Transcript for:
Resumo ESS - tópicos 2.1 a 2.5

[Music] Welcome to our exploration of topic 2.1 in environmental systems and societies today we're going to examine the fundamental building blocks of ecosystems from Individual organisms to the entire biosphere let's get into it let's start by understanding the biosphere the largest ecological system on our planet the biosphere encompasses all parts of our planet where life exists from the deepest trenches in the oceans to the tops of the highest mountains and everything in between biosphere is composed of many interconnected systems each one of which plays a vital role in maintaining Earth's ecological balance this hierarchical organization helps us understand how different components interact and how they influence one another at the most basic level we have individual organisms according to the biological species concept a species comprises organisms that can interbreed and produce fertile off spring to illustrate this concept let's look at some examples different dog breeds despite having really varied appearances they all belong to the same species because regardless of their breed they can interbreed and produce puppies that can also interbreed and produce Offspring that's why we say that their offspring are fertile however when we look at crosses between different species like horses and donkeys or between lions and tigers while those species can mate their offspring mules and ligers respectively are sterile that means their offspring cannot reproduce to make more copies of The Offspring this reproductive barrier is what defines horses and donkeys and tigers and lions as separate species to manage the immense diversity of life on earth scientists use classification systems this systematic organization allows for the efficient identific ation and prediction of characteristics among different organisms taxonomists are scientists who work specifically on the classification of life on Earth taxonomists use different tools to identify organisms classification is really important to help us understand the degree of biodiversity and relationships among organisms within ecosystems one primary tool is the dichotomus key and that uses a series of paired choices yes or no questions to identify organisms based on observable characteristics each choice leads to another pair of options and you keep doing this and breaking down larger groups of organisms into smaller and smaller groups until you have an organism that meets all the criteria of all the different questions that you've gone through another important method involves comparing specimens to established collections some collections are in museums but other collections are in field guides right so those field guides might be a book or it might be a digital app and they are really valuable reference tools for species identification especially because you can carry them with you out into the field and do species identification on the Fly modern taxonomy also utilizes DNA surveys where genetic material is analyzed to identify species this process involves collection extraction amplification sequencing analysis and interpretation of DNA samples it's cool because we can simply collect a sample of soil or of water and then we extract from that tiny little microscopic bits of DNA and we compare the genome sequences in that tiny sample that we've got after we've Amplified it we've multiplied it and we compare that to libraries of DNA samples around the world and we can figure out which species are there because they're leaving their DNA behind in the environment moving up from Individual organisms we counter populations a population is a group of organisms of the same species living in the same place at the same time in which are capable of interbreeding consider African elephants as an example while they're the same species different populations exist in various locations across their range which are separated by geographical barriers or human development take this map of Tanzania for example in the top part of this map we have elephants in the enoro serenti area and in the bottom part of the map in this reddish orangish areas we see elephant populations in the Raha area the elephants in the purple areas in the northern part of Tanzania can interact with one another they might migrate back and forth between the purple zones and they can interact and they interbreed same thing will happen with the populations or the groups of elephants that are in the different orange zones they are capable of walking across the landscape and meeting up with one another and interacting with one another to breed produce fertile offspring however because of the road Network and all of the Agricultural areas and places with human populations like cities that separate the purple zones from the orange zones elephants from the purple areas don't interact with elephants in the orange areas therefore the elephants in the purple zones are considered one population of African elephants and the elephants in the orange zones are considered a different population of elephants even though they're all the same species they're not in the same place at the same time so they can't interbreed similarly Asian elephant populations face isolation due to Habitat fragmentation and the fact that a bunch of them live on that are islands surrounded by the ocean and while elephants can swim the distances between islands are generally too great for them to swim across and interact this leads to genetic challenges because those elephants don't have opportunities to interbreed with one another the distribution of populations is influenced by both biotic and abiotic factors in the environment abiotic factors include physical and chemical conditions such as temperature light pH and soil characteristics while biotic factors involve interactions with other organisms temperature is an important abiotic factor affecting species distribution and this can be demonstrated by the Sea surface temperature patterns globally we find some species in the warm areas and different species in cool areas light intensity also plays an important important role in ecosystems particularly in aquatic ecosystems where light levels decrease the deeper you go in water the less light there is and that limits photosynthesis and the overall productivity of the system inter terrestrial ecosystems such as a forest the forest structure influences light penetration and light penetration affects temperature and evaporation rates beneath the forest canopy so in an area where there is less canopy like a place that's just been cut recently and the trees haven't had the opportunity to grow and mature into into their full size you'll find very different abiotic factors in that Forest than you will in a mature Forest where the tree canopy has all grown together and closed it off and it makes that ground level nice and shadowy and cool and dark pH levels particularly in aquatic environments will also significantly impact species distribution and survival some species thrive in more acidic environments and other species perer more alkaline environments this is also true of plants because you'll find that in acidic soils you'll have one plant population and in more basic or alkaline soils you'll have a very very different collection of plant species that are growing ocean acidification which is shown here by pH level is becoming an increasingly important factor in marine ecosystems as climate change leads to increasing acidification and decreasing pH levels solinity patterns influence ocean currents and that in turn affects the distribution of different marine species around the world dissolved oxygen levels are another important abiotic factor for the distribution of aquatic organisms because different species have different tolerance ranges of the amount of dissolved oxygen in water soil texture which is determined by the ratio of sand silt and Clay particles in a soil affects water retention it affects FS nutrient availability for plants it affects how quickly the soil evaporates or how quickly it drains and all of those things affect the plants that grow there all these factors contribute to defining a species ecological niche the specific set of conditions and resources that it requires for survival and reproduction consider the African Savannah where a bunch of different herbivores occupy distinct niches despite sharing the same habitat zebras wilderbeast and gazel all feed on different parts of the grasses or on different stages of the grass growth and therefore they occupy different niches first the zebras come in and they eat the top parts of the grasses the tall grasses leaving just the short grasses behind that's the stuff that the wilderbeast love and so the wilderbeast follow the zebras they come in after the zebras are there so they occupy a different niche in time and wilder beast eat those grass remnants all the way down essentially to the roots but the roots have energy left over it has stored carbohydrates in them and so the roots are able to sprout new grasses and the gazel are the ones who love all those new grass Sprouts so after the wilderbeast have grazed everything down to essentially bare ground and the grasses have had a chance to resprout then the gazel come in after the zebras and the wilderbeast have moved on so the same area can support three different species of herbivores because they all occupy different ecological niches there are a bunch of different population interactions that you need to know in ESS and in particular you need to know herbivory predation parasitism mutualism disease and competition so we're going to quickly go through each of those individually herbivory is exemplified by caterpillars feeding on Plants it's basically hunting plants and herbivory can significantly impact primary productivity the more herbivores there are the more herbivory there is the lower the plant populations go predation or hunting is when one consumer organism eats another consumer organism in the example you see here on the slide ladybugs are consuming aphids both of those organisms are consumers and when ladybugs eat aphids they help regulate the population of the aphids and that actually benefits the plants because the aphids are eating the plants or they're feeding on the plant set parasites are organisms that live in or on another organism and harm the host mistletoe despite its association with the Christmas holidays is a tree parasite and mistletoe can affect the resource distribution particularly water and nutrients in the parts of the tree so where the mistletoe grows it blocks the distribution of water to the branches Beyond and it takes the water that the tree intended to send out to its leaves and its branches for itself mutualism and symbiosis are where both organisms in a relationship benefit so a really nice example of symbiosis or mutualisms are clownfish and sea anemones because the clown fish are protected by the stinging sea an enemies and the Anemones then have additional cleaning and they get nutrients from the feces from the clownish they have this really nice co-evolutionary relationship where the clown fish protect the Anemones from potential Predators they provide additional nutrients for the Anemones to grow and likewise the Anemones protect the clownish from clownish predators both species equally benefit diseases can dramatically alter ecosystem composition and structure here on the background of this slide you can see these gigantic trees this is the American chestnut at one point it was the most dominant Tree in eastern North America it's a fantastic wood it was used for building all kinds of things homes furniture and then in the early 20th century a fungus appeared it was first identified in the Bronx I think in New York it was brought in from Asia by accident on some boats with Timber on it and that fungus has attacked Chestnut trees and so what has happened then is in something like 4 billion Chestnut trees vanished they all died off as a result of chestnut blight in the first 50 years that we knew it was around all of these interactions influence the carrying capacity of an area the carrying capacity is the maximum sustainable population size that a particular environment or ecosystem can sustain indefinitely various factors limit population size including both biotic and abiotic components look at the components that are here on the right side of this slide and identify which ones you think are biotic and which ones you think are abiotic population regulation occurs through density dependent factors and negative feedback mechanisms we've already seen this back in topic one when we looked at Predator prey relationships some fact factors are density independent that means they are not related to the density of the population natural disasters are a classic example of density independent factors volcanic eruptions affect populations regardless of the size or the density of the organisms that live there everything in the path of that lava flow is at equal risk of dying competition for food intensifies as population density increases this is exemplified by deer populations As the deer population increases they are all trying to eat the same kind of plants and so those plants have a harder time reproducing and growing which means there's less food available for the deer and the deer population then gets stressed out you have greater mortality and less successful reproduction it's exactly the same relationship as we've seen with a classic wolf and moose or lynx and hair Predator prey relationships disease transmission becomes easier with dense populations because the pathogens don't have to travel as far to infect new individuals so transmission comes a lot easier in very dense areas as we've already mentioned predation pressure often increases with the density of the prey population so the more Little Critters there are for bigger Critters to eat then the greater the population the bigger Critters whatever it is that these sharks are going to feed on as their population increases the shark population will increase but then as the population of the prey the PO as the population of the shark prey decreases the shark populations will also decrease that's how the Predator prey relationship regulates population density as you see in these pictures of the Atlantic puffins in Scotland competition for breeding territories can intensify in crowded conditions there's only so much space where you can make a nest and lay eggs as the population density increases there's greater competition for those nesting sites and when it becomes too stressful there's more fighting more of those nesting sites get destroyed some of the eggs may may get destroyed and that has a negative impact on population size finally competition for mates becomes pretty intense as population density increases males will fight over access to females and those fights can result in injuries they can result in death and those affect population sizes so when we understand the relationships between these biotic factors and the abiotic factors in ecosystems and how those factors influence populations as well as understanding density dependent and density independent factors we can better comprehend how ecosystems function and how human activities can impact those ecosystems I'll be back soon with another video for the rest of topic 2.1 in the meanwhile happy learning hi welcome back to another IV environmental systems in society's video today I'm going to take you through five real world examples to help you understand fundamental versus realized niches let's get into it when studying ecology two big Concepts help us understand where species live and why they live there the fundamental Niche and the realized Niche think of the fundamental niche as a species theoretical home to all the places it could potentially live if nothing else got in its way the realized Niche however is where the species actually lives after accounting for all the real world limitations like competition and human activity let's go through five different examples from around the world the first example is probably the most common one that you'll see and that's Barnacles on the Pacific coast of North America Amica there are two species we're concerned with calamus status and balanis balanoides both species could theoretically live anywhere in the intertitle zone the inter tidal zone is the Zone along the coast between the mean low tide line and the average high tide line that's their fundamental Niche however in reality they divide the space the larger Banis dominates the lower zones where it can physically Crow out the calamus Barnacles but the calamus Barnacles Survive by occupying the higher zones where it's better at handling the dry conditions because that's where land is exposed to air above the water line for longer periods of time each species realized Niche is just a portion of where it could potentially live in the Arctic we see a similar pattern with foxes the red fox vulpes vulpes and the arctic fox vulpes lagopus could theoretically inhabit the entire Arctic region that's their fundamental Niche but in reality they divide the territory the bigger red fox dominates the more productive Southern regions while the arctic foxes are pushed into the harsher northern areas their realized niches are determined by competition for prey like Lemmings and VES and they also compete for dens sites for breeding purposes moving to Tropical coastlines different mango species like avenia Marina Risa for mangle and Bugera Giza could potentially grow anywhere along the coast again that's their fundamental Niche however all three species compete for root space light and nutrients and when you combine that with different tolerances for saltwater this creates distinct zones where each species is found each of these Mangrove species realized Niche is a specific band along the shoreline where it has competitive advantages over the other two species example four is the andian Condor the andian Condor volter griffi presents an interesting case its fundamental Niche includes any mountainous region with sufficient updrafts and food however its realized Niche is much smaller it's restricted to the highest parts of the Andes Mountains this is due primarily to competition with other scavengers like the black vulture which it competes for carryon and nesting sites with but the andian Condor also competes with people mainly through habitat loss and persecution when we say persecution we mean that people hunted the fifth example is that of the giant panda in China the giant panda whose Latin name is ilota melanca could potentially inhabit any temperate forest with bamboo that's its fundamental Niche but the Panda's realized Niche is limited to specific mountain ranges in central China this is mainly due to human development in competition with livestock for space but interestingly competition with other Wildlife is limited because the panda has such a specialized bamboo diet in each of these cases you can see how the realized Niche is always smaller than the fundamental Niche competition whether with other species or with people forces organisms to occupy only those areas where they have specific advantages over other species I hope you found that helpful until next time happy learning welcome to another IB environmental systems and societies video this is part one of our exploration of topic 2.2 energy and biomass in ecosystems we're going to start by understanding how ecosystems are sustained through the continuous flow of energy and the cycling of matter let's get into it ecosystems are open systems which means both energy and matter can move in and out energy flows through ecosystems in One Direction while matter cycles repeatedly within ecosystem this fundamental concept is governed by the first law of thermodynamics which states that energy can be transformed from one type of energy into another type but it cannot be created or destroyed in ecosystems the primary energy transformations occur through two main processes first is photosynthesis and next is cellular respiration during photosynthesis producers like plants convert light energy into chemical energy and they store it in glucose molecules during cell respiration organisms break down those glucose molecules to release the energy that's stored in them and that energy is in a form that they can use for their life processes which we call metabolism producers which can include Plants algae phytoplankton and photosynthetic bacteria form the foundation of ecosystem energy flow they're unique because they can produce their own food through photosynthesis making them autot tropes which means self feeders when they store energy in glucose molecules some of this energy can be converted into biomass the total mass of living organisms in an ecosystem cellular respiration is crucial for all living organisms because it releases the energy that's stored in glucose however this process isn't perfectly efficient some chemical energy is always transformed into heat which is then lost to the environment this inefficiency is described by the second law of Thermodynamics consumers obtain their energy by feeding on other organisms there's remarkable diversity in consumer feeding strategies herbivores feed directly on producers while Predators hunt other animals parasites might extract resources from living hosts and detritivores consume dead organic matter Sapar trops like fungi and certain bacteria secrete digestive enzymes to break down and absorb nutrients from dead material and scavengers will feed on organisms they haven't killed themselves in an ecosystem all of these feeding relationships create food chains where organic matter and energy flow from producers through different levels of consumers each level in the chain is called a trophic level producers from the first trophic level followed by primary consumers those are usually herbivores then we have secondary consumers often omnivores sometimes carnivores and then finally we'll have tertiary consumers which are your carnivores and sometimes will even have apex predators which are always carnal throughout these trophic transfers there are inevitable energy losses at each step some energy is lost as heat through cellular respiration some is not consumed or digested and some energy goes into movement and other life processes this inefficiency in energy trans transfer is a fundamental principle that shapes ecosystem structure and function in the next section we're going to explore how these principles affect ecosystem productivity and biomass distribution and until next time happy learning welcome to another IB environmental systems and societies video this is part two of our exploration of standard level topic 2.2 energy and biomass in ecosystems let's get into it in ecosystems carbon compounds and the energy that they contain move from one organism to the next through food chains each stage in a food chain represents a different trophic level when we study food chains we typically don't include decomposers because they obtain carbon compounds from multiple different trophic levels rather than following a linear progression however decomposers play a really important role in energy transformation in food chains because they break down dead organic material and they make it available as nutrients in the soil for producers again as energy moves through trophic levels there are significant losses at each step not all available food is consumed by organisms at the next level there's always some left over then of the food that is consumed not all of it is absorbed some passes through as waste like excrement and urine and then of all of the stuff that's absorbed not all of it becomes new biomass because some of the energy is lost as heat during respiration these energy losses explain why food chains typically only have three or four trophic levels when we measure productivity in ecosystems we're really looking at two key metrics first is gross productivity and second is net productivity gross productivity represents the total gain in biomass by an organism or trophic the net productivity is what remains after we take away the losses due to cellular respiration it's like having a gross salary that's everything that you earn and the net salary is what you take home after your deductions for things like taxes and insurance food webs show us the complex feeding relationships in communities of living organisms unlike simple food chains food webs reveal how species may feed at multiple trophic levels and also how energy can flow through different Pathways within an ecosystem the arrows in food webs always indicate the direction of energy flow and biomass transfer between organisms that means your arrows are always going to go from lower trophic levels to higher trophic levels to study energy flow quantitatively meaning we measure it with numbers ecologists measure biomass at different levels this involves collecting and carefully drawing samples to remove all of the water content leaving only the dry organic matter as biomass this biomass data can then be used to construct ecological pyramids that represent the relative numbers of organisms in an ecosystem the relative biomass at each trophic level or the energy at each trophic level unfortunately some substances that enter food webs can have harmful effects as they move between trophic levels we have nonbiodegradable pollutants like pcbs and DDT or Mercury these can bioaccumulate within an organism over time that means that as that organism feeds repeatedly on the same type of food that is has that pollutant in it that organism that individual organism absorbs more and more of the pollutant so the concentration the total amount of pollutant in that organism builds up up over time similar to bioaccumulation is something called biomagnification the biomagnification means that toxins become more concentrated at higher trophic levels as larger and larger Predators consume many contaminated prey this problem is made worse by microplastics because microplastics can absorb these pollutants and that helps increase their transmission through food chains human activities significantly impact the flow of energy in matter in ecosystems burning fossil fuels releases stored carbon and pollutants that can affect primary productivity deforestation can remove huge amounts of biomass and it can also disrupt photosynthesis urbanization replaces natural ecosystems with built infrastructure and modern agriculture frequently creates simplified systems with only a few species and that reduces biodiversity all these changes alter the complex networks of energy flow that have evolved in natural ecosystems over many millions of years when we understand these Concepts that helps us recognize how human actions affect ecosystem function and its stability when we study energy flow and trophic relationships then we can better manage our resources and work to maintain mainin the ecological balance and processes that sustain life on our planet that's it for topic 2.2 if you found this video helpful please consider liking and subscribing until next time happy learning welcome to another IB environmental systems and societies video today we're going to be examining the higher level content in topic 2.2 energy and biomass and ecosystems let's get into it first we're going to explore how organisms acquire carbon compounds which raises interesting questions about resource use in ecosystems all living organisms can be classified as either autotrophs or heterotrophs autot trops are the self feeders they synthesize carbon compounds from inorganic sources and other elements heterotrophs on the other hand they have to obtain their carbon compounds from other organisms this fundamental division shapes how energy and resources flow through every ecosystem within the autot tropes we have two distinct strategies photo autotrophs like plants use light as their external energy source for photosynthesis photo means light but there's also a fascinating group called the chemo autotrophs and they use exothermic inorganic chemical reactions as their energy source for chemosynthesis chemosynthesis is like photosynthesis except it doesn't use light it uses those exothermic inorganic chemical reactions in a similar process to produce energy containing compounds or biomass these chemosynthetic organisms are often found in deep sea hydrothermal vents and they demonstrate how life can thrive in seemingly inhospitable environments without relying on sunlight this diversity of strategies raises important questions about how we value different types of ecosystems primary productivity measures the rate at which biomasses produced using external energy sources and inorganic materials we measure productivity in units like kilos of carbon per square met per year understanding primary productivity is essential for making ethical decisions about Resource Management when we measure productivity in different ecosystems we gain insight into their capacity to sustain life and support biodiversity on Earth secondary productivity represents the gain in biomass by consumers when they use the carbon compounds absorbed from their food which was produced by The Producers this is more complex to measure than primary productivity because it involves Tracking not just what organisms eat but how efficiently they convert that food into new biomass these measurements help us understand the true environmental cost of producing food at different trophic levels net primary productivity forms the foundation of food chains because it represents the quantity of carbon compounds sustainably available to primary consumers this idea is really important because it helps us understand the ethical implications of food production when we know how much energy is actually available to Consumers we can make better decisions about resource allocation and about sustainable harvesting maximum sustainable yield or MSY represents the highest Harvest that can be taken without depleting a resource this idea applies to both primary productivity like forestry as well as secondary productivity like fisheries and aquaculture the challenge lies in accurately determining these yields s while considering the needs of both human societies and natural ecosystems one critical ethical consideration emerges when we recognize that sustainable yields are higher for lower trophic levels this scientific fact has profound implications for food security and environmental justice it's generally more efficient and sustainable to consume organisms from lower trophic levels particularly plant-based Foods this should inform some of our decisions about glal food production systems ecological efficiency measures the percentage of energy that's transferred from one trophic level to another one the transfer typically ranges from somewhere in the 5 to 20% range and it varies between ecosystems and species a lot of times you'll see this referred to as the 10% rule because it's kind of right in the middle of that range when we understand these efficiency rates that helps us evaluate the environmental impact of different food production methods and it helps us make more ethical choices about resource use finally the second law of Thermodynamics shows us how entropy or disorder increases as biomass passes through ecosystems this principle helps explain why some resource use patterns are inherently unsustainable living systems can maintain their organization only by increasing entropy elsewhere in the system and that has implications for how we think about e ecosystem management and resource conservation these ideas help us understand both the scientific principles that govern the movement of energy and biomass and ecosystems as well as the ethical considerations we have to weigh when we make decisions about how we use resources and how we produce our food when we combine what we know about ecosystem energetics with ethical reasoning we can work towards more sustainable and more Equitable resource management practices and particularly when it comes to Agriculture and aquaculture I hope you found this video helpful and until next time happy learning welcome to another IB environmental systems and societies video today we're going to learn about the standard level content for topic 2.3 Earth's biogeochemical cycles let's get into it today we're going to examine how chemical elements move between living and non-living components of ecosystems and how human activities impact these vital Cycles let's begin with the carbon cycle which is essential for organic molecules and energy storage this diagram shows the major carbon stores and flows on Earth notice how carbon moves between the atmosphere the plants the soils oceans and Earth's crust human activities significantly impact the carbon cycle industrial emissions from facilities like this one increase atmospheric CO2 concentrations and that alters the Natural Balance that has existed from M lenia deforestation represents another major human impact when forests are cleared we lose critical carbon storage capacity trees that once sequestered carbon are removed and the stored carbon is then often released through burning or decomposition the nitrogen cycle is equally important being essential for protein and DNA synthesis this diagram illustrates how nitrogen moves through an ecosystem with bacteria playing crucial roles in processes like nitrogen fixation and denitrification human impacts on the nitrogen cycle are particularly evident in industrial agriculture factory farming as you can see here with these confined chickens concentrates nitrogen waste in small areas this concentration can lead to water pollution through runoff and soil degradation that can eventually lead to Aquatic pollution like nutrification the water cycle or hydrological cycle is fundamental to all life on Earth you already know that this diagram shows how water moves between the atmosphere land and oceans through processes like evaporation precipitation and transpiration human infrastructure like this Dam significantly impacts the water cycle while dams provide benefits like hydroelectric power and flood control they do disrupt natural River flow regimes and they can alter local ecosystems now let's examine how these Cycles function as systems biogeochemical cycles have three key components stores sinks and sources physical factors like temperature and moisture biological factors like microbial activity and chemical factors like pH all influence how these biogeochemical systems operate looking more closely at Carbon stores we can categorize them as either organ organic or inorganic organic stores include Forest biomass soil organic matter marine organisms and fossil fuels that's because they were all derived from living organisms inorganic stores include atmospheric carbon dioxide ocean carbonates and Limestone deposits carbon flows between these stores through both biological and physical processes biological processes include photosynthesis cellular respiration and decomposition physical processes include ocean atmosphere gas exchange and the weathering of rocks carbon sequestration is Nature's Way of capturing and storing atmospheric carbon dioxide trees are particularly effective at this absorbing CO2 through photosynthesis and then converting it into solid biomass over very long periods this organic matter can become fossilized into coal oil and natural gas different ecosystems sequester carbon in different ways tropical forests store carbon in Woody biomass while Pete lands accumulate thick layers of organic matter in water logged conditions that don't decompose very quickly grasslands store significant carbon in their extensive root systems marine ecosystems like mangroves or seagrass Meadows and coral reefs also play crucial roles in carbon sequestration and that role is often referred to as blue carbon these natural carbon storage systems bring us to an important concept ecosystems can act as carbon stores as sinks or as sources depending on their conditions and how they're managed to understand this Dynamic we need to look at productivity when an ecosystem performs photosynthesis it builds biomass this is called gross productivity some energy is used by organisms for respiration that's the energy they need just to stay alive what remains is net productivity the actual gain in biomass or growth of the organisms the balance between these processes determines whether an ecosystem stores carbon or releases it in healthy ecosystems snc conditions occur when photosynthesis exceeds respiration that means there's more photosynthesis than there is respiration we see this in undisturbed forests where biomass steadily accumulates under stable environmental conditions the more carbon dioxide is absorbed through photosynthesis compared to what's released through respiration the more effective the sink is however when this balance is disrupted ecosystems can become carbon sources this usually happens when decomposition rates increase when there are frequent disturbances or when systems experience climate stress often human activities will transform carbon sinks into carbon sources through activities like Mining and deforestation Forest succession provides an excellent example of how these roles can shift over time young forests act as carbon sinks because they are growing really rapidly and they're accumulating a lot of biomass as the forests mature they become carbon stores when growth and loss reach an equilibrium but when forests burn or when they're cut they transform into carbon sources releasing more carbon dioxide than they absorb this brings us to fossil fuels perhaps the most dramatic example of carbon storage and release in Earth's history these fuels represent carbon that was stored m millions of years ago when ancient ecosystems acted as powerful carbon sinks without human intervention these deposits would have essentially unlimited residence times that means they would have stayed in the ground for millions and millions of years however our extraction processes transform these stable stores into major carbon sources through Mining and Drilling and processing agricultural systems can also play a big role in carbon cycling regenerative practices like crop rotation promote carbon sequestration by enhancing soil organic matter by minimizing disturbance and by improving soil biology cover crops prevent soil carbon loss while no till farming can maintain soil structure and help it hold on to the carbon that was already there long-term approaches like agroforestry and sustained carbon storage as we see in shade grown coffee systems but some agricultural practices actually release stored carbon when we drain Wetlands that exposes soil carbon to oxidation monoculture deplete soil organic matter by repeatedly extracting the same nutrients over and over again intensive tilling breaks up soil structure and that accelerates decomposition and the release of carbon to the atmosphere the oceans represent another vital component of global carbon cycling their ability to absorb and release carbon dioxide depends on several factors cold water absorbs more carbon dioxide while warm water releases it surface mixing in biological processes also influence this Exchange the more surface mixing there is the more gas exchange there is however climate change is altering this system too warming reduces the ability of the oceans to absorb carbon it changes circulation patterns and that affects carbon dioxide transport and perhaps most concerning ocean acidification is occurring as carbon dioxide dissolves in seawat it forms carbonic acid even small decreases in PH interfere with calcium carbonate deposition in marine organisms this makes it really hard for them to build more shells and it slows the way that corals build their skeletons while some species may adapt many marine ecosystems face really serious challenges including Reef collapse food web disruptions and overall declines in biodiversity given these impacts we must take action to address human effects on the carbon cycle this includes transitioning to lowc carbon Technologies like renewable energy and electric transport reducing fossil fuel use through improved standards and limited extraction protecting soil structure slowing deforestation and actively increasing carbon capture through reforestation and Wetland restoration these Solutions require coordinated effort at all scales from Individual actions to International cooperation and by understanding how these biogeochemical cycles work and how we impact them we can work towards more sustainable management of Earth's carbon systems that's it for the standard level topic 2.3 I hope you found this video helpful and until next time happy learning welcome to another IB environmental systems and societies video today we're going to explore the higher level content of topic 2.3 biogeochemical cycles diving deeper into how carbon nitrogen and other Essential Elements move through Earth's systems let's get into it let's start with the lithosphere the solid Rocky outer layer of Earth that contains important carbon stores the lithosphere includes both fossil fuels and carbonate rocks like Limestone these carbon stores took millions of years to form and they play an important role in the global carbon cycle looking at fossil fuel formation we see that it required very specific conditions in past geological eras most coal formed during the Carboniferous period between 359 to about 299 million years ago when vast swamps and Forest provided abundant plant material in warm wet conditions oil and natural gas formed mainly in the Jurassic and Cretaceous periods between 2011 and 66 million years ago and those were formed from marine organisms buried in fine sediments under shallow Seas one of the major carbon stores in the lithosphere is limestone it forms through a three-step process first calcium carbonate precipitates from seawater to form calite often in the form of marine organism shells then these shells settle to the bottom and they become compacted on the ocean floor finally with increased pressure and temperature over time as these layers are buried deeper and deeper these deposits transform into limestone Rock one thing you need to understand when studying carbon stores is the idea of residence time that's the average period of carbon atom remains in a particular store or Reservoir without human interference through activities like mining carbon in the lithosphere would have a residence time measured in hundreds of millions of years but our extraction of fossil fuels has dramatically accelerated its release rapidly returning millions of years of stored carbon to the atmosphere and just a few hundred years Reef building corals and mollusks play a special role in Limestone formation through their calcium carbonate structures as we just saw a few moments ago when these organisms die their hard Parts can become fossilized and contribute to Limestone deposits over time looking at a coral reef we can see the living Limestone builders in action the calcium carbonate skeletons of corals accumulate over thousands or millions of years to create massive restructures these biological processes eventually form Limestone deposits and those Limestone deposits are Earth's largest carbon Reservoir Limestone can also form through non-biological processes calcium carbonate can precipitate directly from water when the conditions change and are just right this usually happens through evaporation changes in water temperature or pressure or shifts in pH level similar processes create cave formation like stalactites and stalagmites and they also form travertine around geothermal Springs like the ones you see here in past geological eras different types of organic matter underwent distinct fossilization processes plant material in swamps and forests became coal through one pathway while marine organisms in Ocean sediments became oil and natural gas through another pathway the type of fossil fuel form formed depended both on the starting material and the environmental conditions fossil fuel deposits formed during specific geological periods when conditions were just right the Carboniferous period named for its abundant coal deposits provided perfect conditions for coal formation with its warm swampy environments several million years later the shallow Seas of the Jurassic and cous periods created ideal conditions for oil and gas formation from marine organisms moving to another important part of the carbon cycle we need to understand the role of methanogenic bacteria methanogenic bacteria are specialized microorganisms that produce methane as a byproduct of their metabolism but only under anerobic conditions those are environments lacking oxygen these electron microscope images show the bacteria responsible for methane production these methanogenic bacteria thrive in several types of oxygen poor environments swamp in Wetlands flooded rice patties and notably in the digestive systems of ruminant animals like cattle each of these environment provides the anerobic conditions these bacteria require for methane production remember anerobic means without oxygen methane's behavior in the atmosphere is distinct from other greenhouse gases it has a relatively short residence time of about 10 years before being oxidized to carbon dioxide this is particularly important for understanding 's role in climate change because methane is much more effective at trapping heat than carbon dioxide the methane cycle involves both natural and anthropogenic or man-made sources on the natural side we see contributions from Wetlands from the ocean floor hydrates and from forest fires human activities add methane through fossil fuel extraction waste management and agriculture particularly rice cultivation and livestock farming all this methane eventually ox oxidizes in the atmosphere through various chemical Pathways to become CO2 check out these Global methane measurements over time you can see a really clear upward Trend these measurements which were all taken at monitoring stations around the world show how atmospheric methane concentrations have increased significantly since the 1980s notice how the rate of increase is sharper in recent years that means we're adding more carbon to the atmosphere faster the nitrogen cycle is another important biogeochemical process and it also has distinct organic and inorganic stores organic nitrogen stores include proteins and other nitrogen containing compounds and living organisms and dead organic matter inorganic stores include atmospheric nitrogen gas and various nitrogen compounds in soil and water this diagram shows how nitrogen moves through different stores in an ecosystem notice how the cycle connects atmospheric nitrogen to soil nutrients and then to plants and animals and then back again each transformation requires a specific set of conditions and often involves specialized bacteria speaking of bacteria they play essential roles throughout the entire nitrogen cycle different types of bacteria are responsible for key Transformations that make nitrogen available to living organisms without them there is no nitrogen cycle on Earth let's Trace these bacterial processes nitrogen fix ing bacteria transform atmospheric nitrogen gas into ammonia which makes the nitrogen available to plants nitrifying bacteria then transform ammonia into nitrites and ultimately into nitrates then we have decomposer bacteria break down organic nitrogen compounds back into ammonium through a process called ammonification the cycle continues with denitrifying bacteria which convert nitrates back into at atmospheric nitrogen gas under anerobic conditions this completes the nitrogen cycle and maintains the balance of nitrogen in Earth's different systems however human activities particularly Agriculture and Industry have pretty significantly altered these natural cycles through the use of synthetic fertilizers and other interventions let's look at denitrification in more detail denitrification only occurs in anerobic conditions particularly in water logged soils where oxygen is absent in these anoxic environments specialized bacteria convert nitrates back into nitrogen gas through a series of steps first reducing nitrates NO3 to nitrates NO2 then to nitrogen monoxide no o and nitrous oxide n2o and then finally back to diatomic nitrogen gas which is N2 this process completes the nitrogen cycle returning nitrogen gas from the lithosphere and soils back into the atmosphere an interesting adaptation to these low nitrogen conditions can be seen in certain plants like pitcher plants and sundus and those plants have evolved to capture insects as an alternative nitrogen Source plants face a significant challenge they can't directly use atmospheric nitrogen however Nature has developed An Elegant solution through mutualistic relationships between plants and nitrogen fixing B bacteria these beneficial Partnerships allow both organisms to thrive the bacteria provide fixed nitrogen that plants can use while the plants Supply carbohydrates to the bacteria here's a classic example of this mutualism legumes and their rium bacterial Partners these edamame or soybean pods represent the legume family which forms specialized root nodules that house the ryian bacteria this partnership is so effective that farmers often use legumes in crop rotation to naturally replenish soil nitrogen between plantings of more demanding crops like corn or wheat another remarkable example is found in acacia trees which form relationships with multiple nitrogen fixing bacteria species these acacia trees dominate nutrient poor savanas precisely because of these Partnerships not only do they enrich the soil with nitrogen but they also provide vital nutrients to browsing animals like Gira rafts while offering shade in hot environments Alder trees demonstrate yet another variation of this mutualistic relationship partnering with frankia bacteria species as pioneer species Alders are often among the first trees to colonized Disturbed sites their nitrogen fixing abilities help facilitate ecological succession by enriching poor soils making it possible for other species that need more nutrient-rich soils to eventually establish themselves the nitrogen cycle involves both transfers and Transformations which you can see in this diagram if we start with mineral uptake by producers we can follow the movement of nitrogen through various biological processes plants absorb nitrogen compounds through their Roots they incorporate them into organic molecules through photosynthesis and then these compounds move through food webs via consumption when organisms die or excrete waste de composition and ammonification return that nitrogen to inorganic forms this systems diagram helps us visualize these complex flows notice how nitrogen moves between different stores from atmospheric nitrogen gas through various transformations in soil then to nitrogen compounds and producers and consumers and then back again to the atmosphere the Red Arrows indicate transfers while the blue arrows show Transformations each process whether carried out by bacteria or plant plants plays a really important role in maintaining the nitrogen cycle human activities have dramatically altered natural nitrogen cycling we're going to examine four major impacts deforestation agriculture aquaculture and urbanization each one disrupts different aspects of the nitrogen cycle in different ways when forests are cleared several disruptions occur simultaneously the removal of trees reduces nitrogen uptake from soils and that leads to increased nitrogen loss through erosion Additionally the disturbance of soil structure disrupts those microbial communities that are responsible for nitrogen cycling agricultural practices might have the most profound impact on nitrogen cycle of any of these intensive farming especially monocultures like this one often relies heavily on synthetic fertilizers while soil compaction from heavy machinery can affect bacterial activity irrigation changes soil conditions and monoculture farming reduces natural nitrogen fixation that would typically occur more diverse plant communities aquaculture introduces its own set of challenges to nitrogen cycling Fish Farms concentrate waste production in small areas leading to nutrient enrichment of surrounding Waters the addition of feed and various additives further Alters natural nitrogen Cycles in aquatic systems in urban environments the natural nitrogen cycle faces multiple disruptions impermeable surfaces increase nitrogen runoff while concentrated human waste creates localized nitrogen hotpots m look at this picture it's all Concrete where nothing penetrates and think of the number of people living in these buildings and the number of toilets they're flushing every single day that's a lot of nitrogen concentrated in a very small space vehicle emissions also add nitrogen oxides to the atmosphere and the sealing of soils prevents natural cycling processes combined these human activities lead to significant changes in the nitrogen cycle excess nitrogen disrupts aquatic ecosystems and contributes to air pollution especially Urban smog our actions are shifting the complex balance of flows within the nitrogen cycle disrupting equilibria that have been established over millions of years of evolution the habber process represents one of Humanity's most significant interventions in the nitrogen cycle this industrial process converts atmospheric nitrogen into ammonia for fertilizer production fundamentally changing how nitrogen moves through Earth's systems you don't have to know all the different steps of the ha process but you should understand the Essential Elements of it the habber process takes nitrogen from the atmosphere where nitrogen makes up 78% of our air and combines it with hydrogen under specific conditions of temperature and pressure the result is ammonia which becomes a key ingredient in commercial fertilizers while this process has revolutionized Agriculture and helped feed billions of people it comes with pretty significant environmental costs the hab process presents us with a complex trade-off on the positive side it enables large scale fertilizer production and that dramatically increases crop yields and helps feed our growing Global human population however these benefits come at a pretty high cost high energy consumption significant CO2 emissions contribution to water pollution and soil acidification perhaps most concerning is how it creates dependence on Industrial fertilizers while potentially damaging natural nitrogen cycling processes the accumulated effects of human nitrogen use have now pushed us beyond the planetary boundary for the nitrogen cycle this means we've exceeded Earth's capacity to maintain a stable nitrogen balance or equilibrium potentially leading to irreversible changes in Earth's ecosystems look at the Stockholm resilience Center's planetary boundaries diagram which we first saw back in ESS topic 1.3 sustainability Frameworks you can see that biogeochemical flows particularly nitrogen have moved well into the high-risk Red Zone several key indicators demonstrate this crossing of the boundary atmospheric nitrous oxide levels are now significantly higher than in pre-industrial levels we're seeing widespread Coastal dead zones that are caused by excess nutrients we've got declining biodiversity and nitrogen enriched ecosystems and there's been an alarming increase in harmful algal blooms Rising nitrate levels in groundwater and changes to soil microbial communities provide further evidence of this kind of disruption given these serious challenges Global collaboration has become essential to address the use of nitrogen in industry and agriculture we need coordinated efforts to bring the nitrogen cycle back within planetary boundaries agricultural reform represents a key area for improvement by implementing Precision agricultural techniques we can optimize F fertilizer application and reduce excess nitrogen use promoting organic fertilizers and crop rotation helps restore natural nitrogen cycling planting are maintaining buffer zones along waterways can also prevent nitrogen runoff while additional sustainable farming practices support long-term soil Health policy changes form another important part of nitrogen management these include setting stricter limits on nitrogen emissions implementing nitrogen pollution taxes and requiring improved waste management practices we can look to successful examples like the EU nitrates directive China's zero growth in fertilizer use policy and Denmark's nitrogen quota system as models for Effective regulation industrial changes must also play a role in addressing disruptions to the nitrogen cycle this includes improving the efficiency of the hab process developing alternative fertilizer production methods and enhancing wastewater treatment promising Innovations include green ammonia production that uses renewable energy plasma activated water for fertilizer production and biological nitrogen removal systems these changes illustrate how we can work to bring the nitrogen cycle back into balance through coordinated action at multiple levels from Individual Farms to International agreements success will require continued technological innovation policy reform and Global cooperation that's it for the higher level content about biogeochemical cycles remember that the biogeochemical cycles that sustain life on Earth are remarkably resilient but they do require careful stewardship until next time happy learning welcome to another IB environmental systems and societies video today's topic is the standard level content for topic 2.4 climate and biomes this map behind me shows how Earth's major ecological zones are distributed around the world these patterns aren't random they're the result of complex interactions between atmospheric and oceanic systems that create distinct climatic conditions in different regions we're going to examine how these conditions shape Earth's biomes and how they're responding to environmental change so let's get into it let's begin with a fundamental distinction in environmental systems the difference between climate and weather climate describes the atmospheric conditions that are averaged over long periods typically 30 years or more weather refers to the conditions at a particular moment or over a short period think of temperature humidity air pressure and wind speed these factors comprise both weather and climate but on very different time scales this desert scene perfectly ill illustrates the distinction between weather and climate while we see evidence of rainfall with this rainbow that's weather the climate of the region remains consistently hot and dry when averaged over decades the sparse vegetation and the exposed rock formations testify to the long-term Aid conditions that truly Define this environment regardless of the occasional precipitation events like this storm a biome represents a group of comparable ecosystems that have developed under similar CL climatic conditions wherever they occur on Earth what's fascinating is how similar conditions produce similar ecological communities even when they're separated by really big distances tropical rainforests share key characteristics whether they're in South America in Africa in Southeast Asia because they experience similar temperature and rainfall patterns ecosystems that develop under similar conditions show remarkable parallels in their structure and their function REM main factors determine biome distribution precipitation temperature and insulation that's the amount of solar radiation reaching Earth's surface these abiotic factors create the conditions that shape plant and animal communities resulting in distinct biome types across the globe abiotic factors are the nonliving components that determine where different biomes develop for any given combination of temperature and rainfall a particular type of natural ecosystem is like likely to emerge the Whitaker diagram we see here shows how temperature and precipitation work together to create different biome types from Tundra to tropical rainforest this graph demonstrates how temperature and precipitation interact to create distinct biom types notice how tropical rainforests occur where both temperature and rainfall are high but deserts develop in areas where the temperature is high but the precipitation is low Tundra appears where temperatures are low regardless of the precipitation levels this relationship helps us predict what kind of an ecosystem is going to develop under specific climatic conditions and here we see how precipitation temperature and light all influenced by latitude and altitude interact to create distinct biomes the pattern shows how these factors vary systematically across different latitudes that creates zones where specific biomes are likely to develop understanding these relationships helps us predict how climate change can affect the distribution of biomes biomes can be categorized into several major groups freshwater Marine Forest grassland desert and Tundra each of these has characteristic abiotic limiting factors and those factors affect its productivity and its biodiversity these categories can be further divided into subcategories for instance forests include temperate tropical and Boreal types each with its own distinct characteristics let's examine the tropical rainforests its key limiting factors include nutrients being locked in biomass rather than the soil and high rainfall that leeches nutrients out of the soils despite these limitations tropical rainforests have very high productivity due to year- round warm temperatures high solar radiation and very consistent precipitation every month this results in the highest biodiversity of any terrestrial ecosystem anywhere on the planet hot deserts present a stark contrast to rainforests their primary limiting factors are minimal precipitation High evaporation rates and extreme temperature differences between day and night these conditions severely restrict productivity because water is essential for photosynthesis the harsh environment results in low biodiversity because few species can adapt to such extreme conditions tundra biomes face different challenges short days severely limit photosynthesis and productivity while Frozen winter conditions and waterlogged summer soils further restrict plant growth the slow nutrient cycles and extreme conditions result in limited biodiversity it's simply too cold for reptiles amphibians and most invertebrates to survive outside of a few short summer months temperate grasslands also known as steps or prairies occupy a middle ground they receive less precipitation than forests but more than deserts they have seasonal temperature extremes and relatively slow nutrient cycling and that limits productivity however these ecosystems support really high biodiversity because they have so many different plant species and their nutrient-rich soils support really extensive food webs aquatic biomes face unique limiting factors water absorbs light and that restricts photosynthesis at depth in deep oceans there's no light at all for photosynthesis in temperate and polar regions surface waters may freeze seasonally this creates varying levels of productivity from the high productivity coral reefs in the tropical areas to low productivity deep ocean zones this table helps us compare how different biomes respond to limiting factors notice how each biome type has evolved distinct strategies to cope with its particular environmental challenges these adaptations influence both the productivity of the system and its capacity to support biodiversity the productivity patterns we see across biomes directly relate to their abiotic conditions from the high productivity of tropical rainforests to the low productivity of deserts and Tundra we can trace these differences back to the availability of water light and nutrients biodiversity patterns follow similar Trends but aren't identical to productivity patterns some biomes like temperate forests maintain High biodiversity despite having lower productivity than tropical rainforests this reminds us that multiple factors influence species diversity the tricellular model of atmospheric circulation helps explain a bunch of these global patterns this model shows how air moves in three major cells in each hemisphere Distributing heat and water around the planet this circulation creates predictable patterns of rainfall and temperature at different latitudes when we look at this diagram we can see the three main cells the Hadley cell near the equator the feral cell in the mid latitudes and the Polar cell near Earth's poles hot air contains more energy and water vapor than cold air which explains why tropical zones typically receive more precipitation than polar regions oceans play a really important role alongside atmospheric circulation in determining climate patterns they absorb solar radiation and distribute heat through ocean currents this Oceanic con a belt helps moderate temperatures globally and it influences local climate patterns especially in coastal regions this map shows how tropical oceans absorb sunlight and distribute heat towards the poles the warm surface flow and cool subsurface flow at depth creates a global circulation pattern that helps regulate earth's climate system ocean currents have a profound effect on Coastal climates notice how the maritime locations experience moderate temperature differences throughout the year doesn't go as high it doesn't go as low but Continental areas that are far away from the oceans show more extreme seasonal variations they have cold Winters and hot summers global warming is fundamentally altering these long-established patterns as average temperatures rise we're seeing shifts in biome boundaries and changes in ecosystem function these changes are happening more rapidly than many species can adapt these maps of the hardiness zones in North America show how climate zones are shifting towards the poles compare the hardiness zones from 1960 to 1990 with projections for 2050 notice how zones are moving northward that requires species to either adapt to migrate or face local Extinction looking at these changes across Africa we can see that there are some dramatic shifts in tree biomass in Grass biomass and total biomass from 2008 project Ed into 2100 the tricellular model helps us understand why these changes follow particular patterns as global temperatures rise that's it for standard level ESS topic 2.4 climate and biomes if you can explain the relationships between climatic factors like light temperature and precipitation with the productivity and biodiversity of different biomes around the world you're going to do just fine on your ESS exams until next time happy learning welcome to another IB environmental systems and societies video video today we're going to explore the standard level content for topic 2.5 zonation succession and change in ecosystems specifically we're going to examine how ecological communities change across space and over time let's get into it zonation occurs when communities change along an environmental gradient think of it as nature organizing itself into distinct band or zones Each of which hosts specific communities and species that are adapted to the conditions right there these patterns appear predictably wherever environmental factors change gradually across a landscape here's a clear example of zation at a continental scale plant hardiness zones across North America you can find these on plant labels anytime you go to a nursery in Canada or the United States notice how these zones create distinct bands based on temperature tolerance the 1960 to 1990 map shows traditional patterns but look at the 2050 prediction climate change is pushing zones northward which means plants will need to adapt or migrate to survive mountains provide another dramatic example of zonation in the central Alps distinct vegetation zones stacked vertically from the Foothills at about 400 m up to the Peaks around 4500 m each Zone Foothill Montaine subalpine Alpine and the snow Zone each of those represents a community precisely adapted to conditions at that elevation mountain zonation is complex because multiple environmental factors change with elevation temperature decreases predictably about 1° C for every 100 m we climb but moisture often increases up to a certain elevation due to orographic precipitation and then it decreases as the air becomes too cold to hold much water so you get this Zone where there's a lot of precipitation that falls out as snow and then above that it gets quite dry Coastal environments show particularly clear zonation patterns in this Mangrove ecosystem no how different species occupy specific tidal zones some mangroves thrive in frequently flooded areas While others prefer Higher Ground with occasional flooding this creates distinct bands of vegetation parallel to the Shoreline the influence of tidal water extends underground moving Inland from the shore groundwater transitions from saltwater through brackish water to freshwater this salinity gradient creates another form of zonation with plants distributed according to their salt tolerance each tidal Zone supports a unique community of plants and animals the subtitle channels remain underwater even at low tide and that provides habitat for fish mud flats emerge at low tide and that hosts invertebrates that can tolerate exposure to air the low Marsh supports cord grass and waiting Birds while the high Marsh contains more terrestrial species in Marine environments zonation extends from the Splash Zone above high tide down through the subtitle Zone that's the Zone below the low tide each Zone presents unique challenges exposure to air to wave action changing pressure and decreasing light the deeper you go each of these requires specific adaptations from the organisms that live there to measure zonation patterns scientifically we need systematic methods transex allow us to measure both biotic and abiotic factors along an environmental gradient by collecting data at regular intervals we can quantify exactly how communities change across space a belt transect combines a line transect with regularly spaced quadrats look at the blue squares in this diagram these are our sampling quadrats where we count plants or estimate cover the red asteris mark points along the transect where we measure environmental factors like temperature soil moisture or pH this systematic approach allows us to plot the populations or coverage of different plant species against different levels of abiotic factors and that gives us reliable repeatable data to understand how communities of organisms change along environmental gradients here's how we visualize transect data using a kite diagram each horizontal band represents a different species and the width of the band shows that species abundance at different points along the transcept notice how some species like the malier are most abundant in the back mangroves that's cv1 one in the diagram While others peak in different zones when we interpret kite diagrams you should ask yourself which species is most common in each sampling location where do we find the greatest diversity of species so which site has the most bands in the diagram the answers reveal patterns of species distribution and community structure along an environmental gradient now that we understand the spatial changes in communities that's called zonation let's explore how communities change over time through the process of succession succession describes how communities replace each other over time in a given location unlike zonation which shows spatial patterns across a landscape succession reveals temporal changes or changes over time as ecosystems develop and mature this diagram shows how a pond might transform into a forest over time notice how each stage builds upon the previous one gradually filling in the pond with organ iic matter until terrestrial plants can establish themselves these photographs document real succession in action they're all taken on the same site over a period of years you can see in the top one what the original Community was like and then in the next one down you see there was a fire that came through and it cleared out all of the vegetation but left the soil behind each image represents a different stage in the process from early colonizing species through to a mature mature Forest Community after the disturbance each stage in succession is called a seral community or a seir that's spelled s each sear modifies the environment in ways that make it more suitable for the next Community while potentially making it less suitable for itself so it's a process of continuous change let's examine each stage of primary succession in detail starting with bare rock in this initial stage we have extremely harsh condition light levels are intense with direct sunlight and no shade there's virtually no soil present just weathered rock particles biodiversity is extremely low since very few organisms can survive in these kind of conditions the only species present are R strategists Pioneers like lyans cyanobacteria and maybe a few mosses that can withstand really extreme conditions and begin the process of soil formation as we move into the early Pioneer Community conditions remain challenging but they do show the first signs of improvement light levels are still really high because there are no plants tall enough to provide shade and then there's a thin layer of organic matter developing just a few millimeters deep and that starts to mix with those Rock particles to form early soils while biodiversity is still low it is beginning to increase we still see mostly our strategist and very few K strategists are appearing more Mosses are establishing themselves along with drought resistant herbs and some lens these plants tend to be pretty small in their low growing to resist wind and drought conditions in stage three we have the developing community and it shows more significant changes light levels become moderate as taller plants create some shading for the for the soil soil depth continues to increase to several centimeters and it contains more organic matter biodiversity is moderate and it continues to grow while our strategists are still dominant we're beginning to see more K strategist appearing annual herbs grasses and small perennial plants become established importantly this is when we first see invertebrates like insects and worms which help develop the soil further stage four the intermediate stage we're going to see much more complexity developing light levels become variable because there's more shading from Plants as they grow taller and this creates multiple niches for different species the soil is now welldeveloped with distinct Horizons forming biodiversity is relatively high with roughly equal numbers of rnk strategists perennial herbs and small shrubs dominate the vegetation while invertebrate communities become more diverse the first small vertebrates like lizards and small mammals begin to appear as we approach stage five in late succession the ecosystem becomes increasingly complex a layered structure creates varied light environments throughout the entire Community the soil is deep it's well structured it has clear Horizons biodiversity is high with complex food webs developing K strategists begin to dominate the community we see large shrubs and small trees establishing themselves along with a pretty diverse animal community more complex ecological interactions then emerge at this stage finally in succession we reach the climax community the canopy structure is complex it's closed frequently and that creates multiple light zones from really bright conditions higher up to darker areas close to the ground the soil is deep it's mature it has full Horizon development and this stage shows the highest biodiversity with complex interactions between species K strategists predominate large trees and shade tolerant understory species form the plant Community while a full range of vertebrates inhabits different niches both vertically and horizontally across the landscape the system remains stable unless it is Disturbed externally usually by human forces but also sometimes by natural disasters let's pull together the key patterns we see across all stages of succession we observe increasing soil depth and complexity over time from early to late stages biodiversity and Niche specialization both increase as more species find their place in the ecosystem there's a clear shift from R selected species to K selected species as the environment becomes more stable food webs become increasingly complex and the system develops greater stability and resilience to disturbance finally nutrient cycling becomes more efficient as the ecosystem matures primary succession occurs when an ecological Community develops for the for the very first time on newly exposed rock or substrate nothing has ever lived there before it's primary because it's the first time this process starts completely from scratch with no soil no previous biological influence let's look at some specific examples of where primary succession takes place one classic example is after volcanic activity when lava cools to form Solid Rock it creates a completely sterile environment this virgin Rock has to be weathered before any organisms can colonize it we see this process beautifully Illustrated in places like Iceland where new lava flows provide perfect conditions for observing primary succession from its very beginning another example occurs where glaciers Retreat as the ice pulls back it exposes bare rock that was previously buried for thousands of years like volcanic rock this new exposed surface first has to be weathered before organisms can establish themselves we observe this process today in places like sard in Norway where retreating glaciers leave behind terminal morines that are ready for colonization Coastal Dune ecosystems provide another example of primary succession here succession moves Inland from bare sand at the beach through successive communities at studland peninsula in the UK for example we see maram grass communities give way to Heath and eventually Woodland as we move Inland what makes this site particularly interesting is that you can literally walk through time from Young Dunes near the shore to mature ecosystems Inland that began developing hundreds of years ago so it's like succession that you can see all the different stages at the same time as long as you move horizontally across the landscape in river deltas and estuaries we see primary succession occurring on newly deposited sediments at the mouth Rivers like you see here in this map of Louisiana aluvial sediment accumulates to form new land primary succession may happen faster here compared to other substrates because the sediments have already been weathered right they're particles of rock that have already been broken down into smaller pieces and they already contain a bunch of nutrients that flowed there from Upstream in contrast to primary succession secondary succession occurs where there's been a pre-existing Community this happens on bare soil rather than bare rock an important distinction because soil is already present and that soil usually contains nutrients seeds and other biological materials common examples of second succession include abandoned agricultural Fields or forests that are recovering after fires looking back at primary succession for comparison remember that it always starts with bare rock completely sterile conditions where no life has existed before the process of soil formation must begin from scratch through physical and biological weathering and that makes primary succession a much slower process than what we're about to see in secondary succession that soil formation is what takes such a long time when secondary succession begins it has significant advantages over primary succession since the soil is already present along with a bunch of organic matter and often a seed bank the early stages progress much more rapidly after a disturbance like a fire or the abandonment of Farmland pioneer species can establish themselves pretty quickly and that leads to a much faster development of the subsequent communities in succession the 1988 Yellowstone National Park fires preside an excellent example of secondary succession in action these devastating fires destroyed most of the existing ecological communities over just a few weeks however because soil remained largely intact containing seeds and nutrients the recovery process could begin almost immediately secondary succession in Yellowstone National Park is well documented and it continues to be studied because the disturbance was relatively recent and due to the site's cultural importance as one of America's most famous national parks scientists have been able to track how different species have recolonized the burned areas and that provides valuable insights into the process of ecosystem recovery after major disturbances let's examine how key ecosystem characteristics change throughout succession whether it's primary or secondary succession we're going to look at several important factors including energy flow productivity species diversity soil development and nutrient cycling each of these shows distinct patterns of change as succession progresses through different Sears or stages looking at early versus late succession stages we see clear differences in several key characteristics gross primary productivity starts low in Pioneer communities due to harsh conditions and low plant density but gpp becomes quite high in climax communities where dense vegetation and optimal conditions allow for maximum efficiency of photosynthesis interestingly net primary productivity shows the opposite pattern it's high early on because most energy goes towards growth but it's lower in climax communities where a lot of the energy is used for cellular respiration biomass increases dramatically from early to late stages as organic matter accumulates in the soil and above ground the number of ecological niches also increases from early to late stages in succession as habitat structure becomes more complex and more varied species richness increases from early to late succession as more stable conditions support greater diversity organic matter content follows a similar pattern increasing substantially as dead material accumulates and de composes in the soil this means that soil depth progresses from shallow in early stages to deeper and mature profiles in climax communities perhaps most notably nutrient cycling shifts from an open system with significant losses in early succession to a relatively closed system with efficient internal recycling in climax communities let's explore how an ecosystem's capacity to tolerate disturbances and maintain equilibrium depends on its diversity and resilience we've already looked at this back in topic 1.2 before but let's revisit it because it's really important to this idea of succession the concept of resilience the ability to resist damage and recover from disturbance is crucial for understanding ecosystem stability consider this example if disease wipes out a wood rat population the system can remain stable because rattlesnakes and red tail hawks can shift their predation to Alternative prey species like analou squirrels and grasshopper mice this demonstrates how diversity provides stability through alternative Pathways in food webs generally speaking the more complex the food web the more resilient the system becomes this is because multiple alternate energy and matter Pathways exist throughout the food web when one pathway is disrupted others can compensate and that helps maintain overall ecosystem function and stability we've also got to consider how human activities affect these processes activities like logging Agriculture and artificially induced fires all tend to reduce diversity often reverting ecosystems to earlier stages of succession this diminishes both resilience and stability late succession communities typically have high diversity and therefore greater resilience while early succession or human Disturbed communities show lower diversity and therefore reduced stability that's it for the SL content in topic 2.5 remember that zonation is Chang Long and environmental gradient while succession is change in an ecological community over time until next time happy learning