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The short film opens with two questions: "So what determines how many species live in a given place? Or how many individuals of the species can live somewhere?" The research that provided answers to these questions was set in motion by key experiments by ecologists Robert Paine and James Estes. Robert Paine's starfish exclusion experiments on the coast of Washington state showed that removing starfish from this marine ecosystem has a big impact on the population sizes of other species, establishing the starfish as a keystone species. James Estes and colleague John Palmisano discovered that the kelp forest ecosystems of the North Pacific are regulated by the presence or absence of sea otters, which feed on sea urchins that consume kelp. These direct and indirect effects of sea otters on other species describe a trophic cascade. These early studies were the inspiration for hundreds of investigations on other keystone species and trophic cascades, as well as ongoing studies into the regulation of population sizes and species numbers.

It is now well known that non-native species have the potential to be harmful to an ecosystem, but that wasn't always the case, and getting rid of non-native invasive species is usually a difficult task. This brief, interrupted case study tells the story of kudzu's introduction into the United States in the late 1800s. It also examines (and even questions) how we define words like "native" versus "non-native" and "invasive" versus "non-invasive." Students will learn how invasive species impact ecosystems and why some non-native species never become established. They also will address questions related to eradicating non-native invasive species. For example, is it okay to attempt to get rid of a non-native species with another non-native species? As part of the activity, students also will have to decide whether or not kudzu should be considered "native" since it has been in the United States since 1876. Originally designed for a general biology course for majors, the case has also been used in a biology class for non-majors as well as an environmental biology class.

I'm sure you've probably heard of at least a few invasive species. Maybe you've heard of the Cane Toad. It's one of the classic introductions of invasive species gone wrong. It was introduced to eat pests in cane fields and then turned into a plague of epic proportions in Northern Australia. But here is the question. Now that these species are here, is it worth fighting their spread, or should we spend time and effort on other things. It's worth asking, and not just for the ethical implications. We live in a modern world and I think there is a real financial element to this as well. See if you can follow my logic through this video short. Do you agree with my thoughts? Should we keep fighting? Do you have any personal experience with an invasive species?

This case study focuses on the intersection of defining a scientific species and defining a legal species. The compelling story of Lolita, an orca whale in captivity, is used to highlight the legal significance of species declaration. Students will work through scientific species definitions and data on Orca whales before deciding if Orca whales should be considered as one or several species. After an introduction to Lolita and a mock town hall meeting, students are thrown into the real life situation of contemplating the fate of an Orca in captivity that suddenly has protected legal status. This case was developed for use in a first-year biology course focusing on ecology, genetics, and evolution. It also could be used in upper or lower division courses on ecology, evolution, or conservation.

This case study centers on symbiotic relationships between insects and bacteria using Drosophila melanogaster, the common fruit fly, and the recently discovered bacterial species Sodalis praecaptivus. Until recently, the only known Sodalis species of bacteria were symbiotically associated with several different species of insects. However, free-living non-symbiont Sodalis species are being tested in several different insect species to determine if they can transition into symbiotic relationships. A pre-class assignment (see Supplemental Materials) directs students to read an open access research journal article providing a comprehensive review of S. praecaptivus and describing an experimental weevil model that parallels that of the fruit fly. A PowerPoint presentation shown in class (see Supplemental Materials) provides further background before students work in small groups to complete the case study focusing on results from D. melanogaster and S. praecaptivus model experiments.  Although developed for a genetics course, this interrupted case is appropriate for an upper-level biology course. It can be completed within a 75-minute class meeting, or adapted for shorter time periods.

Such descriptions of GMOs raises fears about whether gene transfer between species is outside of how evolution operates and therefore unnatural. Research, however, has repeatedly shown the opposite to be true. In May 2015, researchers showed that practically every known species of cassava (sweet potato) contained genes from Agrobacterium, a bacterial species whose genes we have also harnessed to create other GM crops. The genes were inserted over 8,000 years ago and may have helped the tuber evolve into its current, edible form. This phenomenon of genetic transfer during evolution between species, also known as 'horizontal gene transfer' is not restricted to plants.

Malaria has long been a problem in Mali. But in 2006, the situation got worse: a malaria-carrying mosquito species named Anopheles coluzzii became increasingly resistant to common insecticides. Scientists searched for an explanation in its genes. Somehow, the species had acquired mutations that were previously only found in another species, Anopheles gambiae - despite the fact that these two species didn't usually mate with each other, and that their hybrids tended to die without producing offspring of their own, the mutations were identical.

This clicker case addresses several important concepts related to evolution. First, it explores artificial selection and selective breeding. Charles Darwin used artificial selection as an example to support his Theory of Evolution by Natural Selection. Belyaev's Fox-Farm experiment is used as an example of a study that used selective breeding as the primary experimental procedure to investigate changes in a lineage. Second, it addresses an interesting observation made by Charles Darwin in The Origin of Species in which he noted how domesticated species also show interesting traits such as drooping ears which seem to be common in domesticated species. The "Farm-Fox Experiment" not only demonstrates how a research team can thoroughly investigate an intriguing question, but also serves as a classic example of elegant experimental design. Designed for use in a large introductory-level biology class, this case study would also be appropriate for smaller classes as well as for upper-level evolution courses.

Dr. Carolyn Henry, a veterinary oncologist at the University of Missouri veterinary school, says that, unlike lab mice, dogs get cancer naturally, just like humans. So their cancers are more likely to behave like human cancer when treated. "It's the same disease, it really doesn't matter what the species is," Henry says. "It's the same disease if it occurs naturally. And so, answers in one species should translate to answers in other species in many cases."

Despite existing for hundreds of years, the science of classification is far from dead. Classification of many species, old and new, continues to be hotly disputed as scientists find new information or interpret facts in new ways. Arguments are fierce and species do change names, but only after a wealth of information has been gathered to support such a big step. One of the new reasons why species are being re-evaluated is because of DNA analysis.

This case study introduces students to the "Red Queen Hypothesis." The hypothesis states that when two species compete for a limited resource or exist in a predator-prey relationship, in order for the antagonists to remain in relative population equilibrium, there must be ongoing and reciprocal adaptation on each side. If one species fails to adapt, it may quickly face extinction. Students are introduced to the Red Queen Hypothesis through an excerpt from Lewis Carroll's novel, Through the Looking Glass, in which Alice meets the Red Queen. They then review experiments from the research literature to evaluate the validity of the hypothesis in extant populations.  Students culminate their learning by contrasting their knowledge of the Red Queen Hypothesis to Darwinian evolutionary theory based on a passage from On the Origin of Species.  Students then craft a letter to Darwin helping to explain his "wedge" theory, a notion he originally developed but removed from later iterations of his book due to a lack of experimental evidence. Originally developed for advanced high school biology students, the case also may be used in a college-level introductory course on evolutionary biology.

In the broadest review on this topic that has been carried out to date, we found that, so far, 386 marine fish species are known to have ingested plastic debris, including 210 species that are commercially important. But findings of fish consuming plastic are on the rise. We speculate that this could be happening both because detection methods for microplastics are improving and because ocean plastic pollution continues to increase.

In this activity, students analyze scientific figures to understand principles of island biogeography theory that determine the number of species in an isolated habitat. This activity uses a jigsaw approach to explore the processes that determine the equilibrium number of species in a habitat and how they are affected by both area and isolation. Two "Student Handouts" are provided as options for the activity. The "Analyzing Graphical Data" handout engages students in graph interpretation and sensemaking from data. The "Building the Equilibrium Model" handout facilitates a scaffolded investigation of the dynamic equilibrium model of island biogeography; students construct immigration and extinction curves to demonstrate the effects of area and isolation on the equilibrium number of species. 

Lyme disease, Ebola and malaria all developed in animals before making the leap to infect humans. Predicting when such a 'zoonotic' disease will spark an outbreak remains difficult, but a new study suggests that artificial intelligence could give these efforts a boost. A computer model that incorporates machine learning can pinpoint, with 90% accuracy, rodent species that are known to harbour pathogens that can spread to humans, researchers report this week in the Proceedings of the National Academy of Sciences1. The model also identified more than 150 species that are likely to be disease reservoirs but have yet to be confirmed as such.

It turns out that some monkeys make better hunting partners than prey. That's the case on the Ethiopian highlands, where two unusual species have developed an equally unusual co-dependency. The relationship benefits both canine and primate, although at least one or two nearby rodent species might regret it.

"Survival of the Fittest: Variations in the Clam Species Clamys sweetus" is a guided inquiry. This series of hands-on activities complements the HHMI DVD Evolution: Constant Change and Common Threads and requires simple materials such as M&Ms, Reese's Pieces, food storage bags, and paper cups. This activity has been designed to engage students in thinking about the mechanism of natural selection by encouraging them to formulate questions that can be answered through scientific investigation, data collection, and pattern recognition.

31min video  The epic voyages of Darwin and Wallace led each to independently discover the natural origin of species and to formulate the theory of evolution by natural selection.

In this video Paul Andersen explains how biodiversity measures the variety of genes, species, and ecosystems on the planet. Biodiversity provides resources and ecosystem services for humans on the planet. He also explains how biodiversity is decreasing on the planet due to habitat destruction, invasive species, climate change, over harvesting, and pollution. Relevant treaties and laws designed to preserved biodiversity is also included.

Scientists have cloned the first U.S. endangered species, a black-footed ferret duplicated from the genes of an animal that died over 30 years ago.

Massive vines that blanket the southern United States, climbing high as they uproot trees and swallow buildings. A ravenous snake that is capable of devouring an alligator. Rabbit populations that eat themselves into starvation. These aren't horror movie concepts - they're real stories. But how could such situations exist in nature? Jennifer Klos gives the facts on invasive species.