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Ecosystems Introduction • Many ecosystems around the world are currently experiencing significant changes in species composition, abundance, and diversity due to the influence of human activity. – These changes have, more often than not, led to a reduction in species diversity. • The issue is whether the biogeochemical functioning of an ecosystem will be impaired by a loss of species or the introduction of a new species. Misconceptions about Ecosystems • Ecosystems are not an organized whole, but a collection of organisms. • Forest fires are harmful to terrestrial ecosystems and should not be allowed to burn. • An organism cannot change trophic levels. Misconceptions about Ecosystems • An animal that is high on the food web preys on all populations below it. • The top of the web has the most energy. • Characteristics of a population are created according to the needs of the individual or according to a predetermined grand plan. Misconceptions about Ecosystems • Characteristics are passed on by the bigger, stronger organisms. • Species live together in an ecosystem because they have compatible needs and behaviors. • A change in the prey population has no effect on the predator. What is an Ecosystem? What is Ecology? • physiological ecology - relationships between organisms and their physical environments • population ecology - between organisms of the same species • community ecology - between organisms of different species • ecosystem ecology - between organisms and the fluxes of matter and energy through biological systems Major Terrestrial & Aquatic Biomes • The most important factors are temperature ranges, moisture availability, light, and nutrient availability, which together determine what types of life are most likely to flourish in specific regions and what environmental challenges they will face. What are biomes? • Biomes are regions of the world with similar climate (weather, temperature) animals and plants. There are terrestrial biomes (land) and aquatic biomes, both freshwater and marine. How many biomes are there? • Some say there are only 5 major types of biomes: aquatic, desert, forest, grassland, and tundra. • Others split biomes further. Forests are separated into rainforest, temperate forest, chaparral, and taiga; grasslands are divided into savanna and temperate grasslands; and the aquatic biome is split into freshwater and marine. Additional Info AQUATIC BIOMES •Freshwater •Freshwater wetlands •Marine •Coral reef •Estuaries TERRESTRIAL BIOMES: •Tundra •Rainforest •Savanna •Taiga •Temperate forest •Temperate grassland •Alpine •Chaparral •Desert Biodiversity Gradient • Biodiversity varies with change in latitude or altitude. The diversity increases as we move from high to low latitudes (i.e., from poles of equator). In the temperate region, the climate is severe with short growing period for plants while in tropical rain forests the conditions are favorable for growth throughout the year. Here’s a thought … Life is an improbable occurrence. The conditions for life are a rare, if not unique, event in the universe. Both the evolution and maintenance of life depends on an unusual blend of the rare and the common, which allow an organism to survive. One of the most important of these conditions is climate – predictable ranges of temperature and humidity; another is the availability and flow of certain organic and non-organic nutrients. Energy Flow Through Ecosystems • Without autotrophs, there would be no energy available to all other organisms that lack the capability of fixing light energy. • However, the continual loss of energy due to metabolic activity puts limits on how much energy is available to higher trophic levels (this is explained by the Second Law of Thermodynamics). Energy Flow Through Ecosystems Trophic levels are simply a feeding level, as often represented in a food chain or food web. Energy Flow Through Ecosystems • Only a fraction of the energy available at one trophic level is transferred to the next trophic level. The rule of thumb is 10%, but this is very approximate. • Typically the numbers and biomass of organisms decrease as one ascends the food chain. Energy Flow Through Ecosystems • A rabbit eats or ingests plant matter; we'll call this ingestion. • Part of this material is processed by the digestive system and used to make new cells or tissues, and this part is called assimilation. • What cannot be assimilated exits the rabbit’s body and this is called excretion. • Assimilation = Ingestion - Excretion. Energy Flow Through Ecosystems secondary production maintaining a high, constant body temperature, synthesizing proteins, and hopping about. This energy used (lost) is attributed to cellular respiration. The remainder goes into making more rabbit biomass by growth and reproduction. Energy Flow Through Ecosystems • The efficiency with which an organism converts assimilated energy into primary or secondary production varies because of the differing metabolic requirements of the organism. • Some organisms have such low net production efficiencies because they are homeotherms, or they maintain a constant internal body temperature. • Poikilotherms, organisms that do not regulate their temperatures internally, have a greater net production efficiency. Energy Flow Through Ecosystems • Other processes that reduce the energy transferred between trophic levels include respiration, growth and reproduction, defecation, and nonpredatory death (organisms that die but are not eaten by consumers). • The low rate of energy transfer between trophic levels makes decomposers generally more important than producers in terms of energy flow. – Decomposers process large amounts of organic material and return nutrients to the ecosystem in inorganic form, which are then taken up again by primary producers. – Energy is not recycled during decomposition, but rather is released Energy Flow Through Ecosystems • An ecosystem's gross primary productivity (GPP) is the total amount of organic matter that it produces through photosynthesis. • Net primary productivity (NPP) describes the amount of energy that remains available for plant growth after subtracting the fraction that plants use for respiration. • In equation form, we have net production efficiency = (production / assimilation), or for plants = (NPP / GPP). Energy Flow Through Ecosystems • Many factors influence primary productivity rates, but the most important on land are temperature and water availability. Energy Flow Through Ecosystems • In contrast to land, where vascular plants carry out most primary production, most primary production in the oceans is done by microscopic algae. Energy Flow Through Ecosystems • How many trophic levels can an ecosystem support? • The amount of energy entering the ecosystem • Energy loss between trophic levels • The form, structure, and physiology of organisms at each level. – At higher trophic levels, predators generally are physically larger and are able to utilize a fraction of the energy that was produced at the level beneath them, so they have to forage over increasingly large areas to meet their caloric needs. Energy Flow Through Ecosystems • An important consequence of the loss of energy between trophic levels is that contaminants collect in animal tissues—a process called bioaccumulation. • Bioaccumulation is the gradual build up over time of a chemical in a living organism. – This occurs either because the chemical is taken up faster than it can be used, or because the chemical cannot be broken down for use by the organism (that is, the chemical cannot be metabolized). Energy Flow Through Ecosystems Biogeochemical Cycling in Ecosystems • Along with energy, water and several other chemical elements cycle through ecosystems and influence the rates at which organisms grow and reproduce. • About 10 major nutrients and six trace nutrients are essential to all animals and plants. • The most important biogeochemical cycles affecting ecosystem health are the water, carbon, nitrogen, and phosphorus cycles. Biogeochemical Cycling in Ecosystems • Earth's water is always in movement, and the natural water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above, and below the surface of the Earth. • Water is always changing states between liquid, vapor, and ice, with these processes happening in the blink of an eye and over millions of years. Biogeochemical Cycling in Ecosystems Atmosphere · Condensation · Evaporation · Evapotranspiration · Freshwater storage Groundwater discharge · Groundwater storage · Ice and snow · Infiltration · Oceans Precipitation · Runoff · Snowmelt · Springs · Streamflow · Sublimation Biogeochemical Cycling in Ecosystems Biogeochemical Cycling in Ecosystems Carbon exists in the nonliving environment as: • carbon dioxide (CO2) in the atmosphere and dissolved in water (forming HCO3−) • carbonate rocks (limestone and coral = CaCO3) • deposits of coal, petroleum, and natural gas derived from once-living things • dead organic matter, e.g., humus in the soil Biogeochemical Cycling in Ecosystems • While CO2 is only a very small part of the atmosphere (0.04%), it plays a large role in the energy balance of the planet. • CO2 in the atmosphere acts like a blanket over the planet by trapping long wave radiation, which would otherwise radiate heat away from the planet. Biogeochemical Cycling in Ecosystems The NOAA global cooperative air sampling network used to determine the AGGI. Red dots are weekly flask sampling sites and blue circles are continuous measurement sites. Biogeochemical Cycling in Ecosystems The nitrogen cycle represents one of the most important nutrient cycles found in terrestrial ecosystems. Nitrogen is used by living organisms to produce a number of complex organic molecules like amino acids, proteins, and nucleic acids. Despite its abundance in the atmosphere, nitrogen is often the most limiting nutrient for plant growth. This problem occurs because most plants can only take up nitrogen in two solid forms: ammonium ion (NH4+ ) and the ion nitrate (NO3- ). Biogeochemical Cycling in Ecosystems Biogeochemical Cycling in Ecosystems • Phosphorus is an essential nutrient for plants and animals in the form of ions PO43- and HPO42-. • It is a part of DNA-molecules, of molecules that store energy (ATP and ADP) and of fats of cell membranes. • Phosphorus is also a building block of certain parts of the human and animal body, such as the bones and teeth. Biogeochemical Cycling in Ecosystems • The amount of phosphate available to plants depends on soil pH. • As a result, the highest concentrations of available phosphate occur at soil pH values between 6 and 7. • Excessive phosphorus can also contribute to over-fertilization and eutrophication of rivers and lakes. Population Dynamics • Every organism in an ecosystem divides its energy among three competing goals: growing, surviving, and reproducing. • Ecologists refer to an organism's allocation of energy among these three ends throughout its lifetime as its life history strategy. Population Dynamics • Organisms at the first of the two extremes (those adapted to unstable environments) as r-selected. • The other extreme, organisms adapted to stable environments, are termed K-selected because they live in environments in which the number of individuals is at or near the environment's carrying capacity (often abbreviated as K). Population Dynamics Feature Reaches sexual or reproductive maturity Norway rat (rselected) African elephant (Kselected) 3-4 months 10-12 years Average gestation period Time to weaning Breeding interval (female) 22-24 days 22 months 3-4 weeks Up to 7 times per year 48-108 months Offspring per litter 2-14 (average 8) Every 4 to 9 years 1 average, 2 high Population Dynamics • In a growing population, survival and reproduction rates will not stay constant over time. • Eventually resource limitations will reduce one or both of these variables. • Populations grow fastest when they are near zero and the species is uncrowded. • A simple mathematical model of population growth implies that the maximum population growth rate occurs when the population size (N) is at one-half of the environment's carrying capacity, K (i.e., at N = K/2). Regulation of Ecosystem Functions • What factors limits the activity within an ecosystem? • Resources influence ecosystem activity differently depending on whether they are essential, substitutable, or complementary. • Essential resources limit growth independently of other levels. Regulation of Ecosystem Functions • If two resources are substitutable, then population growth is limited by an appropriately weighted sum of the two resources in the environment (replacement). • Resources may also be complementary, which means that a small amount of one resource can substitute for a relatively large amount of another, or can be complementary over a specific range of conditions (range). Regulation of Ecosystem Functions Regulation of Ecosystem Functions • A keystone species is a plant or animal that plays a unique and crucial role in the way an ecosystem functions. • Without keystone species, the ecosystem would be dramatically different or cease to exist altogether. Regulation of Ecosystem Functions • Foundation species play a major role in creating or maintaining a habitat that supports other species. • An umbrella species is a large animal or other organism on which many other species depend. – Umbrella species are very similar to keystone species, but umbrella species are usually migratory and need a large habitat. Regulation of Ecosystem Functions • An indicator species is a plant or animal that is very sensitive to environmental changes in its ecosystem. • This means it is affected almost immediately by damage to the ecosystem and can give early warning that a habitat is suffering. Ecological Niches Type of interaction Effect of interaction Symbols Competition Both species are harmed (population growth rates are reduced). -- Predation Parasitism One species benefits, one is harmed. Mutualism Both species benefit. Relationship may not be essential for either. Commensalism One species benefits, one is not affected. +++ +0 Amensalism One species harms another (typically by releasing a toxic substance), but is not affected itself. 0- Ecological Niches • Each species in an ecosystem occupies a niche, which comprises the sum total of its relationships with the biotic and abiotic elements of its environment—more simply, what it needs to survive. Ecological Niches • The full range of habitat types in which a species can exist and reproduce without any competition from other species is called its fundamental niche. • A species' realized niche can be thought of as its niche in practice—the range of habitat types from which it is not excluded by competing species. – Realized niches are usually smaller than fundamental niches. – Species may occupy different realized niches in various locations if some conditions, such as a certain predator, is present in one area but not in another. Ecological Niches • Many key questions about how species function in ecosystems can be answered by looking at their niches. • Species with narrow niches tend to be specialists, relying on comparatively few food sources. • In contrast, species with broad niches are generalists that can adapt to wider ranges of environmental conditions within their own lifetimes and survive on diverse types of prey. Ecological Niches Evolution and Natural Selection in Ecosystems • But natural selection doesn't lead to the development of a new species. In most cases, the process simply allows a species to better adapt to its environment by changing the genetic make up from one generation to the next. • If a species lacks a certain trait that will allow it to survive, there are two options: Either the species dies out or it develops the missing trait Evolution and Natural Selection in Ecosystems • Most people think of biologist and naturalist Charles Darwin as the father of the theory of evolution, but the truth is that the concept of evolution is much older. Evolution and Natural Selection in Ecosystems • As species interact, their relationships with competitors, predators, and prey contribute to natural selection and thus influence their evolution over many generations. • Predators - to find, catch, and kill prey • Prey - avoid detection and make organisms harder to handle or less biologically profitable to eat. Evolution and Natural Selection in Ecosystems • Mimicry - Evolving to appear similar to another successful species or to the environment in order to dupe predators into avoiding the mimic, or dupe prey into approaching the mimic. Evolution and Natural Selection in Ecosystems • Predators are more likely to survive and reproduce if they restrict their diets to prey that provide the most energy per unit of handling time and focus on areas that are rich with prey or that are close together. • This tends to suggest herding/pack behavior among some species of animals. Evolution and Natural Selection in Ecosystems • Avoidance/escape features help prey elude predators. • These attributes may be behavioral patterns, such as animal herding or fish schooling to make individual organisms harder to pick out. • Markings can confuse and disorient predators When the Automeris moth perceives a threat, it moves its forewings to reveal false eye spots on its hindwings and to frighten predators away. Evolution and Natural Selection in Ecosystems . – Spines serve this function for many plants and animals. – Shells make crustaceans and mollusks harder to eat. : – Squid and octopus emit clouds of ink that distract and confuse attackers – Hedgehogs and porcupines increase the effectiveness of their protective spines by rolling up in a ball to conceal their vulnerable underbellies. Evolution and Natural Selection in Ecosystems • Some plants and animals emit noxious chemical substances to make themselves less profitable as prey. Evolution and Natural Selection in Ecosystems • Coevolution - Simultaneous evolution of two or more species of organisms that interact in significant ways. • These ecological relationships where coevolution may occur include: – Predator/prey and parasite/host – Competitive species – Mutualistic species A case study of coevolution: squirrels, birds, and the pinecones they love The plot: In most of the Rocky Mountains, red squirrels are an important predator of lodgepole pine seeds. They harvest pinecones from the trees and store them through the winter. However, the pine trees are not defenseless: squirrels have a difficult time with wide pinecones that weigh a lot but have fewer seeds. Crossbill birds live in these places and also eat pine seeds, but the squirrels get to the seeds first, so those birds don't get as many seeds. However, in a few isolated places, there are no red squirrels, and crossbills are the most important seed predator for lodgepoles. Again, the trees are not defenseless: crossbills have more difficulty getting seeds from cones with large, thick scales. But the birds have a mode of counterattack: crossbills with deeper, shorter, less curved bills are better able to extract seeds from tough cones. The stage is set, but the question remains: has coevolution happened? In order to show coevolution, we need evidence that suggests that the prey (the trees) have evolved in response to the predator (squirrels or birds) and that the predator has evolved in response to the prey. A case study of coevolution • There should be geographic differences in the pinecones. If the trees have evolved in response to their seed predators, we should observe geographic differences in pinecones: • Where there are squirrels, the pinecones are heavier with fewer seeds, but have thinner scales, like the pinecone on the left. • Where there are only crossbills, pinecones are lighter with more seeds, but have thick scales, like the one on the right. A case study of coevolution Lodgepole pine cones adapted to squirrels — easier for crossbills to eat. Lodgepole pine cones adapted to crossbills — easier for squirrels to eat. A case study of coevolution Where the pinecones have thick scales, birds have deeper, less curved bills (below left) than where the pinecones have thin scales (below right). The bill is less curved on this female red crossbill The bill is more deeply curved on this male red crossbill Evolution and Natural Selection in Ecosystems • Competition is an interaction between organisms or species, in which the fitness of one is lowered by the presence of another. • Limited supply of at least one resource (such as food, water, and territory) used by both is required. – Competition among members of the same species is known as intraspecific competition. – Competition between individuals of different species is known as interspecific competition. Natural Ecosystem Change • Just as relationships between individual species are dynamic, so too is the overall makeup of ecosystems. • The process by which one changes into another years to centuries is Natural Ecosystem Change • In the early 20th century, plant biologist Frederic Clements described two types of succession: primary (referring to colonization of a newly exposed landform, such as sand dunes or lava flows after a volcanic eruption) and secondary (describing the return of an area to its natural vegetation following a disturbance such as fire, treefall, or forest harvesting). Natural Ecosystem Change • British ecologist Arthur Tansley distinguished succession based on biotic and abiotic causes. • Autogenic succession—change driven by the inhabitants of an ecosystem (biotic), such as forests regrowing on abandoned agricultural fields. • Allogenic succession - change driven by new external geophysical conditions (abiotic) such as rising average temperatures resulting from global climate change. Natural Ecosystem Change Ecosystem attributes Developmental stages Mature stages Energetics: Production/respiration More or less than 1 Approaching 1 Production/biomass High Low Food chains Linear Web-like Community structure: Niches Broad Narrow Species diversity Low High Nutrient conservation Poor; detritus unimportant Good; detritus important Nutrient exchange rates Rapid Slow Stability Low High Natural Ecosystem Change • Many natural disturbances have interrupted the process of ecosystem succession throughout Earth's history, including natural climate fluctuations, the expansion and retreat of glaciers, and local factors such as fires and storms. • An understanding of succession is central for conserving and restoring ecosystems because it identifies conditions that managers must create to bring an ecosystem back into its natural state. Resources • http://kids.nceas.ucsb.edu/biomes/index.html general information • http://www.globalchange.umich.edu/globalchan ge1/current/lectures/kling/energyflow/highertro phic/trophic2.html - trophic levels • Bioaccumulation - Food, Pollutant, Toxic, and Fish - JRank Articles http://science.jrank.org/pages/854/Bioac cumulation.html#ixzz2LmYt9VUo – biological magnification Resources • http://ga.water.usgs.gov/edu/watercycle.html - water cycle • http://www.lenntech.com/phosphoruscycle.htm#ixzz2LqdTCC00 – phosphorus cycle • http://www.globalchange.umich.edu/globalch ange1/current/lectures/kling/ecosystem/ecos ystem.html - global change • http://www.sustainablescale.org/areasofconc ern/Biodiversity/BiodiversityandScale/QuickFa cts.aspx - fast facts Resources • http://www.pbs.org/nationalparks/watchvideo/#914 – the story of the National Parks • http://education.nationalgeographic.com/edu cation/encyclopedia/keystonespecies/?ar_a=1 – keystone species information • http://evolution.berkeley.edu/evolibrary/articl e/evo_33 - coevolution notes Resources • http://en.wikipedia.org/wiki/Competition_(bi ology)