 Let's try to let's try to get started. So we make sure we get through everything We have people in the adjoining rooms So if you need to go over there, please do or you're more than welcome to find a find a spot on the on the stairs If it's comfortable. I received a title wave of emails in the last 24 hours Thanks very much Anything that came in after like 2 a.m Probably I haven't read it yet, but I will and if it didn't if we don't cover What's in your email if we don't cover it here, then I'll I'll respond to you So this is this is essentially a review of the whole section now And I've exclusively chosen slides That's cover material. I got emails about I Had to choose some way to limit it and that was the choice so For the most part I've covered everything I heard from you about there will be exceptions and ask us in office hours or Send another email if I if I neglect it. This is it finally You can move on now to evolution, but You also have two lectures in evolution before your exam, so you're gonna have to You're gonna have to come on Wednesday and come on Friday and Shift your thinking to evolution in the lecture Please come to these lectures the I've said it before I think that it's been demonstrated that those who come to lectures Do on average a full grade better in this course They're you know, whether we continue the webcasts in this course partly depends on attendance attendance goes down so much with the webcasts They might just have to get dropped We never wanted to do that because it penalizes the students who come to lectures and use the webcasts But if you like the webcasts one way to make sure they continue is to come to lectures Okay, I Wish I had a good excuse for my black eye That I was fighting bad guys or something Not not so much a bad hop playing softball yesterday at shortstop Yeah Could have been worse. All right, so Let's Start by reviewing I'm going to go through the lecture sequentially and address questions I received in the context of when the material was presented the first Lecture was mostly storytelling about the history of ecology an introduction to the phenomenon of natural history the the pursuit of natural history and how ecology as a science Derived from natural history and how ecology as a science is based in good natural history today and discussion of from chauvet cave through Linnaeus and Darwin and With looks at some exemplary naturalists the second lecture In in this I'm trying to suggest a nice link Although it's still somewhat unfounded in the history of science between ethology the science of animal behavior and ecology Because ecology at least the ecology of animals is Fundamentally related to the activity of individual organisms and the activity of individual organisms animals at least Concerns their behavior their physiology and their individual interactions with the environment and This is a this is a bridge that needs to be better formed between the science of individuals and the study of ecosystems We do that somewhat better in the study of plants and for that I gave you an example from eco physiology, which I'll address In a little while, but we talked about some of the founders of ethology some discussion of group behavior in organisms and modes of learning in animals in Relation to their environments and their foraging strategies. I Didn't have too many questions on on those topics The levels of organization concept this general this orienting generalization that we use in biology and in science One one aspect of this that I wanted to highlight That's important partly as a result of the evolution of language and the evolution of terminology Is the fact that the ecosystem is considered a distinct level above the community and below the biosphere and The landscape is sometimes used in addition to this or as a substitute for this But the term ecosystem gets much wider usage now We use the prefix eco for just about everything these days, which is just fine It's a sign of the times that we have a greater awareness of ecology in popular Popular culture, but the term ecosystem is also used very frequently as a shorthand for Ecological system and any living system is in interaction with its physical environment There are two sides of one biological coin the living phenomenon and the abiotic phenomenon and That's just a that's a very adequate shorthand for any System at any level of biological organization the ecosystem or the ecological system in This way you can see that an individual organism such as yourself or your dog or cat is a kind of ecosystem It has a bunch of other organisms living in it and on it and it's in constant communication with the physical environment through exchange processes, so I'm perfectly okay with people referring to a cellular ecosystem even an Atomic ecosystem. I'm not sure about that I think that stretches our definitions because part of our definition of an ecosystem is the living component, right? So you can look at these as levels of organization in the in the ecological hierarchy and then think about each of these things as an ecosystem in the narrow sense as well Then we started to move into population ecology. We tried to follow the hierarchy of levels from the individual now to the population We discussed sampling techniques With direct counts and relative measurements of individual numbers and density I Think I have a slide pertaining to that in case I don't a couple people asked The difference between numbers of individuals in a population and density. It's just density concerns the area the space The spatial context for the number of individuals whether it's the area of land or the volume of water The density is the total number of individuals per unit space Number of individuals is just how many there are without reference to that We talked about metapopulation ecology gave a quick example Dispersion patterns This is an as an example of Uniform dispersion in desert plants as a result possibly of resource competition or allele apathy and we talked about an example of Squirrels from the sierras in in how we construct life tables and survivorship tables and then We define these terms Itero Paris and Semmel Paris, which a lot of people had problems with so I'll cover those. Yeah, this was my slide to cover density You just go count the trees out in the eucalyptus growth and you get the total number of trees but if you measure how measure the plot of land on which they grow and Give your estimate of the number of trees relative to that plot of land. You'll have your density Itero Paris just means reproduction repeated During the lifetime of an individual and it you can see the root of the word Iterare To repeat in there. So an organism that repeats more than repeats reproduction more than once and Couple people asked our humans Itero Paris Are they? Yeah As a species yes, I mean We are capable of reproducing more than once in our lifetimes Semmel Paris Semmel from once Reproduces once people ask does the organism have to die right after it reproduces? Not necessarily, but most organisms don't continue to live after they've completed reproduction What's the point in a Darwinian context, right? humans are and I alluded to that humans are somewhat unique in our in our Long life after menopause for example And the roles that grandparents play in human cultures You can think about that on your own time if you want lots people had questions about population models and The equations behind them and I can't review everything here. Of course. You've done a lot in your labs already See me in office hours go to the GSIs office hours for details on this It's you know, we've spent a lot of time on it in the labs also I'll do a little bit here on particular points, but We'll have to save it for outside. Yes Yes, it the definitions of those terms don't concern that Usually an organism that that reproduces so Without rephrasing the question. I'll just try to clarify Usually an organism that reproduces once produces a lot of offspring. It's a big bang Episode of reproduction that's as a general rule. You have one chance and you might as well produce a lot of offspring Does that help okay, yeah, but the definitions don't really concern The the numbers of offspring produced technically it's just as a general rule though the Semmel Paris organisms produce a lot okay, so we We used our little sparrows as a general model for For estimating population numbers as a function of births and emigrations and deaths and births Did I say that right? Immigrations and emigrations and births and deaths this is a death as dictating population numbers You can see this very phenomenon. I saw an attack at least this weekend up in the park You can see this in the hills. We have great bird eating birds here in the Bay area and They're hard to watch because they move so fast for one thing but you can see them Yes, and we started with a discussion of exponential growth and gave a few examples of real-world exponential growth and humans represent a great example of that but we looked at elephants and elephant seals and then limits to Limits to population growth particularly with reference to to competition but other factors Limits population growth relative to the density of the population for example predation could if Predators turn their focus to a growing population. They can serve as a check on that growing population Then we built in the concept of carrying capacity of an environment the carrying capacity of an environment I have a couple slides to talk about that and Added a term in our population growth equation to accommodate carrying capacity and I tried to stress the complexity of population growth dynamics we we tend to use nice smooth curves in our examples and Use examples from the lab or nature that fit these nicely, but most populations grow With complex dynamics chaotically sometimes which is not to say without order Chaotic population growth may be highly ordered, but extremely hard to predict this is a a step we just glossed over and and For good reason because you don't need to understand calculus to use these equations in here We glossed over this step from our equation for fixed growth in fixed intervals so growth in Intervals of time for example one year of time or one reproductive cycle of time to instantaneous growth represented by this differential equation We glossed over that transition because it's the it requires calculus You don't need to understand that step But what you need to recognize is that this equation differs from this equation as the one concerns fixed intervals of time and the other the latter Time instantaneously measured moment by moment and that's a lot more useful for Most purposes in ecology to think of population growth instantaneously and not to have to wait across seasons To really apply our models So dndt as we as we say it equals the per capita rate of growth Times the number of individuals in the population dndt equals r times n right now r is a difficult topic and Your textbook handles it okay, it's but you look at other textbooks and they all many of them handle it differently So try to keep it simple in your understanding of r we we defined it as r equals little b Minus little d r equals the per capita birth rate minus the per capita death rate but you sometimes see r as Defined as the intrinsic rate of increase of a population or the intrinsic rate of growth of a population Suggesting somehow that it's an intrinsic It's an intrinsic part of the biology of an organism and That's how we use it in many of these models. We assume that r doesn't change over time. We assume that r is fixed and Other aspects of the ecology of the organism change So we assume it's intrinsic to the species in question the population in question and that's fine But if we if we go back to the way we defined our Mathematically as births minus deaths per capita births minus per capita deaths. We can see that those are dynamic Properties of the organism and if they change then r is going to change So keep that complexity in mind, but Try to keep it simple because I won't do anything fancy on the exams in relation to this And just just reminds me, you know, you'll never be asked to define something These are multiple-choice exams and if my definitions differ from the book I don't think they're contradicting anything in the book. At least I haven't heard of any But they may emphasize different things and that's fine. It's the only problem only problem arises if there's a contradiction So you can see the effect of r on growth, of course I think you're probably understanding this now a higher r is going to lead to lead to a steeper steeper j in this exponential growth context, but growth does not continue unchecked. It's that's that's an impossibility on earth because of a limitation of resources usually and There are and Population growth is regulated This is where the terms density dependent and density independent come in a lot of confusion around those terms as well Recognize that density dependence and density independence is in relation to population growth and regulation, so this is the classic type of curve for Density dependent growth regulate regulation in this context its competition with an increase in the number of plants per unit per in the neighborhood of an individual sorry an Increase in the number of plants in a unit area Leads to a decrease in the number of seeds of the individuals in that area fecundity is affected by density and You see the typical negative relationship between the two That's density dependent regulation because as density increases Reproduction is affected its dependent reproduction is dependent on density and the population is is regulated as a result by density density factors and that's an example from Competition but these are these are also types of density dependent forces that could regulate population growth Including the fouling of the environment by the inevitable production of waste by organisms as they grow or other factors density independent factors Again, I don't have a slide for it Would it would limit growth would regulate growth without reference to how many individuals are present in the area that's the sense in which it's density independent the effect of these factors and Natural disasters are usually cited as primary ones physical abiotic Forces that affect population growth They often affect they sometimes affect populations without reference to their density They're density independent in their effects in that sense, okay When you really delve into them, they often have some relationship to density an example would be a Cataclysmic windstorm if it were to strike now and hit the eucalyptus grove The trees will either fall down or they won't fall down Right depend doesn't really matter. How many trees are in the grove? Well, wait, it kind of does because of edge effects the trees on the edges will be much more likely to be affected than trees in The interior so depending on how many trees are there you're going to have greater buffering of the central area One example of something you might at first blush think of as a density independent force a windstorm But in fact when you get into it Density plays a role. So if you want cataclysmic Meteor strike here on Berkeley That should take care of the eucalyptus grove no matter whether there are 10 or 100 trees in it That's a simpler example Ali effects. Yay Everyone's confused by these and And I'm partly to blame for that. Well, maybe wholly to blame for that But it's because I'm trying to add to something that's in the book Much of my understanding is based on a couple of recent reviews of the subject including this one in trends in ecology and evolution The book highlights an important aspect of the alley effect where populations that dip below a certain Number of individuals can be prone to extinction populations that go below a certain size instead of rapidly expanding in their growth which your your exponential model would predict and Even your logistic model would predict Instead some of these populations instead had the other way and had toward extinction that is an Ali effect and it's the one your book highlights and an example might be a an organism that defends itself in groups say a Group of fish that schools and defends itself in schools schooling as we've talked about has a Has an effect on predators that makes it makes that the schooling individuals harder to capture But when that's when that school gets smaller and smaller The it might get to a point where the individuals are extremely easy just to Individuate and pick off by the predators. So below a certain size the population trends to extinction rather than what your models would predict which is Rapid expansion because of an abundance of resources and a lack of competition and so forth so that's the zone of the negative effect where your population size Drops below a certain level this level and your per capita growth rate is Less than zero in that region. It's negative and a negative per capita growth rate is going to lead to local extinction But there's also this zone of positive effect and this is what your book doesn't highlight So if we think of this as one species of organism following this curve, it can experience a negative type Ali effect when its population is below a certain size, but above this Size it's experiencing a positive effect where with increases in density. It's per capita growth rate is going up It's our is growing up going up That's the zone of positive effect and if you want you can think of the same example a fish school That's this big does pretty well against predation, but a fish school. That's this big does really well and the individuals are able to spend more time foraging and more time dedicating resources to reproduction and they'll increase Quite rapidly at some point that school bumps into reality and The trend is to follow your typical logistic pattern and to resemble At those higher levels of density you the standard Relationship of negative density dependence dependence which that very faint line represents So just think about the two types of Ali effect and add the positive type to what's given in your book and Recognize that this is a case of The term became simplified over some years, but now when people are taking a closer look at it they realize it's a more complex problem and Your book doesn't reflect that Logistic growth. I'm not going to spend much time here folks Please talk to me in office hours if this continues to be a struggle, and I know it does for some people the fact the sigmoid growth model Where we've taken carrying capacity and built it in to our equation I Would need a lot more time to To work on that so go back to the webcast see see us in office hours, and if there's anything else beg for help Come to my house and knock on the door Inter-specific relationships. Here's one. I don't think I define the term symbiosis for you But a couple people have asked about it. Maybe I've mentioned it For one reason because there aren't any clear definitions any Fixed definitions of it. I like to use the more general definition a symbiosis the terms just mean sim together Biosys living living together It usually implies a very close or as The textbooks often say intimate type of living together Which means the dynamics of the interacting populations are closely connected There are times when people just mean mutualism by symbiosis the type of cooperation or positive effects on the participating Organisms we certainly don't want to do that But do we want to include something like predation or her bivouary in the context of symbiosis? I'm okay with doing that. It's you know, it's just it's just a word and it's a word that Many people use differently symbiosis. I don't even tend to use it that technically For that reason because it's so it's so loose loosely used. So I don't really care, you know, one of your practice exam questions The answer given was included predation as a type of symbiosis I Won't you know, I wouldn't put that on your exam. I won't put anything about symbiosis on your exam. I promise It's a loose term and you can choose how to use it Narrowness or breadth that you like Those other terms are more specific we started talking about the competitive exclusion principle and Gauss in the discussion of interspecific relationships and I'll talk about the niche concept a little bit people are still struggling with that and we highlighted This categorization scheme of interspecific relationships concerning the effects on the participants whether negative positive or neutral and Then looked at some examples of aposematism or aposematism and mimicry and then Dynamics our population growth dynamics when more than one species is involved in for example predator prey cycles I Just you don't need to memorize these equations. I just want you to recognize This is one way to model interspecific interactions by building in a simple coefficient to the equation that represents in this case competition and the effect of one organism a second species on Another species the more I say the more I'll bring confusion to this. I'm gonna leave it at that for now the challenge here is to build this term in that It puts it in terms of The number of individuals of the first species so you're subtracting these individuals from your first species I've probably confused some of you already. I'll just be quiet on that one. You will not hear much about this on the exam I just want you to understand that Multiple species can be modeled Using our our standard equations. What's the ghost of competition past? What does it refer to can anyone state that succinctly? Realized niches in a sense. Yes this example Shows these lizards in their realized niches where they forage in different parts of the habitat Someone else back here Did someone else want to have a try? Yes, yes, it's it's an explanation for this Distribution of species in the environment these realized niches with reference to competition in the past having resulted in this configuration so somehow and So it's a way to explain the lack of competition, but observed structure in a community with reference to Competition having occurred in evolutionary time in the past In a way, it's explaining away the problem and that's one of the difficulties ecologists have with the idea This reference to a past ghost But quite quite logical also to think that competition could have structured these populations Previously and what we see now is the result of that the niche. I've got to talk about the niche The niche the niche is not just the habitat of an organism the one of the traditional definitions of a niche is an organism's profession or Its place in the community And that's drawing a metaphor from human society, of course the profession of This species of lizard is to occupy the fences and forage for insects there as if it's performing a role in the community That others don't perform It's a shame. I didn't spend more time on this because the in the history of ecology G. Evelyn Hutchinson expanded on that original concept of the niche with his idea of an n-dimensional hyper volume and I wanted to talk about that today, but I decided why add a complex term at this point an N-dimensional hyper volume, but it really does belong in the ecology course So maybe you can look it up yourselves on your own time It was a way to bring a traditional natural history approach to the niche Into a more mathematical concept and it had a great influence on the way we study and model Communities this idea of an n-dimensional hyper volume, but the traditional approach is still okay one of the earliest definitions of a niche was by the founder of our museum here as It's just the natural history of the species in nature what that what that organism does in nature Not just where it lives, but the things that eat it eats its ranges of tolerance to physical factors the total of Total package it's its niche I'm gonna have to go a little faster here Mullerian and Bates in mimicry. Oh my Lots of confusion on that because I glossed over it partly because I bet you you'll get it in the evolution section again But a Mullerian mimic is one that is also distasteful and harmful a Species that mimics a distasteful or harmful species that mimics another distasteful or harmful Species a Bates in mimic is a harmless or a good tasting Species that mimics one that's harmful or bad tasting. So just Memorize that little difference and think about Think about them a bit and hopefully you'll get it reinforced later in the course Just wouldn't be introductory biology without it Community ecology we talked about definitions of communities community boundaries primary and secondary succession Keystone species dominant species ecosystem engineers things like that Edges these are natural edges in this system These are ecotones The boundaries between one community type and another community type these edges represent ecotones In this natural context, we also spoke about edges in the artificial context the anthro Pogenic context and I'll get to that Edges these ecotones are often very diverse in species because they incorporate species from this zone as well as this this zone They incorporate species from the neighboring communities And they have species that are specific to the ecotone itself That makes them so diverse oftentimes they're often very productive as well Remember that diversity we distinguish from species richness Because species richness is just the total number of species in an area in a community, but diversity Also incorporates the relative balance of numbers of individuals of the different species And if you haven't yet plugged this into your calculator, please do no need to memorize it for the exam though You can plug it in with these numbers This second Lecture in community ecology went more into succession and Into our selection and case selection and then we got into island biogeography Our selection and case selection are still confusing I focused on it here in the context of succession and I'll stick stick with that, but You can think of them more widely Our selected Species Are called that Because they tend to influence the dynamics of rapid growth and reproduction the phenomena associated with are with the Intrinsic capacity for growth K selected organisms are called that because they evolve they are thought to have evolved in the context of communities and In populations at or near carrying capacity So if you think about the forces the natural selection forces that would act on populations living in this type of setting in a in a mature forest setting like this They'd be different from the type of forces that would be acting on the plants in these very early successional stages Plants here are going to need to get into this environment start to Absorb resources quickly photosynthesize rapidly under a hot sun and produce more offspring so they can grow in the same conditions quickly whereas organisms in this context are going to be in Perhaps more Direct competition for sunlight and water with other organisms. They're going to have to grow tall perhaps to Even access the sun so they're going to have to invest a lot in in structural growth and It turns out when Organisms are surveyed they show these trend these trends and features that render them Categorizable oftentimes into into these types are selection case selection, but those are really just endpoints of the spectrum and Most species will fall somewhere in between Sometimes as a result of those differences in In the successional context in which they have all Island biogeography. Let's try to clear that up a little bit. Remember MacArthur and Wilson and their studies of mangrove islands off of Florida and that the this equilibrium number of species is this is Can be predicted from the curves of Immigration rate and extinction rate in an area where those curves caught cross where those curves cross you have this Estimate of the equilibrium number of species expected on the site We look at the effects of island size and distance to mainland mainland in How they influence these rates of immigration or extinction a small island is going to have immigration rate is going to decline over time Because the island the island is starting to fill up with species There's only a set number of species in the regional pool from which these from which these islands can draw We're thinking in ecological time here. We're not assuming any organisms are evolving are evolving in situ so we're not thinking about species origination and Whole species extinction we're thinking about the arrival and disappearance of species immigration and extinction Locally from a regional pool of a set number of species on a small island There will be fewer immigrants than on a large island because it's a smaller target if Distance to mainland is held equal On a small island extinction rates will be higher because population numbers are lower than on a large island and Small populations have a greater likelihood of running to extinction So that's the effect of island size on these rates The distance from the mainland also will affect these rates a far island is going to have fewer immigrants than a near island Again, because it's a less likely target to strike. It's far away It's going to have most organisms leaving the mainland will be close to the coasts, right a Far island is going to have a higher extinction rate Just because it will not receive the replenishment of new species as Rapidly and so in near island We'll have a lower number of extinctions because species when species are close to extinction They're more likely to be seeded from the mainland so it's related to the immigration phenomenon and Depending on these curves we have different estimates and predictions about the equilibrium number of species in these environments and It's enough to say on that Our first lecture on ecosystem ecology Concerned trophic chains Trophic Cascades and then ecosystem metabolism a bit this Hubbard Brook example was used as an example of a natural Field study of a whole ecosystem Someone asked what was the point of that it's it's described well in your book, too It's just a famous site for the study of field ecosystems Study of ecosystems in the field Remember we have bottom-up types of causality and top-down types of causality and communities bottom-up causality is Driven by changes in the dynamics at the base of the food web or at the base of the food chain and even from physical factors That might influence the autotrophs and The causes propagate upward so changes in the number of hawks might be related to Changes in the vegetation even though the hawks aren't perching on this vegetation or eating it at all It's a result of causality up the chain The top-down forces Are moving in the opposite direction? They are stimulated by changes higher in the food web higher in the food chains and can run all the way To the base in the example of the trophic cascade from Mount Zion Changes in human Visitation patterns and mountain lion abundance affected soil erosion along streams and rivers. Yes Carnivore production. Oh Yes that question concerning The biomass of Yes, that's related to that practice question. I don't remember it exactly, but It's the one on it's the one on the amount of biomass at different trophic levels and it's you get that answer based on your pyramids of numbers and This is built in terms of energy here in jewels, but the same would apply in terms of biomass Where by a factor of 10? as a as a Realization you have 10% the biomass or energy available at higher trophic levels. I'm gonna have to Avoid questions now with just about seven minutes. I'm gonna use all the full seven minutes, but Probably gonna have to wait on the questions office hours right after class for an hour if you can do that Yeah, so that's this is a way to answer that question with reference to this type of pyramid Remember that net primary production is a function of gross primary production minus respiration gross primary production is just how much How much material how much energy or material is captured by? The autotrophs in a system secondary production is how much material or energy is captured by The consumers whether it's this the secondary consumers tertiary or so forth even the detritus, so that's the difference between primary and secondary production and You can see how much is lost to respiration in the process. That's what gives us this pyramid of energy or pyramid of numbers we usually measure these phenomena in terms of calories jewels or carbon Because all organisms contain carbon, so it's a nice estimate Please check the book if you don't understand why the a system like this is top-heavy Sometimes aquatic systems the standing biomass is higher in the higher trophic level than the lower trophic level than in the zooplankton than the phytoplankton it's a result of rates of consumption rates of death and birth in this in this group This figure can help you understand that the energetic hypothesis This the point of this is to Well the energetic hypothesis is a hypothesis to explain why food chains are short They're short because there's not energy available at high Higher and higher trophic chains as a result of the inefficiency of transfers that we just discussed You if only 10% of the energy or material is making it across levels at some point There's just not going to be enough to sustain Higher and higher levels. That's the energetic hypothesis and it was tested and supported in this study of tree holes tree hole biology People asked about other possibilities, I just didn't go into them, but In some models long food chains are unstable Effects get propagated from low in the food chain and destabilize and drive higher and higher Trophic level occupants to extinction so a dynamic stability hypothesis would be an alternative just for fun Just because a lot of people asked glad you were curious Another possibility is that the consumers higher and higher level consumers tend to have to be larger and there may be constraints on size of organisms So you just can't keep getting bigger and bigger creatures higher and higher in these food chains I gave you the energetic hypothesis because it's the classic one and it's it's quite well supported Global air circulation patterns, you know only focus on these insofar as they are related to the biology If you don't understand the details of this dynamic too much Probably okay, but do recognize why deserts tend to form around 30 degrees north and south latitude That's that's the biological relevance of of the phenomenon. Okay Yeah, people asked why why the fog here in California Cold water currents interacting with warm warmer air masses generates fog and then Through a couple different means including this mechanism that fog is pulled on to land Or it's pushed from behind by other by other systems, but this is one major mechanism warming air pulling the foggy air off of the oceans on to land and We used this example from redwood biogeochemistry as an example of eco physiology physiology is just the study of the organs and tissues of organisms that Intra-organismal focus if you set that intra-organismal focus into a whole ecosystem context you have an eco physiology That's just what the term is a reference to this this great integration between Individual physiology and whole ecosystem dynamics your climographs and your biomes everyone wants to know what they need to know for the biomes, right? You need to know You need to be able to compare and contrast biomes You're not responsible for all the details in the book figure, but this is just good stuff for an earthling to know so certainly know the names of all these different types know something about the differences in physiognomy and The differences in temperature and precipitation regimes under which you find them Things like that pretty general not to the detail that the book requires but in more detail than I gave you in in lecture net primary production we talked about that a bit just now and what it what it means different systems and their productivity in Paleo ecology. Oh my I didn't go over something that a lot of people had a problem with Let me just tell you on this one You're responsible for the generalities here also Definitely don't don't focus on the specifics in the nitrogen cycle but you need to be able to compare and contrast the different types of cycle phosphorus being a a system based in the sedimentate in the sediments and carbon Having a major atmospheric component you need to understand the major components in each of these cycles But certainly not the details particularly in the nitrogen system What I didn't go over was a biopurification of calcium and the trace elements will skip it. I won't test you on it great field of study and Really important in ecology these days biogeochemistry, but I didn't get to it Just whatever's in your book the demographic transition. I made a mistake on I started to refer to the demographic transition as starting in this period the demographic transition really happens Starting in this period Technically when birth rates start dropping in relation to the already decreasing death rates. That was just a simple Simple difference and mistake I made All right gang. I told you I'd finished with a couple pictures of my kids at some point So I have some pictures of my kids at the end. Bye everybody