AP Biology class blog for discussing current research in Biology

Tag: carbon

Trash, Crops, and Even Pets are on the Menu for these Carnivores

In a recent study, researchers at the University of Wisconsin-Madison and the University of New Mexico found that some of North America’s most prominent carnivores—wolves, mountain lions, bobcats, and foxes—are relying more and more on human sources of food such as trash, crops, and even small pets. In the study, the researchers used hair, fur, and bone samples to identify the diets of seven hundred carnivore species across the upper midwest region of the United States. To identify the diets, chemical isotopes of carbon were taken from these samples to distinguish between human-grown and naturally occurring foods.

Phillip Manlick, the lead author of the study, explains that “Isotopes are relatively intuitive: You are what you eat.” Thus, Human foods, heavy in corn and sugar, have their own distinctive carbon signatures in comparison to the carbon signatures of the diets of prey species in the wild. The ratio of these two isotope fingerprints from the predator samples informs the researchers what proportion of the predator’s diet came from human sources, either directly or from their prey that ate human food first. Our AP Biology class learned that carbon is an essential element in organic compounds. Organic compounds make up all living things which include the human food waste and crops these predators are consuming. Carbon is found in all four organic compounds (Carbohydrates, Proteins, Fats, Nucleic Acids), for carbon’s molecular structure allows for it to create multiple stable covalent bonds with different molecules. Carbon’s covalent bonds enable complex molecules, such as carbohydrates and proteins, that are found in food sources to be formed. 

According to the results of the study, foxes, coyotes, fishers, and martens were the most likely to eat from human food sources, getting about half their food by eating domesticated animals or by foraging in areas that have been disturbed by agriculture. But on average, more than “25 percent of all the carnivores’ diets came from human sources in the most human-altered habitats.”

The reliance on human food sources is not good for the ecosystem, for it increases the overlap in competition for food among these carnivores. There will be more conflicts between species for human food. Furthermore, the reliance on human food sources leaves carnivores susceptible to more human attacks or can change the way species of predators hunt. None of these effects are beneficial to the ecosystem and actually may potentially have harmful ecological consequences.

Personally, I find it a little upsetting that human action is having such interference on the ecosystem and food chain of these predators. In addition, it is even more upsetting to hear that there are very limited options to take that would reduce the reliance on human food sources for these carnivores. Other than securing garbage cans and keeping pets inside at night, there are not many more options. These carnivores are adapting to human urbanization, and this trend will continue as humans keep pushing into these carnivores territories and habitats.

How are animal carcasses beneficial?

Studies prove that carcasses of dead animals are important for plant growth. Researcher, Dr. Roel van Klink, conducted an experiment and concluded that carrion, the decaying flesh of dead animals, is essential for many species. Since, carrion of large animals is an extremely nutrient rich, ephemeral resource. The Oostvaardersplassen Nature Reserve found that the leaving the deceased animals on the ground has had a positive effect on biodiversity. The remains attract more insects and other arthropods and increase plant growth. After five months the plants were significantly larger than usual; the biomass was five times larger and nutritional plant quality was higher than the controlled sites.

Many debates have started from this proposition to keep dead animals in nature reserves. The European legislation requires any dead animal to be removed or destroyed, unless the aim is to provide food for endangered scavengers, like vultures. However, in places like Kenya and Tanzania, the Mara River’s ecosystem relies on rotting carcasses for sustenance. The disposal of wildebeests in the river, not only feeds scavengers, but also releases nutrients (phosphorus and carbon) into the river after their body decomposes and releases algae and bacteria, which also nourishes the fish. Although many nature reserves benefit from this concept, the Oostvaardersplassen nature reserve abused their power in 2017-2018. The reserve starved 3,300 deer, horses and cattle to death. These opposing views cause controversy on whether or not decaying animals are beneficial or detrimental to the economy.

Many ecosystems rely on rotting carcasses for sustenance. In the ocean, over 60 species live off of the “whale-fall” communities. This is when a large whale dies and their body sinks to the seafloor, into a new ecosystem. Scavengers (hagfish, sleeper sharks, amphipods, etc.) in the ocean tear away large pieces of soft tissue from the whale and later, “bone-eating” worms help to digest the whale carcass. These new species, developed from the “whale-fall” communities, can last decades in the deep ocean. Unfortunately, many whales suffer from commercial whaling, which also affects the food chain for animals that eat whales. This time of mass slaughter killed off as many as ninety percent of living whales during the 18th and 19th century. Therefore, some of the first extinctions in the ocean have been from whale-fall communities.

Personally, I believe that animal carcasses are beneficial to nature and should be allowed. Though, some people abuse their power to benefit their own land, by slaughtering animals. For that reason, there should be set regulations to ensure the safety of animals so people won’t just go around killing innocent animals for their own advantage.

Climate Change Threatens Drastic Changes to the Food Chain

     Climate change has been an ongoing issue for several decades now, yet there seems to be little improvement and far worse consequences than we could have ever imagined. Aside from the devastating impacts global warming has had on our atmosphere, it has also threatened wildlife that rely on certain habitats and prey for survival. The most crucial changes that have occured are regarding the ocean. Ocean warming specifically has impacted marine environments and ice in the arctic that many animals rely on for breeding and raising their young. This has subsequently transformed the food chain.

     A recent study at Princeton University gives a “specific timeframe for when ocean changes will occur” as a result of atmospheric carbon dioxide due to human activity. The ocean has helped slow global warming because of its ability to absorb heat and carbon from the atmosphere, but we can now see the harmful effects from this, namely ocean warming, and how it will continue to increase in the future. The warming of the oceans has a major impact on the food chain because it causes species to either die out, look for more favorable environments, or look for another food source. Through this recent study, scientists were able to isolate the direct impacts of global warming on the oceans from the more natural changes. Scientists used the Earth System Model which has an interactive carbon cycle to see changes that are likely to occur in the future if ocean warming is not prioritized right now. 


     However, these predicted changes in the oceans have already been affecting marine life starting from the smallest organisms to gray whales. All of these species are a part of the food chain and suffer as a result of changes in the ocean. When the ocean temperatures rise, the population of smaller prey decline and larger predators must search North for alternate food sources. It also causes the amount of arctic ice to become sparser, which affects the population of animals that use the ice to breed and raise their young, as seals do, or use as a tactic for hunting, as polar bears do.  The higher the ocean temperature rises, the more difficult it is for many species to survive. It is also important to note that rising ocean temperatures affect our atmosphere. As permafrost melts, it releases the 1,600 billion tonnes of carbon frozen within it. Similar to the food chain, global warming affects us all, and it is our duty to take action now. U.N. representatives stated that “if we act now, we can reduce carbon emissions within 12 years,” a goal we should all be striving for. 


Another reason to not cut down old trees

Imagine if human growth accelerates, instead of slowing down after adolescence. This way, humans would weigh less than half as much at their middle age than at when they are at their old age.

In a study published in the journal Nature, scientists found out that the growth of the tree accelerates with the tree size. This means that the bigger the tree, the faster it will grow to become even larger.

This discovery is important, as it tells us another reason to save old trees to help protect our planet. The bigger the tree size, the higher the rate of carbon accumulation of the tree. Therefore, one old tree helps lessen the greenhouse gases in our atmosphere much more than a tree that is much younger. Bigger and older trees are important carbon sinks to our environment.

Photo by Author

Photo by Author

Here is a link to a video which showcases a giant tree — the extreme end of the spectrum.

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