What is great about AP Environmental Science (APES)? Science is all around us. Some we can see and some of it we cannot. A good portion of APES you can see and this makes it more enjoyable for a student as they think about the world around them and how it works. AP Environmental Science is interdisciplinary. This means it consists of concepts which are taught in other science disciplines such as Biology, Chemistry, Physics, Geology, Oceanography, Human Geography, and even Astronomy. Join me this year as we learn about the complexities of ecosystems and how they respond to the exponential growth of the human population in addition to learning about the many different strategies we use or have tried to use to maintain biodiversity and maintain ecological balance. We will use words such as tragedy of the commons, dead zones, food deserts, acid precipitation, desertification, and yes…global warming. This course is not just about identifying the problems, but we look at the causes and search for possible solutions. We will take this journey together and in the end you will have learned to become problem-solvers and be slightly more science literate.
To drown a river beneath its own impounded water, by damming, is to kill what it was and to settle for something else. When the damming happens without good reason . . . then it’s a tragedy of diminishment for the whole planet, a loss of one more wild thing, leaving Earth just a little flatter and tamer and simpler and uglier than before. — (David Quammen, “Grabbing the Loop” in The Gift of Rivers: True Stories of Life on the Water)
The U.S. Army Corps of Engineers estimate approximately 75,000 dams greater than 6 feet tall are in the United States. The National Research Council estimate a total of dams in the United States to be over 2.5 million. Of all these dams in the United States, 2,450 of them are hydropower dams. All or most of the remaining dams are of no longer use for the public or the private company which constructed the dam in the first place.
Dams can change the chemical, physical, and biological process of rivers. Dams can hinder the flow of nutrients and sediments which are essential for the food webs downstream. Nearshore ecosystems and estuaries depend on the sediments and woody debris transported downstream to support the aquatic food web in these areas. Nutrients support the growth of producers which support the growth of the consumers.
Reservoirs which are created behind some dams alter the flow of water which in turn alters the behavior of the native fish. Salmon fry swimming downstream are exposed to warmer temperatures, disease and predation when they are swimming across reservoirs created by dams.
There are three primary reasons to raze a dam. Razing dams which are no longer serving a function can help re-establish the surrounding ecosystems, protect the citizens living downstream in case of a breach, and for economic reason because tax payers are usually the ones who are paying to keep these dams from causing in harm to the public.
Removal of dams can help increase genetic diversity of aquatic organisms as well as increase species distribution which both can help increase the chances of survival for some of our endangered and threatened species. Fish which migrate up and downstream as part of their life cycle will be able to reestablish their populations and the ecosystems which depend on these fish can also recover. The removal of the dams on the Elwha River in Washington has allowed salmon to once again travel upstream to spawn. Salmon are a keystone species for the ecosystems they travel through. Nutrients from salmon carcasses are passed on to scavengers such as eagles and bears and to the algae which feeds the zooplankton that is fed upon by salmon smolts as they travel downstream to the ocean. Besides salmon, sturgeon, paddle fish, American shad, and American eels migrate up and downstream.
Some dams were constructed to help with flood control or provide irrigation water for agriculture. Flood control can be accomplished by restoring wetlands, maintaining riparian buffers, and of course moving people out of the floodplains. Agriculture irrigation techniques can be update to more efficient irrigation equipment in addition to planting appropriate crops for the region. Water-thirsty crops should not be planted in arid regions. There are some genetically engineered crops which can tolerate drought conditions and they do well in arid climates.
As of today, thousands of unnecessary dams have been removed from our rivers in the United States. It is a group effort to identify the dams for removal, getting approval, investigating the environmental impact, organizing all the stakeholders, and so on. But this determination pays in the end for the environment and the people.
Wonderful how completely everything in wild nature fits into us, as if truly part and parent of us. The sun shines not on us but in us. The rivers flow not past, but through us, thrilling, tingling, vibrating every fiber and cell of the substance of our bodies, making them glide and sing. The trees wave and the flowers bloom in our bodies as well as our souls, and every bird song, wind song, and; tremendous storm song of the rocks in the heart of the mountains is our song, our very own, and sings our love. — (John Muir, Mountain Thoughts)
Note: photo by Steve Ringman of Seattle Times
Why do we spend time and money to protect species? The bog turtle which is North American’s smallest turtle cannot be so important that we must try to protect it from extinction. This turtle is only about 4 inches long as an adult. How important can it really be?
When Congress passed the Endangered Species Act of 1973 it declared “species of fish, wildlife, and plants are of esthetic, ecological, educational, historical, recreational, and scientific value to the Nation and its people.” And not only should we protect the species, but we also need to conserve the ecosystems which these species depend.
Extinctions occur naturally, but lately the current extinction rate is occurring at a much higher rate than the past. The major cause of extinction and loss of biodiversity is habitat loss. Additional threats is the introduction of invasive species, over-exploitation and environmental pollution. The greatest threats to the critically endangered bog turtle are the loss, degradation and fragmentation of its habitat from wetland alteration, development, pollution, invasive species and advanced plant growth. The species is also threatened by poaching—collection for illegal wildlife trade.
John Muir, co-founder of the Sierra Club, said “When we try to pick out anything by itself, we find it hitched to everything else in the Universe.” All living things are part of a complex network of food webs which all together make up our biosphere. The removal of a species from an ecosystem can set off a chain of events affecting many others. Do you recall how important a keystone species is to its ecosystem? The wolves of Yellowstone, the sea otters of the Pacific Ocean, and the flying fox of the rain forest are just a few examples of species which are so important that their loss can result in the collapse of their ecosystem.
Countless numbers of different organisms be it either plant or animal has contributed to the creation of medicines which we use today. The anti-cancer taxol was originally extracted from the bark of the Pacific yew tree. Scientists say the chemical structure which makes up taxol is so complex they would have never invented it on their own. Taxol is used to treat advanced cases of ovarian cancer and until the discovery the Pacific yew as considered a weed tree which was a pest and no use for anyone.
Do you think we would still be spraying DDT like it was an air freshener in a men’s locker room if it was not for the rapid decline of our birds of prey such as the bald eagle and the peregrine falcon? These birds served as early warning indicators that something was amiss, and we needed rapid action. We have many species which can serve as indicator species such as lichen and the eastern white pine that can detect excess ozone, sulfur dioxide, and other air pollutants. Mayflies and stoneflies are good indicators of healthy streams. The Environmental Protection Agency uses salmon as an indicator of the health of the greater Pacific Rim.
What is an endangered species lacks a known benefit to mankind, should we care? Some people believe every creature has an intrinsic value. Wildlife is also a source of inspiration. Biodiverse ecosystems have provided inspiration for writers and artists who have provided us with countless stories and artwork like that of Henry David Thoreau for his book Walden, Claude Monet for his painting The Water Lily Pond, and the many photographs of Ansel Adams.
Back to the bog turtle. Why does the bog turtle deserve protection? Bog turtles are a flagship species for wetland conservation and water quality. Bog turtles prefer headwater wetlands fed by springs which are clean and highly oxygenated. These headwater wetlands feed into streams and rivers which provide essential habitat for many other species. Like the decline in the bald eagle populations, the decline of the bog turtle is indicating to us we are losing these essential wetland habitats and all of the ecosystem services they provide such as purifying water, recharging underground aquifers, and absorbing floodwaters. The wetlands preferred by the bog turtle are also home to many rare plants and animals like the American woodcock and the dragon’s mouth orchid.
The next time someone says, why should we care about protecting species I hope you now have a response you can provide to them. Remember, ignorance is our enemy.
Coevolution is a reciprocal change in the genetic composition of one species in response to a genetic change in another. Coevolution is likely to happen when different species have close ecological interactions with one another. These relationships include predator/prey, parasite/host, competition, and mutualistic species.
There are some species of plants which evolve a complex relationship with only one specific insect where they both can benefit. Plant pollen is valuable because it contains the genetic material which needs to be passed on to the next generation. When plants can be pollinated by more than one type of pollinator they risk their pollen being wasted on a different species of plant. Not just any insect can access the sweet nectar of Angraecum sesquipedale.
The story of Angraecum sesquipedale and its pollinating insect is a unique example of coevolution. Samples of this orchid were collected from Madagascar in 1862 and sent to Charles Darwin. Charles Darwin was impressed not by the beautiful star-shaped flowers, but the 30 centimeter long nectary. Based upon his knowledge of evolution, Charles Darwin predicted there had to be moth with a proboscis long enough to reach the nectar. In 1907 a moth was discovered on Madagascar which had a proboscis more than 20 centimeters long. But it was not until 1992 when video evidence was collected showing the Angraecum sesquipedale being pollinated by the Xanthopan morganii, Morgan’s sphinx moth. It only took 130 years to prove Darwin’s hypothesis.
An example of an evolutionary arms race between a predator and prey is that of the wax moth and bats. The moths have developed as a defense against echolocating bats is to use their tympanal organs to produce ultrasonic sound in response to detecting the ultrasonic cries of echolocating bats. In some moth species, this acoustic response warns bats that the moths are toxic and unfit for consumption. Another moth, the tiger moth, will emit an ultrasonic sound which acts a jamming device interfering with the bat’s ability to use echolocation. Currently the moths are winning this race.
When an organism uses objects in their habitat to camouflage themselves it is not an example of coevolution. To show coevolution, we need evidence that suggests that the prey have evolved in response to the predator and that the predator has evolved in response to the prey. The decorator crab which uses pieces of its surrounding habitat to decorate its carapace is not an example of coevolution.
Mimicry is an example of coevolution. Mimicry is when an organism has adaptive traits which copies a specific species or behavior. The peacock butterfly if spotted and directly threatened will flash its conspicuous eye-spots to frighten the predator away. The bee beetle looks and sounds a lot like a bumblebee.
Many species have close, regular relationships with other species. If both interacting species have reciprocal effects on the fitness of the other species, the two species may co-evolve.
Evolution is not planned. An organism does not evolve because of a want or a need. Evolution is not organisms adapting to their environment. Evolution is gradual and is looked at through generations, not individuals, and within populations of the same species.
The evolution of plants is the same as it is for animals. Like animals, plants have genetic traits which provide them with advantages over other plants. Take for example the Giant Hogweed and its toxins it produces which can cause people who brush up against the plant to get second degree burns. The toxins produced by the Giant Hogweed was not by choice. The Giant Hogweed shares a common ancestor with carrots and parsnips. A heritable mutation for this toxin gave the plant an advantage to defend itself against herbivory. This allowed the plant to survive and pass on this advantageous heritable trait to its offspring. Eventually after thousands of generations we get the Giant Hogweed.
Maybe because we have anthropomorphized plants and animals we have made evolution a little more difficult to understand which has led to many misconceptions. “Since plants can’t run off to look for a mate and reproduce, many have evolved elaborate mechanisms of pollination — often cheating or bribing animal pollinators into doing the work for them.” This statement from evolution.berkeley.edu uses the terms cheating and bribing which are words we relate to humans more than we do to plants. Plants do not know they are cheating and bribing pollinators.
Pollinators can be birds, flies, bees, butterflies, and bats. We most commonly think of plants providing the pollinator with the reward of nectar in return for carrying the plant’s pollen from plant to plant spreading its genetic diversity. Some plants offer no such reward, but they too need their pollen transferred to other of their kind. Some plants, like the corpse flower, attract flies because they smell of rotten meat.
There is a species of ginger which attracts a very unusual pollinator, the dung beetle. This plant’s flower smells of processed dung attracting the dung beetle. Dung beetles are thieves and will steal the processed dung balls of other dung beetles. Thinking the flower is a processed dung ball the thieving dung beetle travels flower to flower looking for a dung ball to steal and unknowingly is spreading the pollen for the ginger plant.
This ginger plant did not choose to smell like a processed dung ball. Thousands of generations ago a possible heritable mutation caused the flower of a ginger plant to smell like a processed dung ball (and no…I do not know what that smells like). As this heritable mutation was transferred to future plants over and over again it eventually led to this species of ginger plant which has flowers which attract the dung beetle.
There is another plant which dupes the dung beetle. This grass drops its seeds which look like the droppings of an antelope and even smells of dung produced by an herbivore. The dung beetles believing it is the feces of an animal will roll it up in a ball and bury as food storage and thus dispersing the seed of this plant.
Evolution is the change in the inherited traits of a population from generation to generation. These traits are the expression of genes that are copied and passed on to offspring during reproduction. Mutations in these genes can produce new or altered traits, resulting in heritable differences (genetic variation) between organisms. New traits can also come from transfer of genes between populations, as in migration, or between species, in horizontal gene transfer. Evolution occurs when these heritable differences become more common or rare in a population, either non-randomly through natural selection or randomly through genetic drift. (https://www.sciencedaily.com/terms/evolution.htm)
“Biodiversity as a whole forms a shield protecting each of the species that together compose it, ourselves included.” — E.O. Wilson, “Half-Earth”
Biodiversity is the variety of life on Earth at all its levels from genes to ecosystems. Biodiversity is important because it provides us with:
- Our pollinators: bees, butterflies, birds, bats
- Our predators: frogs, ladybugs, wolves, bobcats, lions
- Our food supplies: fish, shellfish, caribou, mushrooms, crop diversity
- Our medicines: asthma drug Theophallin from cacao trees; rosy periwinkle from Madagascar provides a drug to treat leukemia and Hodgkin’s disease; Eribulin is a drug created from a chemical found in sea sponges and is used to treat breast cancer; the Eastern Red Cedar (found here in Georgia) has been discovered to contain a compound that fights antibiotic-resistant bacteria
- Our clean air: photosynthesizing species produce oxygen, can sequester carbon dioxide emissions, and some indoor plants such as the Peace Lily and Spider plant can remove formaldehyde (a carcinogen) from the air
- Our clean water: forest s help soil absorbs rainfall and recharge aquifers; wetlands are excellent at phytoremediation (plants cleaning hazards from soil and water)
- Our healthy soil: soils are ecosystems which help with water storage, nutrient cycling, plant growth, and much more
- Our raw materials: wood, biofuels, and plant oils
- Our livelihoods: besides providing jobs, a diverse natural environment contributes to the emotional and spiritual well-being of humans
- Our Earth: greater biodiversity means a more resilient ecosystem which can better withstand and recover from a variety of disasters
How do we prioritize which areas of the world receive biodiversity protection? Where do we send people and money to protect the biodiversity we have remaining? Who is responsible for protecting biodiversity?
These are all good questions. This job is too big for just one or two organizations. And how would one country respond to another country telling them what they can and cannot do with their natural resources? We do the best we can, one step at a time.
Norman Myers in 1988 coined the term “biodiversity hotspot.” According to Myers a biodiversity hotspot must meet two criteria. It must contain at least 1,500 species of vascular plants as endemics, and it has to have lost at least 70 percent of its original habitat. There have been 34 hotpots identified. This thought is great if one is trying to prioritize where the most good can be done with the limited resources we have available. But what about other areas of the world which do not meet these criteria? Are they not just as worthy of protection?
Ecosystem services provided by biodiversity is not site specific and what we do to protect resources in one area will not necessarily protect the ecosystem services in another area. Protecting Yellowstone National Park provides carbon sequestration for the world, but the jobs, pollinators, and clean water it provides is local and not going to help people living in Madagascar.
In our efforts to systematically determine where the money and resources are directed to protect the most species, we have forgotten that every ecosystem is unique and has a purpose. A desert, although not as biologically diverse as the tropical rainforests of Belize, is just as important for the ecosystem services it provides.
Peter Kareiva and Michelle Marvier wrote an article in American Scientist calling for a protection of “biodiversity coldspots”. They called attention to areas around the world which we consider species-poor such as the world’s steppes, the Serengeti, and the wild Arctic. They claim there are other relevant factors such as ecological theory, ecosystem services, and sociopolitical realism need consideration when we prioritize where we send people, money, and resources.
I guess it is back to the drawing board. How do we protect biodiversity around the world so that all humans benefit from the ecosystem services provided? Do we prioritize on the value of ecosystem services instead of the value of the number of species as Myers has suggested? How much would you value a glass of clean drinking water versus protecting tropical rain forest thousands of miles away from your home?
Photo: Cedar Waxwing on Eastern Red Cedar by Ken Thomas
While on a recent drive through the southeastern part of Georgia I passed by several cotton fields. I was reminded of the class discussion about how human activities influence the biogeochemical cycles. An earlier blog posting shared the importance of our biogeochemical cycles. It is not about finding balance between the needs of humans and the needs of the environment. Without the environment, there is no us. Imbalance between the biogeochemical cycles can lead to environmental refugees, war, and famine.
What is the connection between cotton fields of Georgia and the biogeochemical cycles? As my students have learned, cotton plants require a lot of nitrogen (so does tobacco and corn). This need for nitrogen means farmers will need to fertilize with nitrates more often than they do for other crops such as soybeans. The addition of more nitrate fertilizer to agricultural fields adds more nutrients to the watershed. Excess nutrients can be picked-up by surface runoff during irrigation or rainfall and find its way to lakes, streams, rivers, and the ocean. These excess nutrients cause eutrophication and promote the creation of hypoxic zones in our freshwater and marine ecosystems.
Besides the need of fertilizer for growth, plants also need water. Water for agricultural fields worldwide can come from aquifers, reservoirs, or rivers. Worldwide, agriculture is the biggest user of freshwater. Rivers do not know boundaries such as County lines, State lines, or International lines. The Chattahoochee River shares its boundaries with Georgia, Alabama and Florida and it has led to some disputes as to how its water can be used. Can you imagine the arguments between neighboring countries which share a river?
The Tigris and Euphrates Rivers headwaters are in Turkey and flow through Syria and Iraq on their way to the Persian Gulf. This past Spring Turkey completed the construction of a dam on the Tigris River (they have already constructed a dam on the Euphrates River). The completion of this dam project and the filling of the reservoir behind it has resulted in much less water going downstream to Iraq. Iraq needs the water not only as a supply of drinking water, but also to help irrigate its agricultural fields. Furthermore, the water flowing from the Tigris and Euphrates Rivers feed the Mesopotomian Marshes, a valuable ecosystem. Between the 1950s and 1990s the Mesopotomian Marshes were being drained and degraded for agriculture, decrease mosquito reproduction, and political reasons. Saddam Hussein ordered the draining of parts of the marshes to punish those depending on the marshes for their participation in the uprising against him and his government. Citizens of Iraq are trying to restore this ecosystem and less water coming downstream from the Tigris and Euphrates Rivers could diminish this restoration project. What will happen between Turkey and Iraq if they are unable to agree upon how much water is released downstream? How will climate change influence the amount of water released downstream from Turkey to Iraq? Time will tell.
A major water diversion project has caused what might be considered one of the world’s worst environmental disasters. The Aral Sea, once the world’s fourth largest lake in the world, provided a vast array of resources which supported a healthy economy. In the 1950s Russia began using canals to divert water from the Amu Dayra River and the Syr Dayra River to irrigate the desert as Russia was attempting to become the world’s largest exporter of cotton. These two rivers were the major source of water for the Aral Sea. The diversion of water from these rivers eventually led to the Aral Sea now holding onto about 10% of its original volume. Most of the Aral Sea is now a desert and the people living around the Aral Sea suffer from loss of jobs, clean drinking water, and arable land.
We will always be planting crops to feed people and provide resources to make products. Massive agricultural operations come with an environmental cost. Water diversion projects to provide people with drinking water and irrigation water means less water going downstream. Growing massive amounts of crops require massive amounts of fertilizer which can lead to eutrophication and unwanted algal blooms. Are we capable of providing food and water for everyone without governmental disputes and environmental disasters?
It is hurricane season. The official hurricane season for the northern hemisphere is the beginning of June to the end of November. This morning Tropical Storm Michael in the Gulf of Mexico was promoted to the status of hurricane. As I sit here at the Richmond Hill Hatchery just south of Savannah I am checking on the status of Hurricane Michael to determine when I will begin my journey back home to north of Atlanta.
Hurricanes begin as tropical storms over warm moist waters around the Intertropical Convergence Zone (ITCZ). Hurricanes are heat engines. As Hurricane Michael enters the Gulf of Mexico it will strengthen as it glides across the warm waters of the Gulf.
The ITCZ (pronounced “itch”) is also known as the Equatorial Convergence Zone and it shifts north and south seasonally following the Sun and warmer ocean temperatures. Due to these shifts with the tilt of the Earth’ axis the tropics have wet and dry seasons. The ITCZ is a belt of converging trade winds and rising air. This rising air results in frequent thunderstorms and heavy rainfall.
The heat capacity of the oceans is greater than air over land so in the northern hemisphere the migration of the ITCZ is more prominent over land. Over the oceans, the ITCZ is better defined and the seasonal cycle is subtler because the converging trade winds are constrained by the distribution of ocean temperatures.
It was 1843 when British naturalist Edward Forbes declared life in the ocean cannot exist below 300 fathoms (1800 feet). Ten years later American naturalist Louis F. de Pourtales of the U.S. Coast Survey found indications of life in depths over 1000 fathoms (6000 feet). It was 1867 when Louis F. de Pourtales found conclusive evidence of deep-sea life while conducing dredging operations off the southern coast of Florida. Thanks to new technology and deep-sea submersibles we have discovered so much more about the ocean floor such as hydrothermal-vent communities, bioluminescent organisms, the Giant Squid, and deep-water corals.
At one time it was believed coral polyps only lived in the shallow-waters of the tropical regions of the world. More than 250 years ago fisherman discovered evidence of coral living below the euphotic zone. The past few decades scientists are discovering the true value of these deep-water corals as they explore below the euphotic zone of the ocean in their deep-sea submersibles. Just recently scientists discovered an 85-mile stretch of deep-water coral off the coast of South Carolina.
Deep-water corals are also known as cold-water corals compared to the shallow-water or warm-water corals of the tropics. Deep-water corals are found all over the world including Antarctica and have been found up to 20,000 feet below the surface of the ocean (that is more than 3 miles). Deep-sea submersibles have discovered deep-water coral living in water as cold as -1oC (30.2oF). Half of all known coral species in the world are from deep water.
Unlike their “cousins”, the shallow-water corals, deep-water corals do not have zooxanthellae which provide them food as part of a mutualistic relationship. Deep-water coral obtains their energy needs by trapping tiny organisms and detritus (marine snow) as it drops from above and is passed along in the deep ocean current. These sessile organisms can capture food floating by because they are fan-shaped and have increased their surface-area.
Besides providing habitat for important ecologically and economically fish, deep-water coral and the sponge communities they support may be a source of compounds for the development of new drugs and medical treatments. The green Latrunculia austini sponge found living along side deep-sea corals contains molecules which specifically target and kill pancreatic tumor cells.
Deep-water corals are just as affected by ocean acidification as shallow-water corals. Other threats to deep-water coral is bottom-trawling, mineral extraction, oil and gas exploration, and cable trenching. One can imagine the damage done by bottom-trawling by observing what a forest looks like after they bulldoze the trees to put in a subdivision or shopping mall.
There is so much more we must learn about the deep-sea. What will be discovered next and how will it benefit humans?
Do you want to know more?
What is a wetland? Wetlands have many names such as swamps, marshes, bogs, sedge meadows, wet prairies, fens, and seeps. No matter their name, they share these three characteristics: wetland hydrology, hydrophytic vegetation, and hydric soils.
But have you ever heard of wetlands called “Nature’s Sponges”, “Nature’s Kidneys”, “Biological Supermarkets”, or “Nature’s Gas Stations?” Wetlands provide many ecosystem services. Wetlands act like sponges because their massive organic matter can absorb and store water for a long time. This ability to store water helps to recharge groundwater and serve to help reduce damages caused by flooding. Wetlands unique soils have a high cation exchange capacity which allow wetlands to remove pollutants and nutrients from the water as it flows through. Wetlands can support a diversity of organisms thanks to the variety of food resources they provide for the animals who use wetlands part or all their life.
My favorite ecosystem service wetlands provide are “Nature’s Gas Stations.” Today when you visit a QuikTrip you can fill up your vehicle with fuel, go inside get a snack (some stores you can get lunch or dinner) and purchase a refreshing beverage to quench your thirst. Migrating birds around the world use wetlands as their fueling stations. Some birds such as the Sandhill Cranes can be observed resting and feeding along rivers and wetlands throughout the Great Plains and Pacific Northwest. Some Sandhill Cranes migrate over 2100 miles travelling about 250 to 350 miles per day. This means they need several “gas stations” along their migration path to satisfy their hunger and thirst needs.
Our wetlands around the world are in trouble. Wetlands are drained and filled for either agricultural needs or urban sprawl. In Gwinnett County, Georgia, several wetlands are now covered with parking lots and shopping centers. Although more than half of U.S. wetlands have been destroyed or degraded there is still hope. Wetland restoration projects are happening everywhere. Organizations and companies are also creating artificial wetlands because of the ecosystem services they provide.
How can you help? Volunteer to help with a wetland restoration project. You can purchase a Federal Duck Stamp from your local post office to help support wetland acquisition. And you can educate others about the value of wetlands.
The living components on Earth can survive because all the chemical elements which make up living cells is recycled continuously. This recycling is done through our biogeochemical cycles. We have the gaseous cycles which include nitrogen, oxygen, carbon, and water; and sedimentary cycles which include iron, calcium, phosphorus, sulfur, and other earthbound elements.
These elements within biogeochemical cycles flow from biotic components to abiotic components and then back. The abiotic portion of a cycle is generally slower than the biotic portion. For example, phosphorus in rocks is very slow to be released because weathering of rocks can take a long time. But once the phosphorus is available it is used by a plant such as a blueberry bush for growth. The blueberries from the bush can be then eaten by a black bear. The black bear will do what bears do in the woods and the phosphorus which is not used by the bear for cellular processes can be passed back to the soil.
And the biogeochemical cycles do not act independently of one another. Nutrients such as phosphorus and nitrogen are released by erosion of rocks and decomposition of organic matter in a river and then flow downstream thanks to the water cycle. These nutrients can support the growth of aquatic plants which provide oxygen and food for aquatic organisms.
The next time you sit down to eat dinner think about where your food came from and the different biogeochemical cycles which made this meal possible.