the data support Skye’s hypothesis? Use evidence to explain why or why not. If you feel the data were inconclusive, explain why. Your next steps as a scientist: Science is an ongoing process. What new question(s) should be investigated to build on Skye’s research? What future data should be collected to answer your question(s)?

The Origin of Species

The Origin of Speciesby Kirsten Weir

Is it time to scale back the war on alien plants and animals?The cane toad is the Darth Vader of the amphibian world. A native of Central and South America, the lumpy toad was turned loose in Australia in the 1930s. Farmers hoped it would eat the beetles that were damaging sugarcane crops. The toad made itself at home, spreading steadily across the land.

As the toad multiplied, though, conservationists started to worry. The toad secretes a goo that can be toxic when eaten. Some feared that the imported amphibian would kill off snakes, crocodiles, and other local predators.

Minden Pictures/SuperStock

For years the cane toad has been the poster child of invasive species. An invasive species is a plant or an animal that settles in a new region, where it does harm to the environment, the economy, or human health. Conservationists regularly take up arms against plant and animal invaders by trapping, hunting, poisoning, or bulldozing them.

A growing number of scientists have now begun to argue, however, that conservationists are too hung up on the native versus nonnative distinction. "The public has embraced the idea of hating nonnative species," says Mark Davis, a biologist at Macalester College in St. Paul, Minn. "There's no scientific basis for that."

Hitching A RideIt's easier than ever for people to move around the planet, often bringing other species along for the

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ride. Sometimes that's done on purpose. Gardeners have been moving desirable plants from continent to continent for centuries. Other times, nonnative species are accidental tourists. Zebra mussels arrived in the Great Lakes after being inadvertently toted across the ocean in the ballasts of ships.

Scientists estimate that some 50,000 foreign species have settled in the U.S. Among them is the python, a 6-meter (20-foot) Asian constrictor. Florida pet owners dumped pythons into the wild and they're now spreading across Everglades National Park. Another is kudzu, a vine from Japan that grows as much as a foot in one day and is running rampant across the southeastern U.S. Then there's the zebra mussel, which clogs water pipes and has done hundreds of millions of dollars in damage to power plants and water utilities around the Great Lakes.

Jack Dermid/Photo Researchers, Inc.

Kudzu, an invasive Japanese vine, has spread across the United States. Here it is seen engulfing an old home in North Carolina.

Billions of dollars are spent in the U.S. alone to control invasive species each year. Tim Male, vice president of conservation policy at Defenders of Wildlife, says the country should do even more to fight nonnative species. "It's rarer than it should be that people are going out and trying to control nonnative species in some of our most special habitats," he says.

Male and his colleagues are engaged in the preservation of the country's ecological niches. An ecological niche is a unique position that a species fills in an ecosystem-the species' habitat, the food it eats, and the predators that eat it. If nonnative species are allowed to invade local niches, Male says, "we're affecting the species that are present now, and we're also significantly affecting the future web of life, forever."

Toad HypeDavis agrees that some nonnative species are harmful. And he agrees that vigorous efforts should be made to prevent the accidental introduction of foreign species to new habitats. But too many biologists assume nonnative means harmful, he says. He and 18 other ecologists made that case in the scientific journal Nature this past summer. "It is time for scientists, land managers, and policy makers to ditch this preoccupation" with nonnative species, they wrote.



Some nonnative species aren't as bad as they're made out to be, say the ecologists. Take the cane toad, the horror of which hasn't lived up to the hype. While the toad's presence led to a decline in some predator populations in Australia, most species weren't impacted at all, scientists reported recently. Some species actually benefited from the toad's arrival.

And consider the salt cedar, a shrub brought from Africa and Eurasia to the western U.S. in the 1800s. Between 2005 and 2009, the U.S. government spent $80 million fighting the shrub because it's suspected of soaking up too much valuable groundwater from its desert habitat. But, notes Davis, the shrub is now the favorite nesting site for the southwestern willow flycatcher, an endangered bird. The shrub may be doing more good than harm.

Keith Douglas/All Canada Photos/Corbis

Honeybee

Some nonnative species do nothing but good. Honeybees are an example. They pollinate more than 100 crops in the U.S., providing an estimated value of more than $9 billion a year. Honeybees are an import from Europe, but nobody's suggesting they buzz off.

Native species, on the other hand, aren't always helpful. Mountain pine beetle outbreaks occur periodically in the forests of western North America. Millions of trees perish as the beetle larvae eat their way through the trees' trunks. The mountain pine beetle is currently killing more North American trees than any other bug. It's a homegrown hazard.



Claude Jardel/Biosphoto

Mountain Pine Beetle

Land ManagementInstead of waging war on foreign species, Davis says, conservationists should figure out how to include them in land management plans. In general, he notes, the introduction of nonnative species results in more species in a given habitat, not fewer.

Claude Jardel/Biosphoto

Python

To Davis, the lesson is clear: "Don't judge species on where they came from. Judge them on what they are doing."


The Origin of Species - Comprehension Questions

Name: ___________________________________ Date: _______________

1. What is an invasive species?

A. a species that settles in a new region, where it does harm to the environment, the economy, or human health

B. a species that naturally migrates to a new region, where it can be helpful or harmful to the environment

C. a species that is native to a region, where it does harm to the environment, the economy, or human health

D. a species that is introduced to a new region by human intervention, where it can either do harm or be helpful to the environment

2. Which of the following quotes best summarizes Mark Davis's argument as described

in the passage?

A. "It's rarer than it should be that people are going out and trying to control nonnative species in some of our most special habitats."

B. "The public has embraced the idea of hating nonnative species...There's no scientific basis for that."

C. "Don't judge a species on where they came from. Judge them on what they are doing."

D. "'It is time for scientists, land managers, and policy makers to ditch this preoccupation' with nonnative species."

3. Nonnative species can cause significant damage to the regions where they are

introduced. What evidence from the passage supports this conclusion?

A. Scientists estimate that some 50,000 foreign species have settled in the U.S.

B. The cane toad was introduced in Australia to eat the beetles that were destroying sugarcane crops.

C. The zebra mussels clog pipes, causing millions of dollars in damage to power plants.

D. The salt cedar shrub is now the favorite nesting site for the endangered southwestern willow flycatcher.



4. Which of the following accurately describes Tim Male's view of nonnative species?

A. Male believes that nonnative species pose a threat to the web of life.

B. Male believes that nonnative species should find their own ecological niches.

C. Male believes that adding another species in a region will help the web of life.

D. Male believes that nonnative species should be allowed to invade local niches.

5. What is this passage mostly about?

A. how nonnative species can help the environment they are in

B. whether nonnative species should always be considered hurtful

C. how conservationists work to control nonnative species in an area

D. how nonnative species can hurt the environment they are in

6. Read the following sentences: "Other times, nonnative species are accidental

tourists. Zebra mussels arrived in the Great Lakes after being inadvertently toted

across the ocean in the ballasts of ships."

What does the word "inadvertently" mean?

A. purposefully

B. intentionally

C. meaningfully

D. accidentally

7. Choose the answer that best completes the sentence below.

Many people believe that nonnative species are always harmful to the region;

_________, biologist Mark Davis believes that nonnative species can be beneficial to a

region, given the right circumstances.

A. in particular

B. however

C. finally

D. therefore



8. Describe an example of how nonnative species can be harmful to an environment.

9. Describe an example of how nonnative species can be helpful to an environment.

10. Explain whether nonnative species should be seen as an environmental threat.

Support your answer using information from the passage.


6th grade science chestnut.” complete questions that

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