Activity 3, Humans Effects on Biodiversity. from the Evolution Unit of the SEPUP course. Science in Global Issues

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1 Activity 3, Humans Effects on Biodiversity from the Evolution Unit of the SEPUP course Science in Global Issues For use only by teachers who attended the Biodiversity session at NSTA on March 19, Regents of the University of California. All rights reserved. Lawrence Hall of Science University of California, Berkeley, CA Phone (510) Fax (510)

2 3 Human Effects on Biodiversity Humans, like all species on Earth, are part of the ecosystems in which they live. They have influenced these ecosystems in many ways. Today, many people are concerned that human activities have accelerated the evolution of some species, and the extinction of many others. In this activity, you will look at some examples of how humans have affected the evolution of other species. CHALLENGE In what ways have humans impacted species? MATERIALS PROCEDURE 1. In your group of four, divide the scenarios so that each person is assigned to read one. 2. Work by yourself to read your assigned scenario. As you read, use the Showing Thinking While Reading strategy. Mark three sticky notes as you read. 3. In your science notebook, copy the following chart. Give it an appropriate title. Fill out the table as you summarize the scenarios in your group of four. Scenario Human activity Impact on species Impact on humans (activities) involved other than humans 13

3 Human Effects on Biodiversity Activity 3 Scenario #1: Peppered Moth Prior to the Industrial Revolution of the 19th century, individuals in populations of the peppered moth, Biston betularia, were mostly white with dark specks. This coloration camouflaged them from predators in the environment. Due to natural genetic variation in the population, a few moths were darker colored. By the end of the 1800s, the peppered moth populations had changed. Now they were made up of individual peppered moths that were mostly dark charcoal gray with a few that were white with speckles. What is one factor that caused these populations to change? During the Industrial Revolution, coal burning increased the amount of pollutants in the air. Over time, as pollution built up in the environment, individual peppered moths that were charcoal grey were better camouflaged from predators. These moths were better able to survive and reproduce. Many years later, pollution regulations were put into place. The pollution in the environment decreased. Over time, the peppered moth populations returned to the color distribution that was present before the Industrial Revolution. 14

4 Activity 3 Human Effects on Biodiversity Scenario #2: Antibiotic Resistance Antibiotics are one of the most important scientific discoveries to benefit human medicine and health. Today, there are more than 100 antibiotics to treat many different types of bacterial infections. You have probably used an over-the-counter antibiotic ointment to treat an infected cut or scrape at home or taken an antibiotic prescribed by a doctor for an illness. Over the years since antibiotics were approved, many doctors have prescribed them unnecessarily to prevent illnesses. They have also prescribed them to treat minor infections. Patients requested antibiotics for illnesses that did not require or could not be treated with antibiotics. Farmers also used antibiotics to make animals such as chickens and cows grow faster. These antibiotics were present in the eggs and meat produced by the animals. From a bacterial population s perspective, the frequent use of antibiotics by humans means that bacteria are constantly exposed to antibiotics in their environment. Due to genetic variation in the population, it is possible that a single bacterium has a mutation that prevents it from being killed by the antibiotic. This is called antibiotic resistance. The bacteria with the mutation survive and reproduce bacteria that also have the mutation. This leads to increased numbers of bacteria that cannot be killed by, or are resistant to, the antibiotics. From the human population s perspective, antibiotics are important in modern medicine. However, due to antibiotic resistance, new antibiotics must be created to treat infections caused by antibiotic resistant bacteria. In these new antibiotic environments, there is a chance that some bacteria will have yet another mutation that gives them resistance to the new antibiotic. This cycle creates a constant challenge for humans living with bacteria. Currently, there is a growing worldwide concern about resistance in the bacteria that cause serious diseases. For example, there are an increasing number of the bacteria that cause tuberculosis that are resistant to two of the previously most powerful antibiotics used to treat tuberculosis. 15

5 Human Effects on Biodiversity Activity 3 Scenario #3: Domestic Dog Breeding Domestic dogs are part of the species Canis lupus familiaris. They are the result of thousands of years of dog breeding that began about 14,000 years ago when humans first domesticated the gray wolf, Canis lupus lupus. The wolf population was made up of a variety of genetically different individual wolves. Humans took advantage of the natural variation in the population. They chose parent wolves with traits that would allow them to perform useful and desirable functions such as hunting, herding, and chasing. They bred the parent wolves with the desired traits in a process called artificial selection. Over centuries of artificial selection, the descendants of the wolves became more dog-like, known for their close association with humans. After thousands of years of artificial selection, there are hundreds of breeds of Canis lupus familiaris, including Golden Retrievers, Poodles, Chihuahuas, and Rottweilers. Each breed has unique characteristics selected by the human breeders. For example, Golden Retrievers are obedient and intelligent. Chihuahuas are loyal and a small size. Today there is big business in the art of dog breeding in what the media has labeled Designer Dogs. Designer dogs are not mutts. They are the result of carefully mating two chosen purebred dogs with desirable traits. Such traits include coat length and texture, color, size, and temperament. Some of these dogs are prized for their characteristics and can cost thousands of dollars. For example, the Labradoodle is a mix between a Labrador retriever and a poodle. Labradoodles have traits desirable to humans including a friendly, loyal disposition and a nonshedding coat.. 16

6 Activity 3 Human Effects on Biodiversity Scenario #4: The Dodo Bird The Indian Ocean island of Mauritius was once home to the large, flightless dodo bird. A population of Southeast Asian pigeons arrived on the island several million years ago, and began to colonize it. Over time, through the process of natural selection, the pigeons evolved into dodos. Because the island was isolated, the dodos could freely feed on the fruit on the ground. Also there were no predators of the dodos. Those dodos with the ability to store large amounts of fat in times when food was scarce were better able to survive and reproduce. Over time, the dodos increased in size. This led to a trade-off between being larger and storing more fat and being able to fly. In an environment with no predators, the inability to fly would have had no effect on the dodo s ability to survive, which is common on islands. Over time, the dodos lost flight. Then, in the 16th and 17th centuries, Portuguese and Dutch sailors found their way to the island of Mauritius. A short eighty years later, the dodo was extinct. After millions of years of surviving and thriving as large, flightless birds, the dodos could not flee from the human hunters. The sailors also brought with them pigs, monkeys, and rats that fed on the dodos eggs and chicks, and perhaps even adult dodos. The dodos could not survive the impact and disappeared forever. Flightless birds did not evolve on Mauritius alone. They have evolved on other islands for similar reasons. The dodo is an example of the extinction of species with features common to birds that evolve on islands with no predators. It illustrates what can happen to island organisms when humans and invasive species arrive on the scene. 17

7 Human Effects on Biodiversity Activity 3 ANALYSIS 1. What types of organisms do humans interact with in the environment? 2. a. For which scenario(s) is the human impact positive? b. For whom is it positive? 3. a. For which scenario(s) is the human impact negative? b. For whom is it negative? 4. For each of the four scenarios, explain how humans impacted the diversity of species. 5. Can you think of other examples of humans impacting other organisms? 6. Do you think it is important for humans to be aware of how we are impacting the biodiversity of species? Explain. 18