I currently live in a place that is really different from where I grew up. Because where I live now – we got a lot of trees. Tons of trees. Glorious trees. From Loblolly pines and Live Oaks to Drummond Red Maples and Sweetgums – trees everywhere. I like trees. And we also have a type of insect that I never saw where I grew up. Termites. When I said “termite,” did you think of something negative? We get it if so - termites are known for eating wood and that can include the wood of homes. But before you wish that termite could be cast from this planet into oblivion, did you know termites do a lot of good? They play a huge role in ecosystems by their work of breaking down dead plant matter. In that work, they return nutrients to the ecosystem. They also are part of food chains in many ecosystems. And with this humble termite, let’s take a general, brief review tour of some major concepts in ecology. Since this video is an ecology review, we'll ask questions throughout the video. If you see our pet euglena, Gus, pause the video to quiz yourself! Ecology focuses on the interactions within an environmental system – these interactions include what organisms have with each other and with their environment. So, let’s review some major concepts in ecology and how they impact ecosystem stability. We mentioned that termites are part of food chains in many ecosystems. Let’s review food chains and food webs real quick. Food chains generally start with a producer. Producers are autotrophs; they are able to make their own food. Plants are common producers. Arrows in food webs point to the directional flow of energy so they point to who is doing the eating. The first one being a primary consumer. Next, a secondary consumer. A tertiary consumer. We could keep going but generally at the top of the food chain you got what are known as apex consumers. A food chain could be arranged into an energy pyramid. If we did that, the producers would be here at the base. The primary consumer would be above that, then secondary consumers, tertiary consumers, and you could keep going. Each of these pyramid levels are called trophic levels; producers occupy trophic level 1 which means primary consumers occupy trophic level 2. Secondary consumers have trophic level 3, and tertiary consumers have trophic level 4. By the way, students often get confused by these terms. They see “primary” and think that means it’s the first trophic level or that “secondary” must be the second trophic level. So be careful and remember that producers are found on the first trophic level, and that the second trophic level is where consumers actually begin. But what makes this an energy pyramid is that it can represent the approximate amount of energy at each of these levels. And it follows what is known as a 10% rule. Meaning if this base level had 90,000 kilocalories (that’s a unit of energy), then the primary consumers on trophic level 2 would have approximately 10% of that which would be 9,000 kilocalories. Where did all the other energy go? Most of it is lost as heat during metabolic processes, and some remains in undigested materials. If you follow the 10% rule, how much energy would the remaining trophic levels have? [PAUSE] That’s right: 900 kilocalories for trophic level 3 and 90 kilocalories for trophic level 4. In an ecosystem, in reality, you don’t tend to have one single food chain. You tend to have many organisms that interact together and instead make a food web. This reflects the biodiversity in the ecosystem; biodiversity takes into account the variety of all the species in a given area and the number of individuals of each species as well. If you look at this specific food web here, snakes would be feeding on which consumer levels? [PAUSE] In this food web, snakes feed on primary consumers and secondary consumers. If the population of birds were to decrease in this particular food web, what are some possible effects to other organisms? [PAUSE] In this particular food web, you can have many potential effects if the birds decrease. You might first think of what the birds eat. In this food web, the birds eat a certain type of plant and they also eat grasshoppers – grasshoppers are their prey. Both could increase if the birds decrease. But then the plants may decrease as the grasshoppers increase and feed on the plants. And it’s important to note, that if producers decrease, that could potentially decrease all animal populations since producers are the foundation. Initially when grasshoppers increase, the frogs have an increased food source and could increase, although again if those plant numbers go down, all animal populations could decrease. Additionally, consider the predators of the birds as they can be impacted. In this food web, with fewer birds, the snakes have less food options. The snakes may rely more on the rabbits and frogs for food but that could decrease rabbit and frog numbers. That could increase competition among the snakes now as their food options have decreased; snake numbers could decline. There’s more you could keep going with this so even in this very simplified view of a food web, you can see how complex all these interactions are. This food web is missing some important organisms that break down organic matter though – what would those be called? [PAUSE] Decomposers! If we drew in some popular decomposers – bacteria and fungi for example – all the arrows would eventually point to them. And now it’s time to move in to review ecological relationships. With ecological relationships, we already talked about predator and prey. That’s technically a relationship. We talked about competition. That’s a relationship. But there’s more. Consider symbiotic relationships which mean organisms living together. Not necessarily happily. For example, parasitism is a symbiotic relationship. Consider a flea that may be on this rabbit. The flea benefits here. The rabbit is harmed. One helped; one harmed – that’s parasitism. Parasites like this flea can live on the organism; some parasites live in the organism. In mutualism, both organisms benefit. Want a really cool example? Bring back the termite. Inside this termite are microscopic organisms like bacteria or protists. They have the ability to break down wood. Great for the termite in its digestion; wood is hard to break down. And in return? The microorganisms get a place to live and a steady flow of a food source. And finally there is commensalism. Commensalism is where one organism benefits and another is neither helped nor harmed. We use the popular barnacle on a whale example. As filter feeders, a barnacle can get access to many nutrients on its free whale ride. It’s helped. The whale is neither helped nor harmed by this relationship. But what’s interesting is: with commensalism, it could depend. There are instances where perhaps a lot of barnacles could be helpful or harmful to whales – it could be dependent on different factors – see our further reading. And one last thing on commensalism: you have to really delve into a relationship to determine that there isn’t more to the relationship. For example: did you know there is a type of bat that roosts in pitcher plants? Yes, inside the carnivorous pitcher plants. The bat gets a home in there; it roosts in there. You might think only the bat benefits from that. But actually, the bat’s droppings – its waste – can provide a nitrogen source for the pitcher plant. So what example of an ecological relationship would that be? [PAUSE] Well if they’re both getting a benefit: the bat getting a home and the plant getting nitrogen, that would be mutualism. And speaking of nitrogen, now it’s time to review nitrogen and carbon cycles. Nitrogen is a critical element in amino acids, which are the monomers of proteins and nitrogen is also a critical element in nucleotides, which are the monomers of nucleic acids. Proteins and nucleic acids are important biomolecules for life, if you recall from our biomolecules video. The atmosphere is around 78% nitrogen but nitrogen generally needs to be “fixed” into other forms to be useful for organisms. Nitrogen fixing bacteria, which can be found in the soil or some plant roots, fixes nitrogen into ammonia and ammonium. That’s nitrogen fixation. Then there’s the term nitrification. In nitrification, nitrifying bacteria in the soil can covert ammonia and ammonium to nitrates and nitrites, another form that is ideal for many plants, so plants can use that. Animals eat the plants; they get that nitrogen source. And both plants and animals will decompose, thanks to the help of decomposers we mentioned. In a process called ammonification, decomposers can return nitrogen to the soil in the form of ammonia and ammonium. Not all of the nitrates and nitrites in the soil are used by plants though; some get converted into nitrogen gas by denitrifying bacteria. That’s denitrification. Ok so we mentioned nitrogen fixation, nitrification, ammonification, and denitrification: what generally occurs in each of those again? [PAUSE] Nitrogen fixation is when atmospheric nitrogen is converted into ammonia and ammonium. Nitrification is when nitrifying bacteria convert ammonia and ammonium to nitrates and nitrites. Ammonification is when decomposers convert nitrogen from organic matter back into the form of ammonia and ammonium. Denitrification is when denitrifying bacteria convert the nitrates and nitrites into nitrogen gas. So, all of those are related with nitrogen being converted into different forms. Keep in mind this also happens in aquatic environments and there’s more detail and events you can explore to this fascinating cycle. Let’s take a look at the carbon cycle now! Carbon is a pretty big deal; it has the ability to form tons of compounds. Carbon is often known as a building block in life for this reason. There are a lot of carbon reservoirs – where the carbon is hanging out. It’s dissolved in the ocean. It is in rocks and fossil fuels. It is in living organisms. It can be in the atmosphere. Consider carbon dioxide in the atmosphere. In fact, what process uses carbon dioxide as an input and is performed by many producers? [PAUSE] Photosynthesis; carbon dioxide is an input for photosynthesis. And you might think of land plants doing photosynthesis but it’s not just happening on land- it could be aquatic plants or phytoplankton. Anyway, the carbon becomes a part of photosynthetic organisms. If a photosynthetic organism is eaten by an animal, it becomes a part of that animal too. And the animal that eats that animal. Both plants and animals do cellular respiration which releases carbon dioxide. When plants and animals die, the carbon from their bodies can be stored in sediment ---after a very long time, they can even be converted into a fossil fuels. The burning of fossil fuels produces a lot of carbon dioxide---and this has also led to the concern of excessive carbon dioxide in the atmosphere. Carbon dioxide is a ‘greenhouse gas’ which means that it can trap heat in the atmosphere. This leads us into our last topic: a few examples of how human activity can threaten biodiversity – that is, the diversity of organisms that exist in a given area. Example 1: Greenhouse gas emissions. We already mentioned that burning of fossil fuels produces carbon dioxide and excessive amounts of carbon dioxide can trap heat in the atmosphere. Oceans – which make up approximately 70% of our planet’s surface - are considered a buffer for the planet; they regulate our planet’s climate. A significant portion of heat from the atmosphere is transferred to the oceans, raising the oceans’ temperature. Many ocean organisms are sensitive to temperature changes. Take coral. Coral is ALIVE; it’s actually made up of invertebrate animals. Millions of little invertebrate animals. And there are different kinds of coral; there can be hard coral and soft coral. Overall, corals are critical in providing food and shelter to other animals and then those animals are involved in their own food webs, like we’ve mentioned. Warming ocean temperatures has caused what is called coral-bleaching. To explain what that is: the little invertebrates – coral polyps – have a mutual symbiotic relationship with microscopic algae. The coral polyps give them a home and the photosynthetic algae provide photosynthesis products for the coral. Well, if the coral gets stressed – from high temperatures for example – the coral may expel the algae. With coral bleaching, coral actually turns this whitish color and is vulnerable without its algae partner. It's not just heat that is transferred to the ocean. Oceans also can absorb a significant portion of excessive carbon dioxide and that can change the chemistry of the ocean; shifting its pH lower. Many organisms in the ocean can be sensitive to these changes and this can affect their survival. Example 2: destruction of habitats. My mind always goes to forest clearings – deforestation - as an example, as it can affect the habitat of organisms that consider the forest home . After forests are cleared, soil erosion can occur, which can result in less fertile soil and runoff can affect nearby bodies of water and the organisms that live within it. Speaking of water, if sustainable practices are not used in land development, re-routing water flow or adding dams can affect habitats of aquatic animals. Example 3: Introduction of Invasive Species. An invasive species is a species that wasn’t naturally in an area but was introduced either on purpose or by accident and it can threaten the biodiversity in an area. Take Formosan subterranean termites, which are not native to the United States but they made it here. Sometimes invasive species, like Formosan termites, can make it on ships and thus travel far away to new lands. Formosan termites are actually known as “super” termites because they can consume at such a fast rate – they are extremely destructive to many species of plants- which again, are producers of food webs. Just to add, they are also harmful economically for the damage they cause to homes and buildings. Sometimes invasive species are added to an area on purpose without recognizing how it can harm the biodiversity in an area. For example: kudzu. It’s a plant. It’s also not native to the United States. It was introduced on purpose in the United States for different reasons as a decorative plant or for livestock to feed on to control erosion. But it is a fast growing, stress-tolerating plant and it turns out, it can hurt other native plants by smothering them – even trees. Destroying other producers which food webs depend on. I know we’re focusing on damage to plants with these examples - let’s switch it up - let’s take the lionfish. Beautiful. But whew are they ferocious predators. Introduced to the Atlantic ocean through aquarium releases, these fish can consume and therefore decrease the number of native fish and crustaceans – and therefore, affecting others that depend on them – including coral reefs. And very few predators have been found to eat lionfish in areas where the lionfish are invasive - so lionfish populations can get out of control. Example 4: Overharvesting. Overfishing is well known example to consider. This can have big effects on the biodiversity of an area. Consider a fish that may be a secondary consumer. If it is overfished – meaning it is fished in a way that is not sustainable for the population - the smaller fish that the fish feeds on –could then have an increasing population as their main predator is gone. Now, with this greatly increased primary consumer population, the producer population could significantly decrease, affecting its ability to support trophic levels above it. Overharvesting doesn’t just involve overfishing. For example, some pet trades can involve some kinds of amphibians, birds, or reptiles and if the pet trade is not run in a sustainable way, it can lead to overharvesting. Biodiversity is critical to the stability of ecosystems. And think of all we get from healthy ecosystems: food, medicines, clean water – the list goes on. Our examples focused on ways that biodiversity can be negatively affected by some types of human activity – but what about things humans have been doing to positively affect biodiversity? Can you think of some ways that humans are working right now to protect or support biodiversity in a given area? [PAUSE] A few examples: reforestation, species conservation programs, exploring sustainable practices. Learn about these and more in our video details. Because when we know how important biodiversity is for all of us – it’s important to recognize and improve what work is happening to protect it. Well, that’s it for the Amoeba Sisters, and we remind you to stay curious.